CN106768520B - Pressure sensor and preparation method thereof - Google Patents
Pressure sensor and preparation method thereof Download PDFInfo
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- CN106768520B CN106768520B CN201611237468.8A CN201611237468A CN106768520B CN 106768520 B CN106768520 B CN 106768520B CN 201611237468 A CN201611237468 A CN 201611237468A CN 106768520 B CN106768520 B CN 106768520B
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- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
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Abstract
The invention discloses a pressure sensor and a preparation method thereof, wherein the pressure sensor comprises two external electrodes and two oppositely arranged elastic substrates, a convex structure is arranged on the contact surface of at least one substrate, the contact surface is the opposite surface of the two substrates, the substrates are electric conductors, each substrate is connected with one external electrode, and the surface of the convex structure is covered with a conductive layer. Therefore, the piezoresistive effect that the resistance is changed due to the fact that the elastic conductive substrate deforms under the action of pressure is utilized, the effect that the contact resistance is changed due to the fact that the contact area of the conductive layer on the surface of the protruding structure of the substrate is changed under the action of pressure is utilized, the pressure detection range is greatly expanded through the synergistic effect of the elastic conductive substrate and the substrate, and compared with the mode that a circuit layer is clamped between the two substrates in the prior art, the contact area of the conductive layer is changed greatly when the protruding structure deforms, and therefore the sensitivity and the reliability of the pressure sensor are further improved.
Description
Technical Field
The invention relates to the technical field of sensors, in particular to a pressure sensor and a preparation method thereof.
Background
The pressure sensor is an electronic device capable of converting stress into an electrical signal, and can be widely applied to the fields of flexible touch screens, artificial intelligence, wearable electronics, mobile medical treatment and the like. According to the signal conversion mechanism, pressure sensors are mainly classified into resistive sensors, capacitive sensors, and piezoelectric sensors. The basic working principle of the resistive pressure sensor is to convert the change of the measured pressure into the change of the resistance value of the sensor. The resistance type pressure sensor has the advantages of simple device structure, stable and easily-measured resistance signal, high sensitivity and the like.
Microstructuring the electrode array of the resistive pressure sensor is one of effective ways to improve the sensitivity and reliability of the sensor. For example, a resistive pressure sensor having a microstructure is proposed in the prior art, which includes an upper substrate, a lower substrate, a body circuit layer, and an extraction electrode; the upper substrate and the lower substrate are made of insulating elastic organic materials, one surfaces of the upper substrate and the lower substrate are in the same three-dimensional structure, and the surfaces with the three-dimensional structures are arranged oppositely; the body circuit layer is flexible, and conductive materials are arranged on the body circuit layer to form a conductive circuit layer; the body circuit layer is clamped between the upper substrate and the lower substrate, and electrodes are respectively led out from two ends of the body circuit layer. When pressure acts on the pressure sensor, the contact area of the microstructures on the upper and lower substrate surfaces changes under the action of the pressure, so that the resistance of the main circuit layer between the upper and lower substrate surfaces changes, and the pressure can be detected through the resistance change, so that the pressure sensor has high sensitivity.
However, although the sensitivity of the resistive pressure sensor having the microstructure is high, the range of pressure that can be detected is often small because the amount of deformation of the microstructure is small, thereby limiting the range of application thereof.
Disclosure of Invention
The embodiment of the invention mainly aims to provide a pressure sensor and a manufacturing method thereof, and aims to solve the technical problem that the pressure detection range of a resistance-type pressure sensor in the prior art is small.
In order to achieve the above object, in one aspect, a pressure sensor is provided, where the pressure sensor includes two external electrodes and two oppositely disposed elastic substrates, a protruding structure is disposed on a contact surface of at least one of the substrates, the contact surface is an opposite surface of the two substrates, the substrates are conductive bodies, each substrate is connected to one external electrode, and a conductive layer covers a surface of the protruding structure.
Optionally, the substrate is an elastic polymer-based conductive composite made from an elastic polymer and a conductive filler.
Alternatively, the elastic polymer-based conductive composite is prepared by a physical mechanical blending method, a solution blending method or a melt blending method.
Optionally, the conductive filler comprises one or at least two of metal conductive powder, carbon-based conductive filler, surface-plated conductive filler and bimetallic conductive filler.
