U.S. patent application number 13/650016 was filed with the patent office on 2013-09-19 for electrodynamic field strength triggering system.
This patent application is currently assigned to Senseonics, Incorporated. The applicant listed for this patent is SENSEONICS, INCORPORATED. Invention is credited to Arthur E. Colvin, JR., Andrew Dehennis.
Application Number | 20130241745 13/650016 |
Document ID | / |
Family ID | 48082453 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130241745 |
Kind Code |
A1 |
Colvin, JR.; Arthur E. ; et
al. |
September 19, 2013 |
ELECTRODYNAMIC FIELD STRENGTH TRIGGERING SYSTEM
Abstract
Systems and methods for automatically triggering wireless power
and data exchange between an external reader and an implanted
sensor. The implanted sensor may measure the strength of an
electrodynamic field received wirelessly from the reader and convey
field strength data based on the measured strength of the received
electrodynamic field to the reader. If the field strength data
indicates that the strength of an electrodynamic field received by
the sensor is sufficient for the implanted sensor to perform an
analyte measurement, the reader may convey an analyte measurement
command to the sensor, which may execute the analyte measurement
command and convey measurement information back to the reader. The
systems and methods may trigger the analyte measurement as the
reader transiently passes within sufficient range/proximity to the
implant (or vice versa).
Inventors: |
Colvin, JR.; Arthur E.; (Mt.
Airy, MD) ; Dehennis; Andrew; (Germantown,
MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SENSEONICS, INCORPORATED |
Germantown |
MD |
US |
|
|
Assignee: |
Senseonics, Incorporated
Germantown
MD
|
Family ID: |
48082453 |
Appl. No.: |
13/650016 |
Filed: |
October 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61545874 |
Oct 11, 2011 |
|
|
|
61597496 |
Feb 10, 2012 |
|
|
|
Current U.S.
Class: |
340/870.02 |
Current CPC
Class: |
A61B 5/076 20130101;
A61B 5/0022 20130101; A61B 2562/0257 20130101; A61B 5/0031
20130101; A61B 5/14503 20130101 |
Class at
Publication: |
340/870.02 |
International
Class: |
A61B 5/00 20060101
A61B005/00 |
Claims
1. A method of triggering a sensor implanted within a living animal
to measure a concentration of an analyte in a medium within the
living animal, the method comprising: coupling an inductive element
of an external reader and an inductive element of the sensor within
an electrodynamic field; generating field strength data indicative
of the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor;
determining, based on the field strength data, whether the strength
of the coupling of the inductive element of the external reader and
the inductive element of the sensor is sufficient for the sensor to
perform an analyte concentration measurement and convey the results
thereof to the external reader; and if the strength of the coupling
of the inductive element of the external reader and the inductive
element of the sensor is determined to be sufficient, triggering an
analyte concentration measurement by the sensor and conveyance the
results thereof to the external reader.
2. The method of triggering of claim 1, wherein the external reader
generates the field strength data by producing, using circuitry of
the external reader, a coupling value proportional to the strength
of the coupling of the inductive element of the external reader and
the inductive element of the sensor.
3. The method of triggering of claim 1, further comprising
producing, using circuitry of the sensor, a coupling value
proportional to the strength of the coupling of the inductive
element of the external reader and the inductive element of the
sensor.
4. The method of triggering of claim 3, further comprising
modulating, using circuitry of the sensor, the electrodynamic field
based on the coupling value proportional to the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor; wherein the external reader
generates the field strength data by decoding, using circuitry of
the external reader, the modulation of the electrodynamic
field.
5. The method of triggering of claim 3, further comprising:
converting, using circuitry of the sensor, the coupling value into
a digital coupling value; and modulating, using circuitry of the
sensor, the electrodynamic field based on the digital coupling
value; wherein the external reader generates the field strength
data by decoding, using circuitry of the external reader, the
modulation of the electrodynamic field.
6. The method of triggering of claim 1, wherein the field strength
data is a value proportional to the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor.
7. The method of triggering of claim 6, wherein determining whether
the strength of the coupling is sufficient comprises comparing the
field strength data to a field strength sufficiency threshold.
8. The method of triggering of claim 7, wherein the strength of the
coupling is determined to be sufficient if the field strength data
exceeds a field strength sufficiency threshold.
9. The method of triggering of claim 1, wherein triggering the
analyte concentration measurement by the sensor and conveyance the
results thereof to the external reader comprises conveying, using
circuitry of the external reader, an analyte measurement command to
the sensor.
10. The method of triggering of claim 9, wherein conveying the
analyte measurement command to the sensor comprises modulating,
using circuitry of the external reader, the electrodynamic
field.
11. The method of triggering of claim 10, further comprising:
decoding, using circuitry of the sensor, the modulation of the
electrodynamic field by the circuitry of the external reader;
executing, using the sensor, the analyte measurement command,
wherein the execution of the analyte measurement command comprises:
generating, using the implanted sensor, analyte measurement
information indicative of the concentration of the analyte in the
medium within the living animal; and conveying, using circuitry of
the sensor, the generated analyte measurement information.
12. The method of triggering of claim 11, wherein the conveying the
generated analyte measurement information comprising modulating,
using circuitry of the sensor, the electrodynamic field based on
the generated analyte measurement information.
13. The method of triggering of claim 1, wherein the coupling
comprises moving the sensor and the external reader relative to
each other such that the inductive element of the external reader
and the inductive element of the sensor are coupled within the
electrodynamic field.
14. A method of triggering a sensor implanted within a living
animal to measure a concentration of an analyte in a medium within
the living animal, the method comprising: generating, using an
external reader, field strength data indicative of the strength of
coupling of an inductive element of the external reader and an
inductive element of the sensor within an electrodynamic field;
determining, using the external reader, based on the field strength
data, whether the strength of the coupling of the inductive element
of the external reader and the inductive element of the sensor is
sufficient for the sensor to perform an analyte concentration
measurement and convey the results thereof to the external reader;
if the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor is
determined to be insufficient, repeating the generating and
determining steps; if the strength of the coupling of the inductive
element of the external reader and the inductive element of the
sensor is determined to be sufficient, triggering, using the
external reader, an analyte concentration measurement by the sensor
and conveyance the results thereof to the external reader, wherein
the triggering comprises conveying, using circuitry of the external
reader, an analyte measurement command to the sensor; and decoding,
using circuitry of the external reader, analyte measurement
information conveyed from the sensor.
15. The method of triggering of claim 14, wherein the external
reader generates the field strength data by producing, using
circuitry of the external sensor, a coupling value proportional to
the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor.
16. The method of triggering of claim 14, wherein generating the
field strength data comprises decoding, using circuitry of the
external reader, field strength data conveyed from the sensor.
17. The method of triggering of claim 14, wherein the decoding
field strength data comprises decoding modulation of the
electrodynamic field by the sensor.
18. The method of triggering of claim 14, wherein the field
strength data is a value proportional to the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor.
19. The method of triggering of claim 18, wherein determining
whether the strength of the coupling is sufficient comprises
comparing the field strength data to a field strength sufficiency
threshold.
20. The method of triggering of claim 19, wherein the strength of
the coupling is determined to be sufficient if the field strength
data exceeds a field strength sufficiency threshold.
21. The method of triggering of claim 14, wherein conveying the
analyte measurement command to the sensor comprises modulating,
using circuitry of the external reader, the electrodynamic
field.
22. The method of triggering of claim 14, wherein decoding the
analyte measurement information conveyed from the sensor comprises
decoding the analyte measurement information from modulation of the
electrodynamic field by the sensor.
23. The method of triggering claim 14, wherein the triggering
comprises sending power to the sensor.
24. The method of claim 14, wherein the coupling comprises sending
power to the sensor.
25. A method of triggering a sensor implanted within a living
animal to measure a concentration of an analyte in a medium within
the living animal, the method comprising: producing, using
circuitry of the sensor, a coupling value proportional to the
strength of the coupling of the inductive element of an external
reader and an inductive element of the sensor within an
electrodynamic field; converting, using circuitry of the sensor,
the coupling value into a digital coupling value; conveying, using
circuitry of the sensor, the digital coupling value to the external
reader; decoding, using the circuitry of the sensor, an analyte
measurement command conveyed from the external reader; executing,
using the sensor, the analyte measurement command, wherein the
execution of the analyte measurement command comprises: generating,
using the sensor, analyte measurement information indicative of the
concentration of the analyte in the medium within the living
animal; and conveying, using the inductive element of the implanted
sensor, the analyte measurement information.
26. The method of triggering of claim 25, wherein the conveying the
digital coupling value comprises modulating, using circuitry of the
sensor, the electrodynamic field based on the digital coupling
value.
27. The method of triggering of claim 25, wherein the conveying the
analyte measurement information comprises modulating, using
circuitry of the sensor, the electrodynamic field based on the
analyte measurement information.
28. The method of triggering of claim 25, wherein decoding the
analyte measurement command comprises decoding the analyte
measurement command from modulation of the electrodynamic field by
the external reader.
29. The method of triggering of claim 25, wherein the execution of
the analyte measurement command comprises turning a light source of
the implanted sensor on and off one or more times, wherein the
light source is configured to, when turned on, to irradiate
indicator molecules having an optical characteristic responsive to
the concentration of the analyte with excitation light, the
indicator molecules being configured to interact with the analyte
in the medium within the living animal while the implanted sensor
is implanted within the living animal.
30. A sensor for implantation within a living animal and
measurement of a concentration of an analyte in a medium within the
living animal, the sensor comprising: (a) an inductive element
configured to couple with an inductive element of an external
reader within an electrodynamic field; (b) an input/output circuit
configured to: (i) produce a coupling value proportional to the
strength of the coupling of the inductive element of the external
reader and the inductive element of the sensor within the
electrodynamic field; (ii) convey a digital coupling value to the
external reader; (iii) decode an analyte measurement command
conveyed from the external reader; and (iv) convey analyte
measurement information indicative of the concentration of the
analyte in the medium within the living animal; (c) circuitry to
convert the coupling value into a digital coupling value; and (d) a
measurement controller configured to: (i) control the input/output
circuit to convey the digital coupling value; (ii) in accordance
with the analyte measurement command, generate the analyte
measurement information indicative of the concentration of the
analyte in the medium within the living animal; and (iii) control
the input/output circuit to convey the analyte measurement
information.
31. The sensor of claim 30, wherein the input/output circuit
configured to convey the digital coupling value by modulating the
electrodynamic field based on the digital coupling value.
32. The sensor of claim 30, wherein the input/output circuit
configured to convey the analyte measurement information by
modulating the electrodynamic field based on the analyte
measurement information.
33. The sensor of claim 30, wherein the input/output circuit
configured to decode the analyte measurement command by decoding
the analyte measurement command from modulation of the
electrodynamic field by the external reader.
34. The sensor of claim 30, further comprising: indicator molecules
having an optical characteristic responsive to the concentration of
the analyte, the indicator molecules being configured to interact
with the analyte in the medium within the living animal when the
sensor is implanted within the living animal; a first photodetector
configured to output a first analog light measurement signal
indicative of the amount of light received by the first
photodetector; a second photodetector configured to output a second
analog light measurement signal indicative of the amount of light
received by the second photodetector; and a light source configured
to emit excitation light to the indicator molecules; wherein the
measurement controller configured to control the light source in
accordance with the analyte measurement command.
35. An external reader for triggering a sensor implanted within a
living animal to measure a concentration of an analyte in a medium
within the living animal, the external reader comprising: (a) an
inductive element configured to couple with an inductive element of
an external reader within electrodynamic field; and (b) circuitry
configured to: (i) generate field strength data indicative of the
strength of coupling of an inductive element of the external reader
and an inductive element of the sensor within an electrodynamic
field; (ii) determine based on the field strength data, whether the
strength of the coupling of the inductive element of the external
reader and the inductive element of the sensor is sufficient for
the sensor to perform an analyte concentration measurement and
convey the results thereof to the external reader; (iii) if the
strength of the coupling of the inductive element of the external
reader and the inductive element of the sensor is determined to be
insufficient, repeat the generating and determining steps; (iv) if
the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor is
determined to be sufficient, trigger an analyte concentration
measurement by the sensor and conveyance the results thereof to the
external reader, wherein the triggering comprises conveying an
analyte measurement command to the sensor; and (v) decode analyte
measurement information conveyed from the sensor.
36. The external reader of claim 35, wherein the circuitry is
configured to generate the field strength data by producing a
coupling value proportional to the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor.
37. The external reader of claim 35, wherein the circuitry is
configured to generate the field strength data by decoding field
strength data conveyed from the sensor.
38. The external reader of claim 37, wherein the circuitry is
configured to decode the field strength data by decoding modulation
of the electrodynamic field by the sensor.
39. The external reader of claim 35, wherein the field strength
data is a value proportional to the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor.
40. The external reader of claim 39, wherein the circuitry is
configured to determine whether the strength of the coupling is
sufficient by comparing the field strength data to a field strength
sufficiency threshold.
41. The external reader of claim 40, wherein the circuitry is
configured to determine the strength of the coupling to be
sufficient if the field strength data exceeds a field strength
sufficiency threshold.
42. A method of triggering a sensor implanted within a living
animal to measure a concentration of an analyte in a medium within
the living animal, the method comprising: producing, using
circuitry of the sensor, a coupling value proportional to the
strength of the coupling of the inductive element of an external
reader and an inductive element of the sensor within an
electrodynamic field; determining, using the sensor, based on the
coupling value, whether the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is sufficient for the sensor to perform an analyte
concentration measurement and convey the results thereof to the
external reader; if the strength of the coupling of the inductive
element of the external reader and the inductive element of the
sensor is determined to be sufficient, executing, using the sensor,
the analyte measurement command, wherein the execution of the
analyte measurement command comprises: generating, using the
sensor, analyte measurement information indicative of the
concentration of the analyte in the medium within the living
animal; and conveying, using the inductive element of the implanted
sensor, the analyte measurement information.
43. The method of claim 42, further comprising, if the strength of
the coupling of the inductive element of the external reader and
the inductive element of the sensor is determined to be
insufficient, conveying, using circuitry of the sensor, field
strength data to the external reader, wherein the field strength
data comprises a digitized coupling value and/or an indication that
the coupling is insufficient.
44. The method of claim 42, wherein determining whether the
strength of the coupling is sufficient comprises comparing the
coupling value to a field strength sufficiency threshold.
