U.S. patent application number 15/405166 was filed with the patent office on 2017-06-15 for electronics for detection of a condition of tissue.
The applicant listed for this patent is MC10, Inc.. Invention is credited to Jeffrey D. Carbeck, Alexander Dickson, Kevin Dowling, Yung-Yu Hsu, Isaiah Kacyvenski, Conor Rafferty, Benjamin Schlatka, Henry Wei.
Application Number | 20170164865 15/405166 |
Document ID | / |
Family ID | 47756961 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170164865 |
Kind Code |
A1 |
Rafferty; Conor ; et
al. |
June 15, 2017 |
ELECTRONICS FOR DETECTION OF A CONDITION OF TISSUE
Abstract
Apparatus are provided for monitoring a condition of a tissue
based on a measurement of an electrical property of the tissue. In
an example, the electrical property of the tissue is performed
using an apparatus disposed above the tissue, where the apparatus
includes at least two conductive structures, each having a
non-linear configuration, where the at least two conductive
structures are disposed substantially parallel to each other. In
another example, the electrical property of the tissue is performed
using an apparatus disposed above the tissue, where the apparatus
includes at least one inductor structure.
Inventors: |
Rafferty; Conor; (Cambridge,
MA) ; Carbeck; Jeffrey D.; (Belmont, MA) ;
Dickson; Alexander; (Darien, CT) ; Dowling;
Kevin; (Gibsonia, PA) ; Hsu; Yung-Yu; (San
Jose, CA) ; Kacyvenski; Isaiah; (Weston, MA) ;
Schlatka; Benjamin; (Lexington, MA) ; Wei; Henry;
(Burlingame, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MC10, Inc. |
Lexington |
MA |
US |
|
|
Family ID: |
47756961 |
Appl. No.: |
15/405166 |
Filed: |
January 12, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13603290 |
Sep 4, 2012 |
9579040 |
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15405166 |
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61530283 |
Sep 1, 2011 |
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61540421 |
Sep 28, 2011 |
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61541762 |
Sep 30, 2011 |
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61649035 |
May 18, 2012 |
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61681545 |
Aug 9, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/04 20130101; A61B
5/0537 20130101; A61B 5/0533 20130101; A61B 5/01 20130101; A61B
5/443 20130101; A61B 5/0488 20130101; A61B 5/024 20130101; A61B
5/0245 20130101; A61B 5/0024 20130101; A61B 5/0531 20130101; A61B
5/441 20130101; A61B 5/04012 20130101; A61B 5/0002 20130101; A61B
5/6831 20130101; A61B 8/4416 20130101; A61B 5/112 20130101; A61B
5/7282 20130101; A61B 5/0476 20130101; A61B 5/4266 20130101; A61B
5/442 20130101; A61B 5/0402 20130101; A61B 2562/16 20130101; A61B
5/68335 20170801; A61B 5/6833 20130101 |
International
Class: |
A61B 5/053 20060101
A61B005/053; A61B 5/00 20060101 A61B005/00 |
Claims
1-85. (canceled)
86. A system for monitoring a condition of a tissue, the system
comprising: an ultrasound generator disposed on a first flexible,
stretchable substrate, the ultrasound generator being disposed
proximate a first portion of the tissue and being configured to
generate an ultrasound wave and direct the ultrasound wave into the
first portion of the tissue; an ultrasound receiver disposed on a
second flexible, stretchable substrate, the ultrasound receiver
being disposed proximate a second portion of the tissue and being
configured to detect the ultrasound wave at the second portion of
the tissue; and at least one processor disposed on either the first
or the second substrate, the at least one processor being
configured to determine a propagation velocity of the ultrasound
wave through the tissue and to provide a measure of a hydration
level of the tissue based on the propagation velocity of the
ultrasound wave through the tissue.
87. The system of claim 86, wherein the ultrasound generator
includes a piezoelectric element configured to generate the
ultrasound waves and a focusing element to direct the ultrasound
waves into the first portion of the tissue.
88. The system of claim 87, wherein the piezoelectric element is a
piezoelectric crystal or a piezoelectric disc actuator.
89. The system of claim 87, wherein the piezoelectric element
changes shape responsive to a changing voltage being applied
thereto.
90. The system of claim 86, wherein the measure of the hydration
level of the tissue is determined based at least on a linear
proportionality between the propagation velocity of the ultrasound
waves through the tissue and the hydration level of the tissue.
91. The system of claim 86, further comprising a sensor configured
to measure a composition of a body fluid sample collected from the
tissue.
92. The system of claim 91, wherein the sensor measures a
conductivity of the body fluid sample.
93. The system of claim 91, wherein the sensor measures a
concentration of an ion in the body fluid sample.
94. The system of 93, wherein the ion includes at least one of
sodium, potassium, or calcium.
95. The system of claim 86, wherein the tissue is bicep tissue or
thigh tissue of a person.
96. The system of claim 95, wherein the ultrasound generator, the
ultrasound receiver, and the at least one processor are disposed
within a band configured to be disposed on the bicep tissue or the
thigh tissue of the person.
97. The system of claim 95, wherein the ultrasound generator, the
ultrasound receiver, and the at least one processor are disposed on
a garment configured to be worn by the person.
98. The system of claim 86, wherein the ultrasound wave is a first
ultrasound wave, the system further comprising: a second ultrasound
generator disposed proximate a third portion of the tissue and
configured to generate a second ultrasound wave; and a second
ultrasound receiver disposed proximate a fourth portion of the
tissue and configured to detect the second ultrasound wave; wherein
the at least one processor is further configured to determine a
propagation velocity of the second ultrasound wave through the
tissue and to determine an average propagation velocity based on
the propagation velocity of the first ultrasound wave and the
propagation velocity of the second ultrasound wave, the at least
one processor being further configured to determine the hydration
level of the tissue based on the average propagation velocity.
99. A method of determining a hydration level of a tissue, the
method comprising: generating an ultrasound wave; directing the
ultrasound wave into a first portion of the tissue at a first time;
detecting the ultrasound wave at a second portion of the tissue at
a second time; determining a propagation velocity of the ultrasound
wave through the tissue based on (i) a difference between the first
time and the second time and (ii) a distance between the first
portion of tissue and the second portion of tissue; and determining
the hydration level of the tissue based at least on the propagation
velocity of the ultrasound wave through the tissue.
100. The method of claim 99, wherein the one or more ultrasound
waves are generated by applying a changing voltage to a
piezoelectric element, thereby causing the piezoelectric element to
repeatedly change shape.
101. The method of claim 99, wherein the propagation velocity of
the one or more ultrasound waves is linearly proportional to the
hydration level of tissue
102. The method of claim 99, wherein the ultrasound wave is a first
ultrasound wave, the method further comprising: generating a second
ultrasound wave; directed the second ultrasound wave into a third
portion of the tissue at a third time; detecting the ultrasound
wave at a fourth portion of the tissue at a fourth time;
determining a propagation velocity of the second ultrasound wave
through the tissue based on (i) a difference between the third time
and the fourth time and (ii) a distance between the third portion
of the tissue and the fourth portion of the tissue; determining an
average propagation velocity based on the propagation velocity of
the first ultrasound wave and the propagation velocity of the
second ultrasound wave; determining the hydration level of the
tissue based at least on the average propagation velocity.
103. A system for analyzing tissue, comprising: an ultrasound
generator disposed proximate a first portion of the tissue, the
ultrasound generator configured to generate ultrasound waves and
direct the generated ultrasound waves into the first portion of the
tissue; an ultrasound receiver disposed proximate a second portion
of the tissue, the ultrasound receiver configured to detect the
ultrasound waves at the second portion of the tissue; at least one
processor, the at least one processor being configured to determine
a propagation velocity of the ultrasound waves through the tissue
and to provide a measure of a hydration level of the tissue based
on the propagation velocity of the ultrasound waves; and a sensor
configured to measure a concentration of an ion in a body fluid
sample collected from the tissue, the ion including at least one of
sodium, potassium, or calcium.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/603,290, filed Sep. 4, 2012, now allowed, which claims
priority to and the benefit of U.S. provisional application Ser.
No. 61/530,283, filed Sep. 1, 2011, U.S. provisional application
Ser. No. 61/540,421, filed Sep. 28, 2011, U.S. provisional
application Ser. No. 61/541,762, filed Sep. 30, 2011, U.S.
provisional application Ser. No. 61/649,035, filed May 18, 2012,
and U.S. provisional application Ser. No. 61/681,545, filed Aug. 9,
2012, each of which is hereby incorporated by reference herein in
its entirety.
BACKGROUND
[0002] Effort is being made to develop electronics for application
in measuring electrical properties of biological tissue. For
example, effort is being made to develop electronics that can be
applied to measure a property such as tissue hydration level.
[0003] Tissue hydration is the process of absorbing and retaining
water in biological tissues. In humans, a significant drop in
tissue hydration can lead to dehydration and may trigger other
serious medical conditions. Dehydration may result from loss of
water itself, loss of electrolytes, and/or a loss of blood plasma.
Previous techniques for monitoring tissue hydration have applied,
e.g., an ultrasonic hydration monitor that employs ultrasound
velocity to calculate hydration level. The ultrasound hydration
monitor is generally attached to tissue such as muscles. The device
generally uses a rigid frame to maintain a constant distance
between an ultrasound transducer and a receiver.
[0004] The use of electronics in such medical-related applications
can be hampered by the boxy, rigid way that much electronics are
designed and packaged. Biological tissue is mainly soft, pliable
and curved. By contrast, boxy, rigid electronics can be hard and
angular, which could affect the measurement of tissue.
SUMMARY
[0005] In view of the foregoing, it is recognized and appreciated
herein that both sufficient comfort and accuracy are desirable
attributes of techniques for monitoring tissue condition.
[0006] Various examples described herein are directed generally to
tissue condition monitoring methods, apparatus, and systems
applicable to both consumer and military markets, which can provide
real-time feedback as well as portability. The tissue condition can
be state of hydration or disease state. In some examples, the
methods, apparatus and systems are based at least in part on
measuring electrical properties of the skin and underlying
tissue.
[0007] An example apparatus is described for monitoring a condition
of a tissue. The apparatus includes at least two conductive
structures disposed above the tissue, where each of the at least
two conductive structures has a non-linear configuration, and where
the at least two conductive structures are disposed substantially
parallel to each other; at least two brace structures, each
disposed substantially perpendicularly to the orientation of the at
least two parallel conductive structures, and each being in
electrical communication with at least one of the at least two
parallel conductive structures; and at least one spacer structure
that is physically coupled at each end to a portion of each of the
at least two brace structures, such that a substantially uniform
separation is maintained between the at least two brace structures.
A measure of an electrical property of the tissue using the
apparatus provides an indication of the condition of the
tissue.
[0008] The condition of the tissue can be a hydration state of the
tissue, a volume of sweat lost, a mechanical property of the
tissue, a disease state of the tissue, or a level of SPF protection
of the tissue.
[0009] For the example apparatus, each of the at least two
conductive structures can have a zig-zag conformation, a serpentine
configuration, or a rippled configuration.
[0010] Each of the at least two brace structures can be formed from
a conductive material, and where each of the at least two brace
structures electrically links the at least two conductive
structures to an external circuit.
[0011] The at least two brace structures can be configured to
maintain a separation of neighboring conductive structures of the
at least two conductive structures to a substantially uniform
value.
[0012] Each of the at least one spacer structure can be disposed
substantially parallel to a principal direction of the at least two
parallel conductive structures.
[0013] Each of the at least two brace structure can be in
electrical communication with at least one electrical contact of
the apparatus, where the at least one electrical contact is in
electrical communication with at least one of a power source, a
wireless receiver, a wireless transmitter, a wireless transceiver,
and a temperature sensor.
[0014] The example apparatus can include a plurality of cross-link
structures disposed between neighboring conductive structures, each
cross-link structure of the plurality of cross-link structures
being formed from a dielectric material.
[0015] The example apparatus can include an encapsulation layer
disposed over at least a portion of the at least two conductive
structures. In an example, portions of the encapsulation layer
comprise an adhesive, where the adhesive attaches the portions of
the encapsulation layer to the tissue.
[0016] The apparatus can include a plurality of cross-link
structures disposed between neighboring conductive structures, each
cross-link structure of the plurality of cross-link structures
being formed from the same material as the encapsulation layer.
[0017] In an example, the encapsulation layer is a polymer. In
another example, the polymer is a polyimide.
[0018] The example apparatus can include a backing layer in
physical communication with at least a portion of the at least two
conductive structures, where the backing layer is a polymer.
[0019] The apparatus in this example implementation can include an
ultrasound apparatus, where the ultrasound apparatus provides a
measure of an electrical property of the tissue. The ultrasound an
apparatus can include an ultrasound generator disposed proximate to
a first portion of the tissue of interest, where the ultrasound
generator comprises a piezoelectric crystal, where the ultrasound
generator directs ultrasound waves at a portion of the tissue; and
an ultrasound receiver disposed proximate to a second portion of
the tissue of interest that is different from the first portion.
The ultrasound receiver provides a measure of ultrasound waves
arriving at the second portion of the tissue. The measure of
ultrasound waves arriving at the second portion of the tissue
provides an indication of the condition of the tissue.
[0020] A system for monitoring a condition of a tissue is also
provided. The example system includes at least one of any of the
apparatus of this example implementation and at least one other
component. The at least one other component can be at least one of
a battery, a transmitter, a transceiver, a memory, a
radio-frequency identification (RFID) chip, a processing unit, an
analog sensing block, a UVA sensor, a UVB sensor, and a temperature
sensor.
[0021] A method for monitoring a condition of a tissue is also
provided. The method can include receiving data indicative of an
electrical measurement of the tissue, where the electrical
measurement is performed using at least one apparatus described
herein; and analyzing the data using at least one processor unit,
where the analysis provides an indication of the condition of the
tissue.
[0022] In an example, the analyzing the data can include applying
an effective circuit model to the data, where a value of a
parameter of the model provides the indication of the condition of
the tissue.
[0023] In another example, the analyzing the data can include
comparing the data to a calibration standard, where the comparing
provides the indication of the condition of the tissue. The
calibration standard can include a correlation between values of
electrical measurement and the indication of the condition of the
tissue.
[0024] Another example apparatus for monitoring a condition of a
tissue is described. The apparatus includes a plurality of
conductive structures disposed above the tissue, where each of the
plurality of conductive structures has a non-linear configuration,
and where the plurality of conductive structures are disposed
substantially parallel to each other in an interdigitated
configuration; at least two brace structures, each disposed
substantially perpendicularly to the orientation of the at least
two parallel conductive structures, and each brace structure being
in electrical communication with at least one of the plurality of
conductive structures; and at least one spacer structure that is
physically coupled at each end to a portion of each of the at least
two brace structures, such that a substantially uniform separation
is maintained between the at least two brace structures. A measure
of an electrical property of the tissue using the apparatus
provides an indication of the condition of the tissue.
[0025] For this example apparatus, the condition of the tissue can
be a hydration state of the tissue, a volume of sweat lost, a
mechanical property of the tissue, a disease state of the tissue,
or a level of SPF protection of the tissue.