Optionally, the elastomeric polymer is a silicone rubber, a natural rubber, a styrene-butadiene rubber, a polydimethylsiloxane, a thermoplastic polyurethane elastomer, a styrenic elastomer, a styrene-isoprene-styrene block copolymer, or a hydrogenated styrene-butadiene block copolymer.
Optionally, the conductive layer comprises one or at least two conductive materials of gold, silver, copper, aluminum, nickel, palladium, platinum, carbon, and indium tin oxide.
Alternatively, the conductive layer is prepared by any one of evaporation, chemical deposition, printing and coating.
Optionally, the contact surfaces of the two substrates have the same convex structures, and the convex parts of the contact surfaces of the two substrates are opposite to the convex parts or opposite to the concave parts.
Optionally, the substrate is made of a flexible material and has a thickness of 20 μm to 1 mm.
Optionally, the thickness of the conductive layer is 5nm-500 nm.
In another aspect, a method for manufacturing a pressure sensor is provided, the method comprising the steps of:
preparing two elastic conductive substrates, wherein a convex structure is arranged on the contact surface of at least one substrate;
covering a conductive layer on the surface of the raised structure of the substrate;
the contact surfaces of the two substrates are aligned with each other and then are overlapped and buckled together, and each substrate is connected with an external electrode.
Optionally, the step of preparing two conductive substrates with elasticity comprises:
mixing an elastomeric polymer and a conductive filler into a fluid form of a mixture;
and depositing the mixture on a prefabricated template with a concave structure, and curing and molding the mixture into an elastic polymer-based conductive composite material, wherein the elastic polymer-based conductive composite material is the elastic conductive substrate.
Optionally, the step of mixing the elastomeric polymer and the conductive filler into a fluid-like mixture comprises: the elastic polymer is used as a matrix and is mixed with the conductive filler into a mixture in a fluid state by a physical mechanical blending method, a solution blending method or a melt blending method.
Optionally, the step of depositing the mixture on a prefabricated template with a concave structure and curing and molding the mixture into the elastic polymer matrix conductive composite material comprises the following steps:
depositing the mixture on a prefabricated template with a concave structure by any one of casting, spin coating, blade coating and silk screen printing;
and heating and curing the mixture or forming the mixture into the elastic polymer-based conductive composite material after the mixture is naturally cured.
Optionally, the step of covering the surface of the protruding structure of the substrate with a conductive layer includes: and covering a conductive layer on the surface of the raised structure of the substrate by any one of evaporation, chemical deposition, printing and coating.
Optionally, the contact surfaces of the two substrates have the same protruding structures, and the step of stacking and buckling the contact surfaces of the two substrates after aligning the contact surfaces of the two substrates with each other includes: and aligning and then overlapping the convex parts and the convex parts or the convex parts and the concave parts of the contact surfaces of the two substrates.
According to the pressure sensor provided by the embodiment of the invention, the pair of elastic conductive substrates are arranged, and the surface of the raised structure of each substrate is covered with the conductive layer, so that the piezoresistive effect that the resistance is changed due to the deformation of the elastic conductive substrate under the action of pressure is utilized, the effect that the contact resistance is changed due to the change of the contact area of the conductive layer on the surface of the raised structure of the substrate under the action of pressure is utilized, the pressure detection range is greatly expanded through the synergistic effect of the elastic conductive substrates and the conductive layer, and compared with the mode that the circuit layer is clamped between the two substrates in the prior art, the contact area of the conductive layer in the embodiment of the invention is changed greatly when the raised structure is deformed, so that the sensitivity and the reliability of the pressure sensor are further improved. The pressure sensor provided by the embodiment of the invention has the advantages of simple structure, low cost, convenience in manufacturing, sensitive response, wide pressure detection range and good mechanical flexibility, and is suitable for new fields of wearable electronics, electronic skin, man-machine intelligence and the like.
