U.S. patent application number 13/086962 was filed with the patent office on 2011-11-10 for suspended membrane pressure sensing array.
This patent application is currently assigned to Sierra Scientific Instruments, Inc.. Invention is credited to Chi Cao, Thomas R. Parks.
Application Number | 20110271772 13/086962 |
Document ID | / |
Family ID | 39926270 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110271772 |
Kind Code |
A1 |
Parks; Thomas R. ; et
al. |
November 10, 2011 |
SUSPENDED MEMBRANE PRESSURE SENSING ARRAY
Abstract
An accurate and low cost macro pressure sensor is described. The
pressure sensor includes an array of capacitive sensing elements
formed at the intersections of sets of conductors. A lower set of
conductors is supported by a substrate and an upper set of
conductors is supported on a flexible polymer membrane. Capacitive
sensing elements are formed where a conductor in the upper set
overlaps a spacer in the lower set. Separators hold the membrane
away from the substrate with a separation that, because of
deflection of the membrane, varies in relation to the pressure
applied to the membrane. As a result, the separation of conductors,
and therefore capacitance, in each cell varies in response to the
applied pressure. By attaching the membrane to the separators and
optionally using slits in the membrane between capacitive sensing
elements, measurements made in each capacitive sensing element can
be mechanically decoupled.
Inventors: |
Parks; Thomas R.; (Hermosa
Beach, CA) ; Cao; Chi; (North Hollywood, CA) |
Assignee: |
Sierra Scientific Instruments,
Inc.
Los Angeles
CA
|
Family ID: |
39926270 |
Appl. No.: |
13/086962 |
Filed: |
April 14, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12108479 |
Apr 23, 2008 |
7944008 |
|
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13086962 |
|
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60925720 |
Apr 23, 2007 |
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Current U.S.
Class: |
73/862.046 |
Current CPC
Class: |
G01L 5/228 20130101;
G01L 1/146 20130101 |
Class at
Publication: |
73/862.046 |
International
Class: |
G01L 1/14 20060101
G01L001/14 |
Goverment Interests
GOVERNMENT INTEREST
[0002] Research in connection with this application was supported
by the National Institute of Health under Grant R44DK069131. The
government has certain rights in this invention.
Claims
1. An apparatus for capacitively sensing force or pressure, the
apparatus comprising: a substrate; a plurality of elongated
substrate electrodes disposed at the substrate; a membrane
configured to deflect in response to force or pressure applied to
the membrane; a plurality of elongated membrane electrodes disposed
at the membrane, wherein each of at least two of the plurality of
membrane electrodes intersects each of at least two of the
plurality of substrate electrodes forming a multi-dimensional array
of capacitive elements having a capacitive element at each
intersection; and a plurality of separators fixedly connected with
the substrate and separating the substrate and the membrane,
thereby forming a plurality of sensor regions of the apparatus with
sensor regions positioned between adjacent separators of the
plurality of separators each including at least one capacitive
element; and wherein a membrane portion of each sensor region is
mechanically decoupled from a membrane portion of each adjacent
sensor region.
2. The apparatus of claim 1, wherein the membrane is attached to
each separator in the plurality of separators.
3. The apparatus of claim 1, further comprising a plurality of
elongated slits in the membrane, wherein each sensor region is
bound by one or more separators and one or more slits.
4. The apparatus of claim 1, wherein the plurality of elongated
substrate electrodes comprises a plurality of parallel elongated
substrate electrodes.
5. The apparatus of claim 1, wherein the plurality of elongated
membrane electrodes comprises a plurality of parallel elongated
membrane electrodes.
6. The apparatus of claim 1, wherein an orientation of plurality of
substrate electrodes is substantially perpendicular to an
orientation of the plurality of membrane electrodes.
7. The apparatus of claim 1, wherein the plurality of separators
comprises a plurality of parallel elongated separators and the
sensor regions are mechanically decoupled, at least in part, by
attaching the membrane to the plurality of separators.
8. The apparatus of claim 7, further comprising a plurality of
elongated slits in the membrane, wherein each slit in the plurality
of elongated slits is oriented perpendicular to an orientation of
an elongated separator in the plurality of parallel elongated
separators.
9. The apparatus of claim 1, wherein a side of the substrate facing
the membrane is substantially cylindrically curved.
10. The apparatus of claim 1, wherein the substrate is cylindrical
with a central substrate axis extending along a center of the
cylindrical substrate.
11. The apparatus of claim 10, wherein the membrane substantially
encircles the cylindrically-shaped substrate.
12. The apparatus of claim 10, wherein the separators substantially
encircle the central substrate axis.
13. The apparatus of claim 12, wherein the elongated substrate
electrodes substantially encircle the central substrate axis.
14. The apparatus of claim 10, wherein the elongated membrane
electrodes are substantially parallel to the central substrate
axis.
15. The apparatus of claim 10, wherein: the substrate comprises: an
outer surface comprising a plurality of grooves formed therein,
each groove having a floor; insulting layers disposed on the floors
of the plurality of grooves, each of the plurality of substrate
electrodes being disposed on an insulating layer; a lumen parallel
to the central substrate axis; and a plurality of holes passing
through the substrate from the lumen to a substrate electrode.
16. The apparatus of claim 15, further comprising: a wiring harness
disposed within the lumen, the wiring harness having a plurality of
contact points extending therefrom, each contact point being
electrically coupled through a hole of the plurality of holes to a
substrate electrode.
17. The apparatus of claim 10, wherein the membrane comprises a
plurality of slits.
18. The apparatus of claim 17, wherein the slits are oriented
substantially parallel to the central substrate axis.
19. The apparatus of claim 10, further comprising an elastomeric
sleeve encircling the central substrate axis and covering a side of
the membrane facing away from the substrate.
20. The apparatus of claim 1, wherein the apparatus is cylindrical
with a diameter suitable for use as an instrument to be inserted
into the gastrointestinal tract of a subject.
21. The apparatus of claim 1, wherein a total area of the sensor
regions of the apparatus is at least about 1 square inch.
22. The apparatus of claim 1, wherein the plurality of membrane
electrodes are disposed on a side of the membrane that faces the
substrate.
23. The apparatus of claim 1, further comprising an elastomeric
cover adjacent to a side of the membrane that faces away from the
substrate.
24. The apparatus of claim 1, wherein the membrane comprises a
polyimide and/or a polyethylene terephthalate.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of and claims the benefit
under 35 U.S.C. .sctn.120 of U.S. application Ser. No. 12/108,479,
entitled "SUSPENDED MEMBRANE PRESSURE SENSING ARRAY" filed on Apr.
23, 2008, and claims priority under 35 U.S.C. .sctn.119(e) to U.S.
Provisional Application Ser. No. 60/925,720, entitled "SUSPENDED
MEMBRANE PRESSURE SENSING ARRAY" filed on Apr. 23, 2007, each of
which is herein incorporated by reference in its entirety.
FIELD OF USE
[0003] Embodiments of this invention are directed to a capacitive
two-dimensional pressure sensing array.
BACKGROUND
[0004] Pressure sensing arrays are useful to measure spatial
pressure distributions. Some pressure sensing arrays incorporate
sensors that measure an external pressure applied to a surface by
capacitively relating the applied pressure into an electrical
signal. Some capacitive pressure sensors detect pressure applied to
an outer conductor by measuring a change in capacitance between the
outer conductor and an inner conductor separated by a compliant
layer. The compliant non-fluid separation layer compresses due to
application of the pressure to the outer conductor causing a change
in a separation between the inner conductor and the outer
conductor, which in turn changes the capacitance between the inner
conductor and the outer conductor.
[0005] A different form of capacitive pressure sensor employs a
membrane that suspends an outer conductor over an inner conductor,
where the outer conductor and the inner conductor are separated by
a gap. Semiconductor and/or micro-electromechanical systems (MEMS)
processing techniques have been used to make these types of
pressure sensors, called "suspended membrane deflection" sensors.