45. The method of claim 44, wherein the strength of the coupling is
determined to be sufficient if the coupling value exceeds a field
strength sufficiency threshold.
46. An external reader for obtaining an analyte measurement from an
implanted sensor, comprising: a housing; reader components
configured to wirelessly communicate with the implanted sensor and
obtain an analyte measurement from the implanted sensor, wherein
the reader components comprise a coil configured to inductively
couple with the implanted sensor; and a communication member
configured to communicate the analyte measurement to an electronic
device.
47. The external reader of claim 46, wherein the communication
member is configured to wirelessly transmit information to the
electronic device.
48. The external reader of claim 46, wherein the communication
member is a pin configured to couple with a port in the electronic
device.
49. The external reader of claim 46, wherein the electronic device
is a smartphone.
50. The external reader of claim 46, wherein the reader components
are configured to obtain the analyte measurement from the implanted
sensor in less than one second.
51. An external reader for obtaining analyte measurements from an
implanted sensor and configured to encase a smartphone including a
communication port, comprising: a first casing including a first
coupling member; a second casing including a second coupling member
configured to couple with the first coupling member; a
communication member configured to couple with the communication
port of the smartphone; and reader components configured to
wirelessly communicate with the implanted sensor and obtain an
analyte measurement from the implanted sensor, wherein the reader
components comprise a coil configured to inductively couple with
the implanted sensor.
52. The external reader of claim 51, wherein the communication
member is a protrusion from the second casing.
53. The external reader of claim 51, wherein the reader components
are configured to obtain the analyte measurement from the implanted
sensor in less than one second.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/545,874, filed on Oct. 11, 2011, which is
incorporated by reference herein in its entirety. This application
also claims priority to U.S. Provisional Application No.
61/597,496, filed on Feb. 10, 2012, which is incorporated by
reference herein in its entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a system for obtaining
analyte measurements. Specifically, the present invention relates
to an external reader that can interrogate an implanted analyte
sensor.
[0004] 2. Description of the Background
[0005] In a system in which an external sensor reader provides
power to an implanted sensor for operation (e.g., analyte
measurement) and data transfer, the primary coil of the external
sensor reader must be appropriately aligned with the secondary coil
of the implanted sensor. However, there is a finite and relatively
short range (typically less than one inch) within which the
implanted sensor receives an electrodynamic field from the external
sensor reader of sufficient strength to power the sensor for
analyte measurement and data transfer. In addition, finding the
correct alignment is made more difficult because an implanted
sensor is not visible to the user.
[0006] An attached system that physically maintains the external
sensor reader in alignment with the implanted sensor using, for
example, a fixed wristwatch, armband, or adhesive patch does not
work well for users who do not wish to wear a wristwatch, armband,
adhesive patch, or other fixed system and/or only require
intermittent readings from the implanted sensor during any period
in time. Furthermore, even a system that enabled on-demand
measurement would be unsatisfactory if it required a user to probe
around either by trial and error or by watching a field strength
meter to find the relative position in space from which to initiate
a reading.
[0007] RFID systems and readers are used for animal identification,
anti-theft applications, inventory control, highway toll road
tracking, credit card, and ID cards, but are not applicable in the
context of an implantable sensor and external reader system. RFID
systems are transponders, and the energy supplied must only reflect
a preset numerical sequence as an ID. This requires much less power
than an activated remote/implanted sensor, and an RFID system is
therefore capable of much more range because of the extremely low
operational power requirement from the RFID tag and can allow
operation at ranges of up to 5 feet or more. In contrast, an
implanted analyte sensor must be provided with much more power to
operate its circuitry for making measurements and conveying the
data to the reader. In fact, transfer of power by induction between
two coils is very inefficient at distance, and such systems are
often limited to approximately one inch or less, instead of
multiple feet possible in RFID systems.
[0008] A hobby or utility grade metal detector or stud finder is
also inapplicable in the context of an implanted sensor and
external reader system. Metal detection or stud finding is an
example of motion type operation, but the relationship between the
primary coil and the metal to be detected is completely passive.
Thus, in stark contrast with an implanted sensor and external
reader system, where the implanted sensor requires power for
activation, measurement, and data transfer, no power is required to
activate the metal being detected by a metal detector or stud
finder, and only the relative motion perturbation of the
electromagnetic field is required.
[0009] Accordingly, there is a need for an improved implanted
sensor and external reader system.
SUMMARY
[0010] One aspect of the invention is a triggering mechanism that
triggers/initiates an analyte reading/measurement from an
implantable sensor (e.g., an implantable chemical or biochemical
sensor) as an external reader transiently passes within sufficient
range/proximity to the implant (or vice versa). The movement may be
relative movement (a) between a stationary implant and a transient
reader, (b) between a stationary reader and a transient implant
site (e.g., relative movement of a wrist implant site into and/or
out of a stationary coil), or (c) relative movement between both.
In some embodiments, the triggering mechanism automatically
triggers the system to take a reading from the sensor at just the
moment when relative movement of a handheld reader and the sensor
has placed the reader within sufficient field strength range of the
sensor without the user needing to probe around either by trial and
error or by watching a field strength meter to find the relative
position in space from which to initiate a reading. In one
embodiment, the invention may automate the analyte measurement
sequence and reduce the action required by the user to nothing more
than movement of a handheld sensor reader.
[0011] One aspect of the invention includes a circuitry component
that takes measurements of a current proportional to the field
strength received by the sensor, and that indicates the relative
field strength (current) or magnetic coupling between the primary
coil of the reader and the secondary coil within the sensor. In
some embodiments, the system detects when the sensor is within
range to allow the power and data transfer and immediately sends a
command within the reader to initiate the power transfer and data
receiving sequence. In some embodiments, because the
reading/measurement happens very fast between a sensor and reader
(e.g., on the order of 10 milliseconds), the relative movement may
be dynamic as relative swipe-type hand movements.
[0012] One aspect of the present invention allows either retro
add-on type adaptation of reader capable platforms (e.g., smart
phones) or integrated inclusion in new design of smart phones,
handhelds, dedicated sensor readers, or other compatible electronic
devices. In some embodiments, the present invention may enable
intermittent readings to be taken automatically from an implantable
sensor under the relative motion of the external sensor reader and
sensor/implant site into close-enough proximity.
[0013] One embodiment of the invention is implemented by (i) taking
a measure within a circuitry that contains a value (e.g., current)
proportional to field strength; (ii) when that value reaches a
threshold value of field strength coupling between the two coils of
a reader-sensor pair, indicating that reliable power and data
transfer can occur; and (iii) triggering the regular read command
sequence, which then initiates the reading to be taken by the
reader for subsequent display to the user. The reader may then be
returned to pocket, or purse, or wherever the user keeps it until a
next reading is desired.
[0014] In one aspect, the present invention provides a method of
triggering a sensor implanted within a living animal to measure a
concentration of an analyte in a medium within the living animal.
The method may include coupling an inductive element of an external
reader and an inductive element of the sensor within an
electrodynamic field. The method may include generating field
strength data indicative of the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor. The method may include determining, based on the
field strength data, whether the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is sufficient for the sensor to perform an analyte
concentration measurement and convey the results thereof to the
external reader. The method may include, if the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor is determined to be sufficient,
triggering an analyte concentration measurement by the sensor and
conveyance the results thereof to the external reader.
[0015] In some embodiments, the external reader may generate the
field strength data by producing, using circuitry of the external
reader, a coupling value proportional to the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor.
[0016] In some embodiments, the method may include producing, using
circuitry of the sensor, a coupling value proportional to the
strength of the coupling of the inductive element of the external
reader and the inductive element of the sensor. The method may
include modulating, using circuitry of the sensor, the
electrodynamic field based on the coupling value proportional to
the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor. The
external reader may generate the field strength data by decoding,
using circuitry of the external reader, the modulation of the
electrodynamic field. The method may include converting, using
circuitry of the sensor, the coupling value into a digital coupling
value. The method may include, modulating, using circuitry of the
sensor, the electrodynamic field based on the digital coupling
value. The external reader may generate the field strength data by
decoding, using circuitry of the external reader, the modulation of
the electrodynamic field.
[0017] In some embodiments, the field strength data may be a value
proportional to the strength of the coupling of the inductive
element of the external reader and the inductive element of the
sensor. Determining whether the strength of the coupling is
sufficient may include comparing the field strength data to a field
strength sufficiency threshold. The strength of the coupling may be
determined to be sufficient if the field strength data exceeds a
field strength sufficiency threshold.
[0018] In some embodiments, the coupling may include moving the
sensor and the external reader relative to each other such that the
inductive element of the external reader and the inductive element
of the sensor are coupled within the electrodynamic field.
[0019] In another aspect, the present invention provides a method
of triggering a sensor implanted within a living animal to measure
a concentration of an analyte in a medium within the living animal.
The method may include generating, using an external reader, field
strength data indicative of the strength of coupling of an
inductive element of the external reader and an inductive element
of the sensor within an electrodynamic field. The method may
include determining, using the external reader, based on the field
strength data, whether the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is sufficient for the sensor to perform an analyte
concentration measurement and convey the results thereof to the
external reader. The method may include, if the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor is determined to be insufficient,
repeating the generating and determining steps. The method may
include, if the strength of the coupling of the inductive element
of the external reader and the inductive element of the sensor is
determined to be sufficient, triggering, using the external reader,
an analyte concentration measurement by the sensor and conveyance
the results thereof to the external reader, wherein the triggering
comprises conveying, using circuitry of the external reader, an
analyte measurement command to the sensor. The method may include
decoding, using circuitry of the external reader, analyte
measurement information conveyed from the sensor.
[0020] In yet another aspect, the present invention provides a
method of triggering a sensor implanted within a living animal to
measure a concentration of an analyte in a medium within the living
animal. The method may include producing, using circuitry of the
sensor, a coupling value proportional to the strength of the
coupling of the inductive element of an external reader and an
inductive element of the sensor within an electrodynamic field. The
method may include converting, using circuitry of the sensor, the
coupling value into a digital coupling value. The method may
include conveying, using circuitry of the sensor, the digital
coupling value to the external reader. The method may include
decoding, using the circuitry of the sensor, an analyte measurement
command conveyed from the external reader. The method may include
executing, using the sensor, the analyte measurement command. The
execution of the analyte measurement command may include
generating, using the sensor, analyte measurement information
indicative of the concentration of the analyte in the medium within
the living animal. The execution of the analyte measurement command
may include conveying, using the inductive element of the implanted
sensor, the analyte measurement information.
[0021] In still another aspect, the present invention provides a
sensor for implantation within a living animal and measurement of a
concentration of an analyte in a medium within the living animal.
The sensor may include an inductive element configured to couple
with an inductive element of an external reader within an
electrodynamic field. The sensor may include an input/output
circuit configured to produce a coupling value proportional to the
strength of the coupling of the inductive element of the external
reader and the inductive element of the sensor within the
electrodynamic field. The input/output circuit may be configured to
convey a digital coupling value to the external reader. The
input/output circuit may be configured to decode an analyte
measurement command conveyed from the external reader. The
input/output circuit may be configured to convey analyte
measurement information indicative of the concentration of the
analyte in the medium within the living animal. The sensor may
include circuitry to convert the coupling value into a digital
coupling value. The sensor may include a measurement controller
configured to: (i) control the input/output circuit to convey the
digital coupling value; (ii) in accordance with the analyte
measurement command, generate the analyte measurement information
indicative of the concentration of the analyte in the medium within
the living animal; and (iii) control the input/output circuit to
convey the analyte measurement information.
[0022] In another aspect, the present invention provides an
external reader for triggering a sensor implanted within a living
animal to measure a concentration of an analyte in a medium within
the living animal. The external reader may include an inductive
element configured to couple with an inductive element of an
external reader within electrodynamic field. The external reader
may include circuitry configured to: (i) generate field strength
data indicative of the strength of coupling of an inductive element
of the external reader and an inductive element of the sensor
within an electrodynamic field; (ii) determine based on the field
strength data, whether the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is sufficient for the sensor to perform an analyte
concentration measurement and convey the results thereof to the
external reader; (iii) if the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is determined to be insufficient, repeat the
generating and determining steps; (iv) if the strength of the
coupling of the inductive element of the external reader and the
inductive element of the sensor is determined to be sufficient,
trigger an analyte concentration measurement by the sensor and
conveyance the results thereof to the external reader, wherein the
triggering comprises conveying an analyte measurement command to
the sensor; and (v) decode analyte measurement information conveyed
from the sensor.
[0023] In another aspect, the present invention provides a method
of triggering a sensor implanted within a living animal to measure
a concentration of an analyte in a medium within the living animal.
The method may include producing, using circuitry of the sensor, a
coupling value proportional to the strength of the coupling of the
inductive element of an external reader and an inductive element of
the sensor within an electrodynamic field. The method may include
determining, using the sensor, based on the coupling value, whether
the strength of the coupling of the inductive element of the
external reader and the inductive element of the sensor is
sufficient for the sensor to perform an analyte concentration
measurement and convey the results thereof to the external reader.
The method may include, if the strength of the coupling of the
inductive element of the external reader and the inductive element
of the sensor is determined to be sufficient, executing, using the
sensor, the analyte measurement command. The execution of the
analyte measurement command may include: generating, using the
sensor, analyte measurement information indicative of the
concentration of the analyte in the medium within the living
animal; and conveying, using the inductive element of the implanted
sensor, the analyte measurement information.
[0024] In another aspect, the present invention provides an
external reader for obtaining an analyte measurement from an
implanted sensor. The reader may include a housing, reader
components, and a communication member. The reader components may
be configured to wirelessly communicate with the implanted sensor
and obtain an analyte measurement from the implanted sensor. The
reader components may comprise a coil configured to inductively
couple with the implanted sensor. The communication member may be
configured to communicate the analyte measurement to an electronic
device.
[0025] In another aspect, the present invention provides an
external reader for obtaining analyte measurements from an
implanted sensor and configured to encase a smartphone including a
communication port. The reader may include a first casing including
a first coupling member, a second casing including a second
coupling member configured to couple with the first coupling
member, a communication member configured to couple with the
communication port of the smartphone, and reader components. The
reader components may be configured to wirelessly communicate with
the implanted sensor and obtain an analyte measurement from the
implanted sensor. The reader components comprise a coil configured
to inductively couple with the implanted sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic view of a sensor system, which
includes an implantable sensor and a sensor reader, embodying
aspects of the present invention.