Drawings
Fig. 1 is a schematic structural view of a pressure sensor according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of the pressure sensor of FIG. 1 deformed by a force;
FIG. 3 is a schematic view of another configuration of a pressure sensor in accordance with an embodiment of the present invention;
FIG. 4 is a flow chart of a method of making a pressure sensor of a second embodiment of the present invention;
fig. 5 is a flow chart of the steps of preparing a substrate in an embodiment of the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example one
Referring to fig. 1, a pressure sensor according to a first embodiment of the present invention is provided, which includes two external electrodes 30 and two oppositely disposed substrates 10, wherein the substrates 10 have elasticity and are conductive bodies. As shown in fig. 1, the contact surfaces (the opposite surfaces of the two substrates) of the two substrates 10 have micro-convex structures 11 (or micro-convex structures), the convex structures 11 of the two substrates 10 are preferably the same structure, the convex structures 11 result in convex and concave parts on the contact surfaces, and the convex parts of the contact surfaces of the two substrates 10 can be in direct contact, or the convex parts and the concave parts can be in direct contact. The surface of the raised structures 11 is covered with a conductive layer 20, and each substrate 10 is connected to an external electrode 30 for connection to an external circuit for testing the resistance/current change of the sensor under pressure.
In the embodiment of the present invention, the substrate 10 is an elastic polymer-based conductive composite material made of an elastic polymer and a conductive filler 12, and the elastic polymer-based conductive composite material may be prepared by a physical mechanical blending method, a solution blending method, a melt blending method, and other mixing processes, and is formed by a template having a micro-recessed structure (or concave microstructure). The substrate 10 made of the elastic polymer-based conductive composite material is a flexible material, the thickness is preferably 20 micrometers-1 mm, mechanical deformation such as bending, folding, twisting and stretching can be realized, the flexible composite material is suitable for the field of modern flexible electronic products, and the development requirements of light weight, miniaturization, flexibility and wearability of electronic devices are met.
The elastic polymer may be any one of polymers such as silicone rubber, Natural Rubber (NR), styrene-butadiene rubber (SBR), Polydimethylsiloxane (PDMS), thermoplastic polyurethane elastomer (TPU), styrene elastomer (e.g., styrene-butadiene-styrene block copolymer (SBS)), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butadiene block copolymer (SEBS).
The conductive filler 12 includes one or at least two of metal conductive powder (such as gold powder, silver powder, copper powder, nickel powder, etc.), carbon-based conductive filler (such as carbon black, carbon nanotube, graphite, graphene, etc.), conductive filler with metal plated on the surface (such as gold plated on the surface of glass fiber, silver, copper, nickel, etc., gold plated on the surface of polymer microsphere, silver, copper, nickel, etc.), and bimetallic conductive filler (such as silver-coated copper, nickel-coated copper, etc.).
In other embodiments, the substrate 10 having the raised structures 11 on the surface can also be made by directly processing (e.g., processing by micro-electro-mechanical systems (MEMS) technology) a conductive material having elasticity (e.g., a conductive thermoplastic elastomer, a conductive silicone elastomer, etc.).
The protruding structure 11 on the contact surface of the substrate 10 may be one or a combination of at least two of regular three-dimensional structures such as prisms, pyramids, cylinders, triangular pyramids, spheres, and the like, or irregular three-dimensional structures such as curved protrusions, waves, and the like, and the height of the protruding structure 11 is preferably 200nm-200 μm.
The conductive layer 20 on the surface of the protruding structure 11 can be prepared by any one of evaporation, chemical deposition, printing and coating, and the conductive layer 20 includes one or at least two conductive materials selected from gold, silver, copper, aluminum, nickel, palladium, platinum, carbon and Indium Tin Oxide (ITO). The thickness of the conductive layer 20 is preferably 5nm-500nm, and the conductive layer is tightly combined with the protruding structure into a whole, and completely changes along with the shape change of the protruding structure, so that the conductive layer is more sensitive to deformation, and the contact area changes more during deformation.
The external electrode 30 is preferably connected to an outer surface (i.e., a surface opposite to the contact surface) of the substrate 10, and the external electrode 30 includes one or at least two of gold foil/wire, silver foil/wire, copper foil/wire, and aluminum foil/wire.
The working principle of the pressure sensor of the embodiment of the invention is as follows:
as shown in fig. 2, when an external pressure F is applied to the pressure sensor, on the one hand, the substrate 10 is deformed and becomes smaller in thickness in the pressure direction, which results in narrowing the distance of the conductive filler 12 inside the substrate 10 in the pressure direction, while the length and width of the substrate 10 in the planar direction become larger due to the pressure, which results in widening the lateral distance of the conductive filler 12 inside the substrate 10 in the planar direction. It is known from the tunnel conduction theory of composite conductive materials that the change in distance between the conductive fillers 12 will change the resistance of the composite material. The change in the distance between the conductive fillers 12 varies with the magnitude of the pressure, and the resulting change in the resistance varies.