Through etching and deposition of materials a conductive membrane
can be formed separated from a substrate conductor by a gap. Such
sensors detect external pressure by measuring a change in
capacitance between the membrane conductor and the substrate
conductor caused by changes in a size of the gap, which changes as
pressure is applied to the membrane.
SUMMARY
[0006] The invention relates to an apparatus for capacitively
sensing force or pressure that incorporates a multi-dimensional
array of capacitive sensing elements. Accordingly, in some
embodiments of the invention, a method of making a capacitive
multi-dimensional sensing apparatus is provided. The method
includes providing a substrate having a plurality of elongated
substrate electrodes, a separation layer, and a membrane having a
plurality of elongated membrane electrodes. The separation layer
includes one or more separators and one or more open portions. The
method further includes orienting the membrane relative to the
substrate such that each of at least two of the plurality of
elongated membrane electrodes intersects each of at least two of
the plurality of substrate electrodes forming a multi-dimensional
array of capacitive elements with a capacitive element at each
intersection. The substrate is oriented such that open portions of
the separation layer align with the capacitive elements. The method
also includes attaching the separation layer to the membrane.
[0007] In other embodiments of the invention, an apparatus for
capacitively measuring force or pressure over a multi-dimensional
area is provided. The apparatus includes a substrate having a
plurality of elongated substrate electrodes, a membrane having a
plurality of elongated membrane electrodes, and a separation layer
having one or more separators. The separation layer fixedly
connects and separates the substrate and the membrane. The membrane
is configured to deflect in response to applied pressure. The
membrane and the substrate are oriented such that each of at least
two of the plurality of membrane electrodes intersects each of at
least two of the plurality of substrate electrodes forming a
multi-dimensional array of capacitive elements having a capacitive
element at each intersection. The plurality of separators forms a
plurality sensor regions of the apparatus. Each sensor region
includes at least one capacitive element and a membrane portion of
each sensor region is mechanically decoupled from a membrane
portion of each adjacent sensor region.
[0008] In other embodiments of the invention, a method of operating
a capacitive multi-dimensional sensing apparatus is provided. The
method includes providing a capacitive multi-dimensional sensing
apparatus. The apparatus has a substrate having a plurality of
substrate electrodes and a membrane having a plurality of membrane
electrodes. Each of at least two of the substrate electrodes
intersects more than one membrane electrode in the plurality of
membrane electrodes forming a multidimensional array of capacitive
elements with a capacitive element at each intersection. The
apparatus also includes a separation layer having open portions
corresponding to a plurality of sensor regions.
[0009] The method also includes deflecting a first membrane portion
corresponding to a first sensor region toward the substrate by
stretching the first membrane portion with a first pressure while
mechanically isolating membrane portions corresponding to adjacent
sensor regions from the deflection of the first membrane portion in
at least one direction. The method further includes measuring a
change in capacitance between a substrate electrode and a membrane
electrode corresponding to the deflection of the first membrane
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Other advantages, novel features, and objects of the
invention, and aspects and embodiments thereof, will become
apparent from the following detailed description, when considered
in conjunction with the accompanying drawings, which are schematic
and which are not intended to be drawn to scale. In the figures,
each identical or nearly identical component that is illustrated in
various figures is represented by a single numeral. For purposes of
clarity, not every component is labeled in every figure, nor is
every component of each embodiment or aspect of the invention shown
where illustration is not necessary to allow those of ordinary
skill in the art to understand the invention.
[0011] FIG. 1A schematically depicts a plan view of an exemplary
capacitive two-dimensional sensing apparatus, according to an
embodiment of the invention;
[0012] FIG. 1B schematically depicts a side cross-sectional view of
a portion of the two-dimensional sensing array shown in FIG.
1A;
[0013] FIG. 2A is an exploded schematic plan view of a substrate, a
membrane and separators that are components of the two-dimensional
sensing apparatus depicted in FIGS. 1A and 1B;
[0014] FIG. 2B schematically depicts a plan view of the separators
attached to the substrate, in accordance with some embodiments of
the invention;
[0015] FIG. 2C schematically depicts a plan view of the exemplary
capacitive two-dimensional sensing apparatus with an elastomeric
covering, according to other embodiments of the invention;
[0016] FIG. 3A schematically depicts a side cross-sectional view of
a capacitive two-dimentional sensing apparatus having a separator
that includes an adhesive element between support elements that are
monolithic with the substrate, according to other embodiments of
the invention;
[0017] FIG. 3B schematically depicts a side cross-sectional view of
a sensing array apparatus with a separator that includes an
adhesive element and a support element that is monolithic with the
substrate, according to other embodiments of the invention;
[0018] FIG. 3C schematically depicts a side cross-sectional view of
a capacitive two-dimensional sensing apparatus with the membrane
attached to support elements that are monolithic with the
substrate, according to other embodiments of the invention;
[0019] FIG. 3D schematically depicts a side cross-sectional view of
a capacitive two-dimensional sensing apparatus with each separator
including a rigid spacer adjacent to an adhesive element, according
to other embodiments of the invention;
[0020] FIG. 4A schematically depicts a plan view of a capacitive
two-dimensional sensing apparatus with separators oriented parallel
to an orientation of the substrate electrodes, according to other
embodiments of the invention;
[0021] FIG. 4B schematically depicts a plan view of a capacitive
two-dimensional sensing apparatus with a greater spactial frequency
of separators as compared to the apparatus depicted in FIG. 4A,
according to other embodiments of the invention;
[0022] FIG. 4C schematically depicts a plan view of a capacitative
two-dimensional sensing apparatus with a separation layer that
forms a two-dimensional array of sensor regions, according to other
embodiments of the invention;
[0023] FIG. 4D schematically depicts a plan view of the separation
layer of the apparatus shown in FIG. 4C;
[0024] FIG. 5A schematically depicts a plan view of a capacitive
two-dimensional sensing apparatus with a membrane having a
plurality of continuous slits aligned parallel to membrane
electrodes, according to other embodiments of the invention;
[0025] FIG. 5B schematically depicts a plan view of a capacitive
two-dimensional sensing apparatus with a membrane having a
plurality of segmened slits aligned parallel to the membrane
electrodes, according to other embodiments of the invention;
[0026] FIG. 5C schematically depicts a plan view of a capacitive
two-dimensional sensing apparatus with a membrane having a
plurality of segmented slits aligned perpendicular to the membrane
electrodes, according to other embodiments of the invention;
[0027] FIG. 6A schematically depicts a side view of a cylindrically
shaped multi-dimensional capacitive sensing apparatus including a
cylindrical substrate having a flexible rectangular membrane
wrapped around it, according to other embodiments of the
invention;
[0028] FIG. 6B schematically depicts an axial end view of the
cylindrically shaped multi-dimensional capacitive sensing apparatus
shown in FIG. 6A;
[0029] FIG. 7A schematically depicts a plan view of the flattened
membrane detached from the substrate, according to some embodiments
of the invention;
[0030] FIG. 7C is a schematic enlarged plan view of an portion of
the membrane depicted in FIG. 7A;
[0031] FIG. 8A schematically depicts a side view of the cylindrical
substrate, according to some embodiments of the invention;
[0032] FIG. 8B is a schematic enlarged detail view of the
cylindrical substrate shown in FIG. 8A;
[0033] FIG. 9 is a schematic enlarged cross-sectional view of the
cylindrical substrate with the membrane attached, according to some
embodiments of the invention;
[0034] FIG. 10 is a plan view of a membrane showing membrane
electrodes and segmented slits oriented parallel to the membrane
electrodes, constructed in accordance with some embodiments of the
invention;
[0035] FIG. 11A shows a perspective view of a probe including a
cylindrical sensor array mounted on a handle with connected wiring,
constructed in accordance with some embodiments of the
invention;
[0036] FIG. 11B shows a perspective view of the probe shown in FIG.