[0027] FIGS. 2A-2C illustrate example configurations of the
inductive element of the external sensor reader in accordance with
embodiments of the present invention.
[0028] FIG. 3 illustrates a sensor in alignment with an
electromagnetic field emitted by the inductive element of a
transceiver in accordance with an embodiment of the present
invention.
[0029] FIGS. 4-7 illustrate an external sensor reader that includes
a smartphone and a smartphone case in accordance with an embodiment
of the present invention. FIG. 4 illustrates a perspective view of
an exploded sensor reader in accordance with an embodiment of the
present invention.
[0030] FIGS. 5A and 5B illustrate perspective and side views,
respectively, of the sensor reader with the smartphone case
encasing the smartphone in accordance with an embodiment of the
present invention.
[0031] FIG. 6 illustrates a perspective view of the smartphone case
of the sensor reader without the smartphone in accordance with an
embodiment of the present invention.
[0032] FIG. 7 illustrates a perspective view of the sensor reader
with the smartphone case encasing the smartphone and the bottom
casing shown as transparent in accordance with an embodiment of the
present invention.
[0033] FIG. 8 illustrates an external sensor reader that includes a
smartphone and an adapter in accordance with an embodiment of the
present invention.
[0034] FIG. 9 illustrates an external sensor reader that is a
dedicated reader device in accordance with an embodiment of the
present invention.
[0035] FIG. 10 illustrates an external sensor reader that is an
adaptable reader device in accordance with an embodiment of the
present invention.
[0036] FIG. 11A is a schematic, section view illustrating a sensor
embodying aspects of the present invention.
[0037] FIGS. 11B and 11C illustrate perspective views of a sensor
embodying aspects of the present invention.
[0038] FIG. 11D is block diagram illustrating the functional blocks
of the circuitry of a sensor according to an embodiment in which
the circuitry is fabricated in the semiconductor substrate.
[0039] FIG. 12 illustrates an alternative embodiment of a sensor
embodying aspects of the present invention.
[0040] FIG. 13 is a block diagram illustrating functional blocks of
the circuitry of an external sensor reader according to an
embodiment of the present invention.
[0041] FIGS. 14A-14C illustrate a user using an external sensor
reader according to an embodiment of the present invention.
[0042] FIG. 15 illustrates an exemplary sensor reader control
process that may be performed by the sensor reader in accordance
with an embodiment of the present invention.
[0043] FIG. 16 illustrates an exemplary sensor control process that
may be performed by the sensor in accordance with an embodiment of
the present invention.
[0044] FIG. 17 illustrates a measurement command execution process
that may be performed by the sensor to execute a measurement
command received by the sensor in accordance with an embodiment of
the present invention.
[0045] FIG. 18 illustrates a measurement and conversion process
that may be performed in a step of the measurement command
execution process, in accordance with an embodiment of the present
invention.
[0046] FIG. 19 illustrates a get result command execution process
that may be performed by the sensor to execute a get result command
received by the sensor in accordance with an embodiment of the
present invention.
[0047] FIG. 20 illustrates a get identification information command
execution process that may be performed by the sensor to execute a
get identification information command received by the sensor in
accordance with an embodiment of the present invention.
[0048] FIGS. 21A and 21B illustrate the timing of an exemplary
embodiment of a measurement and conversion process in accordance
with an embodiment of the present invention.
[0049] FIG. 22 illustrates an alternative sensor control process
that may be performed by the sensor in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] FIG. 1 is a schematic view of a sensor system embodying
aspects of the present invention. In one non-limiting embodiment,
the system includes a sensor 100 and an external sensor reader 101.
In the embodiment shown in FIG. 1, the sensor 100 is implanted in a
living animal (e.g., a living human). The sensor 100 may be
implanted, for example, in a living animal's arm, wrist, leg,
abdomen, or other region of the living animal suitable for sensor
implantation. For example, as shown in FIG. 1, in one non-limiting
embodiment, the sensor 100 may be implanted between the skin 109
and subcutaneous tissues 111. In some embodiments, the sensor 100
may be an optical sensor. In some embodiments, the sensor 100 may
be a chemical or biochemical sensor.
[0051] A sensor reader 101 may be an electronic device that
communicates with the sensor 100 to power the sensor 100 and/or
obtain analyte (e.g., glucose) readings from the sensor 100 on
demand. In non-limiting embodiments, the reader 101 may be a
handheld reader. In one embodiment, positioning (i.e., hovering or
swiping/waiving/passing) the reader 101 within range over the
sensor implant site (i.e., within proximity of the sensor 100) will
cause the reader 101 to automatically convey a measurement command
to the sensor 100 and receive a reading from the sensor 100. The
reader 101 may subsequently be returned to a user's storage space,
such as, for example, a user's purse or pocket. In other
non-limiting embodiments, the reader may be stationary, for
example, with a simple loop (i.e., coil) through which a user
thrusts their wrist and a sensor 100 embedded therein. Thus, in
such embodiments, the stationary reader could sit on a table or
bathroom counter (or wherever) for occasional use by the user, and
the user could, for example, wake up each morning and move their
wrist through a coil while brushing their teeth.
[0052] In some embodiments, the sensor reader 101 may include a
transceiver 103, a processor 105 and/or a user interface 107. In
one non-limiting embodiment, the user interface 107 may include a
liquid crystal display (LCD), but, in other embodiments, different
types of displays may be used. In some embodiments, the transceiver
103 may include an inductive element, such as, for example, a coil.
The transceiver 103 may generate an electromagnetic wave or
electrodynamic field (e.g., by using a coil) to induce a current in
an inductive element (e.g., inductive element 114 of FIGS. 11A-11C)
of the sensor 100, which powers the sensor 100. The transceiver 103
may also convey data (e.g., commands) to the sensor 100. For
example, in a non-limiting embodiment, the transceiver 103 may
convey data by modulating the electromagnetic wave used to power
the sensor 100 (e.g., by modulating the current flowing through a
coil of the transceiver 103). The modulation in the electromagnetic
wave generated by the reader 101 may be detected/extracted by the
sensor 100 (e.g., by data extractor 642 of FIG. 11D). Moreover, the
transceiver 103 may receive data (e.g., measurement information)
from the sensor 100. For example, in a non-limiting embodiment, the
transceiver 103 may receive data by detecting modulations in the
electromagnetic wave generated by the sensor 100 (e.g., by
clamp/modulator 646 of FIG. 11D), e.g., by detecting modulations in
the current flowing through the coil of the transceiver 103.
[0053] The inductive element of the transceiver 103 and the
inductive element (e.g., inductive element 114 of FIGS. 11A-11C) of
the sensor 100 may be in any configuration that permits adequate
field strength to be achieved when the two inductive elements are
brought within adequate physical proximity. The inductive element
of the sensor 100 (i.e., the secondary inductive element), which
may comprise a coil (e.g., coil 220 of FIG. 11D), may be contained
within the sensor and may be a fixed element in alignment according
to the implantation of the sensor 100. FIGS. 2A-2C illustrate
examples of the inductive element of transceiver 103 (i.e., the
primary inductive element), which may comprise a coil (i.e., the
primary coil). FIG. 2A illustrates an example of a cylindrical
coil. FIG. 2B illustrates a square or rectangular coil. FIG. 2C
illustrates a FIG. 8 or planar coil. The transceiver may include a
coil in any of these configurations for alignment with the coil of
the sensor 100. Alternatively, the transceiver 103 may have any
coil with natural field alignment vectors sufficiently coaxial with
the secondary coil such that the primary and secondary coils
between the reader 101 and sensor 100, respectively, can achieve
adequate field strength within some physical proximity.
[0054] The primary coil configurations illustrated in FIGS. 2A-2C
(or other suitable primary coil configuration) may or may not have
ferrite cores. FIG. 3 illustrates a non-limiting embodiment of a
sensor 100 in alignment with an electromagnetic field emitted by
the inductive element 313 of transceiver 103. In the illustrated
embodiment, the inductive element 313 is a FIG. 8 or planar coil
having a substrate 315.
[0055] The sensor reader 101 may be capable of communicating with
other electronic devices, like smartphones or computers. In some
embodiments, the reader 101 may communicate with the sensor 100 in
less than one second (e.g., in approximately 10 milliseconds), and
a swiping motion of the sensor reader over the area where the
sensor was inserted may, therefore, be enough to obtain a
reading/measurement from the sensor 100. In some embodiments, the
sensor reader 101 may then communicate with, for example, a
computer, iPhone, or any other smartphone for display purposes. The
sensor reader 101 may have different embodiments and different ways
of communicating with other electronic devices. In one embodiment,
the sensor reader 101 may be a small container or box (or any
convenient form factor) carried in a bag, purse, or pocket (see
FIG. 9). In another embodiment, the sensor reader 101 can be
carried as a key fob or worn on a neck lanyard, or, as noted above,
the sensor reader 101 might sit on a table or a bathroom counter to
be operated and have a loop antenna into which a user transiently
inserts a body part (e.g., wrist) into which a sensor 100 has been
implanted. In these examples, the reader 101 could communicate
through Bluetooth or other wireless radio standard to a smartphone
or computer, or the sensor reader 101 could be physically connected
to the other electronic device through a pin or cable. In some
embodiments, the sensor reader 101 may be a smartphone case (see
FIGS. 4A-7E). The case may contain the same electronics as the
small container or box, and the case may either draw power from the
phone through a port connection or it can require separate
charging. The case may also communicate with the smartphone through
the same port connection. To obtain a glucose reading, the user may
simply swipe the encased smartphone over the sensor and the reading
would be displayed, for example, in the smartphone screen.
[0056] The sensor reader may communicate with and/or power the
implanted sensor, for example, through inductive coupling as
described in U.S. Pat. No. 7,553,280, which is incorporated by
reference herein in its entirety. In an embodiment of the present
invention, the implanted sensor 100 is passive and the sensor
reader 101 powers the sensor 100 through inductive coupling. In one
non-limiting embodiment, the internal sensor unit 100 may include a
secondary coil forming part of a power supply for the sensor unit,
a load coupled to said secondary coil, and a sensor circuit for
modifying said load in accordance with sensor measurement
information obtained by the sensor circuit. The swipe reader 101
may include a primary coil that is mutually inductively coupled to
the secondary coil upon the primary coil coming into a
predetermined proximity distance from said secondary coil, an
oscillator for driving said primary coil to induce a charging
current in said secondary coil, and a detector for detecting
variations in a load on the primary coil induced by changes to the
load in the internal sensor unit and for providing information
signals corresponding to the load changes.
[0057] In some non-limiting embodiments, the inductive element of
the transceiver 103 of the reader 101 may be a coil contained
within an adaptable reader device, such as a smartphone or tablet
(see FIG. 10), or the inductive element of the transceiver 103 may
be a part of an adapter or an add-on to such a device (see FIG. 8),
such as a cover for a smart phone type handheld (see FIGS. 4A-7E),
or a piggyback design connected by wireless protocol or cable, or
may be included in the design and construction of a dedicated
reader device (see FIG. 9) such as a smart phone, dedicated
handheld reader, wand, or adapter that will enable triggered
readings of an implanted sensor during transient proximal motion
within range.
[0058] In some embodiments, the processor 105 may output to the
transceiver 103 the data to be conveyed to the sensor 100 and may
receive from the transceiver 103 the data received from the sensor
100. In one embodiment, the processor 105 may serialize and encode
the data to be conveyed to the sensor 100 before outputting it to
the transceiver 103 for transmission. Similarly, the processor 105
may decode and/or serialize the data received from the sensor 100.
In some embodiments, the data received from the sensor 100 may be
measurement information, and the processor 105 may process the
measurement information to determine a concentration of an analyte.
However, in other embodiments, the sensor 100 may process the
measurement information to determine a concentration of an analyte,
and the data received from the sensor 100 may be the determined
concentration of the analyte. In some embodiments, the processor
105 may cause the user interface 107 to display a value
representing the concentration of the analyte so that a user (e.g.,
the patient, a doctor and/or others) can read the value. Also, in
some embodiments, the processor 105 may receive from the user
interface 107 user input (e.g., a user request for a sensor
reading, such as the concentration of an analyte). Furthermore, in
some embodiments, the sensor reader 101 may include one or more
input/output ports that enable transmission of data (e.g.,
traceability information and/or measurement information) and
receipt of data (e.g., sensor commands and/or setup parameters)
between the sensor reader 101 and another device (e.g., a computer
and/or smartphone).
[0059] FIGS. 4-7 illustrate a non-limiting embodiment of an
external sensor reader 101a that includes a smartphone 206 and an
adapter in the form of a smartphone case. FIG. 4 illustrates a
perspective view of an exploded sensor reader 101a. FIGS. 5A and 5B
illustrate perspective and side views, respectively, of the sensor
reader 101a with the smartphone case encasing the smartphone 206.
FIG. 6 illustrates a perspective view of the smartphone case of the
sensor reader 101a without the smartphone 206. FIG. 7 illustrates a
perspective view of the sensor reader 101a with the smartphone case
encasing the smartphone 206 and the bottom casing 202 shown as
transparent.
[0060] The smartphone 206 may act as the user interface (see user
interface 107 of FIG. 1) of sensor reader 101a. In addition, the
smartphone 206 may provide none, some, or all of the processing
functionality (see processor 105 of FIG. 1) of the sensor reader
101a. The smartphone case may have reading components 225 that may
act as the transceiver (see transceiver 103 of FIG. 1) and may
provide none, some, or all of the processing functionality (see
processor 105 of FIG. 1) of the sensor reader 101a.
[0061] The sensor reader 101a may be configured to read and/or
power an internal sensor (e.g., sensor 100) when swiped or moved
within a maximum distance, e.g., one inch, of the internal sensor.
The smartphone case may include a bottom casing 202 and a top
casing 204. The bottom casing 202 and top casing 204 may be
configured to encase the smartphone 206. In some embodiments, the
smartphone 206 may include a port 208, and the bottom casing 202
may include a coupling member or pin 210 configured to be inserted
into and couple with the port 208 of the smartphone 206. The
smartphone casing may be configured such that, when the pin 210 of
bottom casing 202 is coupled with the port 208 of the smartphone
206, the smartphone casing and the smartphone 206 can communicate
with each other. Additionally or alternatively, the smartphone
casing may be configured such that, when the pin 210 of bottom
casing 202 is coupled with the port 208 of the smartphone 206, the
smartphone 206 supplies power to the sensor reader 101a via the
port connection, i.e., via the pin 210 being inserted into the port
208.
