U.S. patent application number 13/813352 was filed with the patent office on 2013-07-18 for touch surface and method of manufacturing same.
This patent application is currently assigned to NANOMADE CONCEPT. The applicant listed for this patent is Lukas Czornomaz, Jeremie Grisolia, ERIC Mouchel La Fosse, Laurence Ressier, Lionel Songeon, Beno t Viallet. Invention is credited to Lukas Czornomaz, Jeremie Grisolia, ERIC Mouchel La Fosse, Laurence Ressier, Lionel Songeon, Beno t Viallet.
Application Number | 20130181726 13/813352 |
Document ID | / |
Family ID | 43708188 |
Filed Date | 2013-07-18 |
United States Patent
Application |
20130181726 |
Kind Code |
A1 |
Viallet; Beno t ; et
al. |
July 18, 2013 |
TOUCH SURFACE AND METHOD OF MANUFACTURING SAME
Abstract
A device for detecting and quantifying a force applied on a
surface comprising a test specimen, an electrically insulating
substrate, a first electrode bound to the substrate, a second
electrode, an assembly of conductive or semi-conductive
nanoparticles in contact with the two electrodes, and a measurement
device. The measurement device provides proportional information
with respect to an electrical property of the nanoparticles
assembly. The electrical property is measured between the first and
second electrode. The test specimen is the nanoparticles assembly
itself and the electrical property is sensitive to the distance
between the nanoparticles of the assembly. The invention uses the
nanoparticles assembly itself as a test specimen and allows a force
to be quantified even if the nanoparticles assembly is deposited on
a rigid substrate.
Inventors: |
Viallet; Beno t; (Toulouse,
FR) ; Ressier; Laurence; (Toulouse, FR) ;
Grisolia; Jeremie; (Aussonne, FR) ; Songeon;
Lionel; (Tournefeuille, FR) ; Mouchel La Fosse;
ERIC; (Tournefeuille, FR) ; Czornomaz; Lukas;
(Toulouse, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Viallet; Beno t
Ressier; Laurence
Grisolia; Jeremie
Songeon; Lionel
Mouchel La Fosse; ERIC
Czornomaz; Lukas |
Toulouse
Toulouse
Aussonne
Tournefeuille
Tournefeuille
Toulouse |
|
FR
FR
FR
FR
FR
FR |
|
|
Assignee: |
NANOMADE CONCEPT
Toulouse
FR
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Paris
FR
INSTITUT NATIONAL DES SCIENCES APPLIQUEES DE TOULOUSE
Toulouse
FR
|
Family ID: |
43708188 |
Appl. No.: |
13/813352 |
Filed: |
August 1, 2011 |
PCT Filed: |
August 1, 2011 |
PCT NO: |
PCT/EP11/63205 |
371 Date: |
April 3, 2013 |
Current U.S.
Class: |
324/652 ;
324/649; 324/661; 324/691; 427/58 |
Current CPC
Class: |
G01L 1/205 20130101;
G06F 2203/04103 20130101; G06F 3/045 20130101; G01R 27/2605
20130101; G01R 27/02 20130101; G06F 1/16 20130101; G01L 1/146
20130101; G06F 3/041 20130101; G06F 3/0445 20190501; G06F
2203/04105 20130101; G06F 3/0416 20130101; G06F 3/0447 20190501;
G01L 1/144 20130101 |
Class at
Publication: |
324/652 ;
324/649; 324/691; 324/661; 427/58 |
International
Class: |
G01R 27/02 20060101
G01R027/02; G01R 27/26 20060101 G01R027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2010 |
FR |
10 56387 |
Claims
1. A device for detecting and quantifying a force applied on a
surface known as a touch surface comprising: a test specimen; an
electrically insulating substrate; a first electrode bound to the
substrate and fixed in relation to the substrate; a second
electrode; an assembly of conductive or semi-conductive
nanoparticles in contact with the two electrodes; a measurement
device providing proportional information with respect to an
electrical property of the nanoparticles assembly, the electrical
property is measured between the first and second electrode, the
electrical property being proportional to a variation in distance
between the nanoparticles of the assembly; and wherein the test
specimen consists in the nanoparticles assembly itself.
2. The device according to claim 1, wherein the second electrode is
remote from the first electrode and mobile relative to the
substrate, and the nanoparticles assembly is located between the
two electrodes such that a movement of the second electrode causes
a change in the distance between the nanoparticles of the
nanoparticles assembly.