[0026] Each of the plurality of conductive structures can have a
zig-zag conformation, a serpentine configuration, or a rippled
configuration.
[0027] Each of the at least two brace structures can be formed from
a conductive material, and where each of the at least two brace
structures electrically links the plurality of conductive
structures to an external circuit.
[0028] The at least two brace structures are configured to maintain
a separation of neighboring conductive structures of the plurality
of conductive structures to a substantially uniform value.
[0029] Each of the at least one spacer structure can be disposed
substantially parallel to a principal direction of the at least two
parallel conductive structures.
[0030] Each of the at least two brace structure can be in
electrical communication with at least one electrical contact of
the apparatus, where the at least one electrical contact is in
electrical communication with at least one of a power source, a
wireless receiver, a wireless transmitter, a wireless transceiver,
and a temperature sensor.
[0031] In an example, the apparatus can include a plurality of
cross-link structures disposed between neighboring conductive
structures, each cross-link structure of the plurality of
cross-link structures being formed from a dielectric material.
[0032] The example apparatus of this implementation can include an
encapsulation layer disposed over at least a portion of the
plurality of conductive structures. Portions of the encapsulation
layer can include an adhesive, where the adhesive attaches the
portions of the encapsulation layer to the tissue.
[0033] The example apparatus can include a plurality of cross-link
structures disposed between neighboring conductive structures, each
cross-link structure of the plurality of cross-link structures
being formed from the same material as the encapsulation layer.
[0034] The encapsulation layer can be a polymer. In an example, the
polymer is a polyimide.
[0035] The example apparatus can include a backing layer in
physical communication with at least a portion of the plurality of
conductive structures, where the backing layer is a polymer.
[0036] The apparatus in this example implementation can include an
ultrasound apparatus, where the ultrasound apparatus provides a
measure of an electrical property of the tissue. The ultrasound an
apparatus can include an ultrasound generator disposed proximate to
a first portion of the tissue of interest, where the ultrasound
generator comprises a piezoelectric crystal, where the ultrasound
generator directs ultrasound waves at a portion of the tissue; and
an ultrasound receiver disposed proximate to a second portion of
the tissue of interest that is different from the first portion.
The ultrasound receiver provides a measure of ultrasound waves
arriving at the second portion of the tissue. The measure of
ultrasound waves arriving at the second portion of the tissue
provides an indication of the condition of the tissue.
[0037] A system for monitoring a condition of a tissue is also
provided. The example system includes at least one apparatus of of
this example implementation and at least one other component. The
at least one other component can be at least one of a battery, a
transmitter, a transceiver, a memory, a radio-frequency
identification (RFID) chip, a processing unit, an analog sensing
block, a UVA sensor, a UVB sensor, and a temperature sensor.
[0038] A method for monitoring a condition of a tissue is also
provided. The method includes receiving data indicative of an
electrical measurement of the tissue, where the electrical
measurement is performed using at least one of the apparatus
according tto this example implementation and analyzing the data
using at least one processor unit, where the analysis provides an
indication of the condition of the tissue.
[0039] In an example, the analyzing the data can include applying
an effective circuit model to the data, and where a value of a
parameter of the model provides the indication of the condition of
the tissue.
[0040] In another example, the analyzing the data can include
comparing the data to a calibration standard, and where the
comparing provides the indication of the condition of the
tissue.
[0041] The calibration standard can include a correlation between
values of electrical measurement and the indication of the
condition of the tissue.
[0042] Another example apparatus for monitoring a condition of a
tissue is also provided. The apparatus includes at least two
conductive structures disposed above the tissue and running
substantially parallel to each other along substantially an entire
length of the conductive structures, where each of the conductive
structures has a curved configuration; and at least two contact
structures, each being in electrical communication with at least
one of the at least two parallel conductive structures. A measure
of an electrical property of the tissue using the apparatus
provides a measure of the condition of the tissue.
[0043] In this example implementation, the condition of the tissue
can be a hydration state of the tissue, a volume of sweat lost, a
mechanical property of the tissue, a disease state of the tissue,
or a level of SPF protection of the tissue.
[0044] Each of the plurality of conductive structures can have a
zig-zag conformation, a serpentine configuration, or a rippled
configuration.
[0045] Each of the at least two conductive structures is configured
to maintain a separation of neighboring conductive structures of
the at least two conductive structures to a substantially uniform
value of distance.
[0046] Each of the at least two contact structures electrically
links the at least two conductive structures to an external
circuit.
[0047] Each of the at least two contact structures can be in
electrical communication with at least one of a power source, a
wireless receiver, a wireless transmitter, a wireless transceiver,
and a temperature sensor.
[0048] In an example, the apparatus can include an encapsulation
layer disposed over at least a portion of the at least two
conductive structures. Portions of the encapsulation layer can
include an adhesive, where the adhesive attaches the portions of
the encapsulation layer to the tissue.
[0049] The encapsulation layer can be a polymer. In an example, the
polymer is a polyimide.
[0050] The example apparatus according to this implementation can
include at least one cross-link structure coupled at each end
thereof to a portion of each of the least two conductive
structures.
[0051] Each of the at least one cross-link structure can be
disposed substantially perpendicularly to the portion of the at
least two parallel conductive structures.
[0052] The example apparatus can include a plurality of cross-link
structures disposed between the at least two conductive structures,
each cross-link structure of the plurality of cross-link structures
being formed from a dielectric material.
[0053] The example apparatus can include a plurality of cross-link
structures disposed between neighboring conductive structures, each
cross-link structure of the plurality of cross-link structures
being formed from the same material as the encapsulation layer.
[0054] In an example, the encapsulation layer is a polymer. The
polymer can be a polyimide.
[0055] The example apparatus can include a backing layer in
physical communication with at least a portion of the at least two
conductive structures, where the backing layer is a polymer.
[0056] The apparatus in this example implementation can include an
ultrasound apparatus, where the ultrasound apparatus provides a
measure of an electrical property of the tissue. The ultrasound an
apparatus can include an ultrasound generator disposed proximate to
a first portion of the tissue of interest, where the ultrasound
generator comprises a piezoelectric crystal, where the ultrasound
generator directs ultrasound waves at a portion of the tissue; and
an ultrasound receiver disposed proximate to a second portion of
the tissue of interest that is different from the first portion.
The ultrasound receiver provides a measure of ultrasound waves
arriving at the second portion of the tissue. The measure of
ultrasound waves arriving at the second portion of the tissue
provides an indication of the condition of the tissue.
[0057] A system is also provided for monitoring a condition of a
tissue, where the system includes at least one apparatus of this
example implementation and at least one other component. The at
least one other component can be at least one of a battery, a
transmitter, a transceiver, a memory, a radio-frequency
identification (RFID) chip, a processing unit, an analog sensing
block, a UVA sensor, a UVB sensor, and a temperature sensor.
[0058] A method for monitoring a condition of a tissue is also
provided. The method includes receiving data indicative of an
electrical measurement of the tissue, where the electrical
measurement is performed using at least one apparatus of this
example implementation and analyzing the data using at least one
processor unit, where the analysis provides an indication of the
condition of the tissue.
[0059] The analyzing the data can include applying an effective
circuit model to the data, and where a value of a parameter of the
model provides the indication of the condition of the tissue.
[0060] The analyzing the data can include comparing the data to a
calibration standard, and where the comparing provides the
indication of the condition of the tissue.
[0061] The calibration standard can include a correlation between
values of electrical measurement and the indication of the
condition of the tissue.
[0062] Another apparatus for monitoring a condition of a tissue is
provided. The apparatus includes a substrate disposed above the
tissue, where the substrate is formed from a material that changes
a state with a change in the condition of the tissue, and at least
one first inductor structure disposed above the substrate, where at
least one of an electrical property and a physical property of the
at least one first inductor structure changes with a change in the
condition of the substrate. A measure of the electrical property or
the physical property of the at least one first inductor structure
provides an indication of the condition of the tissue.
[0063] The condition of the tissue can be a hydration state of the
tissue, a volume of sweat lost, a mechanical property of the
tissue, a disease state of the tissue, or a level of SPF protection
of the tissue.
[0064] In an example, the first inductor structure can be a spiral
coil structure, a cylindrical coil structure, or a toroidal
structure.
[0065] In an example, the apparatus can include a reader, where the
reader comprises at least one second inductor structure, where a
measure of a change in an electrical property of the at least one
second inductor structure brought in proximity to the at least one
first inductor structure provides the measure of the electrical
property of the at least one first inductor structure.
[0066] In an example, the second inductor structure is the same
configuration as the first inductor structure.
[0067] In an example, the first inductor structure and the second
inductor structure are a spiral coil structure, a cylindrical coil
structure, or a toroidal structure.
[0068] The electrical property measured can be a magnetic flux
density from the at least one first inductor structure.
[0069] In an example, the apparatus includes an encapsulation layer
disposed over at least a portion of the at least one first inductor
structure. The encapsulation layer can be a polymer.
[0070] In an example, portions of the polymer can include an
adhesive, where the adhesive attaches the portions of the polymer
to the tissue.
[0071] In an example, the can include a separator layer disposed
between the at least one inductor structure and the substrate,
where the separator layer is a non-conductive material.
[0072] The separator layer can be formed from a polymer.
[0073] The apparatus in this example implementation can include an
ultrasound apparatus, where the ultrasound apparatus provides a
measure of an electrical property of the tissue. The ultrasound an
apparatus can include an ultrasound generator disposed proximate to
a first portion of the tissue of interest, where the ultrasound
generator comprises a piezoelectric crystal, where the ultrasound
generator directs ultrasound waves at a portion of the tissue; and
an ultrasound receiver disposed proximate to a second portion of
the tissue of interest that is different from the first portion.
The ultrasound receiver provides a measure of ultrasound waves
arriving at the second portion of the tissue. The measure of
ultrasound waves arriving at the second portion of the tissue
provides an indication of the condition of the tissue.
[0074] A system is also for monitoring a condition of a tissue. The
system includes at least one apparatus of this example
implementation, and at least one other component. The at least one
other component is at least one of a battery, a transmitter, a
transceiver, a memory, a radio-frequency identification (RFID)
chip, a processing unit, an analog sensing block, a UVA sensor, a
UVB sensor, and a temperature sensor.
[0075] A method is also provided for monitoring a condition of a
tissue. The method includes receiving data indicative of an
electrical measurement of the tissue, where the electrical
measurement is performed using at least one apparatus of this
example implementation, and analyzing the data using at least one
processor unit, where the analysis provides an indication of the
condition of the tissue.
[0076] The analyzing the data can include applying an effective
circuit model to the data, and where a value of a parameter of the
model provides the indication of the condition of the tissue.
[0077] The analyzing the data can include comparing the data to a
calibration standard, and where the comparing provides the
indication of the condition of the tissue.
[0078] The calibration standard can include a correlation between
values of electrical measurement and the indication of the
condition of the tissue.
[0079] The following publications, patents, and patent applications
are hereby incorporated herein by reference in their entirety:
[0080] Kim et al., "Stretchable and Foldable Silicon Integrated
Circuits," Science Express, Mar. 27, 2008,
10.1126/science.1154367;
[0081] Ko et al., "A Hemispherical Electronic Eye Camera Based on
Compressible Silicon Optoelectronics," Nature, Aug. 7, 2008, vol.
454, pp. 748-753;
[0082] Kim et al., "Complementary Metal Oxide Silicon Integrated
Circuits Incorporating Monolithically Integrated Stretchable Wavy
Interconnects," Applied Physics Letters, Jul. 31, 2008, vol. 93,
044102;
[0083] Kim et al., "Materials and Noncoplanar Mesh Designs for
Integrated Circuits with Linear Elastic Responses to Extreme
Mechanical Deformations," PNAS, Dec. 2, 2008, vol. 105, no. 48, pp.
18675-18680;
[0084] Meitl et al., "Transfer Printing by Kinetic Control of
Adhesion to an Elastomeric Stamp," Nature Materials, January, 2006,
vol. 5, pp. 33-38;
[0085] U.S. Patent Application publication no. 2010 0002402-A1,
published Jan. 7, 2010, filed Mar. 5, 2009, and entitled
"STRETCHABLE AND FOLDABLE ELECTRONIC DEVICES;"
[0086] U.S. Patent Application publication no. 2010 0087782-A1,
published Apr. 8, 2010, filed Oct. 7, 2009, and entitled "CATHETER
BALLOON HAVING STRETCHABLE INTEGRATED CIRCUITRY AND SENSOR
ARRAY;"
[0087] U.S. Patent Application publication no. 2010 0116526-A1,
published May 13, 2010, filed Nov. 12, 2009, and entitled
"EXTREMELY STRETCHABLE ELECTRONICS;"
[0088] U.S. Patent Application publication no. 2010 0178722-A1,
published Jul. 15, 2010, filed Jan. 12, 2010, and entitled "METHODS
AND APPLICATIONS OF NON-PLANAR IMAGING ARRAYS;"
[0089] U.S. Patent Application publication no. 2010 027119-A1,
published Oct. 28, 2010, filed Nov. 24, 2009, and entitled
"SYSTEMS, DEVICES, AND METHODS UTILIZING STRETCHABLE ELECTRONICS TO
MEASURE TIRE OR ROAD SURFACE CONDITIONS;"
[0090] PCT Patent Application publication no. WO2011/084709,
published Jul. 14, 2011, entitled "Methods and Apparatus for
Conformal Sensing of Force and/or Change in Motion;" and
[0091] U.S. Patent Application publication no. 2011 0034912-A1,
published Feb. 10, 2011, filed Mar. 12, 2010, and entitled
"SYSTEMS, METHODS, AND DEVICES HAVING STRETCHABLE INTEGRATED
CIRCUITRY FOR SENSING AND DELIVERING THERAPY."
[0092] It should be appreciated that all combinations of the
foregoing concepts and additional concepts discussed in greater
detail below (provided such concepts are not mutually inconsistent)
are contemplated as being part of the subject matter disclosed
herein. In particular, all combinations of claimed subject matter
appearing at the end of this disclosure are contemplated as being
part of the subject matter disclosed herein. It should also be
appreciated that terminology explicitly employed herein that also
may appear in any disclosure incorporated by reference should be
accorded a meaning most consistent with the particular concepts
disclosed herein.
[0093] The foregoing and other aspects, examples, and features of
the present teachings can be more fully understood from the
following description in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0094] The skilled artisan will understand that the figures,
described herein, are for illustration purposes only. It is to be
understood that in some instances various aspects of the invention
may be shown exaggerated or enlarged to facilitate an understanding
of the invention. In the drawings, like reference characters
generally refer to like features, functionally similar and/or
structurally similar elements throughout the various figures. The
drawings are not necessarily to scale, emphasis instead being
placed upon illustrating the principles of the teachings. The
drawings are not intended to limit the scope of the present
teachings in any way.
[0095] FIG. 1A shows a block diagram of an example system for
monitoring condition of a tissue, according to the principles
herein.
[0096] FIG. 1B shows a block diagram of another example system for
monitoring condition of a tissue, according to the principles
herein.
[0097] FIG. 2 shows examples of tissue conditions or tissue
sections that may be monitored using the example apparatus,
according to the principles herein.