On the other hand, under the action of the external pressure F, the protruding structures 11 on the contact surface of the substrate 10 are significantly deformed, so that the contact area of the conductive layer 20 on the surface of the protruding structures 11 is changed, and the contact resistance between the upper and lower substrates 10 is changed.
The combined action of the two parts enables the resistance of the pressure sensor to change under the action of pressure, and the pressure can be detected through the change condition of the resistance. When the pressure is removed, the deformation of the substrate 10 will return to the initial state as shown in fig. 1 due to its elastic action, and the resistance will also return to the initial value.
In an alternative embodiment, the raised structures 11 may also be provided on the contact surface of only one substrate 10. As shown in fig. 3, the contact surface of the upper substrate 10 has the protruding structures 11 thereon, and the protruding structures 11 are covered with the conductive layer 20, and the contact surface of the lower substrate 10 does not have the protruding structures 11 thereon, and may or may not be covered with the conductive layer 20. Although the lower substrate 10 does not have the protruding structures 11, the lower substrate 10 is made of an elastic conductive material, and still deforms when being pressed, so that the resistance change is contributed, the sensitivity of the sensor is still improved, and the pressure detection range is expanded compared with the prior art.
According to the pressure sensor provided by the embodiment of the invention, the pair of elastic conductive substrates 10 are arranged, and the surface of the convex structure 11 of the substrate 10 is covered with the conductive layer 20, so that the piezoresistive effect that the resistance is changed due to the deformation of the elastic conductive substrates 10 under the action of pressure is utilized, the effect that the contact resistance is changed due to the change of the contact area of the conductive layer 20 on the surface of the convex structure 11 of the substrate 10 under the action of pressure is utilized, the pressure detection range is greatly expanded through the synergistic effect of the two, and compared with the mode that a circuit layer is clamped between the two substrates in the prior art, the contact area of the conductive layer 20 in the embodiment of the invention is changed greatly when the convex structure 11 is deformed, so that the sensitivity and the reliability of the pressure sensor are further improved. The pressure sensor provided by the embodiment of the invention has the advantages of simple structure, low cost, convenience in manufacturing, sensitive response, wide pressure detection range and good mechanical flexibility, and is suitable for new fields of wearable electronics, electronic skin, man-machine intelligence and the like.
Example two
Referring to fig. 4, there is proposed a method of manufacturing a pressure sensor of a second embodiment of the present invention, the method including the steps of:
s11, preparing two conductive substrates with elasticity, and arranging a convex structure on the contact surface of at least one substrate.
In step S11, two elastic conductive substrates are prepared, and at least one of the substrates has a protruding structure on its contact surface, which is the opposite surface when the two substrates are finally stacked together.
Embodiments of the present invention preferably prepare two substrates having the same raised structures, and in other embodiments, the raised structures on the two substrates may not be the same or only one substrate may have raised structures. The protruding structure on the substrate contact surface can be one or the combination of at least two of regular three-dimensional structures such as prisms, pyramids, cylinders, triangular pyramids, spheres and the like or irregular three-dimensional structures such as curved surface protrusions, wavy structures and the like, and the height of the protruding structure is preferably 200nm-200 μm.
The substrate of the embodiment of the invention is an elastic polymer-based conductive composite material, and the manufacturing method thereof is shown in figure 5 and comprises the following steps:
s111, mixing the elastic polymer and the conductive filler into a mixture in a fluid form.
In step S111, the elastic polymer may be used as a matrix, and mixed with the conductive filler by a physical mechanical blending method, a solution blending method, a melt blending method, or the like to form a fluid mixture, such as a mixed solution, a mixed slurry, a mixed paste, or the like.
The elastic polymer may be any one of polymers such as silicone rubber, Natural Rubber (NR), styrene-butadiene rubber (SBR), Polydimethylsiloxane (PDMS), thermoplastic polyurethane elastomer (TPU), styrene elastomer (e.g., styrene-butadiene-styrene block copolymer (SBS)), styrene-isoprene-styrene block copolymer (SIS), and hydrogenated styrene-butadiene block copolymer (SEBS).