3. The device according to claim 1, wherein the electrical property
is the resistance of the nanoparticles assembly.
4. The device according to claim 1 wherein the electrical property
is the electrical capacitance of the nanoparticles assembly.
5. The device according to claim 2, wherein: the first electrode
comprises a plurality of parallel conductive strips extending over
the surface of the substrate in a first direction; the second
electrode comprises a plurality of parallel conductive strips
extending in a plane remote from and parallel to the surface of the
substrate and in a second direction different to the first; and the
nanoparticles assembly, being topographically structured in a
plurality of discrete clusters and located between the two
electrodes at the locations where the directions of the first and
second electrodes' conductive strips intersect.
6. The device according to claim 1, wherein the nanoparticles
assembly is located on the substrate, covering a part of the
surface, and wherein the first and second electrodes comprise
conductive strips bound to the substrate and extending between a
portion of the surface of the substrate not covered by the
nanoparticles assembly and the perimeter of the surface covered by
the nanoparticles.
7. The device according to claim 1, wherein the nanoparticles
assembly is located on the substrate, covering part of the surface,
the first electrode comprising conductive strips bound to the
substrate and extending between a portion of the surface of the
substrate not covered by the nanoparticles assembly and the
perimeter of the surface covered by the nanoparticles and the
second electrode, wherein the second electrode being mobile
relative to the substrate is located on top of the nanoparticles
assembly.
8. The device according to claim 6, wherein the nanoparticles
assembly comprises several superimposed layers of nanoparticles in
a direction substantially normal to the substrate.
9. The device according to claim 7, wherein the nanoparticles
assembly comprises several superimposed layers of nanoparticles in
a direction substantially normal to the substrate.
10. The device according to claim 6, wherein the nanoparticles
assembly extending on the surface of the substrate is a single
layer and whereinthe substrate is compressible with regard to
stresses normal to its surface such that a localized pressure
normal to the nanoparticles assembly produces a change in the
distance between the particles of the assembly.
11. The device according to claim 7, wherein the nanoparticles
assembly extending on, the surface of the substrate is a single
layer and wherein the substrate is compressible with regard to
stresses normal to its surface such that a localized pressure
normal to the nanoparticles assembly produces a change in the
distance between the particles of the assembly.
12. A method for manufacturing a device according to claim 5,
comprising the steps of: depositing a first network of parallel
conductive strips extending in a first direction on an insulating
substrate; depositing clusters of nanoparticles on the first
network of parallel strips, wherein the clusters comprise at least
two superimposed layers of nanoparticles in a direction normal to
the substrate, the clusters being separated from each other and
deposited according to a repeating pattern in a direction parallel
to the direction of the first network of strips; and depositing a
second network of parallel conductive strips extending in a second
direction different to the first network of strips and coming into
contact with the nanoclusters.
13. The method according to claim 12, wherein the step of
depositing nanoclusters according to a repeating pattern comprises
the steps of: depositing an insulating layer comprising holes
opening onto the first network of strips on an ensemble comprising
the substrate and the first network of strips; depositing, in the
holes of the insulating layer, nanoclusters comprising at least two
superimposed layers in a direction substantially normal to the
surface of the substrate and coming into contact with the
underlying conductive strips; and depositing, on the insulating
layer, the second network of parallel conductive strips extending
in a second direction different to the first and coming into
contact with the nanoclusters.
14. The device according to claim 4, wherein the measurement device
comprises a resonant circuit coupling in parallel the nanoparticles
assembly and a tuned inductance.
15. A method for measuring a force applied on a device according to
claim 14, comprising the steps of: subjecting the resonant circuit
to electromagnetic excitation; and measuring the variation in
absorption of the resonant circuit when the nanoparticles assembly
is subjected to the force.
16. The method according to claim 15, wherein the electromagnetic
excitation is realized at a continuous excitation frequency and the
variation measured is the frequency shift of the resonant circuit's
absorption spectrum.
17. The method according to claim 15, wherein the electromagnetic
excitation is realized at a pulsed frequency, and the variation
measured is the emission of the resonant circuit during the
relaxation phases.
18. The method according to claim 16, wherein the excitation is
realized at the resonant circuit's resonance frequency and the
variation measured is the shift in the resonance frequency.
19. The device according to claim 14, wherein the resonant circuit
comprises emitting means for emitting a unique identification code
when the resonant circuit is subjected to an electromagnetic
excitation.