[0098] FIG. 3 shows a cross-section view of an example apparatus
for monitoring condition of a tissue, according to the principles
herein.
[0099] FIG. 4 shows a cross-section view of another example
apparatus for monitoring condition of a tissue, according to the
principles herein.
[0100] FIG. 5 shows an example apparatus that includes
interdigitated conductive structures, according to the principles
herein.
[0101] FIG. 6 is an illustration of the example apparatus of FIG.
5, with selected portions magnified, according to the principles
herein.
[0102] FIG. 7 shows an example of an apparatus with cross-link
structures disposed between interdigitated conductive structures,
according to the principles herein.
[0103] FIG. 8 shows an example apparatus with curved conductive
structures, according to the principles herein.
[0104] FIG. 9 shows another example apparatus with curved
conductive structures and cross-link structures, according to the
principles herein.
[0105] FIG. 10 shows another example with curved conductive
structures, according to the principles herein.
[0106] FIGS. 11A-11I show an example process for fabricating an
example apparatus, according to the principles herein.
[0107] FIGS. 12A-12E show an example apparatus that includes the
interdigitated conductive structures, according to the principles
herein.
[0108] FIG. 13A shows a finite element (FE) model for deformation
of an apparatus, according to the principles herein.
[0109] FIG. 13B shows an apparatus that is stretched at 50%
elongation, according to the principles herein.
[0110] FIGS. 14A-14B show an example apparatus having
interdigitated conductive structures in a relaxed state (FIG. 14A)
and elongated by 50% (FIG. 14B), according to the principles
herein.
[0111] FIGS. 15A-15B show plots of the magnitude and phase,
respectively, of the impedance change with the sweat level at
selected measurement frequencies, according to the principles
herein.
[0112] FIGS. 16A-16B show performance of the example apparatus of
FIGS. 14A-14B versus impedance and capacitance, respectively,
according to the principles herein.
[0113] FIG. 17 shows a simulation of the distance changes between
the conductive structures during stretching of the substrate,
according to the principles herein.
[0114] FIG. 18 shows the simulated out-of-plane deformation while
the inset to FIG. 18 shows the optical image of the stretchable
interconnect, according to the principles herein.
[0115] FIG. 19A-19B show an example apparatus that include an
inductor structure, according to the principles herein.
[0116] FIG. 20 shows a system that includes an example reader
including an inductor structure, according to the principles
herein.
[0117] FIGS. 21-23 show quarter sections of example sensing
patches, according to the principles herein.
[0118] FIG. 24 shows a cross-section of an example ultrasound
system, according to the principles herein.
[0119] FIG. 25 illustrates an example operation of the example
ultrasound system when a voltage is applied, according to the
principles herein.
[0120] FIG. 26A shows an example device mount about a bicep tissue,
according to the principles herein.
[0121] FIG. 26B shows a cross-section of the device mount of FIG.
26A, according to the principles herein.
[0122] FIG. 27 illustrates use of a patch with a handheld device
for monitoring tissue condition, according to the principles
herein.
DETAILED DESCRIPTION
[0123] Following below are more detailed descriptions of various
concepts related to, and examples of, methods and apparatus for
measuring electrical properties of tissue. It should be appreciated
that various concepts introduced above and discussed in greater
detail below may be implemented in any of numerous ways, as the
disclosed concepts are not limited to any particular manner of
implementation. Examples of specific implementations and
applications are provided primarily for illustrative purposes.
[0124] As used herein, the term "includes" means includes but not
limited to, the term "including" means including but not limited
to. The term "based on" means based at least in part on.
[0125] The apparatus and systems described herein provide
technology platforms that use ultra-thin components linked with
stretchable interconnects and embedded in low modulus polymers
which provide a match to biological tissue. The technology platform
implements high-performance active components in new mechanical
form factors.
[0126] In non-limiting example, the technology platforms according
to the principles described herein can be fabricated based on
foundry complimentary metal-oxide-semiconductor (CMOS) wafers and
transferred to polymer-based and/or polymer-coated carriers.
[0127] The technology platforms according to the principles herein
provide apparatus and systems for on-body and in-body applications.
As a non-limiting example, any of the example apparatus or systems
described herein can be mounted directly to tissue. For example,
the apparatus or system can be skin-mounted. In any example
implementation described herein, an apparatus or system may be
disposed on tissue for extended periods without discomfort, while
facilitating continuous monitoring. For implementations inside the
body, an apparatus or system described herein may be mounted to a
catheter or other equivalent instrument which is disposed proximate
to the tissue of a tissue lumen to provide electrical information
about the tissue interior. For example, the tissue lumen can be but
is not limited to the lumen of the heart.
[0128] As described in greater detail below, an apparatus or system
according to the principles described herein can be implemented for
measuring electrical properties of tissue. The apparatus or system
can be configured to measure the electrical properties of the
tissue through a capacitive-based measurement or through an
inductance-based measurement. The measured electrical properties
can be used as an indicator of the tissue condition. For example,
the measurement of electrical properties can be used to monitor,
e.g., the disease state of the tissue, mechanical properties of the
tissue (including tissue firmness), the sweat level of the tissue
(which can be related to its hydration level), or other condition
of the tissue. Information from an ultrasound measurement also can
be used to provide information about the disease state of the
tissue, mechanical properties of the tissue (including tissue
firmness), the sweat level of the tissue (which can be related to
its hydration level), or other condition of the tissue.
[0129] An apparatus according to the principles described herein
can be configured to measure electrical properties of the tissue
through a capacitive-based measurement. An apparatus according to
this example implementation can include at least two conductive
structures disposed above the tissue. The capacitive-based
measurement can be performed by applying a potential across the at
least two conductive structures. The at least two conductive
structures are disposed substantially parallel to each other. Each
of the at least two conductive structures has a non-linear
configuration (such as but not limited to a serpentine
configuration, a zig-zag configuration, or a rippled
configuration). The apparatus also includes at least two brace
structures, each disposed substantially perpendicularly to the
orientation of the at least two parallel conductive structures, and
at least one spacer structure that is physically coupled at each of
its ends to a portion of each of the at least two brace structures.
Each of the at least two brace structures is in electrical
communication with at least one of the at least two parallel
conductive structures. The at least one spacer structure
facilitates maintaining a substantially uniform separation between
the at least two brace structures. A measure of the electrical
property of the tissue using the apparatus is used to provide an
indication of the condition of the tissue according to any of the
principles described herein.
[0130] In another example implementation where the apparatus is
configured to measure electrical properties of the tissue through a
capacitive-based measurement, the apparatus can include at least
two conductive structures that run substantially parallel to each
other along substantially an entire length of the conductive
structures. Each of the conductive structures can have a curved
configuration. An apparatus according to this example
implementation also can include at least two contact structures.
Each of the at least two contact structures is in electrical
communication with at least one of the at least two parallel
conductive structures. The capacitive-based measurement can be
performed by applying a potential across the at least two
conductive structures using the at least two contact structures. A
measure of the electrical property of the tissue using the
apparatus is used to provide an indication of the condition of the
tissue according to any of the principles described herein.
[0131] An apparatus according to the principles described herein
can be configured to measure electrical properties of the tissue
through an inductance-based measurement. An apparatus according to
this example implementation can include a substrate disposed above
the tissue, wherein the substrate is formed from a material that
exhibits a change in a state with a change in tissue condition. As
a non-limiting example, the substrate can be formed from a material
that changes hydration state with a change in the sweat level of
the tissue (which can be related to its hydration level). The
apparatus further includes at least one first inductor structure
disposed above the substrate. As non-limiting examples, the
inductor structure can be a spiral coil structure, a cylindrical
coil structure, or a toroidal structure. The inductance-based
measurement can be performed by applying a signal to the at least
one first inductor structure. An electrical property and/or a
physical property of the at least one first inductor structure
changes with the change in a\the state of the substrate. A measure
of the electrical property or the physical property of the at least
one first inductor structure using the apparatus is used to provide
an indication of the tissue condition.
[0132] In an example implementation, any of the apparatus
configured to measure electrical properties of the tissue through a
capacitance-based or inductance-based measurement may be disposed
directly above the tissue. In this example, the apparatus is used
to measure an electrical property based on the condition of the
tissue in the instant of measurement. A measurement according to
this example can be used to provide an indication of a skin
hydration level.
[0133] In another example implementation any of the apparatus
configured to measure electrical properties of the tissue through a
capacitance-based or inductance-based measurement may be disposed
above the tissue with an absorbing layer positioned between the
apparatus and the tissue. In this example, a measurement of a
change in the state of the absorbing layer can be used to provide
an indication of the condition of the tissue. For example, an
absorbing layer that can absorb sweat may be disposed between the
tissue and the example layer. In this example, the apparatus is
used to measure an electrical property based on the amount of
accumulated sweat in the absorbing layer. That is, each subsequent
measurement of an electrical property is based on the higher amount
of accumulated sweat over time in the absorbing layer. This
measurement based on accumulated sweat can be related to the
hydration level of the tissue. A measurement according to this
example also can be used to provide an indication of a sweat rate
(i.e., an amount of sweat gathered over an interval).
[0134] In an example, the potential applied to any of the apparatus
described herein can be a time-varying potential. That is, any of
the measurements performed herein, including a capacitance
measurement or an inductance measurement, can be performed by
changing the potential with time. The potential can be changed
either periodically, or as a step function from one value of
potential to another.
[0135] FIG. 1A shows a block diagram of a non-limiting example
system according to the principles herein. The example system 100
includes at least one apparatus 102 that can be used to provide a
measurement of the electrical properties of the tissue. The at
least one apparatus 102 can be configured as describe herein to
perform a capacitive-based measurement and/or an inductance-based
measurement of the electrical properties of the tissue. The system
100 includes at least one other component 104 that is coupled to
the at least one apparatus 102. In an example implementation, the
at least one component 104 can be configured to supply the
potential to the apparatus 102. For example, the at least one
component 104 can include a battery or any other energy storage
device that can be used to supply the potential. In an example
implementation, the system 100 can include at least one component
104 for providing an indication of the tissue condition based on
the measured electrical property of the tissue. In an example
implementation, the at least one component 104 can include at least
one processor unit configured for analyzing the signal from the
apparatus based on the measurement of the electrical property of
the tissue. In an example implementation, the at least one
component 104 can be configured to transmit a signal from the
apparatus based on the measurement of an electrical property of the
tissue. For example, the at least one component 104 can include a
transmitter or a transceiver configured to transmit a signal
including data measured by the apparatus measurement from the
apparatus to a hand-held device or other computing device.
Non-limiting examples of a handheld device include a smartphone, a
tablet, a slate, an e-reader, a digital assistant, or any other
equivalent device. As a non-limiting example, the hand-held device
or other computing device can include a processor unit that is
configured for analyzing the signal from the apparatus based on the
measurement of the electrical property of the tissue. The at least
one other component 104 can be a temperature sensor.
[0136] FIG. 1B shows a block diagram of a non-limiting example
system 150 according another implementation of the principles
herein. The example system 150 includes at least one apparatus 102
that can be used to perform a measurement of the electrical
properties of the tissue, including a capacitive-based measurement
and/or an inductance-based measurement. In the non-limiting example
of FIG. 1B, the at least one other component 104 includes an analog
sensing block 152 that is coupled to the at least one apparatus 102
and at least one processor unit 154 that is coupled to the analog
sensing block 152. The at least one other component 104 includes a
memory 156. For example, the memory 156 can be a non-volatile
memory. As a non-limiting example, the memory 156 can be mounted as
a portion of a RFID chip. The at least one other component 104 also
includes a transmitter or transceiver 158. The transmitter or
transceiver 158 can be used to transmit data from the apparatus 102
to a handheld device or other computing device (e.g., for further
analysis). The example system 150 of FIG. 1B also includes a
battery 160 and a charge regulator 162 coupled to battery 160. The
charge regulator 162 and battery 160 are coupled to the processor
unit 154 and memory 156.
[0137] A non-limiting example use of system 150 is as follows.
Battery 160 provides power for the apparatus 102 to perform the
measurements. The processor unit 154 activates periodically,
stimulates the analog sensing block 152, which conditions the
signal and delivers it to an A/D port on the processor unit 154.
The data from apparatus 102 is stored in memory 156. In an example,
when a near-field communication (NFC)-enabled handheld device is
brought into proximity with the system 150, data is transferred to
the handheld device, where it is interpreted by application
software of the handheld device. The data logging and data transfer
can be asynchronous. For example, data logging can occur each
minute while data transfer may occur episodically.
[0138] In a non-limiting example, a system according to the
principles herein can be configured as a self-contained
tissue-based system with power and wireless communication for
monitoring the condition of the tissue (such as but not limited to
monitoring the sweat level of the tissue (which can be related to
its hydration level) and/or the disease of the tissue).
[0139] In a non-limiting example, the system 100 or system 150 can
be mounted on a backing, such as but not limited to a patch. The
backing is disposed over the tissue to be measured.
[0140] In a non-limited example, system 100, system 150 or any f
the apparatus described herein may be covered at least in part by
an excapsulation layer. The encapsulation layer can be formed from
a polymer-based material, such as but not limited to a polyimide.
In an example, the thickness of the encapsulation layer can be
configured such that any of the systems or apparatus according to
the principles herein lies at a neutral mechanical plane (NMP) or
neutral mechanical surface (NMS) of the system or apparatus. The
NMP or NMS lies at the position through the thickness of the device
layers for the system or apparatus where any applied strains are
minimized or substantially zero. The location of the NMP or NMS can
be changed relative to the structure of the system or apparatus
through introduction of materials that aid in strain isolation in
the components of the system or apparatus that are used to perform
the electrical measurements of the tissue. For example, the
thickness of encapsulating material disposed over the system or
apparatus described herein may be modified (i.e., decreased or
increased) to depress the system or apparatus relative to the
overall system or apparatus thickness, which can vary the position
of the NMP or NMS relative to the system or apparatus. In another
example, the type of encapsulating, including any differences in
the elastic (Young's) modulus of the encapsulating material.
[0141] An apparatus or system according to the principles described
herein can be used to monitor tissue condition in conjunction with
a wide range of on-body sensors. Non-limiting examples of tissue
conditions that may be measured using one or more of the apparatus
described herein are shown in FIG. 2. For example, an apparatus or
system herein can include at least one UV sensor configured for
measuring an amount of UV exposure of the tissue. As another
example, an apparatus herein can be configured to include at least
one temperature sensor for measuring the temperature of the
tissue.
[0142] The apparatus and systems of the technology platform
described herein support conformal on-body electronics that can be
used to log sensor data at very low power levels over extended
periods, while providing wireless communication with external
computing devices (including handheld devices).
[0143] For example, the technology platform described herein
support conformal on-body electronics that can be used to monitor
sweat rate of the body (which can be related to its hydration
level). The human autonomic nervous system provides relatively slow
feedback about fluid loss. A hydration sensor that can provide
real-time updates on fluid loss could allow athletes to extend
their performance period while minimizing subsequent ill-effects
and speeding recovery. In a non-limiting example, a system or
apparatus described herein can be configured as a hydration sensor
that records the hydration level of a substrate material that
changes hydration state with change in hydration of the tissue. The
substrate material can be a soft absorbing material that collects
sweat from the skin, and transmits the data of measurement to an
external computing device (including a handheld device).
