Flexible pressure sensor and fabrication method thereof

Abstract

The present invention relates to a sensor, particularly a flexible pressure sensor and a fabrication method thereof. The invention provides a flexible pressure sensor which comprises a sensor body and electrodes. The sensor body comprises a first insulation layer of PET film, a first conductivity layer, an isolation layer, a second conductive layer and a second insulation layer of PET film from top to bottom, respectively. The electrodes are made from the first conductive layer and the second conductive layer connected with external circuit through any electrical wire. The isolation layer is a semi-conductive foamed polymer with adjustable conductivity/resistance. Both of the first insulation layer of PET film and the second insulation layer of PET film have the thickness of 4.5-120 μm with the surface resistance value of 10.sup.13-14. In the process method of the invention, the isolation layer is a foamed polymer with adjustable conductivity. When pressed, the isolation layer deforms, which reduces the resistance between the two electrodes and increases the conductivity. High sensitivity of the isolation layer meets the requirement that a tiny deformation is enough to have a large change in resistance. Hence, the pressure can be detected by computer data processing upon the relationship between any external pressure and related resistance value.

Claims

1. A flexible pressure sensor which comprises a sensor body and electrodes; wherein the sensor body comprises a first insulation layer of PET film, a first conductive layer, an isolation layer, a second conductive layer and a second insulation layer of PET film, wherein the electrodes are connected to (i) the first conductive layer or the second conductive layer, and (ii) an external circuit, wherein the isolation layer is a semi-conductive foamed polymer with adjustable conductivity/resistance, and wherein the first insulation layer of PET film and the second insulation layer of PET film have the same thickness of 4.5-120 μm.

2. The flexible pressure sensor according to claim 1, wherein the isolation layer is foamed polypropylene or foamed polyurethane with a thickness of 400-600 μm.

3. The flexible pressure sensor according to claim 1, wherein the isolation layer has a compression deformation rate of 8-12%.

4. The flexible pressure sensor according to claim 2, wherein the foamed polyurethane comprises polytetramethylene ether glycol (PTMEG) of 60-90 by weight, polyoxypropylene triol of 10-30 by weight, catalytic agent of 1-2 by weight, foaming system of 2-3 by weight, prepolymerized MDI of 75-80 by weight, wherein the molecular weight of PTMEG is 1000-4000 and the OH value is 30-45 mgKOH/g, wherein the molecular weight of polyoxypropylene triol is 700-3000; wherein the prepolymerized MDI is prepolymerized 4-4-MDI with 12%-32% NCO; wherein the foaming system comprises a foaming agent and a foaming stabilizer; wherein the foaming agent and the foaming stabilizer are 3-5:1 by weight; wherein the foaming agent is water, wherein the foaming stabilizer is a mixture of p-cumylphenol polyethenoxy ether and sodium dodecyl sulfate; wherein the p-cumylphenol polyethenoxy ether and sodium dodecyl sulfate are 5-6: 1 by weight.

5. The flexible pressure sensor according to claim 1, wherein the first conductive layer and the second conductive layer are silver nanowire films.

6. The flexible pressure sensor according to claim 5, wherein the silver nanowire films have a thickness of 80-180 nm.

7. The flexible pressure sensor according to claim 5 wherein the silver nanowire films comprise silver nanowires having a diameter ranging from 20-150 nm.

8. A method of preparing the flexible pressure sensor according to claim 1, the method comprising: S1: preparing the isolation layer by micro-foaming of a polymer; S2: coating a first side of the isolation layer in step S1 with conductive materials to form the first conductive layer after drying; S3: coating a side of the first conductive layer in step S2 with PET hot melt adhesive at the temperature of 260-265° C. to form the first insulation layer of PET film after cooling to room temperature; S4: coating a second side of the isolation layer in step S1 with conductive materials to form the second conductive layer after drying; S5: coating a side of the second conductive layer in step S4 with PET hot melt adhesive at the temperature of 260-265° C. to form the second insulation layer of PET film after cooling to room temperature; S6: connecting a pair of electrodes to the conductive material of the first and second conductive layers which is then solidified.

9. The method according to claim 8, wherein the drying in steps S2 and S4 is wind drying.

10. The method according to claim 8, wherein in step S6 the solidifying uses a UV curing resin dispensing method.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 depicts an embodiment of the present flexible pressure sensor. The flexible pressure sensor includes: 1: first insulation layer of the PET film; 2: first conductivity layer; 3: isolation layer; 4: second conductivity layer; and 5: second insulation layer of the PET film.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(2) The following is a further explanation of the present invention in specific embodiments, but the following embodiments are only a further explanation of the present invention, which does not mean that the scope of protection of the present invention is limited to this, and all equivalent substitutions made according to the ideas of the present invention are within the scope of protection of the present invention

Embodiment 1

(3) S1: Polypropylene, maleic anhydride and composite foaming agent were used as main raw materials, with trace peroxide dibenzoyl as initiator, first crosslinking and granulating in twin-screw extruder, and finally extruding in single-screw extruder, then casting (casting temperature 180-200 C.), cooling to produce a 500-micron thickness isolation layer. The melting index of the polypropylene is 1.6-3.6 g/10 min.