20. A touch surface comprising a device according to claim 1.
Description
RELATED APPLICATIONS
[0001] This application is a .sctn.371 application from
PCT/EP2011/063205 filed Aug. 1, 2011, which claims priority from
French Patent Application No. 10 56387 filed Aug. 2, 2010, each of
which is herein incorporated by reference in its entirety.
TECHNICAL FIELD OF INVENTION
[0002] The invention belongs to the field of touch surfaces and
relates to such a surface, its method of realization and its use
for detecting and measuring forces applied on such a surface. This
type of surface is used, for example, in many mass-market
electronic applications, in particular computer applications, under
different forms, called "touch pad", "touch screen", "write pad",
etc.
BACKGROUND OF THE INVENTION
[0003] In these examples of the prior art, the touch surfaces are
configured so as to detect one or more contacts, which can be from
a finger or by means of an accessory such as a stylus. When they
comprise a plurality of sensors arranged according to a matrix
organization, they allow the movement of said points of contact to
be tracked.
[0004] The surfaces of the prior art are made functional, or
functionalized, by means of sensors that measure the variation in a
physical property during the contact with a finger or with an
accessory on the touch surface.
[0005] The main physical properties measured, according the art,
are resistivity or electrical resistance and the variation in
electrical capacitance. There are also technologies based on the
emission of ultrasounds or infrared rays.
[0006] The touch surfaces of the prior art can primarily detect the
contact, but cannot quantify it. `Quantify` means to determine the
pressure or the resulting contact force, the direction of this
resulting force when it comprises components other than normal to
the touch surface, and the coordinates of the point of application
of this force in a reference space linked to the touch surface, the
contact forces applied to such a touch surface being essentially
normal to said surface. According to certain embodiments of the
prior art, said contact must be applied with a sufficient force to
be detected, for example in the case of a measurement of
resistivity or resistance, but does not give information about the
intensity of the contact force with the surface. An example of this
embodiment is described in document US 2008/238882.
[0007] For some applications it can nevertheless be useful to have
information about this force, or about the contact pressure
exerted, about the points of application of the force, in
particular when it is desired that the touch surface is able to
detect several points or areas of contact, especially
simultaneously, and lastly about the direction of the applied
force.
[0008] The invention aims to create touch surfaces which response
makes it possible to quantify the system of contact forces that are
applied to them.
[0009] The technology known from the prior art allowing this need
to be met consists of realizing a test specimen, i.e. a deformable
solid whose modes of deformation under the effect of a loading
system are known or can be calculated by direct methods, said test
specimen being deformed under the action of the forces applied to
it. Then its deformation just needs to be measured in order to
know, by reverse method, the loading system to which it is
subjected. The deformation of the proof body is measured most often
by strain gages, which provide a variation in an electrical
property proportional to their elongation. However, the difficulty
with this method lies in several aspects. Firstly, for this method
to be effective the shape of the test specimen must be simple and
its supporting conditions controlled. As an example, while it is
easy to determine by reverse method the loading mode of a thin flat
test specimen held by its periphery when the forces normal to this
plane are applied at points sufficiently far from the edges, it
becomes significantly more complicated to apply such a method if
the surface of the test specimen is curved or if it is held in a
more complex way.
[0010] In addition, the test specimen must be sufficiently
deformable so that its deformation can be measured by gages.
However, in many applications mentioned above a rigid touch surface
is desired. Therefore strain gages that are especially sensitive
must be used. U.S. Pat. No. 7,116,209 describes especially
sensitive strain gages suitable for a deformation measurement known
as longitudinal, i.e. tangential to the surface on which they are
bonded. These gages of the prior art are based, in their
measurement principle, on the variation in the resistivity of an
assembly of conductive nanoparticles when the distance between said
particles is modified under the effect of the deformation of the
test specimen on which said gages are bonded. Such gages can be
networked to accurately measure the deformation of a test specimen
in response to various loading systems. However, this principle
suffers from the same limitations as the other technologies of the
prior art, namely that the touch function, i.e. the ability to
measure an action essentially normal to the surface, is dependent
on boundary conditions, on the shape of the test specimen and on
the ability to evaluate the latter's stressing by reverse method,
the gages measuring the deformations tangential to the
functionalized surface.