11A with a thin elastomeric sleeve fitted to an outside of the
array, constructed in accordance with some embodiments of the
invention;
[0037] FIG. 12 is a flow chart of a method of making a capacitive
multi-dimensional sensing apparatus, in accordance with other
embodiments of the invention; and
[0038] FIG. 13 is a flow chart of a method of using a capacitive
multi-dimensional sensing apparatus, in accordance with other
embodiments of the invention.
DETAILED DESCRIPTION
[0039] The inventors have recognized and appreciated that
macroscopic pressure sensors that incorporate compliant separation
layers may exhibit problems with the repeatability of measurements,
as the same applied pressure may not always result in the same
deflection due to changes in mechanical properties of the compliant
separation layer. Mechanical properties of the compliant separation
layer may be a function of temperature and other ambient conditions
and/or may change with the age of the layer or its history of
deformation.
[0040] The inventors have also recognized that silicon-based
processing is not well suited for making suspended membrane
deflection pressure-sensing arrays that must cover a large
(macroscopic) area. Further, some applications require that a
pressure-sensing array cover a curved surface, which is not
generally compatible with silicon-based processing.
[0041] Exemplary capacitive multi-dimensional pressure sensing
apparatuses exhibit improved repeatability of pressure measurement
and less thermal sensitivity than comparable capacitive sensing
arrays that employ compliant separation layers, in accordance with
some embodiments of the invention. Exemplary capacitive
multi-dimensional pressure sensing apparatuses may have lower
production cost than some compliant separation layer designs
because exemplary apparatuses may be more easily mass-produced.
[0042] Some exemplary capacitive multi-dimensional pressure sensing
apparatuses may be fabricated, at least in part, using flex
circuit-type processes allowing the sensing apparatus to be wrapped
around curved or other non-flat surfaces, unlike rigid arrays of
capacitive gap sensors produced with traditional silicon-based
processing techniques. Some exemplary capacitive multi-dimensional
pressure sensing apparatuses may have a sensing array covering a
macroscopically large area of a single substrate, which may be
prohibitively expensive with traditional silicon-based processing
techniques.
[0043] Embodiments of the invention provide a macro-capacitive
pressure sensing apparatus with a multi-dimensional array of
capacitive sensing elements, a method of making the apparatus and a
method of operating the apparatus. The apparatus may have, for
example, a two-dimension array of sensing elements. The capacitive
sensing elements may also be referred to as capacitive elements or
sensor cells herein. The apparatus includes a substrate, a membrane
and a separation layer that separates the substrate and the
membrane.
[0044] The substrate has a plurality of elongated substrate
electrodes and the membrane supports a plurality of membrane
electrodes. In assembling the sensing apparatus, the membrane may
be oriented such that the membrane electrodes cross or intersect
the substrate electrodes. The separation layer includes one or more
separators, which hold the membrane away from the substrate. As a
result, each intersection of a substrate electrode and a membrane
electrode forms a capacitive element. The membrane is of a polymer
or other suitable material such that, as positive external pressure
is applied to the membrane, the membrane stretches deflecting into
a gap in the separation layer toward the rigid or semi-rigid
substrate. When the pressure is removed, the membrane returns to
its original position.
[0045] Mechanical decoupling may be provided between the capacitive
elements. As a result, if a first sensor region is mechanically
decoupled from a second adjacent sensor region, a pressure applied
only to a portion of the membrane corresponding to the first sensor
region will not cause a substantial deflection or a change in
tension of a portion of the membrane corresponding to the second
sensor region. Mechanical decoupling may be provided by attaching
the membrane to the separators. The one or more separators may be
positioned to bound, at least partially, the capacitive sensing
elements so as to form sensor regions, with each sensor region
including at least one capacitive element. By attaching the
membrane to the separators, a separator between adjacent sensor
regions mechanically decouples portions of the membrane
corresponding to each adjacent sensor region. Mechanical separation
can alternatively or additionally be provided between sensor
elements by forming slits in the membrane between the sensor
regions to be decoupled.
[0046] Slits in the membrane may also increase the sensitivity of
the apparatus by increasing membrane deflection in a membrane
portion of each sensor region resulting from an applied
pressure.
[0047] By appropriate selection of materials and construction, a
"gap height" or "gap separation" at an intersection of a substrate
electrode and a membrane electrode is a repeatable function of
pressure applied to the membrane at the intersection. The gap
height or gap separation at the intersection is related to the
capacitance between the intersecting electrodes. As a result, a
pressure applied to the membrane at the intersection may be
determined from the measured capacitance of the intersection. Thus,
the apparatus provides an array of capacitive pressure sensors when
the plurality of membrane electrodes and the plurality of substrate
electrodes are connected with electronics that can measure the
capacitance at each intersection of the membrane electrodes and the
substrate electrodes.
[0048] In some embodiments, the substrate and membrane may be
substantially planar. In other embodiments, the apparatus may be
cylindrical, with a cylindrically shaped substrate. The plurality
of substrate electrodes may encircle the cylindrically shaped
substrate and the plurality of membrane electrodes may extend
parallel to a longitudinal axis of the substrate. In other
embodiments, the substrate may have various shapes, as the
invention is not limited in this respect. Fabrication of the
membrane by patterning a flexible circuit patterned with conductors
shaped and positioned to form membrane electrodes allows the
sensing apparatus to be formed in a wide range of shapes. Moreover,
fabrication in this way may be more economical than producing
traditional silicon-based capacitive pressure sensing arrays or
other known sensor array designs.
[0049] For example, cylindrical pressure sensing arrays have been
used in motility visualization system (MVS) catheters. MVS
catheters may be inserted into the gastrointestinal (GI) tract of a
subject to measure sphincter pressure. As is known in the art, a
typical MVS catheter for use with a human subject may require a
macro-scale pressure-sensing array that is between about 4-20
inches long and about 0.25-2 inches in circumference. A description
of an MVS catheter employing an array of discrete pressure sensors
appears in co-pending U.S. patent application Ser. No. 10/961,981
entitled HIGH RESOLUTION SOLID STATE PRESSURE SENSOR (published as
US 2005/0148884 A1), the entirety of which is herein incorporated
by reference. Pressure sensor arrays as fabricated herein may be
used in these and other applications.
[0050] Some exemplary macro-capacitive multi-dimensional pressure
sensing apparatuses in cylindrical form with sufficiently large
sensing arrays may be used for the measurement of sphincter
pressure in the gastrointestinal (GI) tract. Other cylindrical
macro-capacitive pressure sensing apparatuses may be incorporated
into manometry probes.
[0051] Although aspects of the invention are described below
primarily with respect to pressure sensing, one of ordinary skill
in the art knows that pressure is force applied over an area. Thus,
the same apparatus may be used to measure force and/or
pressure.
[0052] FIGS. 1A and 1B schematically illustrate a capacitive
two-dimensional pressure sensing apparatus, in accordance with
embodiments of the invention. Apparatus 10 includes a substrate 20,
a membrane 30 and a separation layer 50 that separates substrate 20
and membrane 30. Substrate 20 may be formed of a rigid or
semi-rigid material. As used herein, the term "non-compliant"
material refers to a rigid material, a semi-rigid material or a
combination of rigid and semi-rigid materials. In some embodiments,
substrate 20 is made of a material that can be machined, cast
and/or molded, such as a metal, a hard plastic, etc.
[0053] A plurality of elongated substrate electrodes 25 may be
supported by substrate 20. In some embodiments, substrate
electrodes 25 may be deposited on substrate 20, attached to
substrate 20 and/or formed in substrate 20, or in any other
suitable manner or configuration, as the invention is not limited
in this respect. For embodiments in which substrate 20 is formed of
a conducting material, a non-conducting material may be used to
separate the electrodes from the conducting portions of the
substrate, such as by providing a coating over the substrate in at
least the regions where the substrate electrodes are to be
supported. Suitable non-conducting materials include
dielectrics.