[0144] Capacitance-Impedance-Based Measurements
[0145] In a non-limiting example, skin hydration can be one of the
major physiological responses for evaluation of dermatology,
effectiveness of medical therapies, and cosmetology. The amount of
sweat generated can provide an indication of a person's change in
overall hydration level. It also can be used to provide an
indication of a person's overall hydration level.
[0146] Sweat is brought to the surface of the skin by pores formed
as channels that go through the skin from deeper levels. Sweating
can be affected over a matter of minutes by, e.g., heat/cold or
exercise/rest. Skin hydration is the water content inside the top
layer of skin (the stratum corneum), and can changes over a period
of days to weeks depending on, e.g., the overall body hydration, or
skin treatment.
[0147] The skin hydration level can be determined by direct
electrical measurements of impedance-capacitance (RC measurement),
or by indirect measurements of the skin's mechanical and optical
properties. Among these methods, RC measurements can be more
reliable, easier to implement, and low cost. To perform a RC
measurements, a physical contact should be maintained between the
measuring electrodes of the apparatus or system and the tissue. The
accuracy of these measurements can be dependent on the contact
force applied to maintain a physical contact between the measuring
electrodes of the apparatus or system and the tissue. If a RC
measurement is performed using a rigid, planar electrodes, contact
force is applied to ensure that these electrodes remain in contact
with the skin's curved, compliant surface. For example, existing
hydration sensors with rigid, planar electrodes that use a RC
measurement approach have built-in pressure sensing devices to
address this issue. Additionally, existing hydration sensors with
rigid, planar electrodes may be limited to instantaneous
measurements due to the lack of a reservoir for sweat storage. As a
result, hydration sensors with rigid, planar electrodes can be
difficult to use and may not provide continuous monitoring.
[0148] In a non-limiting example, the apparatus and systems
described herein provide a new platform for collecting
electrophysiological measurements of tissue. The technology
described herein enables the electronics to be integrated on the
tissue without requiring external mechanical loading to maintain
contact. Novel epidermal skin sweat sensor composed of stretchable
electrodes is described. Taking advantage of small conductive
structures feature size and a discrete open-mesh-type structure,
the apparatus described herein can be conformally applied on the
tissue surface. In an example implementation, to achieve continuous
monitoring capability, a cellulose pad can be mounted between the
conductive structures and the tissue to serve as a sweat storage
layer, and the entire structure is held together by an adhesive
backing layer (such as but not limited to TEGADERM.RTM. (3M, St.
Paul, Minn.). This backing layer provides structural support and
holds the apparatus in tight contact with the tissue during
measurements. With this configuration, the skin sweat sensor
apparatus described herein provides a viable solution for reliable
and continuous sweat monitoring.
[0149] A system, apparatus and method described herein facilitates
measurement of capacitance-based properties of the tissue. The
capacitance-based properties of the tissue can be used to provide
an indication of the tissue condition. As a non-limiting example, a
system, apparatus and method described herein can facilitate
measurement of the sweat rate of the tissue (which can be related
to a level of hydration and/or de-hydration of the tissue). In this
example, measurement of capacitance-based electrical properties can
be used to provide an indication of the level of hydration and/or
de-hydration of tissue.
[0150] FIG. 3 shows a cross-section view of an example apparatus
300 according to an example implementation that includes three
conductive structures 302-a, 302-b and 302-c disposed over a
substrate 301. Substrate 301 can be skin or any other tissue. The
example apparatus 300 also includes a layer 306. Layer 306 can
include an adhesive portion that adheres to a portion of the
substrate 301 to assist in maintaining conductive structures 302-a,
302-b and 302-c in contact with the substrate 301.
[0151] The illustration of FIG. 3 also shows an example electrical
schematic of an effective circuit representation of the electrical
properties of the substrate when the three conductive structures
302-a, 302-b and 302-c are disposed over the substrate 301. As
illustrated in FIG. 3, when a potential (Vin) relative to ground
(Gnd) is applied across neighboring pairs of conductive structures
302-a, 302-b and 302-c, effective variable capacitance terms
develop proximate to the interface between the conductive
structures 302-a, 302-b and 302-c and the substrate 301, and
effective variable capacitance and resistance term develop within
the substrate 301. The effective circuit terms can be represent
electrical properties of the apparatus and the tissue as
follows:
R=.rho.l/A (1)
where R is the electrical resistance, .rho. is the resistivity, l
is the length in the tissue between the conductive structures, and
AR is the cross-sectional area of current path through the
tissue.
C=.di-elect cons.A/d (2)
where C is the electrical capacitance, c is the permittivity, A is
the overlapping area between the conductive structures and the
tissue, and d is the separation distance between the conductive
structures. In an example, the measurement of the electrical
property of the substrate, such as but not limited to the tissue,
among the three conductive structures 302-a, 302-b and 302-c can be
modeled based on the example circuit elements of FIG. 3 and using
the expressions of equations (1) and (2).
[0152] An apparatus or system according to the principles herein
for performing capacitance-based measurements is not limited to
solely three conductive structures. For example, an example
apparatus or system can include 2, 5, 8, 10, 15 or more conductive
structures (E1, E2 and E3, E(n), where n is an integer). For such a
system, the effective circuit model of FIG. 3 can be extended to
any number of effective circuit elements, with effective
capacitance terms (C1, C2, C3, . . . , C(j), where j is an
integer), and effective resistance terms (R1, R2, . . . , R(k),
where k is an integer). FIG. 4 shows a cross-section view of
another example apparatus 400 according to an example
implementation that includes two conductive structures 402-a, 402-b
and 402-c disposed over a substrate 401 (i.e., n=2). Substrate 401
can be skin or any other tissue. The example apparatus 400 also
includes a layer 406. In an example, the measurement of the
electrical property of the substrate 301 or 401 among the
neighboring conductive structures, or conductive structures in
close proximity, of the apparatus can be modeled based on the
example circuit elements of FIG. 3 or FIG. 4, and extrapolated to
model more components. The apparatus can be configured with any
number n of conductive structures. Increasing the number n of
conductive structures may provide for increased accuracy of the
measured capacitance across the system inputs and outputs.
[0153] The conductive structures Ei (i=1, . . . 3) can include any
applicable conductive material in the art, including a metal or
metal alloy, a doped semiconductor, or a conductive oxide, or any
combination thereof. Non-limiting examples of metals include Al or
a transition metal (including Au, Ag, Cr, Cu, Fe, Ir, Mo, Nb, Pd,
Pt, Rh, Ta, Ti, V, W or Zn), or any combination thereof.
Non-limiting examples of doped semiconductors include any
conductive form of Si, Ge, or a Group III-IV semiconductor
(including GaAs, InP).
[0154] One or more of the conductive structures may be covered on
at least one side by a polymer-based material, such as but not
limited to a polyimide. In an example, one or more of the
conductive structures may be encased in the polymer-based material.
The polymer-based material can serve as an encapsulant layer.
[0155] Layer 306 or 406 may be a protective, encapsulating and/or
backing layer made of a stretchable and/or flexible material.
Non-limiting examples of materials that can be used for layer 306
or 406 include any applicable polymer-based materials, such as but
not limited to a polyimide or a transparent medical dressing, e.g.,
TEGADERM.RTM. (3M, St. Paul, Minn.).
[0156] In a non-limiting example, layer 306 or 406 may be an
encapsulation layer that is disposed over at least a portion of the
at least two conductive structures. In an example, the
encapsulation layer can be a polymer. In another example, portions
of the encapsulation layer can include an adhesive, and wherein the
adhesive maintains the portions of the encapsulation layer in
physical contact with the tissue (including attaching it to the
tissue). In this manner, the apparatus can be maintained in contact
with the tissue.
[0157] In another example, an electrically conductive gel can be
disposed between the apparatus and any absorbing layer present
between the apparatus and the tissue. The conductive gel can deform
easily and allow the spacing to change, but maintain the electrical
distance between the apparatus and the absorber at substantially
zero.
[0158] Substrate 301 or 401 may be a portion of tissue, such as but
not limited to the skin, a muscle tissue, heart tissue, etc.
[0159] FIG. 5 shows an example apparatus 500 that includes ten (10)
interdigitated conductive structures 502. The example apparatus 500
can be disposed over the tissue to perform the electrical
measurements according to the principles described herein. The
capacitance-based measurement can be performed by applying a
potential across the interdigitated conductive structures. In the
example of FIG. 5, the interdigitated conductive structures 502 are
disposed substantially parallel to each other. Each of the
interdigitated conductive structures 502 has a non-linear
configuration. In the example of FIG. 5, the conductive structures
502 have a serpentine configuration. In other examples, non-linear
configuration of the conductive structures 502 can be a, a zig-zag
configuration, a rippled configuration, or any other non-linear
configuration. The non-linear configuration of the conductive
structures can facilitate greater sampling of the electrical
properties of the tissue and higher signal to noise than linear
electrodes. The non-linear configuration of the conductive
structures also facilitates more consistent performance of the
apparatus with deformation such as stretching. The example
apparatus 500 also includes two brace structures 504, each disposed
substantially perpendicularly to the overall orientation of the
interdigitated conductive structures 502, and at least one spacer
structure 506 that is physically coupled at each of its ends to a
portion of each of the at least two brace structures. Each of the
brace structures 504 is in electrical communication with
alternating ones of the conductive structures 502. For example,
conductive structures 502-e are in electrical communication with
one of the brace structure 504 while the alternating, interposed
conductive structure 502-f is not in electrical communication with
that brace structure 504. The spacer structure 506 facilitates
maintaining a substantially uniform separation between the brace
structures 504. The spacer structure 506 can also facilitates
maintaining a substantially uniform form factor during deformation
of the apparatus. A measure of the electrical property of tissue
using the example apparatus 500 can be used to provide an
indication of the condition of the tissue according to any of the
principles described herein.
[0160] The example apparatus 500 may also include contacts 508 that
provides for electrical communication between the apparatus 500 and
at least one other component, as described hereinabove and in
connection with FIG. 1A or 1B. For example, the at least one other
component can be a battery that applies a potential across the
contacts 508, and in turn across neighboring conductive structures
502. in an example, a system is provided according to the
principles described herein that includes apparatus 500 and at
least one other component (as described herein above).
[0161] The conductive structures and the brace structures can
include any applicable conductive material in the art, including a
metal or metal alloy, a doped semiconductor, or a conductive oxide,
or any combination thereof. Non-limiting examples of metals include
Al or a transition metal (including Au, Ag, Cr, Cu, Fe, Ir, Mo, Nb,
Pd, Pt, Rh, Ta, Ti, V, W or Zn), or any combination thereof.
Non-limiting examples of doped semiconductors include any
conductive form of Si, Ge, or a Group III-IV semiconductor
(including GaAs, InP). In an example, the conductive structures and
the brace structures can be formed from the same conductive
material. In another example, the conductive structures and the
brace structures can be formed from different conductive
materials.
[0162] The conductive structures and/or the brace structures may be
covered on at least one side by a polymer-based material, such as
but not limited to a polyimide. In an example, the conductive
structures and/or the brace structures may be encased in the
polymer-based material. The polymer-based material can serve as an
encapsulant layer.
[0163] Spacer structure also may be formed from a polymer-based
material.
[0164] Apparatus 500 or a system that includes apparatus 500 may
include a protective and/or backing layer made of a stretchable
and/or flexible material. Non-limiting examples of materials that
can be used for the protective and/or backing layer include any
applicable polymer-based materials, such as but not limited to a
polyimide or a transparent medical dressing, e.g., TEGADERM.RTM.
(3M, St. Paul, Minn.). The protective and/or backing layer can
include an adhesive portion that adheres to a portion of the
substrate to assist in maintaining the conductive structures 502 in
contact with the substrate (including the tissue).
[0165] In a non-limiting example, the dimensions and morphology of
the sensing component can be maintained using the spacer structure
506. In an example, the spacer structure 506 is formed from an
insulating material or another material with lower conductivity
than the conductive structures or the brace structures. The
properties of the spacer structure 506 of the apparatus 500 can
facilitate little or no current directly passing from one brace
structure to the other brace structure by way of the spacer
structure 506. Rather, current passes from one set of the
conductive structures 502 to another set of the conductive
structures 502 by way of the underlying tissue.
[0166] In an example according to FIG. 5, the length of the ripples
of the brace structure may be uniform or may vary from one side of
the apparatus 500 relative to the other.
[0167] In a non-limiting example, the non-linear configuration of
the conductive structures facilitates increased flexibility of the
apparatus. For example, the non-linear geometry can facilitate
increased flexibility of the apparatus to stretching, torsion or
other deformation of the underlying tissue, and the apparatus
maintains substantial contact with the tissue in spite of the
stretching, torsion or other deformation.
[0168] FIG. 6 is an illustration of the example apparatus 500 of
FIG. 5, with selected portions magnified. FIG. 6 shows a
magnification of a portion of the apparatus 500 where a side of the
brace structure 504 (lighter colored segment) forms an interface
510 with the spacer structure 506. FIG. 6 shows a magnification of
an interface 512 between a brace structure 504 and a conductive
structure 502, which also shows that alternating ones of the
interdigitated conductive structure 502 makes physical contact with
the brace structure 504.
[0169] FIG. 7 shows a non-limiting examples of the apparatus 500
including cross-link structures 515 that can be formed according to
the principles herein. The cross-link structures 515 can provide
increased mechanical stability of the structure during fabrication
(e.g., during a transfer process from a substrate and/or a printing
and extraction process to another substrate), and in use, e.g., to
stabilize the sensor against stretching, flexing, torsion or other
deformation of the substrate it is disposed on. For example, the
cross-link structures 515 can aid in maintaining a form factor,
including ratios of dimensions, during and/or after a stretching,
elongation or relaxing of the apparatus. For example, the
cross-link structures 515 can be formed across any pair of the
conductive structures 502 of FIG. 5, at any position along their
length. In the examples shown, the cross-links structures 515 are
formed in a serpentine ("S") shape. In other examples, the
cross-link structures 515 can be formed as substantially straight
crossbars, formed in a zig-zag pattern, formed as arcs, or ripples,
or any other morphology that facilitates maintaining a mechanical
stability and/or a form factor of the apparatus. In addition, the
cross-link structures 515 can be formed as at least two cross-link
structures that are formed across neighboring electrodes. The
cross-link structures 515 can be formed from a polymer-based
material or any other stretchable and/or flexible material. In
addition, while the positioning of the example cross-link
structures 515 are shown to be roughly aligned in the x-direction
of the FIG. 7, cross-link structures 515 also can be displaced
relative to each other in the x-direction.
[0170] In the example of FIG. 7, the cross-link structures 515 can
be formed of substantially the same encapsulant material that
covers portions of the interdigitated conductive structures, and
extend seamlessly from them. In this example, these cross-link
structures 515 can be formed during the same process step that
disposes the encapsulant polymer-based material on portions of the
interdigitated conductive structures. In another examples, the
cross-link structures 515 can be formed of a different material
from the encapsulant material that covers portions of the
interdigitated conductive structures.