OBJECT AND SUMMARY OF THE INVENTION
[0011] To overcome these disadvantages of the prior art, the
invention proposes a device for detecting and quantifying a force
applied on a surface known as a touch surface comprising: [0012] a
test specimen; [0013] an electrically insulating substrate; [0014]
a first electrode bound to the substrate and fixed in relation to
said substrate; [0015] a second electrode; [0016] an assembly of
conductive or semi-conductive nanoparticles in contact with the two
electrodes; [0017] a measurement device providing proportional
information with respect to an electrical property of the
nanoparticles assembly, which property is measured between the
first and second electrode, said electrical property being
proportional to a variation in distance between the nanoparticles
of the assembly; [0018] such that the test specimen consists in the
nanoparticles assembly itself.
[0019] Thus, this invention uses the nanoparticles assembly itself
as test specimen and allows a force, essentially normal to said
assembly, to be quantified even if said assembly is deposited on a
rigid surface. The substrate can be rigid or have some
compressibility, and the deformations of the nanoparticles assembly
can be decoupled from those of the functionalized surface by this
device. Thus, unlike the prior art, where the substrate and its
method of fixing onto the test specimen must ensure a perfect
coupling between the deformations of the test specimen and the
nanoparticles assembly, the device subject of the invention
overcomes this constraint and offers more flexibility of
realization in the shape and nature of the touch surfaces.
[0020] A "nanoparticles assembly" is constituted of one or more
ensembles of nanoparticles bound to each other by a ligand within
each ensemble, said ensembles being bound to each other
electrically.
[0021] "Proportional information" means a measurement that varies
with the property measured, the proportionality function being
linear, exponential or any other mathematical form establishing a
univalent relationship between the value of the measurement and the
value of the measured property .
[0022] The invention can be implemented according to the
advantageous embodiments described below, which can be considered
individually or in any technically effective combination.
[0023] According to a first embodiment, the second electrode is
remote from the first electrode and mobile relative to the
substrate, and the nanoparticles assembly is located between the
two electrodes such that a movement of the second electrode causes
a change in the distance between the nanoparticles of said
nanoparticles assembly. This configuration makes it possible to
create a basic force sensor able to measure the force it is
subjected to at each of its extremities, i.e. on each of its
electrodes. "An electrode mobile relative to the substrate" means
an electrode placed such that a movement of the latter changes the
relative distance between this electrode and the substrate, thus
causing a change in the distance between the nanoparticles. This
movement is in reality a micro-displacement, which is opposed by a
backmoving force that is a function of the stiffness of the
nanoparticles assembly and the substrate.
[0024] Advantageously, regardless of the configuration of
realization, the electrical property measured is the resistance of
the nanoparticles assembly. This electrical property is
particularly easy to measure.
[0025] Alternatively, the electrical property measured is the
electrical capacitance of the nanoparticles assembly. This
electrical property offers the advantage of being suitable for
being measured remotely, without contact, in all the realization
configurations.
[0026] According to an improvement of the first realization
configuration, [0027] the first electrode comprises a plurality of
parallel conductive strips extending over the surface of the
substrate in a first direction; [0028] the second electrode
comprises a plurality of parallel conductive strips in a second
direction different to the first; [0029] the nanoparticles assembly
being topographically structured in a plurality of discrete
clusters, said clusters being located between the two electrodes at
the locations where the directions of the first and second
electrodes' conductive strips intersect.
[0030] In this way the touch surface is made functional by a matrix
network of basic force sensors, and offers the possibility of
determining the points of application of forces stressing said
surface and also the intensity of said forces.
[0031] According to a second embodiment, the nanoparticles assembly
is placed on the substrate, covering a part of the surface of said
substrate, and the electrodes consist in conductive strips bound to
the substrate and extending between a portion of the surface of
said substrate not covered by the nanoparticles assembly and the
perimeter of the surface covered by the nanoparticles. This
configuration allows the touch surface to be functionalized in a
spatially continuous way.
[0032] According to a third embodiment, the nanoparticles assembly
is placed on the substrate, covering a part of the surface of said
substrate, the first electrode consist in conductive strips bound
to the substrate and extending between a portion of the surface of
said substrate not covered by the nanoparticles assembly and the
perimeter of the surface covered by the nanoparticles and the
second electrode, mobile relative to the substrate, is located on
top of the nanoparticles assembly. This configuration makes it
possible to quantify the force applied to the second electrode
acting on the nanoparticles assembly, in intensity and
orientation.
[0033] According to a first variant of the second and third
embodiments, the nanoparticles assembly comprises several
superimposed layers of nanoparticles in a direction substantially
normal to the substrate.