(4) S2: 0.3-1.5 wt % silver nanowires isopropanol solution is coated on the front surface of the isolation layer in step 1 by Slot-Die coating machine. After wind drying, the first conductive layer with thickness of 80-180 nm is formed, and the diameter of the silver nanowires is 20-150 nm.

(5) S3: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the first conductivity layer in step S2, and then the first insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(6) S4: 0.3-1.5 wt % silver nanowires isopropanol solution is slit coated on the reverse side of the isolation layer in step 1 by a Slot-Die coating machine. After wind drying, a second conductive layer with thickness of 80-180 nm is formed. The diameter of the nanowires is 20-150 nm.

(7) S5: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the second conductivity layer in step S4, and then the second insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(8) S6: A pair of electrodes is drawn from the conductive material of the first and second conductive layers, and solidified and packaged according to the required induction range.

(9) The isolation layer is foamed polypropylene resin, the average cell size is about 8-15 micron, and the density is 0.8-1.5×10.sup.8/cm.sup.3. The deformation occurs when subjected to pressure, and then leads a change of the resistance between the two electrodes. A slight deformation is enough to have a large electrical resistance change which achieves high sensitivity of the isolation layer and result in the values of any pressure can be detected.

Embodiment 2

(10) The foamed polyurethane comprises polytetramethylene ether glycol (PTMEG) of 60-90 by weight, polyoxypropylene triol of 10-30 by weight, catalyst of 1-2 by weight, foaming system of 2-3 by weight, prepolymerized MDI of 75-80 by weight, wherein the molecular weight of PTMEG is 1000-4000 and the OH value is 30-45 mgKOH/g, wherein the molecular weight of polyoxypropylene triol is 700-3000, wherein the prepolymerized MDI is 4-4-MDI prepolymerized with 12%-32% NCO. The additives comprise catalytic agent and foaming system. The foaming system comprises a foaming agent and a foaming stabilizer. The foaming agent and the foaming stabilizer are 3-5:1 by weight. The foaming agent is water and the foaming stabilizer is a mixture of p-cumylphenol polyethenoxy ether and sodium dodecyl sulfate. preferably, the p-cumylphenol polyethenoxy ether and sodium dodecyl sulfate are 5-6:1 by weight.

(11) S1: The ingredients of preparing the foamed polyurethane are evenly mixed, coated on a release paper and dried through oven at 110° C. with the speed of 10-20 m/min, and then an isolation layer is formed with a thickness of 500 μm after cooled and released from the release paper.

(12) S2: 0.3-1.5 wt % silver nanowires isopropanol solution is coated on the front surface of the isolation layer in step 1 by Slot-Die coating machine. After wind drying, the first conductive layer with thickness of 80-180 nm is formed, and the diameter of the silver nanowires is 20-150 nm

(13) S3: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the first conductivity layer in step S2, and then the first insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(14) S4: 0.3-1.5 wt % silver nanowires isopropanol solution is slit coated on the reverse side of the isolation layer in step 1 by a Slot-Die coating machine. After wind drying, a second conductive layer with thickness of 80-180 nm is formed. The diameter of the nanowires is 20-150 nm.

(15) S5: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the second conductivity layer in step S4, and then the second insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(16) S6: A pair of electrodes is drawn from the conductive material of the first and second conductive layers, and solidified and packaged according to the required induction range.

(17) The isolation layer is foamed polyurethane resin, the average cell size is about 8-15 micron, and the density is 0.8-1.5×10.sup.8/cm.sup.3. The deformation occurs when subjected to pressure, and then leads a change of the resistance between the two electrodes. A slight deformation is enough to have a large electrical resistance change which achieves high sensitivity of the isolation layer and result in the values of any pressure can be detected.

(18) Contrast 1

(19) The foamed polyurethane comprises polytetramethylene ether glycol (PTMEG) of 60-90 by weight, polyoxypropylene triol of 10-30 by weight, catalytic agent of 1-2 by weight, water of 2-3 by weight, prepolymerized MDI of 75-80 by weight, wherein the molecular weight of PTMEG is 1000-4000; the OH value is 30-45 mgKOH/g, the molecular weight of polyoxypropylene triol is 700-3000; the prepolymerized MDI is prepolymerized 4-4-MDI with 12%-32% NCO; the foaming system comprises a foaming agent and a foaming stabilizer; the foaming agent and the foaming stabilizer are 3-5:1 by weight.

(20) S1: The ingredients of preparing the foamed polyurethane are evenly mixed, coated on a release paper and dried through oven at 110° C. with the speed of 10-20 m/min, and then an isolation layer is formed with a thickness of 500 μm after cooled and released from the release paper.