[0054] Membrane 30 may be configured to deflect by stretching in
response to force or pressure applied to membrane 30. Membrane 30
may be attached to and supported by separation layer 50. Separation
layer 50 may be attached to substrate 20 or may be monolithic with
substrate 20. Separation layer 50 may include one or more
separators 52 that are each attached to membrane 30 and a plurality
of open portions 51 that form "gaps." Separators 52 may form a
plurality of sensor regions 60 positioned between adjacent
separators 52.
[0055] A plurality of elongated membrane electrodes 35 may be
supported by membrane 30. In some embodiments, membrane electrodes
35 may be deposited on membrane 30, attached to membrane 30, or
formed in membrane 30. In some embodiments, membrane electrodes 35
may be disposed on a side of membrane 30 facing toward substrate
20, as depicted. In other embodiments, membrane electrodes 35 may
be disposed on a side of membrane 30 facing away from substrate 20,
may extend through a thickness of membrane 30 and/or may be
sandwiched between other layers of membrane 30 in a multilayer
membrane. For example, membrane electrodes 35 may be formed by
patterning a conductive layer on a flexible substrate using known
flexible circuit fabrication techniques. However, any suitable
fabrication technique may be used, as the invention is not limited
in this respect.
[0056] A capacitive element 40 is formed where a substrate
electrode 25 in the plurality of substrate electrodes intersects a
membrane electrode 35 in the plurality of membrane electrodes.
Intersections of sensor electrodes 25 and membrane electrodes 35
form a multi-dimensional array of capacitive elements 40. As is
apparent to one of skill in the art, based on geometry, each of at
least two of substrate electrodes 25 must intersect each of at
least two of membrane electrodes 35 to form a multi-dimensional
array of capacitive elements 40. In some embodiments, every
substrate electrode 25 intersects every membrane electrode 35, as
depicted in FIGS. 1A and 1B. However, not every substrate electrode
25 need intersect every membrane electrode 35 as long as a
multi-dimensional array of capacitive elements 40 is formed, as the
present invention is not limited in this respect.
[0057] As will be apparent to one of skill in the art, the term
"intersect," as used herein to describe electrodes, means that a
membrane electrode overlays or crosses and, from some aspect
angles, appears to "intersect" a substrate electrode, or vice
versa, as shown in FIG. 1A. However, from other aspect angles, the
substrate electrodes 25 and the membrane electrodes 35 may not
appear to intersect as they are separated by a gap and do not make
physical contact with one another.
[0058] FIG. 1B is a cross-sectional view of a portion of the
apparatus 10 depicted in FIG. 1A that illustrates how applied
pressure P.sub.b reduces a distance h.sub.b between substrate
electrodes 25 and membrane electrodes 35 causing increased
capacitance. Separation layer 50 supports membrane 30 and maintains
a nominal distance (gap height) h.sub.0 between substrate
electrodes 25 and membrane electrodes 35. Though, as can be seen,
separation layer 50 is not a solid layer. Rather, separation layer
50 comprises a plurality of separators 52a, 52b, 52c with spaces
between them, such that the membrane 30 may be suspended over the
spaces by attachment to the members, such as separators 52a, 52b,
52c. However, in other embodiments, separation layer 50 may include
a separator that includes on or more open spaces, as the invention
is not limited in this respect.
[0059] Separators 52a, 52b, 52c may be formed in any suitable way.
In some embodiments separators 52a, 52b, 52c of separation layer 50
are attached to substrate 20, as depicted. In other embodiments,
separators 52a, 52b, 52c may be monolithic with substrate 20.
Separators 52a, 52b, 52c of separation layer 50 are attached to
membrane 30.
[0060] Attachments between separators 52a, 52b, 52c and membrane 30
ensure that membrane deflection under applied force or pressure
P.sub.b is primarily due to stretching of membrane 30. If membrane
30 is not attached to separators 52a, 52b, 52c, membrane 30 may
slip or slide with respect to separators 52a, 52b, 52c, which may
result in unwanted mechanical hysteresis under changes in applied
pressure P.sub.b.
[0061] Gaps or open portions 51a, 51b, 51c between separators 52a,
52b, 52c, or within a separator, may be occupied by air or another
gas. However, in some embodiments gaps may be filled by a liquid,
or other suitable medium. Examples of suitable media include, but
are not limited to, air, nitrogen gas, dielectric liquids, etc.
[0062] FIG. 1B also illustrates how separators 52a, 52b, 52c
mechanically isolate membrane deflections between adjacent sensor
regions 60a, 60b and 60c. As described above, membrane 30 is
attached to and supported by separators 52a, 52b, 52c, which divide
the membrane into membrane portions 30a, 30b, 30c, etc. When
pressure P.sub.b is applied to membrane portion 30b in sensor
region 60b, pressure P.sub.b stretches membrane portion 30b,
deflecting it toward substrate 20. This stretching reduces a height
h.sub.b of the gap that separates membrane portion 30b and
substrate 20. The reduction of the gap height h.sub.b increases a
capacitance between a substrate electrode and a membrane electrodes
in sensor region 60b. As illustrated by FIG. 1B, because membrane
portion 30b in sensor region 60b is fixedly attached at spacers 52b
and 52c, adjacent membrane portions 30a, 30c in sensor regions 60a
and 60c, are not deflected in response to pressure P.sub.b.
[0063] FIG. 2A illustrates an exploded view of components of the
exemplary apparatus 10. The components include substrate 20 with
elongated substrate electrodes 25, membrane 30 with elongated
membrane electrodes 35, and separation layer 50 having separators
52.
[0064] In some embodiments, substrate 20 may be planar, as shown.
In other embodiments, substrate 20 may be curved or have a
different three dimensional configuration, as the invention is not
limited in this respect. Substrate 20 may be rectangular as shown;
though in other embodiments substrate 20 may have other shapes, as
the invention is not limited in this respect. For example, a
cylindrical substrate is depicted and described below with respect
to FIGS. 6A and 6B.
[0065] In some embodiments, substrate electrodes 25 may be
substantially parallel to each other, as shown. In other
embodiments, only some of substrate electrodes 25 may be
substantially parallel to each other, or none of the substrate
electrodes 25 may be substantially parallel to each other, as the
invention is not limited in this respect. For example, substrate
electrodes 25 may be configured as parallel conductive strips. In
some embodiments, substrate electrodes 25 may be rectangular, as
shown; however, other embodiments may include substrate electrodes
25 with other shapes, as the invention is not limited in this
respect.
[0066] Similarly, in some embodiments, membrane electrodes 35 may
be substantially parallel to each other, as shown. In other
embodiments, only some of membrane electrodes 35 may be
substantially parallel to each other, or none of membrane
electrodes 35 may be substantially parallel to each other, as the
invention is not limited in this respect. In some embodiments,
membrane electrodes 35 may be rectangular, as shown; however, other
embodiments may include membrane electrodes 25 with other shapes,
as the invention is not limited in this respect.
[0067] In some embodiments, each substrate electrodes 25 may have
an electrical connection 27, as shown. Similarly, in some
embodiments, each membrane electrode 35 may have an electrical
connection 37, as shown. Electrical connections 27 and 37 allow an
electrical signal to be applied to a pair of electrodes 25, 35.
Using known capacitance measurement techniques, or any other
suitable measurement, an electrical output measured on the same
pair of electrodes can be used to determine capacitance between the
pair of electrodes. As described above, capacitance between
electrodes 25, 35 is a function of a deflection of membrane 30 at
the electrodes, and the deflection of membrane 30 is a function of
pressure. Thus, electrical connections 27 and 37 enable pressure
measurement for an array of locations to be made using the
apparatus 10.