[0034] According to a second variant of these same embodiments, the
nanoparticles assembly extending on the surface of the substrate is
a single layer, said substrate being compressible with regard to
normal stresses such that a localized pressure normal to the
substrate produces a change in the distance between the
nanoparticles of said assembly.
[0035] The invention also relates to a method for manufacturing a
touch surface according to the first embodiment, said method
comprising steps consisting in: [0036] depositing on an insulating
substrate a first network of parallel conductive strips extending
in a first direction; [0037] depositing clusters of nanoparticles
on these strips, which clusters comprise at least two superimposed
layers of nanoparticles in a direction normal to the substrate, the
clusters being separated from each other and deposited according to
a repeating pattern in a direction parallel to the direction of the
strips; [0038] depositing on the ensemble a second network of
parallel conductive strips extending in a second direction
different to the first and coming into contact with the
nanoclusters.
[0039] Thus, such a surface can be prepared by known methods, in
particular by photolithography or by nanoimprinting for depositing
electrodes and by convective capillary deposition or nanoxerography
for the nanoclusters.
[0040] According to a particular embodiment of this method, the
step of depositing nanoclusters according to a repeating pattern
comprises steps consisting of: [0041] depositing on the
substrate/first network of conductive strips ensemble an insulating
layer comprising holes opening onto said strips; [0042] depositing
in the holes of the insulating layer nanoclusters comprising at
least two superimposed layers in a direction substantially normal
to the substrate and coming into contact with the underlying
conductive strips; [0043] depositing on the ensemble a second
network of parallel conductive strips extending in a second
direction different to the first and coming into contact with the
nanoclusters.
[0044] This embodiment of the method can be implemented with the
same means and presents increased reliability of realization.
[0045] Advantageously, when the electrical property measured is
proportional to the capacitance of the nanoparticles assembly, the
measurement device comprises a resonant circuit coupling in
parallel the nanoparticles assembly and a tuned inductance. In this
way it is possible to take a measurement remotely without contact,
by exciting said circuit by electromagnetic excitation.
[0046] To this end, the invention also relates to a method for
measuring a force applied on such a device according to this last
embodiment, said method comprising steps consisting of: [0047]
subjecting the resonant circuit to an electromagnetic excitation;
[0048] measuring the variation in absorption of said circuit when
the nanoparticles assembly is subjected to said force.
[0049] This method allows the variation in electrical capacitance
of the nanoparticles assembly to be used as a property proportional
to the force applied on the touch surface, which capacitance is
measured without contact and remotely.
[0050] According to a first variant of this method, the
electromagnetic excitation is realized at a continuous excitation
frequency and the variation measured is the frequency shift of the
circuit's absorption spectrum. Advantageously, the excitation is
realized at the circuit's resonance frequency and the variation
measured is the shift in this resonance frequency.
[0051] According to a second variant of this method, the
electromagnetic excitation is realized at a pulsed frequency, and
the variation measured is the emission of the resonant circuit
during the relaxation phases.
[0052] Advantageously, the resonant circuit comprises means
emitting a unique identification code when said circuit is
subjected to an electromagnetic excitation.
[0053] The invention also relates to a touch surface comprising the
device object of the invention according to any one of its
embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0054] The invention will now be described more precisely in the
context of preferred embodiments, which are in no way limiting, and
FIGS. 1 to 8 wherein:
[0055] FIG. 1 shows in perspective a schematic diagram of a first
embodiment of a basic force sensor;
[0056] FIG. 2 shows in perspective a synoptic of an embodiment of
the method of manufacturing a touch surface consisting of a matrix
network of basic force sensors;
[0057] FIG. 3 shows in perspective an exemplary embodiment of a
touch surface comprising a nanoparticles assembly, the measurement
electrodes being placed on the perimeter of this nanoparticles
assembly;
[0058] FIG. 4 illustrates according to the principle, in a
perspective view, the response of a nanoparticles assembly similar
to that in FIG. 3 subjected to a system of force;
[0059] FIG. 5 shows, according to a top perspective view, an
exemplary embodiment of a force sensor comprising a nanoparticles
assembly and an ensemble of first electrodes distributed over the
perimeter of the nanoparticles assembly, a second electrode being
placed on the top of the nanoparticles assembly;
[0060] FIG. 6 shows in a top perspective view another embodiment
variant of the device subject of the invention using a
nanoparticles assembly, the electrodes being placed on the
perimeter of the assembly, one of the electrodes being realized by
a plurality of strips;
[0061] FIG. 7 is a schematic diagram of a device according to an
embodiment of the invention using the electrical capacitance as
property sensitive to the distance between the nanoparticles of the
assembly; and
[0062] FIG. 8 shows, according to a cross-section and front view,
the modes of deformation of the nanoparticles assembly of the
subject of the invention placed on a functionalized surface, called
touch, said assembly being single-layered (FIGS. 8B and 8E) or
multi-layered (FIGS. 8A, 8C and 8D), which assembly being deposited
on a rigid substrate (FIG. 8C) or on a compressible substrate
(FIGS. 8D and 8E).