(21) S2: 0.3-1.5 wt % silver nanowires isopropanol solution is coated on the front surface of the isolation layer in step 1 by Slot-Die coating machine. After wind drying, the first conductive layer with thickness of 80-180 nm is formed, and the diameter of the silver nanowires is 20-150 nm

(22) S3: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the first conductivity layer in step S2, and then the first insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(23) S4: 0.3-1.5 wt % silver nanowires isopropanol solution is slit coated on the reverse side of the isolation layer in step 1 by a Slot-Die coating machine. After wind drying, a second conductive layer with thickness of 80-180 nm is formed. The diameter of the nanowires is 20-150 nm.

(24) S5: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the second conductivity layer in step S4, and then the second insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(25) S6: A pair of electrodes is drawn from the conductive material of the first and second conductive layers, and solidified and packaged according to the required induction range.

(26) The insulation layer is a foamed polyurethane resin with an uneven surface. Uniform deformations are not easily occurred when the insulation layer is subjected to pressure, thus the resistances change between the two electrodes are impossible to be measured.

(27) Contrast 2

(28) The foamed polyurethane comprises polytetramethylene ether glycol (PTMEG) of 60-90 by weight, polyoxypropylene triol of 10-30 by weight, catalytic agent of 1-2 by weight, water of 2.5 by weight, p-cumylphenol polyethenoxy ether of 0.5 by weight, prepolymerized MDI of 75-80 by weight, wherein the molecular weight of PTMEG is 1000-4000; the OH value is 30-45 mgKOH/g, the molecular weight of polyoxypropylene triol is 700-3000; the prepolymerized MDI is prepolymerized 4-4-MDI with 12%-32% NCO; the foaming system comprises a foaming agent and a foaming stabilizer; the foaming agent and the foaming stabilizer are 3-5:1 by weight.

(29) S1: The ingredients of preparing the foamed polyurethane are evenly mixed, coated on a release paper and dried through oven at 110° C. with the speed of 10-20 m/min, and then an isolation layer is formed with a thickness of 500 μm after cooled and released from the release paper.

(30) S2: 0.3-1.5 wt % silver nanowires isopropanol solution is coated on the front surface of the isolation layer in step 1 by Slot-Die coating machine. After wind drying, the first conductive layer with thickness of 80-180 nm is formed, and the diameter of the silver nanowires is 20-150 nm

(31) S3: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the first conductivity layer in step S2, and then the first insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(32) S4: 0.3-1.5 wt % silver nanowires isopropanol solution is slit coated on the reverse side of the isolation layer in step 1 by a Slot-Die coating machine. After wind drying, a second conductive layer with thickness of 80-180 nm is formed. The diameter of the nanowires is 20-150 nm.

(33) S5: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the second conductivity layer in step S4, and then the second insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(34) S6: A pair of electrodes is drawn from the conductive material of the first and second conductive layers, and solidified and packaged according to the required induction range.

(35) The insulation layer is a foamed polyurethane resin with an uneven surface. Uniform deformations are not easily occurred when the insulation layer is subjected to pressure, thus the resistances change between the two electrodes are impossible to be measured.

(36) Contrast 3

(37) The foamed polyurethane comprises polytetramethylene ether glycol (PTMEG) of 60-90 by weight, polyoxypropylene triol of 10-30 by weight, catalytic agent of 1-2 by weight, water of 2.5 by weight, p-cumylphenol polyethenoxy ether of 0.25 by weight, sodium dodecyl sulfate of 0.25 by weight, prepolymerized MDI of 75-80 by weight, wherein the molecular weight of PTMEG is 1000-4000; the OH value is 30-45 mgKOH/g, the molecular weight of polyoxypropylene triol is 700-3000; the prepolymerized MDI is prepolymerized 4-4-MDI with 12%-32% NCO; the foaming system comprises a foaming agent and a foaming stabilizer; the foaming agent and the foaming stabilizer are 3-5:1 by weight.

(38) S1: The ingredients of preparing the foamed polyurethane are evenly mixed, coated on a release paper and dried through oven at 110° C. with the speed of 10-20 m/min, and then an isolation layer is formed with a thickness of 500 μm after cooled and released from the release paper.

(39) S2: 0.3-1.5 wt % silver nanowires isopropanol solution is coated on the front surface of the isolation layer in step 1 by Slot-Die coating machine. After wind drying, the first conductive layer with thickness of 80-180 nm is formed, and the diameter of the silver nanowires is 20-150 nm

(40) S3: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the first conductivity layer in step S2, and then the first insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(41) S4: 0.3-1.5 wt % silver nanowires isopropanol solution is slit coated on the reverse side of the isolation layer in step 1 by a Slot-Die coating machine. After wind drying, a second conductive layer with thickness of 80-180 nm is formed. The diameter of the nanowires is 20-150 nm.

(42) S5: A PET hot melt adhesive is extruded at the temperature of 260-265° C. on the top of the second conductivity layer in step S4, and then the second insulation layer of PET film is formed with a thickness of 4.5-120 μm after cooled to room temperature.

(43) S6: A pair of electrodes is drawn from the conductive material of the first and second conductive layers, and solidified and packaged according to the required induction range.

(44) The insulation layer is a foamed polyurethane resin with an uneven surface. Uniform deformations are not easily occurred when the insulation layer is subjected to pressure, thus the resistances change between the two electrodes are impossible to be measured.