[0068] In the embodiment illustrated, membrane 30 may be fabricated
using flex-circuit manufacturing techniques. The electrodes 35 as
well as connections 37 to those electrodes may be formed as part of
the flex-circuit fabrication.
[0069] Separators 52 are shown as elongated strips running parallel
to membrane electrodes 35, in the depicted embodiment. Separators
52 are also shown with a spacing that approximates a distance
between membrane electrodes 35. However, neither this orientation,
nor this spacing is a limitation on the invention, and any suitable
orientation or spacing may be used.
[0070] Separators 52 may be formed of any suitable material. In the
embodiment illustrated, in FIG. 2A, separators 52 may be formed of
or be coated with adhesive material allowing attachment to
substrate 20 and membrane 30. An example of a suitable material is
an uncured or partially cured epoxy strip. However, any suitable
material may be used to coat and/or form separators 52.
[0071] FIG. 2B depicts substrate 20 with separation layer 50
attached. Such a structure may be formed according to a proces in
which separation layer 50 is formed on substrate 20, then membrane
30 is attached to separation layer 50.
[0072] Separators 52 of separation layer 50 may be attached to
substrate 20 and/or membrane 30 by any suitable process or means
including, but not limited to: adhering, bonding, affixing,
mechanically fixing, welding, etc. Maintaining a controlled height
h.sub.0 (see FIG. 1B) of separation layer 50 may be important to
maintain a desired relationship between capacitance and applied
pressure and for having a uniform response among capacitive
elements 40 formed by the intersecting regions of substrate
electrodes 25 and membrane electrodes 35. In some embodiments, this
control of the height may be effected by use of epoxy strips for
separators 52 in separation layer 50 where the epoxy has small or
predictable changes in thickness during the bonding process.
Though, in other embodiments, fillers or other members may be
incorporated into a matrix. As a specific example, separators 52
may be formed of epoxy containing spacing aggregates such as glass
beads.
[0073] Alternatively or additionally, jigs, fixtures or other
fabrication techniques may be used to hold substrate 20 and
membrane 30 in a desired position while the components of the
apparatus are being assembled. For example, temporary spacers, such
as strips of the desired gap thickness h.sub.0, may be installed
between the epoxy strips during the epoxy bonding operation and
then removed after substrate 20, separation layer 50 and membrane
30 have been coupled. In some embodiments, the temporary spacers
may be formed of a material with a high melting temperature to
resist melting during the bonding process. In some embodiments, the
temporary spacers may be formed of a material with a low
coefficient of friction for easy removal. For example, teflon
strips may be used as temporary spacers. These and similar
techniques allow for control of the separation height that might
otherwise be adversely affected during the bonding process when the
separation layer 50 may be placed under compressive load.
[0074] FIG. 2C schematically depicts an elastomeric outer layer 80
that may be applied over membrane 30 to protect apparatus 10 from
contamination by media such as particulates, liquids or vapors.
Also, the elastomeric outer layer 80 separates fluid (i.e. gas or
liquid) outside the apparatus from fluid (i.e. gas or liquid)
within the gaps between membrane 30 and substrate 20, which may be
desirable when membrane 30 includes slits as described below with
respect to FIGS. 5A to 5C. Elastomeric outer layer 80 may be a
permanent part of apparatus 10, or elastomeric outer layer 80 may
be removable and replacable. In some embodiments, elastomeric outer
layer 80 may be a sheath that covers a cylindrical apparatus 110
which is incorporated into a probe, as described below with respect
to FIG. 118. In some embodiments, both an elastomeric layer 80,
which is attached to membrane 30, and a disposable sheath may be
employed.
[0075] In FIGS. 2A and 2B, separation layer 50 is formed separate
from both substrate 20 and membrane 30. However, such a fabrication
process is not required as separation layer 50 may be monolitic
with substrate 20, deposited onto substrate 20, formed together
with membrane 30, etc., in accordance with embodiments of the
invention. FIGS. 3A-3D schematically illustrate side
cross-sectional detail views of other embodiments of the apparatus
10 showing different configurations for separation layers. FIGS.
3A-3D illustrate that separation layer 50 need not be separate from
substrate 20 and membrane 30. In some embodiments, part or all of
the separation layer is monolithic with the substrate, as shown in
FIGS. 3A, 3B and 3C.
[0076] FIGS. 3A-3D also illustrate that a separator 52 of the
separation layer 50 need not be a single element that both
separates and secures membrane 30 to substrate 20. In some
embodiments, each separator may include a spacer element and an
adhesive element, as shown in FIGS. 3A, 3B and 3D. In each of FIGS.
3A-3D, an example operating condition is depicted with a pressure
P.sub.b is applied to a center sensor region 60b causing center
membrane portion 30b to stretch and deflect toward a substrate.
[0077] In FIG. 3A, a substrate 21 is shaped to provide double "rib
type" features that control the undeflected height of the gap, in
accordance with embodiments of the invention. Each separator 72
includes an adhesive element 72b disposed between spacer elements
in the form of two "ribs" 72a that are monolithic with a substrate
21. The two ribs 72a may be machined into substrate 21 or formed in
any other suitable way. Adhesive element 72b is attached to the
substrate 21 and the membrane 30 using any suitable process or
means including but not limited to: adhering, bonding, affixing,
mechanically fixing, welding etc.
[0078] In FIG. 3B, a substrate 22 is shaped to provide single
"rib-type" features that control the undeflected height of the gap,
in accordance with other embodiments of the invention. Each
separator 74 may include a rib 74a that is monolithic with the
substrate 22 and an adhesive element 74b that is attached to the
membrane 30 and the substrate 22, as depicted.
[0079] In FIG. 3C, each separator is a rib 76 that is monolithic
with the substrate 23, in accordance with other embodiments. The
rib 76 controls the undeflected height of the gap and is attached
to the membrane 30. The embodiments depicted in FIGS. 3A to 3C
incorporating monolithic "rib" features can provide for precise gap
height if the rib height can be precisely controlled during
fabrication of the substrate.
[0080] In FIG. 3D, each separator 78 includes a spacer element 78a
and an adhesive element 78b, in accordance with another embodiment
of the invention. Because spacer elements 78a need not be adhesive,
they may be formed of plastic, metal or any other suitable
materials, and can be secured to the adhesive elements 78b either
before or after the adhesive elements are attached to either
substrate 24 or membrane 30. In some embodiments, spacer element
78a may have a same cross-sectional width and a height as those of
adhesive element 78b, as depicted. However, in other embodiments,
spacer element 78a may have a different width than that of adhesive
element 78b and/or spacer element 78a may have a greater height
that adhesive element 78b.
[0081] FIGS. 4A to 4D schematically depict apparatuses with
different separation layer configurations, in accordance with other
embodiments of the invention. In some embodiments, separators 54
are elongated so that more than one intersection between membrane
electrodes 35 and substrate electrodes 25 lies between adjacent
separators 54 forming more than one capacitative element 40 in each
sensor region 60, as shown in FIG. 4A.
[0082] In some embodiments separators 52 may be oriented parallel
to membrane electrodes 35, as shown in FIG. 2B and described above.
In some embodiments, separators 54 may be oriented parallel to
substrate electrodes 25, as shown in FIG. 4A. In other embodiments,
separators may not be oriented parallel to substrate electrodes 25
or membrane electrodes 35, as the invention is not limited in this
respect.
[0083] In some embodiments adjacent separators 54 may be spaced on
approximately the same pitch as the electrodes, such that adjacent
separators 54 are separated by a substrate electrode 25, as
depicted in FIG. 4A. In other embodiments, separators 56a, 56b may
be situated at a greater spatial frequency than one per substrate
electrode 25. For example, in FIG. 4B some separators 56b are
disposed between substrate electrodes 25 and some separators 56a
are disposed on substrate electrodes 25.