[0062] In some embodiments of the present invention, the smartphone
206 may include a display 212. The display 212 can be configured to
display the analyte (e.g., glucose) measurements obtained from
sensor 100. In some embodiments of the present invention, the top
casing 204 may include openings 214 configured to allow the
interactive and functional features of the smartphone 206 (e.g.,
volume control, power button, and/or audio ports) to remain
unobstructed when the smartphone casing encases the smartphone 206.
In some non-limiting embodiments, the bottom casing 202 may include
a port 216 configured to receive a pin. The bottom casing port 216
can be used to communicate information to another electronic device
(e.g., a computer or different smartphone). In some embodiments,
the port 216 may also be used to allow electronic devices to
communicate with the smartphone 206.
[0063] In some embodiments of the present invention, the bottom
casing 202 may include a coupling member 218, and the top casing
204 may include a coupling member 221 (see FIG. 6). The coupling
members 218 and 221 may be configured to couple such that the
bottom casing 202 and the top casing 204 encase the smartphone 206.
In a non-limiting embodiment of the present invention, the bottom
casing coupling member 218 may be a protrusion, and the top casing
coupling member 221 may be an opening configured to receive the
bottom casing coupling member 218. The coupling members 218 and 221
may be configured to allow a user to couple and decouple the casing
from the smartphone 206 (i.e., the coupling members 218 and 221 do
not permanently couple).
[0064] In some embodiments, the bottom casing 202 may include the
circuitry and components for reading the sensor 100. The bottom
casing 202 may include a housing 223 and reading components 225, as
illustrated in FIG. 7. The reading components may include an
inductive element (e.g., a coil), an oscillator, and/or a detector.
Such reading components are described in further detail in U.S.
Pat. No. 7,553,280, which is incorporated by reference herein in
its entirety. In a non-limiting embodiment of the present
invention, the bottom casing 202 may additionally include a power
source, such as a battery.
[0065] FIG. 8 illustrates a non-limiting embodiment of an external
sensor reader 101b that includes a smartphone 304 and an adapter
302. Unlike the adapter of sensor reader 101a, the adapter 302 of
sensor reader 101b is not in the form of a smartphone case. The
adapter 302 of sensor reader 101b may be configured to couple to a
smartphone 304. The adapter 302 may include a pin, as described
above (see pin 210 of FIGS. 4A, 4E, 6A, and 6B), configured to
couple with a port of the smartphone 304. The adapter 302 may
include reading components (see reading components 225 of FIGS.
7A-7E) configured to read and/or power an internal sensor. The
smartphone 304 can include a display 306, which can display the
analyte values obtained from the sensor.
[0066] FIG. 9 illustrates a non-limiting embodiment of an external
sensor reader 101c that is a dedicated reader device, such as a
smart phone, dedicated handheld reader, wand, or adapter, that will
enable triggered readings of an implanted sensor 100 during
transient proximal motion within range. The dedicated reader device
may act as the user interface (see user interface 107 of FIG. 1)
and transceiver (see transceiver 103 of FIG. 1) of sensor reader
101c and may provide all of the processing functionality (see
processor 105 of FIG. 1) of the sensor reader 101c. Furthermore, in
a non-limiting embodiment, the sensor reader 101c may include one
or more input/output ports that enable transmission (e.g., via
wireless radio technology, such as Bluetooth low energy) of and
receipt of data (e.g., sensor commands and/or setup parameters)
between the sensor reader 101 and another device (e.g., a computer
and/or smartphone).
[0067] FIG. 10 illustrates a non-limiting embodiment of an external
sensor reader 101d that is an adaptable reader device, such as a
smartphone or tablet, having an inductive element (e.g., a coil)
contained within the adaptable reader device. The adaptable reader
device may act as the user interface (see user interface 107 of
FIG. 1) and transceiver (see transceiver 103 of FIG. 1) of sensor
reader 101d and may provide all of the processing functionality
(see processor 105 of FIG. 1) of the sensor reader 101d.
[0068] FIG. 11A is a schematic, section view of a sensor 100a,
which is an embodiment of the sensor embodying aspects of the
present invention. In some embodiments, the sensor 100 may be an
optical sensor. In one non-limiting embodiment, sensor 100 includes
a sensor housing 102. In exemplary embodiments, sensor housing 102
may be formed from a suitable, optically transmissive polymer
material, such as, for example, acrylic polymers (e.g.,
polymethylmethacrylate (PMMA)).
[0069] In the embodiment illustrated in FIG. 11A, the sensor 100
includes indicator molecules 104. Indicator molecules 104 may be
fluorescent indicator molecules or absorption indicator molecules.
In some non-limiting embodiments, sensor 100 may include a matrix
layer 106 coated on at least part of the exterior surface of the
sensor housing 102, with the indicator molecules 104 distributed
throughout the matrix layer 106. The matrix layer 106 may cover the
entire surface of sensor housing 102 or only one or more portions
of the surface of housing 102. Similarly, the indicator molecules
104 may be distributed throughout the entire matrix layer 106 or
only throughout one or more portions of the matrix layer 106.
Furthermore, as an alternative to coating the matrix layer 106 on
the outer surface of sensor housing 102, the matrix layer 106 may
be disposed on the outer surface of the sensor housing 102 in other
ways, such as by deposition or adhesion.
[0070] In the embodiment illustrated in FIG. 11A, the sensor 100
includes a light source 108, which may be, for example, a light
emitting diode (LED) or other light source, that emits radiation,
including radiation over a range of wavelengths that interact with
the indicator molecules 104.
[0071] In the embodiment illustrated in FIG. 11A, sensor 100 also
includes one or more photodetectors 110 (e.g., photodiodes,
phototransistors, photoresistors or other photosensitive elements)
which, in the case of a fluorescence-based sensor, is sensitive to
fluorescent light emitted by the indicator molecules 104 such that
a signal is generated by the photodetector 110 in response thereto
that is indicative of the level of fluorescence of the indicator
molecules and, thus, the amount of analyte of interest (e.g.,
glucose).
[0072] As illustrated in FIG. 11A, some embodiments of sensor 100
include one or more optical filters 112, such as high pass or band
pass filters, that may cover a photosensitive side of the one or
more photodetectors 110.
[0073] As shown in FIG. 11A, in some embodiments, sensor 100 may be
wholly self-contained. In other words, the sensor may be
constructed in such a way that no electrical leads extend into or
out of the sensor housing 102 to supply power to the sensor (e.g.,
for driving the light source 108) or to convey signals from the
sensor 100. Instead, in one embodiment, sensor 100 may be powered
by an external power source (e.g., external sensor reader 101). For
example, the external power source may generate a magnetic field to
induce a current in an inductive element 114 (e.g., a coil or other
inductive element). Additionally, the sensor 100 may use the
inductive element 114 to communicate information to an external
data reader (not shown). In some embodiments, the external power
source and data reader may be the same device.
[0074] In some embodiments, sensor 100 includes a semiconductor
substrate 116. In the embodiment illustrated in FIG. 11A, circuitry
is fabricated in the semiconductor substrate 116. The circuitry may
include analog and/or digital circuitry. Also, although in some
preferred embodiments the circuitry is fabricated in the
semiconductor substrate 116, in alternative embodiments, a portion
or all of the circuitry may be mounted or otherwise attached to the
semiconductor substrate 116. In other words, in alternative
embodiments, a portion or all of the circuitry may include discrete
circuit elements, an integrated circuit (e.g., an application
specific integrated circuit (ASIC)) and/or other electronic
components discrete and may be secured to the semiconductor
substrate 116, which may provide communication paths between the
various secured components.
[0075] In some embodiments, the one or more photodetectors 110 may
be mounted on the semiconductor substrate 116, but, in some
preferred embodiments, the one or more photodetectors 110 may be
fabricated in the semiconductor substrate 116. In some embodiments,
the light source 108 may be mounted on the semiconductor substrate
116. For example, in a non-limiting embodiment, the light source
108 may be flip-chip mounted on the semiconductor substrate 116.
However, in some embodiments, the light source 108 may be
fabricated in the semiconductor substrate 116.
[0076] As shown in the embodiment illustrated in FIG. 11A, in some
embodiments, the sensor 100 may include one or more capacitors 118.
The one or more capacitors 118 may be, for example, one or more
tuning capacitors and/or one or more regulation capacitors. The one
or more capacitors 118 may be too large for fabrication in the
semiconductor substrate 116 to be practical. Further, the one or
more capacitors 118 may be in addition to one or more capacitors
fabricated in the semiconductor substrate 116.
[0077] In some embodiments, the sensor 100 may include a reflector
(i.e., mirror) 119. As shown in FIG. 11A, reflector 119 may be
attached to the semiconductor substrate 116 at an end thereof. In a
non-limiting embodiment, reflector 119 may be attached to the
semiconductor substrate 116 so that a face portion 121 of reflector
119 is generally perpendicular to a top side of the semiconductor
substrate 116 (i.e., the side of semiconductor substrate 116 on or
in which the light source 108 and one or more photodetectors 110
are mounted or fabricated) and faces the light source 108. The face
121 of the reflector 119 may reflect radiation emitted by light
source 108. In other words, the reflector 119 may block radiation
emitted by light source 108 from entering the axial end of the
sensor 100.
[0078] According to one aspect of the invention, an application for
which the sensor 100 was developed--although by no means the only
application for which it is suitable--is measuring various
biological analytes in the living body of an animal (including a
human). For example, sensor 110 may be used to measure glucose,
oxygen, toxins, pharmaceuticals or other drugs, hormones, and other
metabolic analytes in, for example, the human body. The specific
composition of the matrix layer 104 and the indicator molecules 106
may vary depending on the particular analyte the sensor is to be
used to detect and/or where the sensor is to be used to detect the
analyte (i.e., in the blood or in subcutaneous tissues).
Preferably, however, matrix layer 104, if present, should
facilitate exposure of the indicator molecules to the analyte.
Also, it is preferred that the optical characteristics of the
indicator molecules (e.g., the level of fluorescence of fluorescent
indicator molecules) be a function of the concentration of the
specific analyte to which the indicator molecules are exposed.
[0079] FIGS. 11B and 11C illustrate perspective views of the sensor
100. In FIGS. 11B and 11C, the reflector 119, which may be included
in some embodiments of the sensor 100, is not illustrated. In the
embodiment illustrated in FIGS. 11B and 11C, the inductive element
114 comprises a coil 220. In one embodiment, coil 220 may be a
copper coil but other conductive materials, such as, for example,
screen printed gold, may alternatively be used. In some
embodiments, the coil 220 is formed around a ferrite core 222.
Although core 222 is ferrite in some embodiments, in other
embodiments, other core materials may alternatively be used. In
some embodiments, coil 220 is not formed around a core. Although
coil 220 is illustrated as a cylindrical coil in FIGS. 11B and 11C,
in other embodiments, coil 220 may be a different type of coil,
such as, for example, a flat coil.
[0080] In some embodiments, coil 220 is formed on ferrite core 222
by printing the coil 220 around the ferrite core 222 such that the
major axis of the coil 220 (magnetically) is parallel to the
longitudinal axis of the ferrite core 222. A non-limiting example
of a coil printed on a ferrite core is described in U.S. Pat. No.
7,800,078, which is incorporated herein in its entirety. In an
alternative embodiment, coil 220 may be a wire-wound coil. However,
embodiments in which coil 220 is a printed coil as opposed to a
wire-wound coil are preferred because each wire-wound coil is
slightly different in characteristics due to manufacturing
tolerances, and it may be necessary to individually tune each
sensor that uses a wire-wound coil to properly match the frequency
of operation with the associated antenna. Printed coils, by
contrast, may be manufactured using automated techniques that
provide a high degree of reproducibility and homogeneity in
physical characteristics, as well as reliability, which is
important for implant applications, and increases
cost-effectiveness in manufacturing.
[0081] In some embodiments, a dielectric layer may be printed on
top of the coil 220. The dielectric layer may be, in a non-limiting
embodiment, a glass based insulator that is screen printed and
fired onto the coil 220. In an exemplary embodiment, the one or
more capacitors 118 and the semiconductor substrate 116 may be
mounted on vias through the dielectric.
[0082] In the embodiment illustrated in FIGS. 11B and 11C, the one
or more photodetectors 110 include a first photodetector 224 and a
second photodetector 226. First and second photodetectors 224 and
226 may be mounted on or fabricated in the semiconductor substrate
116. In the embodiment illustrated in FIGS. 11B and 11C, sensor 100
may include one or more optical filters 112 even though they are
not shown.
[0083] FIG. 11D is block diagram illustrating the functional blocks
of the circuitry of sensor 100 according to a non-limiting
embodiment in which the circuitry is fabricated in the
semiconductor substrate 116. As shown in the embodiment of FIG.
11D, in some embodiments, an input/output (I/O) frontend block 536
may be connected to the external inductive element 114, which may
be in the form of a coil 220, through coil contacts 428a and 428b.
The I/O frontend block 536 may include a rectifier 640, a data
extractor 642, a clock extractor 644, clamp/modulator 646 and/or
frequency divider 648. Data extractor 642, clock extractor 644 and
clamp/modulator 646 may each be connected to external coil 220
through coil contacts 428a and 428b. The rectifier 640 may convert
an alternating current produced by coil 220 to a direct current
that may be used to power the sensor 100. For instance, the direct
current may be used to produce one or more voltages, such as, for
example, voltage VDD_A, which may be used to power the one or more
photodetectors 110. In one non-limiting embodiment, the rectifier
640 may be a Schottky diode; however, other types of rectifiers may
be used in other embodiments. The data extractor 642 may extract
data from the alternating current produced by coil 220. The clock
extractor 644 may extract a signal having a frequency (e.g., 13.56
MHz) from the alternating current produced by coil 220. The
frequency divider 648 may divide the frequency of the signal output
by the clock extractor 644. For example, in a non-limiting
embodiment, the frequency divider 648 may be a 4:1 frequency
divider that receives a signal having a frequency (e.g., 13.56 MHz)
as an input and outputs a signal having a frequency (e.g., 3.39
MHz) equal to one fourth the frequency of the input signal. The
outputs of rectifier 640 may be connected outputs of rectifier 640
may be connected to one or more external capacitors 118 (e.g., one
or more regulation capacitors) through contacts 428h and 428i.
