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.

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 .