[0171] FIGS. 8 through 10 illustrate another example implementation
of an apparatus that is configured to measure electrical properties
of the tissue through a capacitance-based measurement. As shown in
FIG. 8, the apparatus 800 can include at least two conductive
structures 802 that run substantially parallel to each other along
substantially an entire length of the conductive structures 802.
Each of the conductive structures 802 can have a curved
configuration. Apparatus 800 according to this example
implementation also can include at least two contact structures
804. Each of the at least two contact structures 804 is in
electrical communication with at least one of the at least two
parallel conductive structures 802. The capacitive-based
measurement can be performed by applying a potential across the at
least two conductive structures 802 using the at least two contact
structures 804. A measure of the electrical property of the tissue
using the apparatus 800 is used to provide an indication of the
condition of the tissue according to any of the principles
described herein.
[0172] While the examples of FIG. 8 through 10 are illustrated with
two curved conductive structures 802, other examples according to
the principles herein can include three, four or more curved
conductive structures 802 that are disposed substantially
concentrically and are in electrical communication with contacts
804.
[0173] The conductive structures 802 and the contact structures 804
can include any applicable conductive material in the art,
including a metal or metal alloy, a doped semiconductor, or a
conductive oxide, or any combination thereof. Non-limiting examples
of metals include Al or a transition metal (including Au, Ag, Cr,
Cu, Fe, Ir, Mo, Nb, Pd, Pt, Rh, Ta, Ti, V, W or Zn), or any
combination thereof. Non-limiting examples of doped semiconductors
include any conductive form of Si, Ge, or a Group III-IV
semiconductor (including GaAs, InP). In an example, the conductive
structures 802 and the contact structures 804 can be formed from
the same conductive material. In another example, the conductive
structures 802 and the contact structures 804 can be formed from
different conductive materials.
[0174] The conductive structures 802 and/or the contact structures
804 may be covered on at least one side by a polymer-based
material, such as but not limited to a polyimide. In an example,
the conductive structures 802 and/or the contact structures 804 may
be encased in the polymer-based material. The polymer-based
material can serve as an encapsulant layer.
[0175] Apparatus 800 or a system that includes apparatus 800 may
include a protective and/or backing layer made of a stretchable
and/or flexible material. Non-limiting examples of materials that
can be used for the protective and/or backing layer include any
applicable polymer-based materials, such as but not limited to a
polyimide or a transparent medical dressing, e.g., TEGADERM.RTM.
(3M, St. Paul, Minn.). The protective and/or backing layer can
include an adhesive portion that adheres to a portion of the
substrate to assist in maintaining the conductive structures 802 in
contact with the substrate (including the tissue).
[0176] As shown in FIG. 9, the apparatus may include cross-link
structures 815. The cross-link structures 815 can provide increased
mechanical stability of the structure during fabrication (e.g.,
during a transfer process from a substrate and/or a printing and
extraction process to another substrate), and in use, e.g., to
stabilize the sensor against stretching, flexing, torsion or other
deformation of the substrate it is disposed on. For example, the
cross-link structures 815 can aid in maintaining a form factor,
including ratios of dimensions, during and/or after a stretching,
elongation or relaxing of the apparatus. For example, the
cross-link structures 815 can be formed across any pair of the
conductive structures 802 of FIG. 5, at any position along their
length. In the examples shown, the cross-links structures 815 are
formed in a serpentine ("S") shape. In other examples, the
cross-link structures 815 can be formed as substantially straight
crossbars, formed in a zig-zag pattern, formed as arcs, or ripples,
or any other morphology that facilitates maintaining a mechanical
stability and/or a form factor of the apparatus. In addition, the
cross-link structures 815 can be formed as at least two cross-link
structures that are formed across neighboring electrodes. The
cross-link structures 815 can be formed from a polymer-based
material or any other stretchable and/or flexible material.
[0177] In the example of FIG. 9, the cross-link structures 815 can
be formed of substantially the same encapsulant material that
covers portions of the conductive structures, and extend seamlessly
from them. In this example, these cross-link structures 815 can be
formed during the same process step that disposes the encapsulant
polymer-based material on portions of the conductive structures. In
another examples, the cross-link structures 815 can be formed of a
different material from the encapsulant material that covers
portions of the conductive structures 815.
[0178] FIG. 10 shows magnifications 810 and 812 of the interface
between the conductive structures 802 and leads 807. Leads 807
provide for electrical communication between conductive structures
802 and contacts 804. As shown in the magnifications 810 and 812 of
FIG. 10, one of the conductive structures 802 is separated from
lead 807 by a spacer structure 806. In an example, the spacer
structure 806 is formed from an insulating material or another
material with lower conductivity than the conductive structures 802
or the leads 807. The properties of the spacer structure 806 of the
apparatus 800 can facilitate little or no current directly passing
from one conductive structure 802 to the lead 807 by way of the
spacer structure 806. Rather, current passes from one set of the
conductive structures 802 to another set of the conductive
structures 802 by way of the underlying tissue. Spacer structures
806 also may be formed from a polymer-based material.
[0179] A non-limiting example process for fabricating the example
apparatus of any of FIGS. 5 through 10 is illustrated in FIGS.
11A-11I. In FIG. 11A, a fabrication substrate 1100, such as but not
limited to a silicon substrate or a substrate for group III-V
electronics, is coated with a with a sacrificial release layer
1102. In a non-limiting example, the sacrificial release layer 1102
is a polymer such as polymethylmethacrylate (PMMA). In FIG. 11B,
the sacrificial release layer 1102 is patterned. In FIG. 11C, a
first polymer layer 1104 is spin coated onto the sacrificial
release layer 1102. In an example, the first polymer layer 1104 can
be a polyimide. In FIG. 11D, a layer of conductive material 1106 is
deposited over the first polymer layer 1104 to form the conductive
structures. In FIG. 11E, where applicable to the conductive
material 1106 used, a lithography process may be performed to
pattern the conductive material 1106 into any of the configurations
of conductive structures described herein. In FIG. 11F, a second
polymer layer 1108 is spin coated over the conductive structures.
In an example, the second polymer layer 1108 can be a polyimide. In
FIG. 11G, the second polymer layer 1108 is patterned. In FIG. 11H,
the sacrificial release layer material is selectively removed. For
example, where the sacrificial release layer material is PMMA,
acetone can be used for selective removal. At this stage, the
apparatus 1110 is in substantially final form and attached to the
fabrication substrate. In FIG. 11I, a transfer substrate 1112 is
used to remove the apparatus 1110 from the fabrication substrate
1100.
[0180] FIGS. 12A through 12E show an example implementation of an
example apparatus that includes the interdigitated conductive
structures. FIG. 12A shows that the example apparatus can be
fabricated in dimensions comparable to a coin. The dimensions of
the electrodes are 100 .mu.m wide, and 0.5 .mu.m thick. Due to the
open-mesh electrode structure, the strain on the conductive
structures due to tissue stretching can be limited. The turning
angle [7] on the conductive structures is designed as -25 degree.
In addition, the stretchable conductors interconnecting the
conductive structures play a role during stretching. In this
regard, the turning angle of the stretchable conductors is designed
as 0 degree. In this example, both the electrodes and the
stretchable conductors are made of gold (Au) and are fully
encapsulated in polyimide (PI) for mechanical reliability. The
polyimide is 10 .mu.m thick on both top and bottom of the
electrodes. FIG. 12B shows the example apparatus disposed on skin
using a protective layer before a measurement is made. FIG. 12C
shows the example apparatus under a length-wise stretching
deformation. FIG. 12D shows the example apparatus under a diagonal
stretching deformation. In each of these scenarios, the example
apparatus is configured such that it returns to substantially its
original form factor once the deformation force is removed. FIG.
12E shows the example apparatus being removed from the skin.
[0181] An example implementation of a measurement using an example
apparatus or system described herein is as follows. The effective
circuit terms model of an example apparatus or system described
herein (such as but not limited to the effective circuits
illustrated in FIGS. 3 and 4) can be used to model electrical
measurements performed using the apparatus of FIGS. 5 through 7 or
the apparatus of FIGS. 8 through 10. For example, the effective
circuit described in connection with FIG. 3 can be used to model a
measurement across a line through portion "A" of FIG. 5, or
extrapolated to model the plurality of conductive structures of the
entire interdigitated structure. As another example, the effective
circuit described in connection with FIG. 4 can be used to model a
measurement across a line through portion "B" of FIG. 8.
[0182] The analyzed electrical measurements made using an apparatus
according to the principles described herein in connection with any
of FIGS. 5 through 10 can be used to provide an indication of
changes in the tissue condition. For example, the effective circuit
terms near the interface in FIG. 3 or FIG. 4 are observed to be
sensitive to changes in tissue condition, such as but not limited
to the sweat rate of the underlying tissue (which can be related to
its hydration level). Within the substrate, the variable
capacitance and resistance terms develop between the conductive
structures. These effective terms are observed to be sensitive to
the sweat level of the tissue (which can be related to hydration
levels) and//or stretching of the example apparatus or system
and/or the underlying tissue.
[0183] An example method is provided herein for determining tissue
condition based on the measurement of the electrical property of
the substrate using a capacitance-based measurement. The method
includes receiving data in connection with a measurement of the
electrical properties of the tissue, and applying a model to the
data to quantify at least one parameter of the effective circuit
model. The value of the parameter can be used to provide an
indication of the tissue condition.
[0184] In an example system, apparatus and method, any of the
apparatus described hereinabove can be disposed on to perform the
measurement of the electrical properties. In an example, the sensor
is configured to withstand deformation in more than one direction
(for example, in x, y and/or z-direction). In a non-limiting
example system, apparatus and method herein, a fully conformal
sensor that includes an apparatus described herein is provided. The
fully conformal sensor can be placed on, including being attached
on. a variety of surface profiles, with minimal to no effect on the
functionality of the sensor to detect tissue conditions, such as
but not limited to a sweat level (which can be related to a
hydration level), a tissue disease state, or mechanical properties
of the tissue.
[0185] As a non-limiting example, the value of the parameter can be
compared and/or correlated to a calibration standard of tissue
condition versus the value of the circuit parameter. The
calibration standard can be generated based on a training set of
electrical measurements of tissue, or material similar to tissue,
that exhibits the condition that is sought to be characterized. For
example, the training set can include tissue at various stages of a
disease condition, where the correlation between the electrical
measurements and the known disease stage can be used to generate
the calibration standard applied to tissue of unknown disease
state. As another example, the training set can include tissue at
various hydration levels. The correlation between the electrical
measurements and the known hydration levels can be used to generate
the calibration standard applied to tissue of unknown hydration
level.
[0186] The configurations of the apparatus described herein,
including the discrete interdigitated structure, allow the
apparatus deformation to accommodate the natural motions of the
tissue. The mechanics of the apparatus, particularly the stretching
deformation, can affect apparatus performance. The stretching
deformation can change the electrical properties of the system
since the distance between the conductive structures is one of the
parameters in the RC measurement. FIG. 13A shows a finite element
(FE) model for deformation mechanism simulation and FIG. 13B shows
a hydration sensor stretched at 50% elongation. The metal is Au and
can be modeled as a plastic deformable solid obeying the bi-linear
kinematic hardening rule. The Young's modulus is set at 30e.sup.3
MPa, yielding stress is 204 MPa, and the tangent modulus is 4769
MPa. The polyimide of the cross-link structures and the conductive
structures coating is modeled as linear elastic with a Young's
modulus of 3.2e.sup.3 MPa, and the backing layer (TEGADERM.RTM.) is
modeled as a three-factor hyper-elastic Mooney-Rivlin solid. The
three factors of the hyper-elastic Mooney-Rivlin model are:
C.sub.10=-0.13, C.sub.01=0.57, and C.sub.11=0.13. The FE model
corresponds to the stretching test, as shown in FIG. 13B.
[0187] FIG. 14A shows an example apparatus that includes
interdigitated conductive structures in its relaxed state. FIG. 14B
shows the example apparatus of FIG. 14A subjected to about 50%
elongation. Non-limiting examples of the measurement of the
electrical properties of a substrate using an example apparatus
such as shown in FIGS. 14A and 14B are described with reference to
FIGS. 15A through 16B. The measurement can be used to quantify a
complex ratio of the voltage to the current in a circuit through
portions of the tissue as described above. The electrical
properties can be quantified based on a magnitude and/or a phase of
the electrical properties.
[0188] In a non-limiting example, the apparatus of FIG. 14A is used
to measure the hydration level of the patch, which can be related
to the sweat rate of an individual. In this example, the substrate
is a cellulose pad. FIG. 15A shows the magnitude and FIG. 15B shows
the phase of the impedance change with the sweat level range from
20 to 80 percent saturation at selected measurement frequencies
(the radio frequency (RF) range from 20 to 80 kHz). In this example
implementation, the sweat level is defined as the ratio of the
volume of saline to the volume of the substrate, normalized such
that 100 corresponds to full-saturation. The volume of saline added
is varied, and the volume of the cellulose pad is held constant
(450 mm.sup.3). Initial measurements over a range of frequencies
are performed to determine which frequency has the maximum change
of impedance across the hydration levels, thus providing optimal
sensitivity. FIG. 15A shows that the magnitude of the impedance at
20 kHz drops by 0.38 M.OMEGA., while the impedance phase shifts by
-2.13 degrees as the sweat level changes from 20 to 80 percent
saturation. That is, 20 kHz provides the most sensitive output of
impedance magnitude in this RF range. As the sweat level increases,
the impedance drops at the RF range from 20 kHz to 80 kHz. This
behavior can be attributed to an increase in electrical
conductivity: increasing the amount of saline in the cellulose pad
provides more ionic pathway for charge transport.
[0189] When mounted on a sweat-absorbing patch, the response of the
example apparatus to fluid in the patch is quantifiable. The volume
of analyte required to saturate the patch is determined in advance,
then analyte is titrated onto a dry patch to systematically
increase the hydration level. A dramatic drop in impedance is found
between 0 and 20% hydration, after which the decline is more
gradual.
[0190] The electrical performance of the example apparatus and
system is observed to change as they are subjected to deformation.
The change in electrical performance with changes in the tissue
condition, including the changes of "resistive" impedance (R) and
capacitance (C), can be described relative to equation (1) and
(2).
[0191] The changes in electrical property of the substrate with
changes in tissue condition can be described based on a change in
the hydration state of the tissue as follows. As the sweat level in
the substrate increases, the resistivity (.rho.) decreases whereas
the permittivity (.di-elect cons.) increases, resulting in the
impedance (based on the resistance) dropping and capacitance
rising. The decrease in resistivity can be due to the increase of
mobile ions within the substrate. On the other hand, the increasing
of permittivity can be explained by increasing the dipoles
primarily detected by volume of sweat in the cellulose pad. These
two factors (.rho. and .di-elect cons.) are primarily dominated by
the sweat level in the cellulose pad. It should be noted that the
sensor performance is also sensitive to structural parameters such
as the distance between the conductive structures. According to eq.