[0084] In some embodiments, an I/O controller 538 may include a
decoder/serializer 650, command decoder/data encoder 652, data and
control bus 654, data serializer 656 and/or encoder 658. The
decoder/serializer 650 may decode and serialize the data extracted
by the data extractor 642 from the alternating current produced by
coil 220. The command decoder/data encoder 652 may receive the data
decoded and serialized by the decoder/serializer 650 and may decode
commands therefrom. The data and control bus 654 may receive
commands decoded by the command decoder/data encoder 652 and
transfer the decoded commands to the measurement controller 532.
The data and control bus 654 may also receive data, such as
measurement information, from the measurement controller 532 and
may transfer the received data to the command decoder/data encoder
652. The command decoder/data encoder 652 may encode the data
received from the data and control bus 654. The data serializer 656
may receive encoded data from the command decoder/data encoder 652
and may serialize the received encoded data. The encoder 658 may
receive serialized data from the data serializer 656 and may encode
the serialized data. In a non-limiting embodiment, the encoder 658
may be a Manchester encoder that applies Manchester encoding (i.e.,
phase encoding) to the serialized data. However, in other
embodiments, other types of encoders may alternatively be used for
the encoder 658, such as, for example, an encoder that applies
8B/10B encoding to the serialized data.
[0085] The clamp/modulator 646 of the I/O frontend block 536 may
receive the data encoded by the encoder 658 and may modulate the
current flowing through the inductive element 114 (e.g., coil 220)
as a function of the encoded data. In this way, the encoded data
may be conveyed wirelessly by the inductive element 114 as a
modulated electromagnetic wave. The conveyed data may be detected
by an external reading device by, for example, measuring the
current induced by the modulated electromagnetic wave in a coil of
the external reading device. Furthermore, by modulating the current
flowing through the coil 220 as a function of the encoded data, the
encoded data may be conveyed wirelessly by the coil 220 as a
modulated electromagnetic wave even while the coil 220 is being
used to produce operating power for the sensor 100. See, for
example, U.S. Pat. Nos. 6,330,464 and 8,073,548, which are
incorporated herein by reference in their entireties and which
describe a coil used to provide operative power to an optical
sensor and to wirelessly convey data from the optical sensor. In
some embodiments, the encoded data is conveyed by the sensor 100
using the clamp/modulator 646 at times when data (e.g., commands)
are not being received by the sensor 100 and extracted by the data
extractor 642. For example, in one non-limiting embodiment, all
commands may be initiated by an external sensor reader (e.g.,
sensor 1500 of FIG. 15) and then responded to by the sensor 100
(e.g., after or as part of executing the command). In some
embodiments, the communications received by the inductive element
114 and/or the communications conveyed by the inductive element 114
may be radio frequency (RF) communications. Although, in the
illustrated embodiments, the sensor 100 includes a single coil 220,
alternative embodiments of the sensor 100 may include two or more
coils (e.g., one coil for data transmission and one coil for power
and data reception).
[0086] In an embodiment, the I/O controller 538 may also include a
nonvolatile storage medium 660. In a non-limiting embodiment, the
nonvolatile storage medium 660 may be an electrically erasable
programmable read only memory (EEPROM). However, in other
embodiments, other types of nonvolatile storage media, such as
flash memory, may be used. The nonvolatile storage medium 660 may
receive write data (i.e., data to be written to the nonvolatile
storage medium 660) from the data and control bus 654 and may
supply read data (i.e., data read from the nonvolatile storage
medium 660) to the data and control bus 654. In some embodiments,
the nonvolatile storage medium 660 may have an integrated charge
pump and/or may be connected to an external charge pump. In some
embodiments, the nonvolatile storage medium 660 may store
identification information (i.e., traceability or tracking
information), measurement information and/or setup parameters
(i.e., calibration information). In one embodiment, the
identification information may uniquely identify the sensor 100.
The unique identification information may, for example, enable full
traceability of the sensor 100 through its production and
subsequent use. In one embodiment, the nonvolatile storage medium
660 may store calibration information for each of the various
sensor measurements.
[0087] In some embodiments, the analog interface 534 may include a
light source driver 662, analog to digital converter (ADC) 664, a
signal multiplexer (MUX) 666 and/or comparator 668. In a
non-limiting embodiment, the comparator 668 may be a transimpedance
amplifier, in other embodiments, different comparators may be used.
The analog interface 534 may also include light source 108, one or
more photodetectors 110 (e.g., first and second photodetectors 224
and 226) and/or a temperature transducer 670. In a non-limiting,
exemplary embodiment, the temperature transducer 670 may be a
band-gap based temperature transducer. However, in alternative
embodiments, different types of temperature transducers may be
used, such as, for example, thermistors or resistance temperature
detectors. Furthermore, like the light source 108 and one or more
photodetectors 110, in one or more alternative embodiments, the
temperature transducer 670 may be mounted on semiconductor
substrate 116 instead of being fabricated in semiconductor
substrate 116.
[0088] The light source driver 662 may receive a signal from the
measurement controller 532 indicating the light source current at
which the light source 108 is to be driven, and the light source
driver 662 may drive the light source 108 accordingly. The light
source 108 may emit radiation from an emission point in accordance
with a drive signal from the light source driver 662. The radiation
may excite indicator molecules 104 distributed throughout a matrix
layer 106 coated on at least part of the exterior surface of the
sensor housing 102. The one or more photodetectors 110 (e.g., first
and second photodetectors 224 and 226) may each output an analog
light measurement signal indicative of the amount of light received
by the photodetector. For instance, in the embodiment illustrated
in FIG. 11D, the first photodetector 224 may output a first analog
light measurement signal indicative of the amount of light received
by the first photodetector 224, and the second photodetector 226
may output a first analog light measurement signal indicative of
the amount of light received by the second photodetector 226. The
comparator 668 may receive the first and second analog light
measurement signals from the first and second photodetectors 224
and 226, respectively, and output an analog light difference
measurement signal indicative of the difference between the first
and second analog light measurement signals. The temperature
transducer 670 may output an analog temperature measurement signal
indicative of the temperature of the sensor 100. The signal MUX 666
may select one of the analog temperature measurement signal, the
first analog light measurement signal, the second analog light
measurement signal and the analog light difference measurement
signal and may output the selected signal to the ADC 664. The ADC
664 may convert the selected analog signal received from the signal
MUX 666 to a digital signal and supply the digital signal to the
measurement controller 532. In this way, the ADC 664 may convert
the analog temperature measurement signal, the first analog light
measurement signal, the second analog light measurement signal and
the analog light difference measurement signal to a digital
temperature measurement signal, a first digital light measurement
signal, a second digital light measurement signal and a digital
light difference measurement signal, respectively, and may supply
the digital signals, one at a time, to the measurement controller
532.
[0089] In some embodiments, the circuitry of sensor 100 fabricated
in the semiconductor substrate 116 may additionally include a clock
generator 671. The clock generator 671 may receive, as an input,
the output of the frequency divider 648 and generate a clock signal
CLK. The clock signal CLK may be used by one or more components of
one or more of the I/O fronted block 536, I/O controller 538,
measurement controller 532 and analog interface 534.
[0090] In a non-limiting embodiment, data (e.g., decoded commands
from the command decoder/data encoder 652 and/or read data from the
nonvolatile storage medium 660) may be transferred from the data
and control bus 654 of the I/O controller 538 to the measurement
controller 532 via transfer registers and/or data (e.g., write data
and/or measurement information) may be transferred from the
measurement controller 532 to the data and control bus 654 of the
I/O controller 538 via the transfer registers.
[0091] In some embodiments, the circuitry of sensor 100 may include
a field strength measurement circuit. In embodiments, the field
strength measurement circuit may be part of the I/O front end block
536, I/O controller 538, or the measurement controller 532 or may
be a separate functional component. The field strength measurement
circuit may measure the received (i.e., coupled) power (e.g., in
mWatts). The field strength measurement circuit of the sensor 100
may produce a coupling value proportional to the strength of
coupling between the inductive element 114 of the sensor 100 and
the inductive element of the external reader 101. For example, in
non-limiting embodiments, the coupling value may be a current or
frequency proportional to the strength of coupling. In some
embodiments, the field strength measurement circuit may
additionally determine whether the strength of coupling/received
power is sufficient to perform an analyte concentration measurement
and convey the results thereof to the external sensor reader 101.
For example, in some non-limiting embodiments, the field strength
measurement circuit may detect whether the received power is
sufficient to produce a certain voltage and/or current. In one
non-limiting embodiment, the field strength measurement circuit may
detect whether the received power produces a voltage of at least
approximately 3V and a current of at least approximately 0.5 mA.
However, other embodiments may detect that the received power
produces at least a different voltage and/or at least a different
current. In one non-limiting embodiment, the field strength
measurement circuit may compare the coupling value field strength
sufficiency threshold.
[0092] In the illustrated embodiment, the clamp/modulator 646 of
the I/O circuit 536 acts as the field strength measurement circuit
by providing a value (e.g., I.sub.couple) proportional to the field
strength. The field strength value I.sub.couple may be provided as
an input to the signal MUX 666. When selected, the MUX 666 may
output the field strength value I.sub.couple to the ADC 664. The
ADC 664 may convert the field strength value I.sub.couple received
from the signal MUX 666 to a digital field strength value signal
and supply the digital field strength signal to the measurement
controller 532. In this way, the field strength measurement may be
made available to the measurement controller 532 for use in
initiating an analyte measurement command trigger based on dynamic
field alignment. However, in an alternative embodiment, the field
strength measurement circuit may instead be an analog oscillator in
the sensor 100 that sends a frequency corresponding to the voltage
level on a rectifier 640 back to the reader 101.
[0093] FIG. 12 is a schematic, section view illustrating sensor
100b, which is an alternative embodiment of the sensor 100. The
sensor can be an implanted biosensor, such as the optical based
biosensor described in U.S. Pat. No. 7,308,292, the disclosure of
which is incorporated by reference herein in its entirety. The
sensor 100b may operate based on the fluorescence of fluorescent
indicator molecules 104. As shown, sensor 100b may include a sensor
housing 102 that may be formed from a suitable, optically
transmissive polymer material. Sensor 100b may further include a
matrix layer 106 coated on at least part of the exterior surface of
the sensor housing 102, with fluorescent indicator molecules 104
distributed throughout the layer 106 (layer 106 can cover all or
part of the surface of housing 102). Sensor 100b may include a
radiation source 108, e.g., a light emitting diode (LED) or other
radiation source, that emits radiation, including radiation over a
range of wavelengths which interact with the indicator molecules
104. Sensor 100b also includes a photodetector 110 (e.g., a
photodiode, phototransistor, photoresistor or other photosensitive
element) which, in the case of a fluorescence-based sensor, is
sensitive to fluorescent light emitted by the indicator molecules
104 such that a signal is generated by the photodetector 110 in
response thereto that is indicative of the level of fluorescence of
the indicator molecules. Two photodetectors 110 are shown in FIG.
12 to illustrate that sensor 100b may have more than one
photodetector.
[0094] The sensor 100b may be powered by an external power source
such as the sensor reader 101 of the present invention. For
example, the external power source may generate a magnetic field to
induce a current in inductive element 114 (e.g., a copper coil or
other inductive element). Circuitry 166 may use inductive element
114 to communicate information to the sensor reader 101. Circuitry
166 may include discrete circuit elements, an integrated circuit
(e.g., an application specific integrated circuit (ASIC), and/or
other electronic components). The external power source and data
reader may be the same device.
[0095] In some embodiments, the circuitry 166 of sensor 100b may
include a field strength measurement circuit. The field strength
measurement circuit may measure the received (i.e., coupled) power
(e.g., in mWatts). The field strength measurement circuit of
circuitry 166 of sensor 100b may produce a coupling value
proportional to the strength of coupling between the inductive
element 114 of the sensor 100 and the inductive element of the
external reader 101. For example, in non-limiting embodiments, the
coupling value may be a current or frequency proportional to the
strength of coupling. In some embodiments, the field strength
measurement circuit may additionally determine whether the strength
of coupling is sufficient for the sensor to perform an analyte
concentration measurement and convey the results thereof to the
external sensor reader 101. For example, in some non-limiting
embodiments, the circuitry 166 of sensor 100b may detect whether
the strength of coupling is sufficient to produce a certain voltage
and/or current. In one non-limiting embodiment, the field strength
measurement circuit may compare the coupling value field strength
sufficiency threshold.
[0096] In some embodiments, the external sensor reader 101 may
include a field strength measurement circuit instead of (or in
addition to) having a field strength measurement circuit in the
sensor. FIG. 13 illustrates one non-limiting embodiment of an
external sensor reader 101 having a field strength measurement
circuit. As illustrated in FIG. 13, the external sensor 101 may
include an inductive element (e.g., coil) 1302, power amplifier
1304, and a counter 1306, and the sensor 100 may include an
inductive element (e.g., coil) 220, rectifier and power regulator
640, clamp/modulator 646, rectifier capacitor C.sub.Rectifier
master reset block 1308, power on reset block 1310, and initiate
modulation block 1312. The counter 1306 may act as a field strength
measurement circuit by counting/detecting the amount of time
between when the reader 101 begins supplying power (i.e., generates
an electrodynamic field) and when the sensor 101 conveys a response
communication (e.g., by modulating the electrodynamic field), which
is detected/decoded by the external reader 101. The longer it takes
for the response communication to be conveyed, the lower the field
strength. In this way the counter 1306 may produce a value
proportional to the strength of coupling of the inductive element
1302 of the external reader 101 and the inductive element 220 of
the sensor 100. In some embodiments, the value may be the count or
a current or voltage based on the count.
[0097] In the illustrated embodiment, once the reader 101 begins
supplying power, a sensor 100 within the electrodynamic field may
begin to build charge in the rectifier capacitor C.sub.Rectifier.
Once a certain amount (i.e., the reset charge level) of charge is
built up, the master reset block 1308 may reset the sensor 101.
Subsequently, the power on reset block 1310 may start up the sensor
100, and the initiate modulate block 1312 may cause a response
communication to be conveyed to the reader 101 via the
clamp/modulator 646. The strength of the coupling of the inductive
element 1302 of the external reader 101 and the inductive element
220 of the sensor 100 determines the amount of time it takes for
the rectifier capacitor C.sub.Rectifier to charge up to the reset
charge level, which determines the length of time it takes for the
sensor 101 to convey a response communication to the reader 101.