The conductive filler comprises one or at least two of metal conductive powder (such as gold powder, silver powder, copper powder, nickel powder and the like), carbon conductive filler (such as carbon black, carbon nano tubes, graphite, graphene and the like), conductive filler with metal plated on the surface (such as gold plated on the surface of glass fiber, silver, copper, nickel and the like, gold plated on the surface of polymer microsphere, silver, copper, nickel and the like), and bimetallic conductive filler (such as silver-coated copper, nickel-coated copper and the like).
And S112, depositing the mixture on a prefabricated template with a concave structure, and curing and molding the mixture into the elastic polymer matrix conductive composite material.
In step S112, the mixture is deposited on a prefabricated template having a concave structure by casting, spin coating, blade coating, screen printing, or the like, and then the mixture is heated to cure or the mixture is naturally cured after the solvent in the mixture is volatilized, and then a flexible film is formed, and the film is torn off from the template, so as to obtain an elastic polymer-based conductive composite material having a convex structure corresponding to the concave structure on the surface, that is, a flexible conductive substrate having a convex structure on the surface. The thickness of the flexible conductive substrate is preferably 20 mu m-1mm, mechanical deformation such as bending, folding, twisting and stretching can be realized, the flexible conductive substrate is suitable for the field of modern flexible electronic products, and the development requirements of light weight, miniaturization, flexibility and wearability of electronic devices are met.
When it is desired to fabricate a substrate without raised structures, the mixture is deposited using a template without recessed structures.
When the elastic polymer-based conductive composite material is prepared, the filling amount of the conductive filler is preferably adjusted to be close to the percolation threshold value, so that the elastic polymer-based conductive composite material can obtain a high voltage resistance effect. The percolation threshold is related to the parameters of the conductive filler such as size, morphology and density, and is determined according to the parameters of the conductive filler in the implementation process.
In the embodiment of the present invention, the template having the recess structure may be prepared by the following method:
a silicon wafer is used as a substrate, a miniature concave structure array is manufactured on the surface of the silicon wafer through an MEMS technology, the concave structure can be one or the combination of at least two of regular three-dimensional structures such as prisms, pyramids, cylinders, triangular pyramids, spheres and the like or irregular three-dimensional structures such as concave curved surfaces, wavy structures and the like, and the depth of a concave part of the concave structure is preferably 200nm-200 mu m.
In other embodiments, the substrate with the raised structure on the surface can also be made by directly processing (e.g., processing by MEMS technology) a conductive material with elasticity (e.g., a conductive thermoplastic elastomer, a conductive silicone elastomer, etc.).
And S12, covering a conductive layer on the surface of the raised structure of the substrate.
In step S12, a conductive layer including one or at least two conductive materials selected from gold, silver, copper, aluminum, nickel, palladium, platinum, carbon, and indium tin oxide may be coated on the surface of the protruding structure of the substrate by any one of evaporation, chemical deposition, printing, and coating. The thickness of the conductive layer is preferably 5nm to 500 nm.
And S13, aligning the contact surfaces of the two substrates, overlapping and buckling the two substrates together, and connecting an external electrode on each substrate.
In step S13, when the contact surfaces of the two substrates have the protruding structures, and there are protruding portions and recessed portions on the contact surfaces, the protruding portions and the protruding portions or the protruding portions and the recessed portions of the contact surfaces of the two substrates are aligned and then overlapped, and the protruding structures on the two substrates contact each other. And an external electrode is led out from each substrate and is used for being connected with an external circuit to test the resistance/current change condition of the sensor under the action of pressure. The external electrode is preferably led out from the outer surface (i.e. the surface opposite to the contact surface) of the substrate, and the external electrode comprises one or at least two of gold foil/wire, silver foil/wire, copper foil/wire and aluminum foil/wire.
By the method, the flexible pressure sensor which is low in cost, simple in structure, convenient to manufacture, sensitive in response and wide in test pressure range is manufactured finally.
The method for manufacturing the pressure sensor according to the embodiment of the present invention will be described in detail below by way of specific examples:
example 1:
(1) a silicon wafer is used as a substrate, a semicircular spherical hole array (a concave structure array) is processed on the surface of the silicon wafer through an MEMS technology, the diameter of the array is 20 micrometers, and the processed silicon wafer is used as a micro template.