[0084] Although the embodiments depicted above include "strip-like"
separators being parallel and in-between either membrane electrodes
35 or substrate electrodes 25, many other configurations fall
within the scope of the present invention. Examples of other
configurations include, but are not limited to: squares of
separators bordering each intersection of substrate electrodes 25
and membrane electrodes 35, squares or strips of separators at some
bias angle with respect to the substrate electrodes 25 and/or at
some bias angle with respect to the membrane electrodes 35,
etc.
[0085] As discussed above, securing membrane 30 to separators 54 is
one mechanism to reduce or eliminate mechanical cross-coupling
between adjacent sensor regions 60 by mechanically decoupling a
membrane portion of one sensor region 60 from a membrane portion of
an adjacent sensor region 60. Within a sensor region 60 containing
multiple capacitive sensing elements 40, a capacitive sensing
element 40 may be mechanically decoupled from adjacent capacitive
sensing elements 40 in at least one direction due to a
configuration of the separators 52, even though it is not
mechanically decoupled from adjacent capacitative sensing elements
40 in a different direction.
[0086] In some embodiments, one or more separators may form a
multi-dimensional array of sensor regions 60. FIGS. 4C and 4D
illustrate a grid shaped separation layer 176 that separates a
substrate 172 and a membrane 174 forming a two-dimensional array of
sensor regions 180aa, 180ab, 180ba, . . . , in accordance with some
embodiments of the invention. As depicted, the separation layer 176
may be formed from a single member, such as separator 177. However,
separation layer 176 may include many members that collectively
form a grid shaped separation layer 176.
[0087] In the embodiment illustrated, separation layer 176 is
formed as a grid, with each square of the grid enclosing a sensor
region with a single capacitive sensing element. As illustrated,
each sensor region 180aa, 180ab, 180ba, . . . includes one
capacitive sensing element 179aa, 179ab, 179ba, . . . formed at an
intersection of membrane electrodes 175 and substrate electrodes
173. However, in other embodiments, even when separation layer 176
is formed as a grid, each sensor region 180aa, 180ab, 180ba, . . .
may include more than one capacitive sensing element 179aa, 179ab,
179ba, . . . , as the invention is not limited in this respect.
[0088] In other embodiments, an apparatus may also include slits,
which can also decouple adjacent sensor regions. FIGS. 5A-5C
illustrate exemplary apparatuses that each includes a membrane
having a plurality of slits. Slits 100a, 100b, . . . allow for
reduction or elimination of mechanical cross-coupling in applied
loads, such as pressure or force. That is, if a load is applied at
a sensor region 60ab on one side of a slit 100b, the resulting
membrane deflection and increase in membrane tension is largely
isolated to sensor region 60ab and is not transmitted to an
adjacent sensor region 60aa across slit 100b. For example, an
apparatus 94 in FIG. 5A has separators 57a, 57b . . . that are
parallel to substrate electrodes 25 and continuous silts 100a, 100b
. . . that are perpendicular to separators 57a, 57b . . . . Sensor
region 60aa is mechanically isolated from sensor region 60ba by
separator 57b and mechanically isloated from sensor region 60ab by
slit 100b. The slits 100 also are useful in the control of the
effective "stiffness" of the membrane 31. That is, they can limit
stretch of the membrane 31 to be primarily in a direction between
adjacent separation strips as indicated by arrow 105 rather than
being bi-directional. Limiting stretch to stretch along one
direction can also increase the sensitivity of a capacitive element
via increased membrane deflection for a given applied pressure.
This increase in sensitivity may be especially pronounced for
circular or curved surfaces where hoop stiffening of the membrane
is consequently reduced. Apparatuses with circular or curved
surfaces are described in detail below with respect to FIGS. 6A to
11B.
[0089] FIG. 5B schematically illustrates an apparatus 98 having a
membrane 33 with a two-dimensional array of slits 104, in
accordance with other embodiments of the invention. The slits 104
are oriented parallel to an orientation of membrane electrodes 35
and perpendicular to an orientation of separators 58.
[0090] FIG. 5C schematically illustrates an apparatus 96 having a
two-dimensional array of slits 102 with an orientation
perpendicular to an orientation of membrane electrodes 36, in
accordance with other embodiments of the invention. The slits 102
are perpendicular to separators 59 and perpendicular to membrane
electrodes 36. In the embodiment illustrated, an individual slit
102 does not extend through an entire width W.sub.E of a membrane
electrode 36, allowing the membrane electrode 36 to maintain
electrical contract along its length.
Example #1
[0091] An exemplary planar sensor array of 8.times.8 format was
built according to the construction similar to that of FIG. 5B with
non-continuous slits oriented parallel to membrane electrodes and
an elastomeric outer layer. The planar sensor array was tested
relative to two sensors of a more conventional elastomeric
separation mechanism labeled conventional transducer (1) and hybrid
transducer (2). Both the conventional transducer (1) and the hybrid
transducer (2) employ compliant separations strips that separate
opposing electrodes. In the conventional transducer (1) and the
hybrid transducer (2), pressure causes the compliant separation
strips to compress, which reduces a spacing between opposing
electrodes. In contrast, in the exemplary planar sensor array a
spacing between opposing electrodes is changed by pressure applied
to the membrane, which stretches the membrane, deflecting it into
the gap. Results of the tests of the exemplary planar sensor array,
and tests of the conventional and hybrid sensor arrays employing
compliant separation strips, are given in Table 1. The exemplary
design (3) provided roughly 3.times. improvement in baseline
repeatability relative to the conventional transducer (1) and the
hybrid transducer (2). The exemplary design (3) provided a
10.times. to 50.times. improvement in thermal stability and
2.times. improvement in sensitivity relative to the more
conventional devices (1) and (2).
TABLE-US-00001 TABLE 1 Construction and Testing of Tactile Array
Prototypes Under Phase I for Use in the HD-MVS Probe Baseline
Transducer Repeatability Thermal Stability Sensitivity Construction
Method Description (mmHg) (mmHg) (mV/mmHg) 1. Conventional
Compliant separation strips not 4.3, (.sigma. = 0.3) -36.7,
(.sigma. = 16.5) 3.5 aligned with electrode strips 2. Hybrid - Same
as above except compliant 5.3, (.sigma. = 0.4) -10.3, (.sigma. =
5.9) 3.1 thermal optimized separation strips placed between
electrode strips 3. Membrane with Base same as hybrid. Rigid 1.8,
(.sigma. = 1.3) 0.8, (.sigma. = 1.6) 6.3 suspended air gap
suspension of top membrane electrodes with geometric avoidance of
capacitive air gap. Sensing electrodes pre-tensioned with slits cut
for mechanical decoupling.
[0092] In other exemplary embodiments, an apparatus may have a
cylindrical form factor. Details of a membrane 130, a separation
structure 152, and electrical interconnections (e.g. substrate
electrodes 125, membrane electrodes 135 and connections 137) for a
cylindrical capacitive pressure sensing array apparatus 110 are
shown and described with respect to FIGS. 6A through 11B, in
accordance with aspects of the invention.
[0093] FIG. 6A schematically depicts a side view and FIG. 6B
schematically depicts an axial view of the cylindrical apparatus
110. As shown in the axial view of FIG. 6B, the cylindrical
apparatus 110 includes a flexible membrane 130 wrapped around a
cylindrical substrate 120. The surface view of FIG. 7A shows that
the flexible membrane 130 may include slits 106 oriented parallel
to an axis 121 of the cylindrical apparatus 110.
[0094] FIG. 7A schematically depicts a plan view of the rectangular
flattened membrane 130 before it is wrapped around the cylindrical
substrate 120. Membrane electrodes 135 may be oriented parallel to
the axis 121 of cylindrical substrate 120 as shown by FIGS. 7A and
7B. In some embodiments, membrane electrodes 135 are conductive
metal films deposited on the membrane, whether by patterning a
metal coating or in any other suitable way. As schematically
depicted by detail 131 of membrane 130 shown in FIG. 7B, slits 106
of membrane 130 may be oriented parallel to membrane electrodes
135. Slits 106 may be non-continuous and spaced to lie between
separators of cylindrical substrate 120. Membrane 130 may include
connections 137 that connect membrane electrodes 135 to other
electrical components.