After receiving the response communication, the sensor reader 101
may stop supplying power.
[0098] In some embodiments, the reader 101 may use the value
proportional to the strength of coupling produced by the counter
1306 to determine whether the strength of coupling is sufficient
for the sensor 100 to perform an analyte measurement and to convey
the result back to the reader 101.
[0099] FIGS. 14A-14C illustrate a user using a handheld external
sensor reader 101 according to an embodiment of the present
invention. The user moves or swipes the sensor reader 101 within a
distance, e.g., six inches, of the internal sensor 100, as shown in
FIG. 14B. When the sensor reader 101 is moved within the proximity
of the sensor 100, and the strength of the electrodynamic field
emitted by the inductive element of the sensor reader 101 and
received by the inductive element of the sensor 100 is sufficient
for the sensor 100 to perform an analyte measurement, the sensor
reader 101 may convey an analyte measurement command to the sensor
100, which executes the analyte measurement command and conveys the
analyte measurement information to the sensor reader 101. The
sensor reader 101 may use the analyte measurement information to
display information representing the concentration of the analyte
in a medium within a living animal using the user interface 107 of
the sensor reader 101.
[0100] In one non-limiting embodiment, the measurement controller
532 of the sensor 100 may iteratively compare the value
proportional to the coupling strength (e.g., I.sub.couple) as an
indicator of relative field strength, and, when the value meets or
exceeds a threshold value such that the reader and sensor are
sufficiently coupled within the field to successfully exchange
power and data, the measurement controller 532 may issue a command
to the reader to take an analyte reading/measurement, which is the
motion transient trigger event. Following a successful reading, the
system may reset.
[0101] FIG. 15 illustrates an exemplary sensor reader control
process 1500 that may be performed by the sensor reader 101 in
accordance with an embodiment of the present invention. The sensor
reader control process 1500 may begin with a step 1502 of coupling
the inductive element of the external reader 101 and the inductive
element 114 of the sensor 100 within an electrodynamic field. In
one embodiment, the sensor reader 101 may generate an
electrodynamic field via an inductive element of the transceiver
103 of the sensor reader 101 and may, thereby supply power to a
sensor 100 coupled within the electrodynamic field. In one
non-limiting embodiment, the coupling may comprise moving the
sensor 100 and the external reader 101 relative to each other such
that the inductive element of the external reader 101 and the
inductive element 114 of the sensor 100 are coupled within the
electrodynamic field.
[0102] In step 1504, the sensor reader 101 may generate field
strength data. In some embodiments, the reader 101 may generate the
field strength data by producing a coupling value proportional to
the strength of the coupling of the inductive element of the
external reader 101 and the inductive element 114 of the sensor
100. In one non-limiting embodiment, the coupling value may be
produced, for example, by the counter 1306 of the reader 101.
[0103] In other embodiments, the sensor 100 may produce the
coupling value proportional to the strength of the coupling of the
inductive element of the external reader 101 and the inductive
element 114 of the sensor 100 and may convey the coupling value to
the reader 101 (e.g., by modulating the electrodynamic field in
accordance with the coupling value). In these embodiments, the
reader 101 may generate the field strength data by decoding
coupling value conveyed by the sensor 100. In some embodiments, the
sensor 100 may convert (e.g., via ADC 664) the coupling value to a
digital coupling value before conveying it to the reader 101. In
some embodiments, the sensor 100 may additionally or alternatively
convey an indication that the strength of the electrodynamic field
received by the sensor 100 is either sufficient or insufficient for
the sensor 100 to perform the analyte measurement and convey the
analyte measurement results to the reader 101.
[0104] In step 1506, the sensor reader 101 may determine whether
the strength of the electrodynamic field received by the sensor 100
is sufficient for the sensor 100 to perform an analyte measurement
based on the received field strength data. In some non-limiting
embodiments, step 1506 may be performed by the processor 105 of the
sensor reader 101. In some non-limiting embodiments, the processor
105 of the sensor reader 101 may determine whether the strength of
the electrodynamic field received by the sensor 100 is sufficient
by comparing the value proportional to the strength of the
electrodynamic field to an analyte measurement field strength
sufficiency threshold. In other embodiments, the processor 105 of
the sensor reader 101 may determine whether the strength of the
electrodynamic field received by the sensor 100 is sufficient based
on an indication conveyed from the sensor 100 that the strength of
the electrodynamic field received by the implanted sensor 100 is
either sufficient or insufficient.
[0105] If the sensor reader 101 determines that the strength of the
electrodynamic field received by the sensor 100 is insufficient for
the sensor 100 to perform an analyte concentration measurement and
convey the results thereof, the sensor reader control process 1500
may return to step 1504 to receive generate additional field
strength data. In some non-limiting embodiments, if the sensor
reader 101 determines that the strength of the electrodynamic field
received by the sensor 100 is insufficient for the sensor 100 to
perform an analyte measurement, the sensor reader 101 may notify
the user that the strength of the electrodynamic field received by
the sensor 100 is insufficient. For example, the user may be
notified by using the user interface 107 of the sensor reader 101.
In some non-limiting embodiments, the user interface 107 of the
sensor reader 101 may display a signal strength indicator whenever
the field strength data is available. In a non-limiting embodiment,
the sensor reader 101 may display the value proportional to the
strength of the electrodynamic field, in an indication (e.g., a
percentage, ratio, or bars) of the strength of the electrodynamic
field received by the sensor 100 relative to the received strength
that would be sufficient for the sensor 100 to perform an analyte
measurement.
[0106] If the sensor reader 101 determines that the strength of the
electrodynamic field received by the sensor 100 is sufficient for
the sensor 100 to perform an analyte measurement, in step 1508, the
sensor reader 101 may automatically convey an analyte measurement
command and power to the sensor 100. In a non-limiting embodiment,
the sensor reader 101 may additionally or alternatively convey
other types of commands. In some embodiments, the sensor reader 101
may convey the analyte measurement command by modulating the
electrodynamic field using the inductive element of the transceiver
103 of the sensor reader 101.
[0107] In step 1510, the sensor reader 101 may decode analyte
measurement information conveyed from the sensor 100. The analyte
measurement information may be received using the inductive element
of the transceiver 103 of the sensor reader 101, and the analyte
measurement information may be decoded from modulation of the
electrodynamic field. In a non-limiting embodiment, the user
interface 107 of the sensor reader 101 may notify the user that the
analyte measurement information was successfully received. In some
non-limiting embodiments, the processor 105 of the sensor reader
101 may subsequently process the received analyte measurement
information to determine a concentration of an analyte, and the
user interface 107 may display a value representing the
concentration of the analyte so that a user (e.g., the patient, a
doctor and/or others) can read the value.
[0108] FIG. 16 illustrates an exemplary sensor control process 1600
that may be performed by the sensor 100, which may be, for example,
implanted within a living animal (e.g., a living human), in
accordance with an embodiment of the present invention. The sensor
control process 1600 may begin with a step 1602 of coupling the
inductive element of the external reader 101 and the inductive
element 114 of the sensor 100 within an electrodynamic field. The
sensor 100 may use the electrodynamic field to generate operational
power. In one embodiment, the electrodynamic field may induce a
current in inductive element 114 of sensor 100, and the
input/output (I/O) front end block 536 may convert the induced
current into power for operating the sensor 100. In a non-limiting
embodiment, rectifier 640 may be used to convert the induced
current into operating power for the sensor 100.
[0109] In step 1604, circuitry of the sensor 100 may produce a
coupling value proportional to the strength of the coupling of the
inductive element of the external reader 101 and the inductive
element 114 of the sensor 100. In some non-limiting embodiments,
the clamp/modulator 646 of the I/O circuit 536 may produce a
coupling value (e.g., I.sub.couple) proportional to the strength of
coupling based on the current induced in the inductive element 114
by the electrodynamic field. In one non-limiting embodiment, the
coupling value I.sub.couple proportional to the field strength may
be converted (e.g., by ADC 664) to a digital coupling value
proportional to the received field strength.
[0110] In some non-limiting embodiments, the coupling value may be
used by the sensor 100 to determine whether the strength of the
electrodynamic field received by the sensor 100 is sufficient for
the sensor 100 to perform an analyte measurement. For instance, in
one non-limiting embodiment, the measurement controller 532 may
compare the coupling value to an analyte measurement field strength
sufficiency threshold and produce an indication that the strength
of the electrodynamic field received by the sensor is either
sufficient or insufficient for the implanted sensor to perform the
analyte measurement.
[0111] In step 1606, the sensor 100 may convey the analog or
digital coupling value to the sensor reader 101 (e.g., by
modulating the electrodynamic field). In one embodiment, the
measurement controller 532 may output the digital coupling value to
the data and control bus 654. The data and control bus 654 may
transfer the digital coupling value to the command decoder/data
encoder 652, which may encode the digital coupling value. The data
serializer 656 may serialize the encoded digital coupling value.
The encoder 658 may encode the serialized digital coupling value.
The clamp/modulator 646 may modulate the current flowing through
the inductive element 114 (e.g., coil 220) as a function of the
encoded digital coupling value. In this way, the encoded digital
coupling value may be conveyed by the inductive element 114 as a
modulated electromagnetic wave. In some embodiments, the encoded
digital coupling value conveyed by the sensor 100 may be decoded by
the sensor reader 101.
[0112] In step 1608, the sensor 100 may determine whether a command
has been decoded (e.g., from modulation of the electrodynamic
field). In one non-limiting embodiment, the I/O front end block 536
and I/O controller 538 may convert the induced current into power
for operating the sensor 100 and extract and decode any received
commands from the induced current. In a non-limiting embodiment,
rectifier 640 may be used to convert the induced current into
operating power for the sensor 100, data extractor 642 may extract
data from the current induced in inductive element 114,
decoder/serializer 650 may decode and serialize the extracted data,
and command decoder/data encoder 652 may decode one or more
commands from the decoded and serialized extracted data. Any
decoded commands may then be sent to measurement controller 532 via
the data and control bus 654. In some embodiments, the one or more
commands and power received by the sensor 100 may be transmitted by
the transceiver 103 of sensor reader 101.
[0113] If a command has not been decoded, the sensor control
process 1600 may return to step 1602. If a command has been
decoded, in step 1610, the sensor 100 may execute the decoded
command. For example, in one embodiment, the sensor 100 may execute
the decoded command under control of the measurement controller
532. Example command execution processes that may be performed by
the sensor 100 in step 1610 to execute the decoded commands are
described below with reference to FIGS. 17-20.
[0114] Examples of commands that may be received and executed by
the sensor 100 may include analyte measurement commands, get result
commands and/or get traceability information commands. Examples of
analyte measurement commands may include measure sequence commands
(i.e., commands to perform a sequence of measurements, and after
finishing the sequence, transmitting the resulting measurement
information), measure and save commands (i.e., commands to perform
a sequence of measurements and, after finishing the sequence,
saving the resulting measurement information without transmitting
the resulting measurement information) and/or single measurement
commands (i.e., commands to perform a single measurement). The
single measurement commands may be commands to save and/or transmit
the measurement information resulting from the single measurement.
The analyte measurement commands may or may not include setup
parameters (i.e., calibration information). Measurement commands
that do not have setup parameters may, for example, be executed
using stored setup parameters (e.g., in nonvolatile storage medium
660). Other analyte measurement commands, such as measurement
commands to both save and transmit the resulting measurement
information, are possible. The commands that may be received and
executed by the sensor 100 may also include commands to update the
stored the setup parameters. The examples of commands described
above are not exhaustive of all commands that may be received and
executed by the sensor 100, which may be capable of receiving and
executing one or more of the commands listed above and/or one or
more other commands.
[0115] FIG. 17 illustrates an analyte measurement command execution
process 1700 that may be performed in step 1610 of the sensor
control process 1600 by the sensor 100 to execute an analyte
measurement command received by the sensor 100 in accordance with
an embodiment of the present invention. In a non-limiting
embodiment, the analyte measurement command execution process 1700
may begin with a step 1702 of determining whether the field
strength is sufficient to execute the received measurement command.
In other words, in step 1702, the sensor 100 may determine whether
the electromagnetic field or wave that may induce a current in
inductive element 114 is strong enough to generate sufficient
operating power for execution of the decoded measurement command,
which, as described below, may include using light source 108 to
irradiate indicator molecules 104. In one embodiment, step 1702 may
be performed by a field strength measurement circuit, which may be
part of the measurement controller 532 or may be a separate
component of the circuitry 776 on the silicon substrate 116.
[0116] In some embodiments, if the sensor 100 determines in step
1702 that the field strength is insufficient to execute the
received measurement command, the analyte measurement command
execution process 1700 may proceed to a step 1704 in which the
sensor 100 may convey (e.g., by way of the input/output (I/O) front
end block 536, I/O controller 538, and inductive element 114) data
indicating that that the wirelessly received power is insufficient
to execute the received analyte measurement command. In some
embodiments, the insufficient power data may merely indicate that
the power is insufficient, but in other embodiments, the
insufficient power data may indicate the percentage of the power
needed to execute the received measurement command that is
currently being received.
[0117] In one embodiment, upon detection that the received power is
insufficient, the measurement controller 532 may output
insufficient power data to the data and control bus 654. The data
and control bus 654 may transfer the insufficient power data to the
command decoder/data encoder 652, which may encode the insufficient
power data. The data serializer 656 may serialize the encoded
insufficient power data. The encoder 658 may encode the serialized
insufficient power data. The clamp/modulator 646 may modulate the
current flowing through the inductive element 114 (e.g., coil 220)
as a function of the encoded insufficient power data. In this way,
the encoded insufficient power data may be conveyed by the
inductive element 114 as a modulated electromagnetic wave. In some
embodiments, the encoded insufficient power data conveyed by the
sensor 100 may be received by the sensor reader 101, which may
display a message on user interface 107 a message indicating that
the power received by the sensor 100 is insufficient and/or the
extent to which the received power is insufficient.
[0118] In some alternative embodiments, steps 1702 and 1704 are not
performed, and the sensor 100 assumes that, if an analyte
measurement command has been decoded, the field strength is
sufficient.