(2) Selecting a silver sheet with the particle size of 1-10 mu m as a conductive filler, taking Polydimethylsiloxane (PDMS) as a matrix, and mechanically stirring and uniformly mixing a PDMS prepolymer and a curing agent thereof with the silver sheet to obtain the flexible conductive paste (a mixture in a fluid form). The mass ratio of the PDMS prepolymer to the curing agent thereof is 12: 1-5: 1, and the mass ratio of the PDMS and the curing agent thereof (the total mass of the PDMS prepolymer and the curing agent thereof) to the silver sheet is 1: 1-1: 4.
(3) And (3) depositing the flexible conductive paste prepared in the step (2) on the silicon micro template prepared in the step (1) by a mask blade coating printing method, heating at 80 ℃ for 2 hours to solidify the flexible conductive paste into a film, and tearing the solidified film from the silicon micro template to obtain the flexible conductive substrate with the hemispherical convex structure. The thickness of the substrate can be adjusted through the thickness of the mask plate, and the thickness of the flexible conductive substrate in the example is controlled within 200 mu m.
(4) And (4) placing the flexible conductive substrate prepared in the step (3) in evaporation equipment, and evaporating a nano-gold conductive thin layer on the surface of the convex structure of the substrate by adopting a magnetron sputtering method, wherein the thickness of the nano-gold is 10nm, so as to obtain the flexible conductive substrate with the conductive layer.
(5) Two flexible conductive substrates with conductive layers are oppositely overlapped and buckled together (the hemispherical convex structures are mutually contacted), and copper foil external electrodes are respectively led out from the outer surfaces of the upper substrate and the lower substrate to be connected with an external circuit for use, so that the resistance type flexible pressure sensor is manufactured.
Example 2:
(1) a silicon wafer is used as a substrate, an inverted triangular conical hole array (a concave structure array) is processed on the surface of the silicon wafer through an MEMS technology, the depth of the inverted triangular conical hole array is 100 micrometers, the width of the bottom surface of the inverted triangular conical hole array is 100 micrometers, and the silicon wafer is used as a micro template.
(2) Selecting carbon nanotubes with the diameter of 5-100 nm and the length of 2-30 mu m as conductive fillers, and uniformly dispersing the carbon nanotubes by using a chloroform solvent to obtain a carbon nanotube dispersion liquid. Styrene-butadiene-styrene block copolymer (SBS) is used as a matrix, SBS granules are added into the carbon nano tube dispersion liquid, and the mixture is stirred until SBS is completely dissolved to obtain uniform composite slurry (mixture in a fluid state). The mass ratio of the carbon nano tube to the SBS is 1: 19-1: 4.
(3) And (3) depositing the composite slurry prepared in the step (2) on the silicon micro template prepared in the step (1) by a spin coating method, standing at room temperature for 24 hours until chloroform is completely volatilized, naturally forming a film, and tearing the film from the silicon micro template to obtain the flexible conductive substrate with the triangular conical bulge structure. The thickness of the substrate can be adjusted by spin coating process such as spin coating time, spin coating speed, etc., and the thickness of the flexible conductive substrate in this example is controlled within 500 μm.
(4) And (4) placing the flexible conductive substrate prepared in the step (3) in evaporation equipment, and evaporating a nano platinum (Pt) conductive thin layer on the surface of the convex structure of the substrate by adopting a magnetron sputtering method, wherein the thickness of Pt is 30nm, so that the flexible conductive substrate with the conductive layer is obtained.
(5) Two flexible conductive substrates with conductive layers are oppositely overlapped and buckled together (the triangular conical convex structures are mutually contacted), and external electrodes of silver leads are respectively led out from the outer surfaces of the upper substrate and the lower substrate to be connected with an external circuit for use, so that the resistance type flexible pressure sensor is manufactured.
Example 3:
(1) a silicon wafer is used as a substrate, an inverted pyramid-shaped hole array (a concave structure array) is processed on the surface of the silicon wafer through an MEMS technology, the height of the inverted pyramid-shaped hole array is 2 micrometers, the width of the lower bottom surface is 1 micrometer, the width of the upper bottom surface is 4 micrometers, and the silicon wafer is used as a micro template.