[0063] The purpose of all these figures is to show in an
understandable way the structural characteristics of the device
according to its various embodiments and they are in no way
representative of the dimensions or scale of the various
components.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0064] FIG. 1: according to a first exemplary embodiment of a
device according to the invention comprising a nanoparticles
assembly consisting of several superimposed layers, said device
comprises an electrically insulating substrate (10) to which a
first electrode (31) is bound, such that this first electrode is
fixed in relation to said substrate. Measurement means (40) make it
possible to measure the variation in an electrical property between
this first electrode (31) and a second electrode (32) placed in a
remote plane substantially parallel to the substrate (10). A
nanoparticles assembly (20) is placed between the two electrodes
(31, 32). This assembly comprises a plurality of conductive or
semi-conductive nanoparticles (21), organized in several layers,
said nanoparticles being bound to each other by an electrically
resistant ligand. This ligand is advantageously chosen from
compounds comprising functions able to bond chemically with the
nanoparticles. As a non-limiting example it can concern citrate,
amine, phosphine or thiol functions. As an example: [0065] sodium
citrate, C.sub.6H.sub.5O.sub.7.sup.3-, 3Na.sup.+, for a compound
comprising a citrate function; [0066] bis-p-sulfonatophenyl
phenylphosphine dihydrate of sodium for a compound comprising a
phosphine function; [0067] an alkylamine, C.sub.12H.sub.25NH.sub.2,
for a compound comprising an amine function.
[0068] The particles are deposited on the substrate in the form of
a colloidal suspension, suspended in water for the ligands
comprising a phosphine or citrate function, suspended in toluene
for the ligands comprising an amine function.
[0069] The dimension of the nanoparticles (21) is between
2.10.sup.-9 meters or nanometers, and can reach 1 .mu.m, such that
the thickness of the assembly (20) of nanoparticles between the two
electrodes (31, 32) is between 2.10.sup.-9 and 100.10.sup.-6
meters, depending on the dimension of the nanoparticles and the
number of layers deposited. The nanoparticles are, for example,
nanoparticles of gold.
[0070] The ensemble comprising the first electrode (31), the
nanoparticles assembly (20) and the second electrode (32) is
advantageously covered by an insulating film (not shown). When a
force substantially normal to the surface of the second electrode
(32) is applied to this ensemble, this displaces the nanoparticles
and changes the distance between them within said assembly. When an
electrical property is sensitive to the distance between said
nanoparticles, measuring this property with the help of suitable
means (40) between the two electrodes provides proportional
information with respect to the deformation of the nanoparticles
assembly under the effect of the stress. According to this
exemplary embodiment, said stress is applied to the second
electrode in a way substantially normal to it. The substrate (10)
can be either rigid or flexible, the nanoparticles assembly forms
the test specimen of this microsensor (100). Such a microsensor can
advantageously be used to measure forces, or any other physical
dimension of the same type. For example, by depositing a micro-mass
on the second electrode it can form a micro-accelerometer.
[0071] FIG. 2: in order to functionalize a touch surface of
significant dimension and detect on this surface the coordinates of
the point of application of the force, such microsensors (100) can
be combined according to a matrix arrangement. To this end, a
plurality of conductive strips (310 to 314) is deposited by any
known deposition method on an insulating substrate (10) and forms
the first electrode. According to an example of realization, an
insulating layer (50) is then deposited, by any known method, such
as photolithography, on said conductive strips (FIG. 2A). The
insulating layer (50) is structured with holes (51) distributed
according to a transverse pitch perpendicular to the extension
direction of the conductive strips (310 to 314) and equal to the
deposition pitch of said strips on the substrate in this same
direction.