[0119] In step 1706 in which a measurement and conversion process
may be performed. The measurement and conversion process may, for
example, be performed by the analog interface 534 under control of
the measurement controller 532. In one embodiment, the measurement
and conversion sequence may include generating one or more analog
measurements (e.g., using one or more of temperature transducer
670, light source 108, first photodetector 224, second
photodetector 226 and/or comparator 668) and converting the one or
more analog measurements to one or more digital measurements (e.g.,
using ADC 664). One example of the measurement conversion process
that may be performed in step 1706 is described in further detail
below with reference to FIG. 18.
[0120] At step 1708, the sensor 100 may generate measurement
information in accordance with the one or more digital measurements
produced during the measurement and conversion sequence performed
in step 1706. Depending on the one or more digital measurements
produced in step 1706, the measurement information may be
indicative of the presence and/or concentration of an analyte in a
medium in which the sensor 100 is implanted. In one embodiment, in
step 1706, the measurement controller 532 may receive the one or
more digital measurements and generate the measurement
information.
[0121] At step 1710, the sensor 100 may determine whether the
analyte measurement information generated in step 1708 should be
saved. In some embodiments, the measurement controller 532 may
determine whether the analyte measurement information should be
saved. In one embodiment, the measurement controller 532 may
determine whether the measurement information should be saved based
on the received measurement command. For example, if the analyte
measurement command is a measure and save command or other
measurement command that includes saving the resulting measurement
information, the measurement controller 532 may determine that the
analyte measurement information generated in step 1708 should be
saved. Otherwise, if the analyte measurement command is a measure
sequence command or other analyte measurement command that does not
include saving the resulting measurement information, the
measurement controller 532 may determine that the analyte
measurement information generated in step 1708 should not be
saved.
[0122] In some embodiments, if the sensor 100 determines in step
1710 that the analyte measurement information generated in step
1708 should be saved, the analyte measurement command execution
process 1700 may proceed to a step 1712 in which the sensor 100 may
save the measurement information. In one embodiment, after
determining that the analyte measurement information generated in
step 1708 should be saved, the measurement controller 532 may
output the analyte measurement information to the data and control
bus 654, which may transfer the analyte measurement information to
the nonvolatile storage medium 660. The nonvolatile storage medium
660 may save the received analyte measurement information. In some
embodiments, the measurement controller 532 may output, along with
the analyte measurement information, an address at which the
measurement information is to be saved in the nonvolatile storage
medium 660. In some embodiments, the nonvolatile storage medium 660
may be configured as a first-in-first-out (FIFO) or
last-in-first-out (LIFO) memory.
[0123] In some embodiments, if the sensor 100 determines in step
1710 that the analyte measurement information generated in step
1708 should not be saved, or after saving the analyte measurement
information in step 1712, the analyte measurement command execution
process 1700 may proceed to a step 1714 in which the sensor 100 may
determine whether the analyte measurement information generated in
step 1708 should be conveyed. In some embodiments, the measurement
controller 532 may determine whether the measurement information
should be transmitted. In one embodiment, the measurement
controller 532 may determine whether the measurement information
should be conveyed based on the received measurement command. For
example, if the analyte measurement command is a measure sequence
command or other measurement command that includes transmitting the
resulting measurement information, the measurement controller 532
may determine that the measurement information generated in step
1708 should be conveyed. Otherwise, if the analyte measurement
command is a measure and save command or other measurement command
that does not include conveying the resulting analyte measurement
information, the measurement controller 532 may determine that the
analyte measurement information generated in step 1708 should not
be conveyed.
[0124] In some embodiments, if the sensor 100 determines in step
1714 that the analyte measurement information generated in step
1708 should be conveyed, the analyte measurement command execution
process 1700 may proceed to a step 1716 in which the sensor 100 may
convey the analyte measurement information. In one embodiment,
after determining that the measurement information generated in
step 1708 should be convey, the measurement controller 532 may
output the measurement information to the data and control bus 654.
The data and control bus 654 may transfer the analyte measurement
information to the command decoder/data encoder 652, which may
encode the measurement information. The data serializer 656 may
serialize the encoded measurement information. The encoder 658 may
encode the serialized measurement information. The clamp/modulator
646 may modulate the current flowing through the inductive element
114 (e.g., coil 220) as a function of the encoded measurement
information. In this way, the encoded measurement information may
be transmitted wirelessly by the inductive element 114 as a
modulated electromagnetic wave. In some embodiments, the encoded
measurement information wirelessly transmitted by the sensor 100
may be received by the sensor reader 101, which may display a value
representing the concentration of the analyte so that a user (e.g.,
the patient, a doctor and/or others) can read the value.
[0125] In some embodiments, after the sensor 100 (a) conveyed
insufficient power data in step 1704, (b) determined in step 1714
that the measurement information generated in step 1708 should not
be conveyed or (c) conveyed measurement information in step 1716,
the analyte measurement command execution process 1700 that may be
performed in step 1610 of the sensor control process 1600 by the
sensor 100 to execute an analyte measurement command received by
the sensor 100 may be completed, and, at this time, the sensor
control process 1600 may return to step 1602.
[0126] In some alternative embodiments, steps 1710, 1712, and 1714
are not performed, and the sensor 100 proceeds directly to step
1710 to convey the analyte measurement information after completing
the measurement information generation in step 1708.
[0127] FIG. 18 illustrates a measurement and conversion process
1800, which is an example of the measurement and conversion process
that may be performed in step 1706 of the analyte measurement
command execution process 1700, in accordance with an embodiment of
the present invention.
[0128] At step 1802, the sensor 100 may load setup parameters
(i.e., calibration information) for performing one or more
measurements in accordance with the received measurement command.
For example, in one embodiment, the measurement controller 532 may
load one or more setup parameters by setting up one or more
components (e.g., light source 108, first photodetector 224, second
photodetector 226, comparator 668 and/or temperature transducer
534) of the analog interface 534 with the setup parameters. In some
embodiments, the nonvolatile storage medium 660 may store saved
setup parameters. Further, as noted above, in some embodiments, the
measurement commands may or may not include setup parameters. In a
non-limiting embodiment, if the measurement command includes one or
more setup parameters, the measurement controller 532 may setup one
or more components of the analog interface 534 with the setup
parameters with the one or more setup parameters included in the
measurement command. However, if the measurement command does not
include one or more setup parameters, the measurement controller
532 may obtain saved setup parameters stored in the nonvolatile
storage medium 660 and setup one or more components of the analog
interface 534 with the saved setup parameters obtained from the
nonvolatile storage medium 660.
[0129] At step 1804, the sensor 100 may determine whether to
execute a single measurement or a measurement sequence. In some
embodiments, the measurement controller 532 may make the single
measurement vs. measurement sequence determination by referring to
the received measurement command (i.e., is the measurement command
to execute a single measurement or to execute a measurement
sequence?). For example, in some embodiments, if the measurement
command is a measure sequence command, a measure and save command
or other command for a measurement sequence, the measurement
controller 532 may determine that a measurement sequence should be
executed. However, if the measurement command is a single
measurement command, the measurement controller 532 may determine
that a single measurement should be executed.
[0130] In some embodiments, if the sensor 100 determines in step
1804 that a measurement sequence should be performed, the sensor
100 may perform measurement and conversion sequence steps 1806-1820
of measurement and conversion process 1800. However, in other
embodiments, the sensor 100 may perform a portion of measurement
and conversion sequence steps 1806-1820 and/or additional
measurement and conversion sequence steps.
[0131] At step 1806, the sensor 100 may perform a light source bias
measurement and conversion. For example, in some embodiments, while
the light source 108 is on (i.e., while the light source 108, under
the control of the measurement controller 532, is emitting
excitation light and irradiating indicator molecules 104), the
analog interface 534 may generate an analog light source bias
measurement signal. In one embodiment, the ADC 664 may convert the
analog light source bias measurement signal to a digital light
source bias measurement signal. The measurement controller 532 may
receive the digital light source bias measurement signal and
generate (e.g., in step 1708 of the measurement command execution
process 1700) the measurement information in accordance with the
received digital light source bias measurement signal. In a
non-limiting embodiment, the analog interface 534 may generate the
analog light source bias measurement signal by sampling the voltage
and the current in the output of the current source that feeds the
light source 108.
[0132] At step 1808, the sensor 100 may perform a light source-on
temperature measurement and conversion. For example, in some
embodiments, while the light source 108 is on (i.e., while the
light source 108, under the control of the measurement controller
532, is emitting excitation light and irradiating indicator
molecules 104), the analog interface 534 may generate a first
analog temperature measurement signal indicative of a temperature
of the sensor 100. In one embodiment, the temperature transducer
670 may generate the first analog temperature measurement signal
while the light source 108 is on. The ADC 664 may convert the first
analog temperature measurement signal to a first digital
temperature measurement signal. The measurement controller 532 may
receive the first digital temperature measurement signal and
generate (e.g., in step 1708 of the measurement command execution
process 1700) the measurement information in accordance with the
received first digital temperature measurement signal.
[0133] At step 1810, the sensor 100 may perform a first
photodetector measurement and conversion. For example, in some
embodiments, while the light source 108 is on (i.e., while the
light source 108, under the control of the measurement controller
532, is emitting excitation light and irradiating indicator
molecules 104), the first photodetector 224 may generate a first
analog light measurement signal indicative of the amount of light
received by the first photodetector 224 and output the first analog
light measurement signal to the signal MUX 666. The signal MUX 666
may select the first analog light measurement signal and, the ADC
664 may convert the first analog light measurement signal to a
first digital light measurement signal. The measurement controller
532 may receive the first digital light measurement signal and
generate (e.g., in step 1708 of the measurement command execution
process 1700) the measurement information in accordance with the
received first digital light measurement signal.
[0134] In a non-limiting embodiment, first photodetector 224 may be
a part of a signal channel, the light received by the first
photodetector 224 may be emitted by indicator molecules 104
distributed throughout the indicator membrane 106', and the first
analog light measurement signal may be an indicator
measurement.
[0135] At step 1812, the sensor 100 may perform a second
photodetector measurement and conversion. For example, in some
embodiments, while the light source 108 is on (i.e., while the
light source 108, under the control of the measurement controller
532 is emitting excitation light and irradiating indicator
molecules 104), the second photodetector 226 may generate a second
analog light measurement signal indicative of the amount of light
received by the second photodetector 226 and output the second
analog light measurement signal to the signal MUX 666. The signal
MUX 666 may select the second analog light measurement signal and,
the ADC 664 may convert the second analog light measurement signal
to a second digital light measurement signal. The measurement
controller 532 may receive the second digital light measurement
signal and generate (e.g., in step 1708 of the measurement command
execution process 1700) the measurement information in accordance
with the received second digital light measurement signal.
[0136] In a non-limiting embodiment, second photodetector 226 may
be a part of a reference channel, the light received by the second
photodetector 226 may be emitted by indicator molecules 104
distributed throughout the reference membrane 106'', and the second
analog light measurement signal may be a reference measurement.
[0137] At step 1814, the sensor 100 may perform a difference
measurement and conversion. For example, in some embodiments, while
the light source 108 is on (i.e., while the light source 108, under
the control of the measurement controller 532, is emitting
excitation light and irradiating indicator molecules 104), (i) the
first photodetector 224 may generate a first analog light
measurement signal indicative of the amount of light received by
the first photodetector 224, and (ii) the second photodetector 226
may generate a second analog light measurement signal indicative of
the amount of light received by the second photodetector 226. The
comparator 668 may receive the first and second analog light
measurement signals and generate an analog light difference
measurement signal indicative of a difference between the first and
second analog light measurement signals. The comparator 668 may
output the analog light difference measurement signal to the signal
MUX 666. The signal MUX 666 may select the analog light difference
measurement signal and, the ADC 664 may convert the analog light
difference measurement signal to a digital light difference
measurement signal. The measurement controller 532 may receive the
digital light difference measurement signal and generate (e.g., in
step 1708 of the measurement command execution process 1700) the
measurement information in accordance with the received digital
light difference measurement signal.
[0138] In a non-limiting embodiment, first photodetector 224 may be
a part of a signal channel, second photodetector 226 may be a part
of a reference channel, and the analog light difference measurement
signal may be indicative of the difference in light emitted by (a)
indicator molecules 104 distributed throughout indicator membrane
106' and affected by the concentration of an analyte in the medium
in which sensor 100 is implanted, and (b) indicator molecules 104
distributed throughout reference membrane 106'' and unaffected by
the concentration of the analyte in the medium in which sensor 100
is implanted.
[0139] At step 1816, the sensor 100 may perform a second
photodetector ambient measurement and conversion. For example, in
some embodiments, while the light source 108 is off (i.e., while
the light source 108, under the control of the measurement
controller 532 is not emitting light), the second photodetector 226
may generate a second analog ambient light measurement signal
indicative of the amount of light received by the second
photodetector 226 and output the second analog ambient light
measurement signal to the signal MUX 666. The signal MUX 666 may
select the second analog ambient light measurement signal and, the
ADC 664 may convert the second analog ambient light measurement
signal to a second digital ambient light measurement signal. The
measurement controller 532 may receive the second digital ambient
light measurement signal and generate (e.g., in step 1708 of the
measurement command execution process 1700) the measurement
information in accordance with the received second digital ambient
light measurement signal.
[0140] In a non-limiting embodiment, second photodetector 226 may
be a part of a reference channel, the light received by the second
photodetector 226 may be emitted by indicator molecules 104
distributed throughout the reference membrane 106'', and the second
analog ambient light measurement signal may be an ambient reference
measurement.
[0141] At step 1818, the sensor 100 may perform a first
photodetector ambient measurement and conversion. For example, in
some embodiments, while the light source 108 is off (i.e., while
the light source 108, under the control of the measurement
controller 532, is not emitting light), the first photodetector 224
may generate a first analog ambient light measurement signal
indicative of the amount of light received by the first
photodetector 224 and output the first analog ambient light
measurement signal to the signal MUX 666. The signal MUX 666 may
select the first analog ambient light measurement signal and, the
ADC 664 may convert the first analog ambient light measurement
signal to a first digital ambient light measurement signal. The
measurement controller 532 may receive the first digital ambient
light measurement signal and generate (e.g., in step 1708 of the
measurement command execution process 1700) the measurement
information in accordance with the received first digital ambient
light measurement signal.
[0142] In a non-limiting embodiment, first photodetector 224 may be
a part of a signal channel, the light received by the first
photodetector 224 may be emitted by indicator molecules 104
distributed throughout the indicator membrane 106', and the first
analog ambient light measurement signal may be an ambient indicator
measurement.