(1) and (2), as the length (l and d) between conductive structures
increases because of stretching, the electrical resistance
increases whereas the capacitance decreases.
[0192] As described herein, an example apparatus can be
mechanically designed for comfortable wear on tissue by employing
nonlinear conductive structures in a stretchable structure. The
example apparatus can be configured to be sensitive to measuring
frequency, sweat level and stretching deformation.
[0193] In an example implementation described in connection with
FIGS. 16A and 16B, a 20 kHz signals is observed to provide
sensitive performance: electrical impedance changes 50% while sweat
level increases from 20 to 80 percent saturation. In addition,
sensor elongation from 15 up to 50% affected the measurement
sensitivity of both electrical impedance and capacitance. FIGS. 16A
and 16B show performance of the example apparatus versus impedance
and capacitance, respectively, while the example apparatus is being
subjected to stretching at various sweat levels.
[0194] Specifically, FIGS. 16A and 16B show the impedance and
capacitance change, respectively, of the example apparatus while
stretched and at sweat level ranging from 20 to 80 percent
saturation. The measurements are conducted at 50 kHz. As shown in
FIG. 16A, the impedance increases nonlinearly with stretching due
to the increasing length (l) between electrodes. In addition, the
apparatus appears to lose sensitivity with respect to the sweat
level when elongations become very large. FIG. 16B shows a similar
trend for capacitance: the performance of the apparatus decreases
nonlinearly about 80% when stretching for 15% elongation. The
performance of the apparatus appears to degenerate substantially
when it is stretched beyond 40% and neither impedance nor
capacitance can be measured respective to the sweat level. The
performance reduction may be due to the out-of-plane deformation on
the stretchable interconnects causing conductive structures to lose
contact with the substrate. Also, the resistive impedance and
capacitance are not linear relationship to the structural
parameters, l and d, as described in connection with equations (1)
and (2). During stretching, however, there is a more complex
deformation mechanism that causes the nonlinear relationship to the
output of the electrical performance.
[0195] FIG. 17 shows a simulation of the distance changes (d)
between the conductive structures during stretching of the
substrate. The distance change between the conductive structures
and the elongation are not one-to-one proportional factors. At 15%
elongation, the distance changes 9% between electrodes. However, at
the same elongation, the electrical performance of the sensor drops
80%. This performance drop may be due to out-of-plane deformation
on the stretchable interconnects during stretching. FIG. 18 shows
the simulated out-of-plane deformation while the inset to FIG. 18
shows the optical image of the stretchable interconnect. The color
difference of the stretchable interconnect in the inset image is
due to the out-of-plane deformation causes the light to reflect
differently. At 15% elongation, the stretchable interconnect
deforms by 0.14 mm in a Z-direction. This out-of-plane deformation
can increase both the separation distance (d) and the length of the
resistive impedance (l). As a result, not only the distance between
electrodes but also the out-of-plane deformation affects the
electrical performance.
[0196] An example method is provided herein for determining tissue
condition based on the measurement of the electrical property of
the substrate using a capacitance-based measurement at performed at
an optimal frequency. The method includes receiving data in
connection with a measurement of the electrical properties of the
tissue, where the measurement is performed at a frequency that
provides the most sensitive output of impedance magnitude in the RF
range, and applying a model to the data to quantify at least one
parameter of the effective circuit model. In an example, the
frequency is about 20 kHz. The value of the parameter can be used
to provide an indication of the tissue condition and/or to quantify
the amount of stretching of the example apparatus.
[0197] Another example method provided herein for determining
tissue condition based on the measurement of the electrical
property of the substrate using a capacitance-based measurement
that allows for a certain degree of deformation of the example
apparatus. The method includes receiving data in connection with a
measurement of the electrical properties of the tissue, where the
example apparatus used to make the measurement is subjected to a
degree of deformation during the measurement, and applying a model
to the data to quantify at least one parameter of the effective
circuit model. The value of the parameter can be used to provide an
indication of the tissue condition.
[0198] With respect to other hydration monitoring techniques, sweat
analysis, blood analysis, muscular ultrasound analysis, and
electrical analysis also can be performed. These other hydration
monitoring techniques can be used to provide potential ways of
corroboration or calibrating a hydration monitoring measurement
performed according to a principle herein. Sweat analysis (via
ionic concentration analysis) and blood analysis (via hemoglobin
concentration) both may present practical issues in non-invasive
sample collection as well as the scalability of the necessary
components.
[0199] Using capacitance sensing to monitor hydration can present
several benefits as compared to blood and sweat analysis: [0200]
Blood and sweat analysis may likely require disposable, adhesive
sensor units and may be costly. [0201] There are specific
locations, including the thigh and upper bicep, at which
capacitance sensing works better for hydration monitoring, and
these locations are conducive to use of a device during vigorous
activity. The best locations for a sweat or blood monitoring system
might be harder to determine. [0202] The capacitance sensing can be
completely non-invasive.
[0203] Such sensors have been worn for periods of up to a week
without discomfort, and survive daily activities such as exercise
and showering. Lifetime is primarily limited by the turnover of
cells in the skin.
[0204] A system, apparatus and method according to a principle
herein provides the following benefits: [0205] The sensor circuitry
can be configured to be fully flexible, stretchable and conformable
for a more comfortable and portable user experience, whether
incorporated into an arm/leg band or a form-fitted garment. [0206]
Hydration status may be viewed in real-time based on measurements
using a sensor incorporated in an article of clothing or gear,
including an arm/leg band or form-fitted clothing item, or a patch
placed on the skin. [0207] An example device may include a sensor
coupled to LED indicator lights for indicating sweat level (which
can be related to hydration level). [0208] An example device may
include a sensor described herein in a patch placed on the skin, or
an article of clothing or gear, that is configured to transmit data
(including by wireless communication or using IR); a handheld
device (such as but not limited to a smartphone), can be brought in
proximity to the sensor to receive a quantitative indication of the
electrical measurement performed by the sensor [0209] The arm/leg
band may be wireless and transmit data to mobile devices and
portable music players. [0210] Through innovative low-power
management techniques the circuit can operate on a very small power
source. [0211] Through innovative electronic circuit design, small
changes in capacitance (and in some examples impedance measurements
as well) can be detected.
[0212] A sensor for performing capacitance measurements may be
fabricated on a flexible and/or stretchy substrate that may be worn
on the skin, including as a skin patch, or integrated into
form-fitted clothing or other gear (such as an arm or leg band). In
one example, the sensor is designed with a serpentine geometry to
allow the sensor to flex with the flexible and/or stretchy
substrate. The sweat level (which can be related to a state of
hydration) is determined by measuring the capacitance between the
two contacts of the capacitance sensor. Changes in a measured
capacitance can reflect changes in the state of hydration.
[0213] It is also contemplated that this sensor may be used in
combination with other types of sensors that measure the
composition of sweat (e.g., sensors that measure conductivity or
sensors that measure the concentration of selective ions such as
sodium potassium and calcium, and others).
[0214] A system, method and apparatus according to a principle
described herein can be relevant to at least four commercial
segments. The first segment is athletics--including both casual and
highly competitive athletics. Hydration level measurement can help
athletes greatly in monitoring their training routine as well as
offer a safety precaution to help prevent excessive dehydration.
The systems, apparatus and methods disclosed here are used to
indicate when an athlete needs to drink more water or electrolyte
solutions like a sport or energy drink. The second applicable
segment is the military. Soldiers, pilots, etc. may benefit greatly
from hydration monitoring during live combat and training.
Dehydration, even at small levels, can impact physical and mental
performance and pose serious safety issues. Monitoring hydration
levels can help a soldier remain hydrated to avoid any of these
risk factors. The third potential market segment is the beauty and
cosmetics market where local skin hydration may be monitored and
various lotions or other product applied when the state of
hydration is deemed too low. Appropriate levels of hydration can
prevent skin from drying out and, over time, create healthy skin
appearance. In another example, the level of hydration can serve as
an indicator of skin firmness. The fourth segment is in the health
and wellness/medical monitoring market. This may be part of a
general wellness program where hydration levels are monitored as
one of many health measurements and be integrated into general
assessment for health tracking, diagnosis and long-term
monitoring.
[0215] Inductance-Based Measurements
[0216] In an example according to the principles described herein,
an apparatus can be configured to measure electrical properties of
the tissue through an inductance-based measurement.
[0217] A non-limiting example of an apparatus 1900 for performing
inductance-based measurement is shown in FIG. 19A. An apparatus
1900 according to this example implementation can include a
substrate 1902 disposed above the tissue, where the substrate 1902
is formed from a material that exhibits a change in a state with a
change in tissue condition. As a non-limiting example, the
substrate 1902 can be formed from a material that changes hydration
state with a change in the sweat level of the tissue (which can be
related to hydration level). The apparatus 1900 further includes at
least one first inductor structure 1904 disposed above the
substrate. As non-limiting examples, the inductor structure 1904
can be a spiral coil structure, a cylindrical coil structure, or a
toroidal structure. The inductance-based measurement can be
performed by applying a potential to the at least one first
inductor structure 1904. An electrical property and/or a physical
property of the at least one first inductor structure 1904 changes
with the change in the state of the substrate. A measure of the
electrical property or the physical property of the at least one
first inductor structure 1904 using the apparatus is used to
provide an indication of the tissue condition. The apparatus 1900
further includes an encapsulation layer 1906.
[0218] In an example, the electrical property can be a magnetic
flux density from the at least one first inductor structure.
[0219] In an example, the encapsulation layer 1906 can be a
polymer, including a polymer having an adhesive portion. For
example, the adhesive portion of the encapsulation layer 1908 can
be present where the encapsulation layer 1906 makes physical
contact with the tissue (including attaching the apparatus to the
tissue). The adhesive portions can be used to mount the apparatus
1900 to the tissue. In this manner, the apparatus can be maintained
in contact with the tissue.
[0220] In another example, an electrically conductive gel can be
disposed between the apparatus and any absorbing layer present
between the apparatus and the tissue. The conductive gel can deform
easily and allow the spacing to change, but maintain the electrical
distance between the apparatus and the absorber at substantially
zero.
[0221] In an example, the electrical property is a magnetic flux
density from the at least one first inductor structure that reaches
the region.
[0222] As shown in FIG. 19B, an apparatus 1900 for performing
inductance-based measurement can include the substrate 1902, at
least one first inductor structure 1904 and an encapsulation layer
1906. The apparatus further includes a separator layer 1908
disposed between the at least one first inductor structure 1904 and
the substrate 1902.
[0223] In an example, the separator layer is a non-conductive
material, including a material based on a polymer.
[0224] In an example implementation, a reader can be used to
perform the electrical measurement of the tissue. As shown in FIG.
20, an example reader 1910 can include at least one second inductor
structure 1912. A measure of a change in an electrical property of
the at least one second inductor structure 19192 brought in
proximity to the at least one first inductor structure 1904
provides the measure of the electrical property of the at least one
first inductor structure 1904. The measure of the electrical
property or the physical property of the at least one first
inductor structure 1904 using the reader 1901 is used to provide an
indication of the tissue condition. For example, a calibration
standard can be generated as described above (in connection with
the capacitance-based system) based on inductance-based electrical
measurements of a training set of tissue samples in different known
tissue conditions.
[0225] The second inductor structure 1912 can be the same
configuration as the first inductor structure 1904.
[0226] In a non-limiting example, the reader is a handheld device
such as a smartphone, a tablet, a slate, or other handheld
computing device. A processor of the handheld device can be used to
analyze the data from the inductance-based measurement to provide
the indication of the tissue condition.
[0227] RF inductor coils are used that are sensitive to the
impedance of the underlying tissue. Likewise, a passive RF
induction coil on the skin to measure changes in impedance of the
underlying tissue may be correlated with changes in the state of
hydration of the tissue. This offers a simple and non invasive
method for hydration assessment that can easily be integrated into
a wearable (stretchy, flexible or conformal) form factor.
[0228] Using tissue impedance-inductance to monitor hydration has
the several specific advantages over blood and sweat analysis:
Blood and sweat analysis can require disposable, adhesive sensor
units and may be costly. A RF inductor can easily be designed to be
reusable. There are specific locations, including the thigh and
upper bicep, at which RF impedance testing works best for hydration
monitoring, and these locations are conducive to use of a device
during vigorous activity.
[0229] An RF inductor coil may be fabricated on a flexible and/or
stretchy substrate that may be worn on the skin or integrated into
form-fitted clothing. The tissue condition, including its state of
hydration, is determined by measuring the resonant frequency of the
coil. This frequency is related to the impedance of the tissue
adjacent to the coil. Changes in resonant frequency may be
correlated with changes in impedance, which in turn reflects
changes in the state of hydration. The depth of tissue to which the
coil is sensitive to changes in impedance scales with the radius of
the coil. Small coils (<1 cm) are designed to be sensitive
primarily to the hydration of the skin while larger coils (>1
cm) are designed to be sensitive to the state of hydration of
muscle.
[0230] In accordance with various examples herein, the apparatus
can be used to provide real-time data giving information such as:
[0231] 1. Total volume of sweat lost; [0232] 2. Composition of the
sweat lost (major electrolytes lost in sweat are Sodium, Potassium,
Calcium) with an active monitor.
[0233] Example apparatus and systems herein for real-time
monitoring of hydration through a passive, non-invasive device
based on volume of sweat lost through the placement of RF conductor
coils on a hydrophilic patch (i.e. hydrophilic polyurethane) over a
constant surface area of the skin. The RF coil and the patch may be
housed in a bioadhesive patch that contacts the skin and only
allows for sweat from the specific surface area to be collected.
The hydrophilic patch--such as TECOPHILIC.RTM. (Lubrizol
Corporation, Wickliffe, Ohio)--collects the amount of sweat lost
over that surface area and distributes it uniformly. The changes in
resonant frequency of the RF coil on top of the hydrophilic patch
can be correlated to the changes of impedance in the hydrophilic
patch as the sweat accumulates. The changes can be measured through
the use of a portable (handheld) RF reader. A small RF coil can be
used to measure the uniform distribution of the sweat accumulated
in the hydrophilic polyurethane patch over the surface area noted
above. The correlated data can then give a state of hydration based
on volume of sweat lost over the entire Body Surface Area (BSA) by
extrapolating the surface area of the patch over the surface area
of the entire body. The average BSA is widely taken to be 1.73
m.sup.2 for an adult with 1.9 m.sup.2 for a male and 1.6 m.sup.2
for a female. This can be further customized if both height and
weight are known through the Dubois & Dubois formula for BSA
(or another formula for BSA that is agreed upon):
BSA ( m 2 ) = 0.007184 .times. weight ( kg ) ? .times. height ( cm
) ? = weight ( kg ) ? .times. height ( cm ) ? 139.2 ##EQU00001## ?
indicates text missing or illegible when filed ##EQU00001.2##
The example apparatus can be housed in an elastomeric patch
adhering to the skin. The patch may include a cavity containing an
absorbent wicking hydrophilic material that draws and distributes
sweat lost during exertion. The patch may be designed in such away
that the accumulation of sweat in the hydrophilic materials
correlates directly with flux of sweat through the skin: that is,
amount of sweat per square-meter of skin. This flux multiplied by
the BSA calculated above gives an substantially absolute measure of
the amount of fluids lost over a period of time. The wearer can
then replenish or rehydrate with precisely the amount of fluids
lost. The patch may include an elastomer having pores restricting
access to the skin and allowing a controlled flow of sweat into the
cavity. An RF coil on the outer surface of the patch may be
stimulated by an external swept-frequency RF transceiver. The
center frequency and Q of the coil changes in response to the
moisture content of the patch, which will be detected by the
external transceiver. The baseline for this measurement is the
patch when it is first applied to skin.