[0095] Membrane 130 and membrane electrodes 135 may be formed with
a flex-circuit type processing. As is known to one of skill in the
art, flex-circuit type processing includes depositing conductive
films on flexible materials such as a polyimide, Kapton.RTM.,
polyethylene terephthalate, or other suitable polymer.
[0096] As illustrated by FIG. 8A, the substrate may have any
suitable shape. For example, the substrate 120 may be a cylindrical
tube with circumferential substrate electrodes 125 and
circumferential ring separators 152 disposed longitudinally along
axis 121 of the tube, as shown in FIGS. 8A to 9. Substrate 120 may
be formed in any suitable way, such as by machining, casting,
forming, etc. For example, substrate 120 may be formed of a metal
tube machined into the desired shape with a dielectric layer
covering the metal. In some embodiments, the desired shape may
include ribs 153 that are part of ring separators 152, as shown in
FIG. 9.
[0097] In some embodiments, cylindrical substrate 120 is
substantially encircled by substrate electrodes 125 that are
oriented substantially perpendicular to membrane electrodes 135, as
depicted in FIG. 8A. Each substrate electrode 125 may be deposited
on the substrate 120 between adjacent ring separators 152, making
the substrate electrodes generally ring-shaped.
[0098] Regardless of the configuration of the substrate, some or
all of the fabrication techniques described above may be used to
form a capacitive array sensor. As illustrated by FIGS. 6A and 8A,
ring separators 152 that encircle the substrate 120 are oriented to
mechanically decouple adjacent sensor regions 160aa, 160ba axially
along the cylindrical apparatus 110. Slits 106 of membrane 130 are
oriented to mechanically decouple adjacent sensor regions 160aa,
160ab azimuthally around the cylindrical apparatus 110.
[0099] The detail cross-sectional view of the of substrate 120 and
membrane 130 in FIG. 9, further illustrates separators 152.
Although depicted separators 152 each include an adhesive element
154 between two ribs 153, other configurations of separators 152
may be employed as the invention is not limited in this respect.
However, these examples are illustrative only, and any suitable
shape of non-compliant or minimally compliant separators may be
formed.
[0100] Both the detail plan view of the substrate 120 in FIG. 8B
and the detail side cross-sectional view of the substrate and the
membrane in FIG. 9, further illustrate the substrate electrodes
125a, 125b, 125c, and other aspects of exemplary embodiments. As
illustrated, separators 152 need not have walls perpendicular to
the surface of the substrate, Here, the separators are formed, in
part, by machining concave grooves 162a, 162b, 162c into the
surface of substrate 120. In some embodiments, one or more
insulating layers may be disposed on floors of concave grooves
162a, 162b, 162c. Substrate electrodes 125a, 125b, 125c may be
disposed on the insulating layers.
[0101] In some embodiments, cylindrical substrate 120 may be
tubular, with a substrate lumen 120c. The tube may have an outer
wall including holes 122, 122a, 122b, 122c for accessing substrate
electrodes 125a, 125b 125c from within the substrate lumen 120c.
Wires carrying electrical signals to or from the substrate
electrodes may be routed through the lumen.
[0102] Electrical connections to substrate electrodes 125a, 125b,
125c, such as through wires 123a, 123b, 123c, may extend through
the holes 122a, 122b, 122c. Wires 123a, 123b, 123c, may be part of
a wiring harness. The wiring harness disposed within the substrate
lumen may have a plurality of contact points, each extending
through a hole to a substrate electrode 125a, 125b, 125c,
[0103] In some embodiments, the wiring harness may be implemented
as a flex circuit or using other similar suitable fabrication
techniques. The contact points may be tabs extending from the flex
circuit. Connections may be made to the substrate electrodes
through the holes by soldering or otherwise making electrical
connections between the tabs and the electrodes.
[0104] As a specific example, a metal tube may be machined to have
grooves. The walls of the grooves may form separator elements and
electrodes may be formed on the floors of the grooves. Electrodes
may be formed by first depositing an insulative layer over the
metal and then depositing one or more conductive layers in a
pattern corresponding to the substrate electrodes. As a specific
example, the conductive layers may include a nickel layer with a
gold layer over the nickel.
[0105] A probe formed as described above is insensitive to bending
and shear loads on the probe. Use of circumferential rings of the
rigid or attached separation layer and the rigidity of the
substrate itself make membrane deflection insensitive to bending
and shear loads on the probe.
Example #2
[0106] A probe with a 16.times.16 cylindrical array of sensors was
built using the cylindrical apparatus sensor design depicted in
FIGS. 6A through 8B. The substrate included a cylindrical metal
member coated with dielectric material and plated to effect
conducting electrode rings. FIG. 10 shows a flattened membrane 164
of the probe before it is applied to the cylindrical metal member
of the probe. The flattened membrane includes axially oriented
membrane electrode electrodes 166 in the form of strips that face
the cylindrical member, and slits 168 oriented parallel to the
electrodes. FIG. 11A shows the probe 160 and wiring that connects
the substrate electrodes and the membrane electrodes with
electronics external to the probe 160. FIG. 11B shows the probe 160
with a thin elastomeric sheath 165 fitted to the outside of the
sensor apparatus.
[0107] As shown in FIG. 11A, a sensor array may be sized on a macro
scale for applications requiring an array of sensing element that
covers a macroscopically large area. The probe depicted in FIG. 11A
is sized for measuring a spatial distribution of pressure with a
gastrointestinal tract. As is apparent from the FIG. 11A, the
illustrated GI probe has a macro scale sensing array, with
dimensions between approximately 1-4 inches in length and between
approximately 0.5-2 inches in circumference.
[0108] Another embodiment of the invention provides a method of
making a capacitive multi-dimensional sensing apparatus. Although
the exemplary method may be used to make different configurations
of capacitive multi-dimensional sensing apparatuses, an embodiment
of the method will be described with respect to apparatus 10
depicted in FIGS. 1A to 2C, with respect to apparatus 96 depicted
in FIG. 5C, and with respect to apparatus 110 depicted in FIGS. 6A
to 9 solely for illustrative purposes.
[0109] FIG. 12 is a flow chart illustrating a method 200 of making
a capacitive multi-dimensional sensing apparatus 10, in accordance
with other embodiments of the invention. Initially a substrate 20,
a separation layer (50) and a membrane (30) are provided (step
210). These components may be provided as separate members that are
later integrated. Alternatively, the separation layer 50 may be
provided integrated with either substrate 20 or membrane 30.
[0110] The substrate 20 includes elongated substrate electrodes 25.
The separation layer (50) includes one or more separators 52. The
membrane includes one or more elongated membrane electrodes
(35).
[0111] In some embodiments, providing substrate 20 includes
machining a substrate body. In other embodiments, providing
substrate 20 includes casting substrate 20 or forming substrate 20
using another suitable method. If substrate 20 is machined or
formed from a conductive material, a dielectric layer may be
deposited over the conductive material of the substrate. In some
embodiments, elongated substrate electrodes 25 are deposited onto a
substrate body. For example, standard etching may be used to create
elongated substrate electrodes 25. In other embodiments, elongated
substrate electrodes 25 may be formed separately and attached to
substrate 20 by any suitable means or methods of attachment.
[0112] In some embodiments, at least a portion of separators 52 is
monolithic with substrate 20. Portions of monolithic separators 52
may be formed by machining or etching channels and/or grooves into
a substrate body. For example, portions of monolithic separators 52
may be produced using preformed epoxy strips, and/or computer
numerical control (CNC) machining. In other embodiments, no portion
of separators is monolithic with substrate 20. In other
embodiments, providing substrate 20 and separation layer 50 may
include depositing at least a portion of one or more separators 52
on substrate 20.