(2) Selecting carbon black with the particle size of 10-100 nm as a conductive filler, and dissolving the ultrasonically dispersed carbon black nanoparticles by using toluene to obtain a carbon black dispersion liquid. Thermoplastic polyurethane elastomer (TPU) is taken as a matrix, TPU granules are gradually added into carbon black dispersion liquid, and the mixture is stirred until the TPU is completely dissolved to obtain uniform composite slurry (mixture in a fluid state). The mass ratio of the carbon black to the TPU is 1: 9-1: 3.
(3) And (3) pouring the composite slurry prepared in the step (2) on the silicon micro-template prepared in the step (1), heating at 80 ℃ for 4 hours to completely volatilize the toluene solvent and form a film, and tearing the film from the silicon micro-template to obtain the flexible conductive substrate with the pyramid-shaped convex structure. The thickness of the substrate can be adjusted by the concentration of the composite slurry and the casting volume, and the thickness of the flexible conductive substrate in the example is controlled within 50 μm.
(4) And (4) placing the flexible conductive substrate prepared in the step (3) in evaporation equipment, and evaporating a nano copper conductive thin layer on the surface of the convex structure of the substrate by adopting a magnetron sputtering method, wherein the thickness of the nano copper is 15nm, so that the flexible conductive substrate with the conductive layer is obtained.
(5) Two flexible conductive substrates with conductive layers are oppositely overlapped and buckled together (pyramid micro-convex structures are mutually contacted), and aluminum lead external electrodes are respectively led out from the outer surfaces of the upper substrate and the lower substrate to be connected with an external circuit for use, so that the resistance type flexible pressure sensor is manufactured.
It will be understood by those skilled in the art that the foregoing is merely exemplary of the present invention and is not intended to limit the scope of the invention.
According to the preparation method of the pressure sensor, the elastic substrate with the protruding structure and capable of conducting electricity is prepared, the conducting layer is manufactured on the surface of the protruding structure of the substrate, and the resistance type pressure sensor is constructed on the basis of the elastic substrate with the protruding structure, resistance change generated by piezoresistive effect and contact resistance change of the conducting layer with the protruding structure are combined by the sensor, advantages of the resistance change and the contact resistance change are combined, so that the sensor has higher sensitivity and wider pressure detection range, and development requirements of light weight, miniaturization, flexibility and wearability of electronic devices are met.
In summary, the pressure sensor manufactured by the method has the following advantages:
1) the flexible printed circuit board has good flexibility, can realize mechanical deformation such as bending, folding, twisting, stretching and the like, and is suitable for the field of modern flexible electronic products;
2) the resistance signal is easy to detect and convenient to use;
3) the structure is simple, the manufacture is convenient, and the cost is low;
4) the piezoresistive effect and the contact resistance effect of the microstructure electrode are combined, the sensitivity of the sensor is improved, the pressure detection range is expanded, and the performance of the sensor can be regulated and controlled through the design of materials and structures.
The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, and are not to be construed as limiting the scope of the invention. Those skilled in the art can implement the invention in various modifications, such as features from one embodiment can be used in another embodiment to yield yet a further embodiment, without departing from the scope and spirit of the invention. Any modification, equivalent replacement and improvement made within the technical idea of using the present invention should be within the scope of the right of the present invention.
Claims (15)
1. A pressure sensor comprises two external electrodes (30) and two oppositely arranged elastic substrates (10), wherein a convex structure (11) is arranged on the contact surface of at least one substrate (10), the contact surface is the opposite surface of the two substrates (10), the pressure sensor is characterized in that the substrate (10) is an electric conductor, the substrate (10) is made of a flexible material, the thickness of the substrate is 20 mu m-1mm, and the substrate (10) is made of an elastic polymer-based conductive composite material made of an elastic polymer and conductive fillers (12); each substrate (10) is connected with an external electrode (30), the external electrode (30) is connected with the outer surface of the substrate (10), and the outer surface of the substrate (10) is the surface opposite to the contact surface;
the contact surfaces of the two substrates (10) are provided with the same convex structures (11), and convex parts of the contact surfaces of the two substrates (10) are opposite to the convex parts or the convex parts are opposite to the concave parts; the height of the protruding structure (11) is 200nm-200 μm; the surface of the protruding structure (11) is covered with a conducting layer (20), and the thickness of the conducting layer (20) is 5nm-500 nm.