[0143] At step 1820, the sensor 100 may perform a light source-off
temperature measurement and conversion. For example, in some
embodiments, while the light source 108 is off (i.e., while the
light source 108, under the control of the measurement controller
532, is not emitting light), the analog interface 534 may generate
a second analog temperature measurement signal indicative of a
temperature of the sensor 100. In one embodiment, the temperature
transducer 670 may generate the second analog temperature
measurement signal while the light source 108 is off. The ADC 664
may convert the second analog temperature measurement signal to a
second digital temperature measurement signal. The measurement
controller 532 may receive the second digital temperature
measurement signal and generate (e.g., in step 1708 of the
measurement command execution process 1700) the measurement
information in accordance with the received second digital
temperature measurement signal.
[0144] Accordingly, in an embodiment in which sequence steps
1806-1820 of measurement and conversion process 1800 are performed,
the measurement controller 532 may generate measurement information
in accordance with (i) the first digital temperature measurement
signal, (ii) the first digital light measurement signal, (iii) the
second digital light measurement signal, (iv) the digital light
difference measurement signal, (v) the second digital temperature
measurement signal, (vi) the first digital ambient light
measurement signal and (vii) the second digital ambient light
measurement signal. In a non-limiting embodiment, the calculation
of the concentration of the analyte performed by the measurement
controller 532 of sensor 100 and/or sensor reader 101 may include
subtracting the digital ambient light signals from the
corresponding digital light measurement signals. The calculation of
the concentration of the analyte may also include error detection.
In some embodiments, the measurement controller 532 may incorporate
methods for attenuating the effects of ambient light, such as, for
example, those described in U.S. Pat. No. 7,227,156, which is
incorporated herein by reference in its entirety. In some
embodiments, the measurement controller 532 may generate
measurement information that merely comprises the digital
measurement signals received from the analog interface 534.
However, in other embodiments, the measurement controller 532 may
process the digital signals received from the analog interface 534
and determine (i.e., calculate and/or estimate) the concentration
of an analyte in the medium in which the sensor 100 is implanted,
and the measurement information may, additionally or alternatively,
include the determined concentration.
[0145] In some embodiments, if the sensor 100 determines in step
1804 that a measurement sequence should be performed, the
measurement and conversion process 1800 may proceed to a step 1822
in which a single measurement and conversion is performed. In some
embodiments, based on the measurement command received, the single
measurement and conversion performed in step 1822 may be any one of
the measurements and conversions performed in steps 1806-1820.
Accordingly, in an example where step 1822 of the measurement and
conversion process 1800 is performed, the measurement controller
532 may receive only one digital measurement signal, and the
measurement information generated by the measurement controller 532
(e.g., in step 1708 of the measurement command execution process
1700) may, in one embodiment, simply be the one digital measurement
signal received by the measurement controller.
[0146] In some embodiments, light source 108 may be turned on
before execution of step 1806 and not turned off until after
execution of step 1814. However, this is not required. For example,
in other embodiments, the light source 108 may be turned on during
measurement portions of steps 1806-1814 and turned off during the
conversion portions of steps 1806-1814.
[0147] Furthermore, although FIG. 18 illustrates one possible
sequence of the measurement and conversion process 1800, it is not
necessary that steps 1806-1820 of the measurement and conversion
process 1800 be performed in any particular sequence. For example,
in one alternative embodiment, light measurement and conversion
steps 1806-1814 may be performed in a different order (e.g., 1808,
1812, 1814, 1810, 1806), and/or ambient light measurement and
conversion steps 1816-1820 may be performed in a different order
(e.g., 1818, 1820, 1816). In some embodiments, the light source on
temperature measurement may be used to provide an error flag in
each individual measurement (e.g., by using a comparator to
comparing the light source on temperature measurement to threshold
value). In another alternative embodiment, ambient light
measurement and conversion steps 1816-1820 may be performed before
light measurement and conversion steps 1806-1814. In still another
alternative embodiment, steps 1806-1820 of the measurement and
conversion process 1800 may be performed in a sequence in which all
of the steps of one of light measurement and conversion steps
1806-1814 and ambient light measurement and conversion steps
1816-1820 are completed before one or more steps of the other are
executed (e.g., in one embodiment, steps 1806-1820 may be performed
in the sequence 1806, 1808, 1810, 1818, 1816, 1812, 1814,
1820).
[0148] FIGS. 21A and 21B illustrates the timing of an exemplary
embodiment of the measurement and conversion process 1800 described
with reference to FIG. 18.
[0149] FIG. 19 illustrates a get result command execution process
1900 that may be performed in step 1610 of the sensor control
process 1600 by the sensor 100 to execute a get result command
received by the sensor 100 in accordance with an embodiment of the
present invention. The measurement command execution process 1900
may begin with a step 1902 of retrieving saved measurement
information. For example, retrieved measurement information may be
saved during step 1712 of the analyte measurement command execution
process 1700 shown in FIG. 17. In some embodiments, measurement
information is saved in the nonvolatile storage medium 660. In
response to a request from the measurement controller 532, the
nonvolatile storage medium 660 may output saved measurement
information to the data and control bus 654. In some embodiments,
the data and control bus 654 may transfer the retrieved measurement
information to the measurement controller 532. However, in
alternative embodiments, the data and control bus 654 may transfer
the retrieved measurement information to the command decoder/data
encoder 652 without first transferring the retrieved measurement
information to the measurement controller 532.
[0150] In some embodiments, the nonvolatile storage medium 660 may
output to the data and control bus 654 the measurement information
most recently saved to the nonvolatile storage medium 660. In some
alternative embodiments, the nonvolatile storage medium 660 may
output to the data and control bus 654 the oldest measurement
information most saved to the nonvolatile storage medium 660. In
other alternative embodiments, the nonvolatile storage medium 660
may output to the data and control bus 654 the measurement
information specifically requested by the measurement controller
532 (e.g., by an address sent to the nonvolatile storage medium 660
with a read request).
[0151] After the saved measurement information is retrieved, the
get result command execution process 1900 may proceed to a step
1904 in which the sensor 100 may convey the retrieved measurement
information. In one embodiment, the measurement controller 532 may
output the retrieved measurement information to the data and
control bus 654. The data and control bus 654 may transfer the
measurement information to the command decoder/data encoder 652,
which may encode the retrieved measurement information. The data
serializer 656 may serialize the encoded retrieved measurement
information. The encoder 658 may encode the serialized retrieved
measurement information. The clamp/modulator 646 may modulate the
current flowing through the inductive element 114 (e.g., coil 220)
as a function of the encoded retrieved measurement information. In
this way, the encoded retrieved measurement information may be
conveyed by the inductive element 114 as a modulated
electromagnetic wave. In some embodiments, the encoded retrieved
measurement information conveyed by the sensor 100 may be received
by the sensor reader 1500.
[0152] FIG. 20 illustrates a get identification information command
execution process 2000 that may be performed in step 1610 of the
sensor control process 1600 by the sensor 100 to execute a get
identification information command received by the sensor 100 in
accordance with an embodiment of the present invention. The get
identification information command execution process 2000 may begin
with a step 2002 of retrieving stored identification information.
In some embodiments, identification information is stored in the
nonvolatile storage medium 660. In response to a request from the
measurement controller 532, the nonvolatile storage medium 660 may
output identification information to the data and control bus 654.
In some embodiments, the data and control bus 654 may transfer the
retrieved identification information to the measurement controller
532. However, in alternative embodiments, the data and control bus
654 may transfer the retrieved identification information to the
command decoder/data encoder 652 without first transferring the
retrieved identification information to the measurement controller
532.
[0153] After the stored identification information is retrieved,
the get identification information command execution process 2000
may proceed to a step 2004 in which the sensor 100 may convey the
retrieved identification information. In one embodiment, the
measurement controller 532 may output the retrieved identification
information to the data and control bus 654. The data and control
bus 654 may transfer the identification information to the command
decoder/data encoder 652, which may encode the identification
information. The data serializer 656 may serialize the encoded
identification information. The encoder 658 may encode the
serialized identification information. The clamp/modulator 646 may
modulate the current flowing through the inductive element 114
(e.g., coil 220) as a function of the encoded retrieved
identification information. In this way, the encoded identification
information may be conveyed by the inductive element 114 as a
modulated electromagnetic wave. In some embodiments, the encoded
identification information conveyed by the sensor 100 may be
received by the sensor reader 101.
[0154] The sensor 100 may be capable of executing other commands
received by the sensor. For example, the sensor 100 may perform a
setup parameter update execution process that may be performed in
step 1610 of the sensor control process 1600 by the sensor 100 to
execute a command to update setup parameters. In some embodiments,
the setup parameter update execution process may replace one or
more setup parameters (i.e., initialization information) stored in
the nonvolatile storage medium 660. In one embodiment, upon
receiving a command to update setup parameters, the measurement
controller 532 may output one or more setup parameters received
with the command to the data and control bus 654, which may
transfer the setup parameter(s) to the nonvolatile storage medium
660. The nonvolatile storage medium 660 may store the received
setup parameter(s). In a non-limiting embodiment, the received
setup parameter(s) may replace one or more setup parameters
previously stored in the nonvolatile storage medium 660.
[0155] FIG. 22 illustrates an alternative sensor control process
2200 that may be performed by the sensor 100, which may be, for
example, implanted within a living animal (e.g., a living human),
in accordance with an embodiment of the present invention. The
sensor control process 2200 may begin with a step 2202 of coupling
the inductive element of the external reader 101 and the inductive
element 114 of the sensor 100 within an electrodynamic field. The
sensor 100 may use the electrodynamic field to generate operational
power. In one embodiment, the electrodynamic field may be received
using the inductive element 114 of the sensor 100. The
electrodynamic field may induce a current in inductive element 114,
and the input/output (I/O) front end block 536 may convert the
induced current into power for operating the sensor 100. In a
non-limiting embodiment, rectifier 640 may be used to convert the
induced current into operating power for the sensor 100.
[0156] In step 2204, circuitry of the sensor 100 may produce a
coupling value proportional to the strength of the coupling of the
inductive element of the external reader 101 and the inductive
element 114 of the sensor 100. In some non-limiting embodiments,
the clamp/modulator 646 of the I/O circuit 536 may produce a
coupling value (e.g., I.sub.couple) proportional to the received
field strength based on the current induced in the inductive
element 114 by the electrodynamic field. In one non-limiting
embodiment, the coupling value proportional to the field strength
may be converted (e.g., by ADC 664) to a digital coupling value
proportional to the received field strength.
[0157] In step 2206, the reader may use the analog and/or digital
coupling value to determine whether the strength of the
electrodynamic field received by the sensor 100 is sufficient for
the sensor 100 to perform an analyte measurement. For instance, in
one non-limiting embodiment, the measurement controller 532 may
compare the digital coupling value to an analyte measurement field
strength sufficiency threshold and produce an indication that the
strength of the electrodynamic field received by the sensor is
either sufficient or insufficient for the implanted sensor to
perform the analyte measurement.
[0158] If the sensor 100 determines that the strength of the
electrodynamic field received by the sensor 100 is insufficient, in
step 2208, the sensor 100 may convey the field strength data
including the analog or digital coupling value and/or the
indication that the strength of the electrodynamic field received
by the sensor is either sufficient or insufficient to the external
sensor reader 101 (e.g., by modulating the electrodynamic field
based on the field strength data). In one embodiment, the
measurement controller 532 may output the field strength data to
the data and control bus 654. The data and control bus 654 may
transfer the field strength data to the command decoder/data
encoder 652, which may encode the field strength data. The data
serializer 656 may serialize the encoded field strength data. The
encoder 658 may encode the serialized field strength data. The
clamp/modulator 646 may modulate the current flowing through the
inductive element 114 (e.g., coil 220) as a function of the encoded
field strength data. In this way, the encoded field strength data
may be conveyed by the inductive element 114 as a modulated
electromagnetic wave. In some embodiments, the encoded field
strength data conveyed by the sensor 100 may be received by the
sensor reader 101.
[0159] If the sensor 100 determines that the strength of the
electrodynamic field received by the sensor 100 is sufficient, in
step 2210, the sensor 100 may automatically execute an analyte
measurement sequence (e.g., the analyte measurement command
execution process 1700 shown in FIG. 17) and generate analyte
measurement information.
[0160] In step 2212, the sensor 100 may the sensor 100 may convey
the analyte measurement information to the sensor reader 101 using
the inductive element 114. In one embodiment, the measurement
controller 532 may output the analyte measurement information to
the data and control bus 654. The data and control bus 654 may
transfer the analyte measurement information to the command
decoder/data encoder 652, which may encode the analyte measurement
information. The data serializer 656 may serialize the encoded
analyte measurement information. The encoder 658 may encode the
serialized field strength data. The clamp/modulator 646 may
modulate the current flowing through the inductive element 114
(e.g., coil 220) as a function of the encoded analyte measurement
information. In this way, the encoded analyte measurement
information may be conveyed by the inductive element 114 as a
modulated electromagnetic wave. In some embodiments, the encoded
analyte measurement information conveyed by the sensor 100 may be
received by the sensor reader 101.
[0161] In another embodiment, the field strength system may be
utilized as a convenient sensor locator to be used when physicians
wish to remove the sensor 100 following its useful life in vivo.
The sensor 100 is not visible when implanted in the subcutaneous
space, and it is not always easy to palpate under the skin for some
users that may have more adipose tissue in the space. The field
strength trigger system may be configured as a pinpoint locator
function joined with a set marking on the reader case to provide
physicians with the ability use the reader to place a reference
mark on the skin for use in making a precise incision for removing
the sensor 100 without having to guess the exact location of the
implant and where the incision is to be made for most efficient
removal.
[0162] Embodiments of the present invention have been fully
described above with reference to the drawing figures. Although the
invention has been described based upon these preferred
embodiments, it would be apparent to those of skill in the art that
certain modifications, variations, and alternative constructions
could be made to the described embodiments within the spirit and
scope of the invention. For example, while the invention has been
described with reference to a case or reader coupled to a
smartphone, the sensor reader can be an independent box or a key
fob that communicates to a smartphone or computer through Bluetooth
or a physical cable connection. In addition, circuitry of the
sensor 100 and reader 101 may be implemented in hardware, software,
or a combination of hardware or software. The software may be
implemented as computer executable instructions that, when executed
by a processor, cause the processor to perform one or more
functions.
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