[0113] In some embodiments, one or more of separators 52 may be
formed separately. Method 200 may further include attaching
separators 52 to substrate 20. Separators 52 may be attached to
substrate 20 before membrane 30 is attached to separators 52, after
membrane 30 is attached to separators 52, or while membrane 30 is
attached to separators 52, as the invention is not limited in this
respect.
[0114] In some embodiments, membrane 30 and membrane electrodes 35
are produced with flex-circuit type processing. As is known to one
of skill in the art, flex-circuit type processing may include
patterning, through etching or other suitable processes, conductive
films on flexible substrates such as polyimide or Kapton.RTM.,
polyethylene terephthalate or other suitable polymer membrane
materials or any other material that is stable and elastomeric.
Thus, providing membrane 30 having membrane electrodes 35 may
include patterning conductive film electrodes on a flexible polymer
film in a desired shape.
[0115] In some embodiments, providing a membrane may include
forming a plurality of slits in the membrane. The plurality of
slits may include an array of continuous slits 100a, 100b . . . as
depicted in FIG. 5A and/or the plurality of slits may include a
two-dimensional array of slits 104 as depicted in FIG. 5B. The
plurality of slits may be formed parallel to membrane electrodes 35
as depicted in FIG. 5B, perpendicular to membrane electrodes 36 as
depicted in FIG. 5C or an another angle with respect to membrane
electrodes 35. The slits may be configured to be oriented
perpendicular to an orientation of spacers 42, as shown in FIGS. 5A
to 5C. The slits may be formed in any suitable way, such as by
punching out or laser-cutting regions of the membrane.
[0116] Substrate 20 is oriented relative to membrane 30 so that
each of at least two of elongated membrane electrodes 35 intersects
each of at least two of substrate electrodes forming a
multi-dimensional array of capacitive elements 40 (step 230). As
described above, the term "intersecting" may also be described as
overlaying because substrate electrodes 25 and the membrane
electrodes 35 remain separated by separators or a gap.
[0117] Separators 52 of the separation layer 50 are attached to the
membrane 30 by any suitable method or means (step 240). Substrate
20 may be oriented relative to membrane before separators 52 are
attached to membrane 30 or after separators 52 are attached to
membrane 30. For example, separators 52 may be attached to membrane
30 before substrate 20 is oriented relative to membrane 30, and
separators 52 may be attached to substrate 20 after substrate 20 is
oriented relative to both separators 52 and attached membrane
30.
[0118] Separation layer 50 may be put under a compressive load when
the separation layer is attached to the membrane 20. In some
embodiments, a separation h.sub.0 between the substrate 20 and the
membrane 30 may remain constant while the membrane 30 is being
attached to the separation layer 50. For example, the separation
layer 50 may include epoxy strips where the epoxy contains a matrix
material, such as a spacing aggregate of a controlled diameter,
that minimizes change in thickness during bonding between
separators 52 and membrane 30.
[0119] In some embodiments spacer elements (e.g. glass beads,
teflon strips, etc.) may be positioned in open portions 51 of
separation layer 50. Spacer elements may be positioned before
separators 52 are attached to the membrane 30, while separators 52
are being attached to the membrane 30 or after separators 52 ave
been attached to the membrane 30. For example, if membrane 30 is
attached to separators 52 before separators 52 are attached to
substrate 20, spacer elements may be into open portions 51 of
separation layer 50 after membrane 30 is attached to separators 52,
but before separators 52 are attached to substrate 20. Spacer
elements may remain in the open portions 51 of the separation layer
50 or may be temporary and removed after membrane 30, separation
layer 50 and substrate 20 are connected (step 242).
[0120] In some embodiments, a method 200 of making a
multidimensional array sensing apparatus 10 may include applying an
elastomeric outer layer 80 over membrane 30 (step 245), as shown in
FIG. 2C. As described above, the elastomeric outer layer 80
protects membrane 30 and separates fluid (i.e. liquid or gas) in
the gap between membrane 30 and substrate 20 from fluid outside
apparatus 10 when membrane 30 includes slits.
[0121] Some embodiments of the invention provide a method 260 of
operating a multidimensional capacitive sensing apparatus. Although
exemplary method 260 may be used to operate different
configurations of multidimensional array sensing apparatuses,
embodiment 260 will be described with respect to apparatus 10
depicted in FIGS. 1A to 2C and apparatus 96 in depicted FIG. 5C,
solely for illustrative purposes.
[0122] FIG. 13 is a flow chart illustrating method 260 of operating
a multidimensional array sensing apparatus 10. In accordance with
the illustrated method 260, initially a capacitive
multi-dimensional sensing apparatus 10 is provided (step 270).
Providing the sensing apparatus may include positioning the
apparatus in a bodily lumen or other location where a pressure
measurement is desired.
[0123] The apparatus may include a substrate 20 having a plurality
of substrate electrodes 25 and a membrane 30 having a plurality of
membrane electrodes 35. Each of at least two of the substrate
electrodes 25 may intersect more than one membrane electrode 35.
The intersections of substrate electrodes 25 and membrane
electrodes 35 form a multidimensional array of capacitive elements
40. Apparatus 10 include a separation layer 50 having open portions
51 corresponding to a plurality of sensor regions 60, wherein the
open portions do not comprise solid material.
[0124] As a result of pressure on the apparatus, at least a first
membrane portion 30b corresponding to first a sensor region 60b is
deflected toward the substrate with a first pressure P.sub.b,
stretching the first membrane portion 30b while mechanically
isolating adjacent sensor regions 60a, 60c from the deflection
(step 280). A change in capacitance is measured between a substrate
electrode 25 and a membrane electrode 35 corresponding to the
deflection of membrane portion 30b (step 290). The method may also
include determining a pressure exerted on membrane portion 30b from
the measured change in capacitance (step 295).
[0125] The method may further include deflecting other membrane
portions, such as portion 30a corresponding to a second sensor
region 60a toward the substrate 20 by stretching membrane portion
30a with a second pressure while mechanically isolating adjacent
sensor regions 60b from the second pressure and the increase in
membrane tension, and while deflecting the first membrane portion
60a with the first pressure P.sub.b. The method 260 may include
measuring a change in capacitance between a substrate electrode 25
and a membrane electrode 35 corresponding to the deflected second
membrane portion 30b.
[0126] Having now described some illustrative embodiments of the
invention, it should be apparent to those skilled in the art that
the foregoing is merely illustrative and not limiting, having been
presented by way of example only. Numerous modifications and other
illustrative embodiments are within the scope of one of ordinary
skill in the art and are contemplated as falling within the scope
of the invention. In particular, although many of the examples
presented herein involve specific combinations of method acts or
system elements, it should be understood that those acts and those
elements may be combined in other ways to accomplish the same
objectives. Acts, elements and features discussed only in
connection with one embodiment are not intended to be excluded from
a similar role in other embodiments.
[0127] As used herein, "plurality" means two or more.
[0128] As used herein, a "set" of items may include one or more of
such items.
[0129] As used herein, whether in the written description or the
claims, the terms "comprising", "including", "carrying", "having",
"containing", "involving", and the like are to be understood to be
open-ended, i.e., to mean including but not limited to. Only the
transitional phrases "consisting of" and "consisting essentially
of", respectively, shall be closed or semi-closed transitional
phrases, as set forth, with respect to claims, in the United States
Patent Office Manual of Patent Examining Procedures (Original
Eighth Edition, August 2001), Section 2111.03
[0130] Use Of ordinal terms such as "first," "second," "third,"
etc., in the claims to modify a claim element does not by itself
connote any priority, precedence, or order of one claim element
over another or the temporal order in which acts of a method are
performed, but are used merely as labels to distinguish one claim
element having a certain name from another element having a same
name (but for use of the ordinal term) to distinguish the claim
elements.
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