2. The pressure sensor of claim 1, wherein the elastic polymer-based conductive composite is prepared by a physical mechanical blending method, a solution blending method, or a melt blending method.
3. The pressure sensor according to claim 1, wherein the conductive filler (12) comprises one or at least two of a metal conductive powder, a carbon-based conductive filler, a surface-plated conductive filler, a bimetallic conductive filler.
4. The pressure sensor of claim 1, wherein the elastic polymer is silicone rubber, natural rubber, styrene-butadiene rubber, polydimethylsiloxane, thermoplastic polyurethane elastomer, styrenic elastomer, styrene-isoprene-styrene block copolymer, or hydrogenated styrene-butadiene block copolymer.
5. A pressure sensor according to claim 1, characterized in that the conductive layer (20) comprises one or at least two conductive materials of gold, silver, copper, aluminium, nickel, palladium, platinum, carbon and indium tin oxide.
6. A pressure sensor according to claim 1, wherein the conductive layer (20) is prepared by any one of evaporation, chemical deposition, printing and coating.
7. A method of making a pressure sensor according to claim 1, comprising the steps of:
preparing two elastic conductive substrates, wherein a convex structure is arranged on the contact surface of at least one substrate;
covering a conductive layer on the surface of the raised structure of the substrate;
the contact surfaces of the two substrates are aligned with each other and then are overlapped and buckled together, and each substrate is connected with an external electrode.
8. The method of manufacturing a pressure sensor according to claim 7, wherein the step of manufacturing two conductive substrates having elasticity includes:
mixing an elastomeric polymer and a conductive filler into a fluid form of a mixture;
and depositing the mixture on a prefabricated template with a concave structure, and curing and molding the mixture into an elastic polymer-based conductive composite material, wherein the elastic polymer-based conductive composite material is the elastic conductive substrate.
9. The method of claim 8, wherein the step of mixing the elastomeric polymer and the conductive filler into a fluid mixture comprises:
the elastic polymer is used as a matrix and is mixed with the conductive filler into a mixture in a fluid state by a physical mechanical blending method, a solution blending method or a melt blending method.
10. The method for preparing a pressure sensor according to claim 8, wherein the step of depositing the mixture on a prefabricated template with a concave structure and curing and molding the mixture into the elastic polymer matrix conductive composite material comprises the following steps:
depositing the mixture on a prefabricated template with a concave structure by any one of casting, spin coating, blade coating and silk screen printing;
and heating and curing the mixture or forming the mixture into the elastic polymer-based conductive composite material after the mixture is naturally cured.
11. The method of claim 8, wherein the conductive filler comprises one or at least two of metal conductive powder, carbon-based conductive filler, surface-plated conductive filler, and bimetallic conductive filler.
12. The method of manufacturing a pressure sensor according to claim 8, wherein the elastic polymer is silicone rubber, natural rubber, styrene-butadiene rubber, polydimethylsiloxane, thermoplastic polyurethane elastomer, styrene-based elastomer, styrene-isoprene-styrene block copolymer, or hydrogenated styrene-butadiene block copolymer.
13. The method of manufacturing a pressure sensor according to any one of claims 7 to 12, wherein the step of covering the surface of the protruding structure of the substrate with a conductive layer comprises:
and covering a conductive layer on the surface of the raised structure of the substrate by any one of evaporation, chemical deposition, printing and coating.
14. A method of manufacturing a pressure sensor according to any of claims 7-12, wherein the conductive layer comprises one or at least two conductive materials of gold, silver, copper, aluminum, nickel, palladium, platinum, carbon and indium tin oxide.
15. A method for manufacturing a pressure sensor according to any of claims 7-12, wherein the contact surfaces of the two substrates have the same convex structure, and the step of aligning and snapping the contact surfaces of the two substrates together comprises:
and aligning and then overlapping the convex parts and the convex parts or the convex parts and the concave parts of the contact surfaces of the two substrates.
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| CN201611237468.8A CN106768520B (en) | 2016-12-28 | 2016-12-28 | Pressure sensor and preparation method thereof |
| PCT/CN2017/074257 WO2018120384A1 (en) | 2016-12-28 | 2017-02-21 | Pressure sensor and preparation method therefor |
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