[0234] Another implementation includes a metal mesh on the lower
surface of the elastomer, either on the skin side or the bottom of
the cavity. The mesh isolates the skin surface from the RF sensing
coil and substantially eliminates the natural variation of coil
response depending on individual body composition and starting
hydration, allowing one-time factory calibration of the
patches.
[0235] Another example implementation includes an embedded sensing
coil inside the cavity and providing isolation both above and below
the cavity. The isolation helps protect the sense coil from subject
variations as well as stray electromagnetic fields. A separate
communications coil linked to the sense coil but outside the
shielded cavity may be included in this instantiation. The link may
be either passive or active. A passive link may be AC coupled or DC
coupled. An active link may contain transistors, RF energy
harvesting and storage, Rx, sense, and Tx phases, timing and
control, similar to an RFID tag.
[0236] The example apparatus of FIG. 21 shows a quarter of a
sensing patch 2100 that includes an elastomer substrate 2102, a
TECOPHILIC.RTM. material 2104, an opening 2106 providing a pore
that allows moisture to penetrate from the tissue to the patch, an
elastomer cap 2018, a sensing coil 2110 (first inductor structure)
to detection hydration level of TECOPHILIC.RTM. layer 2104.
[0237] The example apparatus of FIG. 22 shows a quarter of sensing
patch 2200 that includes a shielding mesh 2112 below the
TECOPHILIC.RTM. layer, so that the coil detects only moisture in
the TECOPHILIC.RTM. layer and not in the skin.
[0238] The example apparatus of FIG. 23 shows a quarter of sensing
patch 2300 that includes both top shielding 2114 and bottom
shielding 2112 to provide electromagnetic isolation of the sensing
coil 2110. A second coil 2116 is used for communication of the
tissue condition measurement made using the sensing coil 2110.
[0239] Ultrasound-Based Measurements
[0240] Sweat analysis, blood analysis, and muscular ultrasound
analysis as potential ways of monitoring hydration. Sweat analysis
(via ionic concentration analysis) and blood analysis (via
hemoglobin concentration) both presented practical issues in
non-invasive sample collection as well as the scalability of the
necessary components. Ultrasound velocity to determine tissue
hydration level as an indicator for overall hydration level
utilizes a relationship proven by research and is a method with
minimal potential for complication.
[0241] FIG. 24 shows a cross-section of an example ultrasound
system 2400 that can be used in conjunction with a
capacitance-based system and/or an inductance-based system
described herein to provide data indicative of the electrical
properties of the tissue. Example ultrasound system 2400 includes a
piezoelectric crystal 2402, a hard polymer focusing element 2404, a
metal plate 2406, and the wiring 2408 to supply a voltage to the
piezoelectric crystal 2402.
[0242] FIG. 25 shows an example operation of the example ultrasound
system 2400 when a voltage is applied. The alternating voltage
causes a shape change in the piezoelectric crystal 2402, and the
shape change helps to generate the ultrasound waves.
[0243] FIG. 26A shows an example device mount 2600 about a bicep
tissue. FIG. 26B shows a cross-section of the device mount 2600
disposed about the bicep tissue 2602. The ultrasound system
includes an ultrasound generator 2604 and an ultrasound receiver
2606.
[0244] Using ultrasound velocity or tissue impedance to monitor
hydration has the several specific advantages over blood and sweat
analysis: [0245] Blood and sweat analysis would likely require
disposable, adhesive sensor units and may be costly. An ultrasound
device can easily be designed to be reusable. [0246] There are
specific locations, including the thigh and upper bicep (see FIG.
26A), at which ultrasound velocity assists in hydration monitoring,
and these locations are conducive to use of a device during
vigorous activity. The optimal locations for a sweat or blood
monitoring system might be harder to determine. [0247] The
ultrasonic device can be made non-invasive.
[0248] Non-limiting examples of benefits of the present disclosure
include the following: [0249] The sensor circuitry is fully
flexible, stretchable and conformable for a more comfortable and
portable user experience, whether incorporated into an arm/leg band
or a form-fitted garment. [0250] Hydration status readings will be
derived using the average of velocity readings taken from multiple
transducer-sensor pairs stationed in multiple arrays throughout the
band. An increased number of trials will help to increase the
accuracy of the readings. Additionally, the average reading will
help mitigate any inconsistencies caused by small potential changes
in transducer-sensor separation due to the conformal nature of the
band. [0251] Hydration status may be viewed in real-time on the
arm/leg band or form-fitted clothing item via the included LED
indicator lights. [0252] The arm/leg band may be wireless and
transmit data to mobile devices and portable music players. [0253]
Through innovative low-power management techniques the circuit can
operate on a very small power source.
[0254] An RF inductor coil may be fabricated on a flexible and/or
stretchy substrate that may be worn on the skin or integrated into
form-fitted clothing. The state of hydration is determined by
measuring the resonant frequency of the coil. This frequency is
related to the impedance of the tissue adjacent to the coil.
Changes in resonant frequency may be correlated with changes in
impedance, which in turn reflects changes in the state of
hydration. The depth of tissue to which the coil is sensitive to
changes in impedance scales with the radius of the coil. Small
coils (<1 cm) are designed to be sensitive primarily to the
hydration of the skin while larger coils (>1 cm) are designed to
be sensitive to the state of hydration of muscle.
[0255] In various examples, these sensors--ultrasound and impedance
(inductance-based and/or capacitance-based)--may be used alone or
in combination. It is also contemplated that these
sensors--ultrasound and impedance (inductance-based and/or
capacitance-based)--may be used in combination with other types of
sensors that measure the composition of sweat (e.g., sensors that
measure conductivity or sensors that measure the concentration of
selective ions such as sodium potassium and calcium, and
others).
[0256] Example components are the ultrasonic transducer/receiver
array circuits. The ultrasonic transducers and receivers are
piezoelectric disc actuators laid into a circuit with a series of
analog-to-digital converters (ADCs) that process the signals from
the transducer-receiver pairs.
[0257] These transducer/receiver circuits are laid into the sleeve
of a t-shirt, the leg of a pair of compression shorts, or a sport
armband or legband made of a formfitted, flexible, stretchable
material such as neoprene, spandex or other types of polymer
materials. One exemplary configuration is three or more arrays of
transducers and receivers spaced equidistant from each other. Each
section contains two transducers and two receivers. Each transducer
is responsible for communicating with a receiver in an adjacent
array and vice versa. The transducer-receiver sections do not
communicate with diagonal sections due to bone interference, only
adjacent sections.
[0258] Hydration status is monitored based upon the velocity of
ultrasound waves through the muscular tissue. There is a proven
linear proportionality between tissue hydration level and the
velocity of ultrasonic waves through the tissue (Topchyan, et al.
Ultrasonics 44, 2006, 259-264). As the muscle tissue becomes more
dehydrated, ultrasound velocity will become faster. This linear
relationship does not hold at extreme levels of dehydration. The
ADCs within the circuits measure the time differential between the
ultrasound signal propagation at the transducer and signal
reception at the receiver. This time differential is then divided
by the distance between the transducer and receiver to obtain an
ultrasound velocity. This is measured at regular intervals. In an
example where these measurements are made every thirty seconds, one
overall velocity will be calculated from an average of the readings
from each of the eight transducer-receiver pairs. Each pair will be
activated once during each thirty-second interval to retrieve a
velocity reading, and only one pair will be activated at a time to
eliminate any possibilities of constructive or destructive
interference.
[0259] Example Systems for Using Apparatus for Measuring Tissue
Properties
[0260] In an non-limiting example, an apparatus or system according
to any of the principles described herein can be mounted to the
tissue as a part of a patch. An example of a patch 2702 that can
include at least one of any of the apparatus described herein is
shown in FIG. 27. The patch 2702 may be applied to tissue, such as
skin. A handheld device 2704 can be used to read the data in
connection with the electrical measurement performed by the
apparatus of the patch 2702. For example, the patch 2702 can
include a transmitter or transceiver to transmit a signal to the
handheld device 2704. The data in connection with the electrical
measurement can be analyzed by a processor of the handheld device
2702 to provide the indication of the tissue condition according to
the principles described herein.
[0261] As shown in FIG. 27, the patch may be used in connection
with a substance 2706 that is applied to the tissue. The substance
2706 may be configured to change the condition of the tissue,
including treating a disease of the tissue. For example, the
substance 2706 may be configured to be applied to the skin tissue
to provide protection against the UV. In this example, the
apparatus of the patch would be configured to perform electrical
measurements to provide an indication of UV and/or SPF sensing on
the tissue, to prevent sun damage and/or to recommend protective
products. In another example, the substance 2706 may be configured
to be applied to the tissue to treat a disease or other
malformation of the tissue.
[0262] In an example, the patch 2702 may be a disposable adhesive
patch that is configured for comfort and breathability.
[0263] In another example, the patch 2702 may be a more durable
sensor patch that is configured for comfort and long-term wear. The
sensor patch may include onboard sensors to measure the tissue
condition of interest, a memory to log the data in connection with
the electrical communication, and a near-field communication device
that allows a scan of the sensor patch with a handheld device to
perform a status check and download. Non-limiting examples of the
handheld device include a smartphone, tablet, slate, an e-reader or
other handheld computing device. The sensor patch may include an
energy storage device, such as a battery, to provide the voltage
potential used for performing the measurements as described
hereinabove.
[0264] In an example, the system may include the patch 2702 and a
charging pad (not shown). The patch 2702 may be placed on the
charging pad to charge the energy storage component of the patch
2702. The charging pad may be charged in an AC wall socket. The
charging pad may be an inductive charging pad.
[0265] In an example implementation, the patch 2702 can include an
apparatus for performing SPF monitoring based on the electrical
information from a capacitance-based and/or an inductance-based
measurement. The example apparatus according to this implementation
can include an onboard UVA and/or UVB sensor. The tissue condition
that is reported is the sun protection effectiveness of a sunscreen
product for protection of the tissue. An example disposable patch
according to this implementation can provide a surface that is
engineered to simulate skin wetting properties to, accurately
represent sunscreen distribution.
[0266] The example SPF monitoring system can use a durable sensor
patch along with disposable adhesive patches. In an example method
for use of the SPF monitoring system, the patch 2702 can be placed
in a discreet high-exposure location on a person's body if extended
sun exposure is expected. Over time, e.g., throughout the day, a
NFC-enabled handheld device can be placed in proximity to the patch
2702 to check how much sun protection still remains. The handheld
device can include an application (an App) to log and track "SPF
state." That is, the App on the handheld device can include
machine-readable instructions such that a processor unit of the
handheld device analyzes the electrical measurements from the
apparatus of the patch 2702 and provides the indication of the
tissue status (SPF state) based on the analysis. The App can
include machine-readable instructions to provide (i) product
recommendations, (ii) suggestions to re-apply a product, or (iii)
present an interface that facilitates the purchase of, or obtaining
a sample of, recommended products. After use, such as at the end of
the day, a consumer may dispose of the Adhesive patch, and retain
the sensor patch reuse at a later time. The sensor patch can be
re-charged using a charging pad as described herein.
[0267] In another example implementation, the patch 2702 can
include an apparatus to perform as a UV dosimeter based on the
electrical information from a capacitance-based and/or an
inductance-based measurement. The example apparatus according to
this implementation can include an onboard UVA and/or UVB sensor.
The tissue condition that is reported is the UV dosage exposure of
an individual.
[0268] The example UV dosimeter system can use a durable sensor
patch along with disposable adhesive patches. In an example method
for use of the UV dosimeter system, the patch 2702 can be placed in
a discreet high-exposure location on a person's body if extended
sun exposure is expected. Over time, e.g., throughout the day, a
NFC-enabled handheld device can be brought in proximity to the
Adhesive patch to download logged data, gathered throughout use of
the patch 2702. The App can be used to track "personal sun exposure
state." That is, the App on the handheld device can include
machine-readable instructions such that a processor unit of the
handheld device analyzes the electrical measurements from the
apparatus of the patch 2702 and provides the indication of the
tissue status (personal sun exposure state) based on the analysis.
The App can include machine-readable instructions to provide and
can provide (i) product recommendations, (ii) suggestions to
re-apply products, or (iii) present an interface that facilitates
the purchase of, or obtaining a sample of, recommended products.
After use, such as at the end of the day, the individual may
dispose of the Adhesive patch, and retain the sensor patch for
reuse at a later time. The sensor patch can be re-charged on
charging pad, e.g., overnight.
[0269] In another example implementation, the patch 2702 can
include an apparatus to perform as a hydration and/or firmness
monitor based on the electrical information from a
capacitance-based and/or an inductance-based measurement. The
example apparatus according to this implementation can include an
onboard hydration sensor. The tissue condition that is reported is
the tissue hydration and/or firmness of an individual. Based on the
indication, the patch 2702 can perform diagnosis and recommendation
for personalized skin hydration and firmness product
treatments.
[0270] The example hydration and/or firmness monitoring system can
use a durable sensor patch along with disposable adhesive patches.
In an example method for use of the hydration and/or firmness
monitoring system, the individual may create a personal profile and
affiliate a product choice with that profile on a handheld device.
An App that can be used to generate the profile may be downloaded
to the handheld device. After application of a product, e.g., at
night, an individual may place one or more patches 2702 on an area
of interest on the body. The individual may bring the NFC-enabled
handheld device in proximity to the patch(es) 2702 to download data
gathered intermittently during use of the patch(es) 2702. The App
can include machine-readable instructions to track "personal
hydration and firmness states." In another example, the App can
include machine-readable instructions to provide (i) product
recommendations, (ii) suggestions to re-apply products, or (iii)
present an interface that facilitates purchase of, or obtaining a
sample of, recommended products. The individual may repeat the
procedure with varying products and beauty routines and update the
profile based on the results.
[0271] Systems for Indicating and/or Transmitting Measurements
[0272] In one example implementation, the status of the tissue
condition (including hydration status) may be monitored with a
series of LED indicator lights. That is, the LED lights can be used
according of any of the examples described herein to provide the
indication of the tissue condition.
[0273] As one example of many ways to illustrate the value or the
change in value of tissue condition (including hydration levels),
LED indicator lights may be lit to indicate the percent change in
sensor measurement from the initial reading. The LEDs are grouped
in pairs which light up together depending upon hydration level as
displayed in the table below:
[0274] All LED indicators leading up to the specific measurement
change can remain lit, but they may go off if/when the subject
rehydrates. For example, at a 4% change in a measurement, two green
pairs and one yellow pair of LEDs may be lit. If that increase
drops to 0.5%, only one green pair may be lit.