[0072] FIG. 2B: nanoclusters comprising at least two superimposed
layers are deposited in the holes, in contact with the conductive
strips (310 to 314), by any known method such as convective
capillary deposition. Second conductive strips (320 to 322),
extending in a different direction to that of the first conductive
strips deposited on the substrate, are deposited on the surface of
the insulating layer (50) such that said second conductive strips
are in contact with the nanoclusters (200) placed in the holes (51)
of the structured insulating layer (50), and form the second
electrode. Preferably the deposition direction of the second
conductive strips (320 to 322) forming the second electrode is
perpendicular to the direction of the first conductive strips (310
to 314) deposited on the substrate. An insulating film (not shown)
advantageously covers everything. According to an alternative
embodiment, the insulating layer comprising a network of holes is
not deposited and the nanoclusters are deposited in a structured
way directly on the conductive strips forming the first
electrode.
[0073] The ensemble can then be deposited on a surface to
functionalize it and make it touch-sensitive. Alternatively, the
substrate can itself form the functionalized surface.
[0074] When a pressure, e.g. from a finger or by means of a stylus,
is applied on a surface made functional in this way, a larger or
smaller area of said surface is affected by this pressure according
to its mode of application. The distance between the nanoparticles
of the clusters (200) located in this affected area is changed,
thus changing an electrical property of coupling between the first
electrode, placed on the substrate (10), and the second electrode,
placed on the insulating layer (50) in contact with the clusters
(200). For example this electrical property is resistivity.
[0075] Thus, by measuring the resistance between the first and
second electrode proceeding by pairs of conductive strips, it is
possible, via suitable processing of the measurements to locate the
points of application of the force resulting from the pressure and
also the intensity of said force. For example, if the force is
applied at the center of the surface thus made functional, the
resistance measured between the conductive strips (312, 321)
passing by the middle of the surface will be affected more than the
resistance measured between the conductive strips (314, 322)
extending along the edges of said surface.
[0076] FIG. 3: according to a second embodiment, the device that is
the subject of the invention comprises an insulating substrate
(10), on which is deposited a nanoparticles assembly (20) covering
most of its surface. Said nanoparticles assembly can be
single-layered or comprise several layers superimposed in a
direction normal to the surface of the substrate (10).
[0077] A first ensemble of conductive strips (315, 316) is
deposited on the substrate so as to form the first electrode, such
that said strips extend between a portion of the substrate not
covered by the nanoparticles assembly and said assembly in contact
with the latter. A second ensemble of strips (323, 324), forming
the second electrode, is deposited in the same way as the first
strips, in symmetry with them in relation to the center of the
center of the nanoparticles assembly. Finally, an insulating film
(60) is deposited over everything.
[0078] FIG. 6: according to a variant of this embodiment, the
discrete strips forming the first electrode are grouped into one or
more strips (315', 316').
[0079] FIG. 4: when a system of forces (501, 502) essentially
normal to the surface thus functionalized is applied to said
surface, this affects larger or smaller areas (511, 512) of the
nanoparticles assembly. In these affected areas (511, 512), the
distance between the nanoparticles of the assembly is changed, such
that the electrical properties are also changed. By taking one or
more measurements of an electrical property between the first
electrode (315, 316) and the second electrode (322, 324) and by
proceeding by pairs of conductive strips, profiles (601, 602) are
obtained giving the variation in said electrical property as a
function of the direction joining the two strips between which the
measurement was taken. Based on these variation profiles, the
intensity of the forces (501, 502) and also their point of
application can be determined by suitable processing of the
signal.
[0080] FIG. 5: according to a third embodiment, the device that is
the subject of the invention comprises an insulating substrate (10)
on which a nanoparticles assembly (20) covering a portion of the
surface of said substrate is deposited. The first electrode is
formed of an ensemble of strips (317) deposited on the substrate
and extending between a portion of the substrate that is not
covered and the nanoparticles assembly (20), in contact with the
latter. The second electrode (325) is placed on the nanoparticles
assembly, the ensemble being covered by an insulating film (not
shown). When a force is applied to the second electrode (325), both
the normal and tangential components of said force change the
distance between the nanoparticles of the assembly (20). The point
of application of the force being known, i.e. substantially at the
center of the second electrode (325), measuring an electrical
property between said second electrode (325) and each of the strips
(317) forming the first electrode makes it possible to determine,
by suitable processing of the signal, the intensity and orientation
of the force with regard to the nanoparticles assembly. A
three-dimensional force microsensor is thus created, which can be
combined in a matrix network in order to cover a larger surface
thus functionalized.