[0275] This is one example of many ways in which indication of
hydration level may be presented to the user. Numerical
seven-segment LED or LCD displays can also be used to provide
numerical or percentage values. Linear arrangements of LEDs can
`chart` hydration levels where longer runs of illuminated LEDs
indicate greater hydration. Brightness level can also indicate
hydration level or sequential patterns or other many ways to
indicate increasing, decreasing or absolute values of hydration
levels may be displayed and made integral to the unit.
[0276] In yet other implementations, rather than employing external
power sources, "on-board" power sources may be employed. In one
instantiation, the power source may be a small 12V battery
contained in rigid housing. Such power management techniques can
use a variety of well-known battery and energy storage management
methods.
[0277] In another aspect, data transmissions to a cellular phone,
portable music player, such as an mp3 player, or other mobile
device in order may be supported to allow for data logging and
audible hydration status alerts via an accompanying software
application. In one example, processing circuitry as well as a
Bluetooth data transmitter (or other wireless techniques such as
WiFi (802.11 protocols), ANT or other wireless means and protocols)
are employed to facilitate such transmission.
[0278] In yet another aspect, the LED light indicator system may be
replaced or supplemented by other indication mechanisms. For
example, the LED light indicator system may be replaced by a
display which gives a precise read out of the percent change in
sensor measurement from a previously measured baseline, and
therefore of the percent change in hydration level. Another
solution is to remove on-board indication and require integration
with a mobile device or mp3 player. This takes advantage of
processing power that is available within the phone or other mobile
device and reduce or eliminate processing resources on the sport
band.
[0279] According to other examples, hydration monitoring apparatus
may include a thin, flexible and/or stretchable capacitance-based
sensor on a conformal substrate. The sensor electrode is a passive
device and is applied to the skin in a variety of locations like a
decal or temporary tattoo, or it may be integrated into form-fitted
clothing. The capacitance-impedance between the conductive
structures are measured and correlated with the state of
hydration.
[0280] According to yet other examples, hydration monitoring
apparatus may include a thin, flexible and/or stretchable inductor
structure (such as but not limited to a RF inductor coil) on a
conformal substrate. The coil is a passive device and is applied to
the skin in a variety of locations like a decal or temporary
tattoo, or it may be integrated into form-fitted clothing. The coil
needs can be placed near the skin and does not have to be direct
contact. The resonance frequency of the coil is then measured and
correlated with the state of hydration.
[0281] Such information about tissue condition (including
hydration) may be stored, transmitted and recorded to tie into
other health information from a particular activity or series of
activities to give a long term profile of body hydration over time.
This information may be furthered integrated into other health
related information over time and presented to the user, parent,
doctor, coach or other interested party, in a software application
or in web-based tools, to give graphical and visual information of
status over time. This may be used to spot trends and provide early
diagnosis of issues related to hydration and other physiological
signs.
[0282] The information can also be used in ways to automatically
update such health status and information to social media sites and
forums to allow friends, fellow athletes and colleagues to compare
and contrast similar information in a convenient form. Additional
features would allow comments and other communication in an online
fashion to provide competitive information and entertainment.
[0283] The apparatus is applied to locations where skin or muscle
hydration is to be monitored. A baseline reading is taken at the
beginning of an active period, and then measurements are taken
periodically. Changes in the electrical information from the
measurement can be correlated with changes in tissue condition,
such as but not limited to hydration state.
[0284] Specific activity may be tied to specific changes in the
hydration state, such as changes in level of activity, drinking
more water, or other fluids such as a sport drink, or applying
certain creams or lotions that change the hydration level of the
skin.
[0285] For apparatus that include components for measuring based on
ultrasound techniques, the apparatus may be wrapped around the
user's upper arm (the biceps/triceps area), as illustrated in FIG.
26A, or lower leg (the calf) and secured using means such as, but
not limited to, adhesives or hook-and-loop style fasteners
(commercially available as VELCRO.RTM.) components. The apparatus
is then powered on and a baseline ultrasound velocity reading is
taken before activity begins. The apparatus may be used regardless
of clothing or other equipment used, so long as the apparatus has
direct contact with the skin.
[0286] Hydration Monitoring
[0287] Various examples of the present disclosure provide a direct,
specific targeting of the use case for the hydration monitor. The
specific medical applications can be broad, but specifically this
can have an application for wound healing, rehabilitation,
detoxification, and monitoring while in and out of the hospital for
hydration levels.
[0288] With wound healing and physical rehabilitation, dehydration
can result in diminished healing ability since water is a major
component of healthy cells. A large, exposed wound--or even a
draining wound--may also exude a large amount of fluids, resulting
in dehydration and electrolyte imbalance. Maintaining body cell
mass helps promote wound healing. The body enters a type of
hypermetabolic state during wound healing as an increase of 10-50%
of energy expenditure is common during the repair and recovery
process. This hypermetabolic state can lead to dehydration, and
dehydration can then affect the breakdown of proteins that are
absolutely crucial in the healing process, as water aids the body
in nutrient absorption and deployment. Hydration plays a role in
wound healing as dehydrated skin is less elastic, more fragile and
more susceptible to breakdown. Dehydration can also reduce
efficiency of blood circulation, which can impair the supply of
oxygen and nutrients to the wound. Water and hydration play a
massive role in the healing process.
[0289] During the detoxification process, hydration plays a role in
the body's function to excrete toxins and waste. Hydration is the
foundation for detoxification based on a flow of water in and out
of the cells. pH balance in the body is dependent on detoxification
of built up toxins inside the cells. Water and hydration plays a
role in this process, and it has been shown that people do not
drink enough water on a daily basis to maintain an optimal level of
hydration that rids the body of toxins and provides an overall
health and wellness well being. Those who have lived for many years
without proper water intake are the most likely to succumb to the
buildup of toxins in the body. It is difficult to perform accurate
monitoring of the level of tissue hydration on a day-to-day
basis--other than the crude method of comparing colors of urine.
This hydration monitor can provide a way for people to lead a
healthier life through all of the benefits of hydration (signs of
dehydration range from drops in physical and mental performance,
migraines, muscle aches, and constipation, to even more severe
episodes requiring hospitalization).
[0290] Monitoring patients (even self-monitoring) while in and out
of the hospital for hydration levels can be beneficial when
considering the extremely dehydrating effects of painkillers and
antibiotics. Just as in wound healing above, the body has an
increased need for hydration while taking painkillers and
antibiotics. Many painkillers and many antibiotics have a
dehydrating effect on the body, thus making it difficult to recover
from injury. Painkillers have a double effect, they use a large
amount of cellular water to be processed, and they also mute the
body's natural response to dehydration; thirst. The process of
progressive cellular dehydration can occur over time. Also, many
antibiotics cause diarrhea, which can cause severe dehydration over
time. Monitoring levels of dehydration is both preventative and
pro-active in this setting.
[0291] There is also an application for the weight-loss market for
the hydration monitor. Staying hydrated is very important in
general health/well-being from day-to-day (focus benefits,
short-term health, long-term health, etc.) but it has been
well-documented that far too many people just do not drink enough
water throughout the day and can develop dehydration that can be
chronic. The diet and/or athletics industry may derive great
benefit by using hydration as a way to manage appetite, leading to
healthy weight loss and a healthy life style at a very low-cost
with no side effects. Water is a form of hydration that is readily
available and very inexpensive. It has long been known that water
is the essential key to weight loss by suppressing appetite (the
"full-feeling", reducing caloric intake when properly hydrated,
etc.), boosting metabolism, and increasing energy production.
Hydration studies have shown that dehydration can affect both mood
and willpower: a poor mood and willpower makes you much more likely
to eat food high in fat, sugar and calories. Proper hydration
brings an absolute huge shift in the diet/fitness market, and the
monitors described herein facilitate that. In non-limiting example
implementation, the apparatus is used as a hydration monitor.
[0292] The data provided by an apparatus or system herein, in
performing a capacitance-based or an inductance-based measurement,
can be used to determine the timing of replacing body fluids. Not
replacing enough fluids and electrolytes lost can lead to severe
cramping, drop-off in athletic performance, and mental confusion
that can be traced to the changes at cellular level upon
dehydration. Replacing too much fluids and electrolytes can lead to
an electrolyte imbalance and gastrointestinal problems, not to
mention a bloated, full feeling while in competition or training.
Changes in temperature, humidity, altitude, level of activity and
the degree of heat acclimation the athlete or soldier has further
complicates the process. Measuring the loss of fluids from the skin
can be a reliable way to measure dehydration or more generally the
state of hydration in real-time.
[0293] The apparatus and systems described herein can provide a
real-time proxy for total volume of sweat lost in a
workout/practice/game/battle/training or any specified period of
time from when the monitor is placed on the body. Thus, the issue
of replacing fluids lost is made simpler; replace what is lost in
real-time during the activity, training or battle, thus assisting
to reduce or substantially eliminate avoiding the drop-off in
performance mentally and physically.
CONCLUSION
[0294] All literature and similar material cited in this
application, including, but not limited to, patents, patent
applications, articles, books, treatises, and web pages, regardless
of the format of such literature and similar materials, are
expressly incorporated by reference in their entirety. In the event
that one or more of the incorporated literature and similar
materials differs from or contradicts this application, including
but not limited to defined terms, term usage, described techniques,
or the like, this application controls.
[0295] The section headings used herein are for organizational
purposes only and are not to be construed as limiting the subject
matter described in any way.
[0296] While various examples have been described and illustrated
herein, those of ordinary skill in the art will readily envision a
variety of other means and/or structures for performing the
function and/or obtaining the results and/or one or more of the
advantages described herein, and each of such variations and/or
modifications is deemed to be within the scope of the examples
described herein. More generally, those skilled in the art will
readily appreciate that all parameters, dimensions, materials, and
configurations described herein are meant to be exemplary and that
the actual parameters, dimensions, materials, and/or configurations
will depend upon the specific application or applications for which
the teachings is/are used. Those skilled in the art will recognize,
or be able to ascertain using no more than routine
measurementation, many equivalents to the specific examples
described herein. It is, therefore, to be understood that the
foregoing examples are presented by way of example only and that,
within the scope of the appended claims and equivalents thereto,
examples may be practiced otherwise than as specifically described
and claimed. examples of the present disclosure are directed to
each individual feature, system, article, material, kit, and/or
method described herein. In addition, any combination of two or
more such features, systems, articles, materials, kits, and/or
methods, if such features, systems, articles, materials, kits,
and/or methods are not mutually inconsistent, is included within
the scope of the present disclosure.
[0297] The above-described examples of the invention can be
implemented in any of numerous ways. For example, some examples may
be implemented using hardware, software or a combination thereof.
When any aspect of an example is implemented at least in part in
software, the software code can be executed on any suitable
processor or collection of processors, whether provided in a single
device or computer or distributed among multiple
devices/computers.
[0298] In this respect, various aspects of the invention, may be
embodied at least in part as a computer readable storage medium (or
multiple computer readable storage media) (e.g., a computer memory,
one or more floppy discs, compact discs, optical discs, magnetic
tapes, flash memories, circuit configurations in Field Programmable
Gate Arrays or other semiconductor devices, or other tangible
computer storage medium or non-transitory medium) encoded with one
or more programs that, when executed on one or more computers or
other processors, perform methods that implement the various
examples of the technology discussed above. The computer readable
medium or media can be transportable, such that the program or
programs stored thereon can be loaded onto one or more different
computers or other processors to implement various aspects of the
present technology as discussed above.
[0299] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computer or other processor to implement various aspects of the
present technology as discussed above. Additionally, it should be
appreciated that according to one aspect of this example, one or
more computer programs that when executed perform methods of the
present technology need not reside on a single computer or
processor, but may be distributed in a modular fashion amongst a
number of different computers or processors to implement various
aspects of the present technology.
[0300] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically the
functionality of the program modules may be combined or distributed
as desired in various examples.
[0301] Also, the technology described herein may be embodied as a
method, of which at least one example has been provided. The acts
performed as part of the method may be ordered in any suitable way.
Accordingly, examples may be constructed in which acts are
performed in an order different than illustrated, which may include
performing some acts simultaneously, even though shown as
sequential acts in illustrative examples.
[0302] All definitions, as defined and used herein, should be
understood to control over dictionary definitions, definitions in
documents incorporated by reference, and/or ordinary meanings of
the defined terms.
[0303] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0304] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Multiple elements listed with "and/or" should be construed in the
same fashion, i.e., "one or more" of the elements so conjoined.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified. Thus, as a
non-limiting example, a reference to "A and/or B", when used in
conjunction with open-ended language such as "comprising" can
refer, in one example, to A only (optionally including elements
other than B); in another example, to B only (optionally including
elements other than A); in yet another example, to both A and B
(optionally including other elements); etc.
[0305] As used herein in the specification and in the claims, "or"
should be understood to have the same meaning as "and/or" as
defined above. For example, when separating items in a list, "or"
or "and/or" shall be interpreted as being inclusive, i.e., the
inclusion of at least one, but also including more than one, of a
number or list of elements, and, optionally, additional unlisted
items. Only terms clearly indicated to the contrary, such as "only
one of" or "exactly one of," or, when used in the claims,
"consisting of," will refer to the inclusion of exactly one element
of a number or list of elements. In general, the term "or" as used
herein shall only be interpreted as indicating exclusive
alternatives (i.e. "one or the other but not both") when preceded
by terms of exclusivity, such as "either," "one of," "only one of,"
or "exactly one of" "Consisting essentially of," when used in the
claims, shall have its ordinary meaning as used in the field of
patent law.
[0306] As used herein in the specification and in the claims, the
phrase "at least one," in reference to a list of one or more
elements, should be understood to mean at least one element
selected from any one or more of the elements in the list of
elements, but not necessarily including at least one of each and
every element specifically listed within the list of elements and
not excluding any combinations of elements in the list of elements.
This definition also allows that elements may optionally be present
other than the elements specifically identified within the list of
elements to which the phrase "at least one" refers, whether related
or unrelated to those elements specifically identified. Thus, as a
non-limiting example, "at least one of A and B" (or, equivalently,
"at least one of A or B," or, equivalently "at least one of A
and/or B") can refer, in one example, to at least one, optionally
including more than one, A, with no B present (and optionally
including elements other than B); in another example, to at least
one, optionally including more than one, B, with no A present (and
optionally including elements other than A); in yet another
example, to at least one, optionally including more than one, A,
and at least one, optionally including more than one, B (and
optionally including other elements); etc.
[0307] In the claims, as well as in the specification above, all
transitional phrases such as "comprising," "including," "carrying,"
"having," "containing," "involving," "holding," "composed of," and
the like are to be understood to be open-ended, i.e., to mean
including but not limited to. Only the transitional phrases
"consisting of" and "consisting essentially of" shall be closed or
semi-closed transitional phrases, respectively, as set forth in the
United States Patent Office Manual of Patent Examining Procedures,
Section 2111.03.
[0308] The claims should not be read as limited to the described
order or elements unless stated to that effect. It should be
understood that various changes in form and detail may be made by
one of ordinary skill in the art without departing from the spirit
and scope of the appended claims. All examples that come within the
spirit and scope of the following claims and equivalents thereto
are claimed.
* * * * *