[0081] FIG. 7: the electrical property sensitive to the distance
between the nanoparticles of the assembly is, for example, the
electrical resistivity of said assembly. The variation in this
electrical property with the variation in distance between the
nanoparticles of the assembly is known from the prior art and has
been attributed to a variation in the tunnel effect between the
nanoparticles, without the present invention being in any way
linked to any theory. According to an alternative embodiment of the
device that is the subject of the invention, it is possible to
measure the variation in capacitance of said assembly. To this end,
the conductive nanoparticles (21) are bound by a suitable ligand,
chosen from the compounds described previously or from other
compounds having great electrical resistivity and similar chemical
bonding properties.
[0082] Each pair of nanoparticles separated by said ligand forms a
nano-capacitor, whose capacitance (29) is notably a function of the
distance between the conductive nanoparticles. Thus, in a similar
way, the application of a force on this nanoparticles assembly
changes the distance between said nanoparticles and the electrical
capacitance of said assembly. This variation in capacitance between
the electrodes (31, 32) can be measured by incorporating said
assembly in series/parallel in an electrical circuit. This
configuration offers the possibility of being able to read the
measurement remotely by means of well-known protocols from the
prior art of the radiofrequency field. To this end, a resonant
circuit is, for example, realized by coupling an inductance (70) in
parallel with the nanoparticles assembly.
[0083] Such a circuit is defined in particular by its resonance
frequency (f.sub.0), which is given by the relationship:
f 0 = 1 2 .pi. LC ##EQU00001##
[0084] where L is the value of the inductance, fixed, and C the
capacitance of the nanoparticles assembly, which varies as a
function of the stresses to which said assembly is subjected. Thus,
by measuring the resonance frequency of such a circuit subjected to
electromagnetic excitation, it is possible to determine the
variation in capacitance of said assembly.
[0085] For example, the circuit is subjected to continuous
electromagnetic excitation of frequency f.sub.0. Initially, the
system absorbs a lot at this frequency.
[0086] The presence of a deformation changes the absorption
spectrum by shifting it to the higher or lower frequencies by
changing the capacitance of the assembly. The absorption
coefficient at frequency f.sub.0 becomes changed.
[0087] According to another embodiment, the circuit is subjected to
pulsed electromagnetic excitation of frequency f.sub.0. After each
excitation pulse, measuring the circuit's emission during its
relaxation makes it possible to measure its absorption coefficient
and to deduce from it the nanoparticles assembly's capacitance.
[0088] To select measurements by pairs of conductive strips, the
device can be coupled to a component containing a unique
identification code. This binary code can be used to activate or
not each resonant circuit between a strip of the first electrode
and a strip of the second electrode.
[0089] FIG. 8: the nanoparticles assembly deposited on the
substrate (10) can be single-layered (FIG. 8B) or comprise several
superimposed layers (FIG. 8A). In its turn the ensemble can be
deposited or stuck on the surface (800) to be functionalized which,
from a practical point of view, is then equivalent to the touch
surface given the thinness of the device that is the subject of the
invention.
[0090] FIG. 8C: in the case where a force (500) is applied to a
nanoparticles assembly in a direction normal to the substrate (10),
the distance between the nanoparticles of an assembly comprising
several superimposed layers is changed both in a direction normal
to the surface and in directions tangential to this surface.
[0091] FIG. 8E: in the case of a single-layered assembly, the
application of a force (500) normal to the surface of the substrate
can only be detected and measured if it produces a movement of the
nanoparticles (21) tangential to the surface of said substrate.
Thus, in the case of a single-layered assembly the substrate (10')
is chosen such that it has some superficial flexibility or
compressibility such that a normal force (500) causes this
tangential movement of the nanoparticles. However, the
nanoparticles assembly remains the test specimen because it is the
deformation of this assembly itself that is measured, the
compressibility of the substrate being only a factor analogous to a
gain.
[0092] FIG. 8D: a superficially compressible substrate can also be
used with a nanoparticles assembly formed of several superimposed
layers.
[0093] The above description clearly illustrates that through its
various features and their advantages the present invention
realizes the objectives it set itself. In particular, it makes it
possible to functionalize a touch surface to make it sensitive to
the intensity and orientation of a system of forces stressing such
a surface.
* * * * *