Preparation method of flexible array type transparent piezoresistive sensor of embedded electrode

Abstract

The invention discloses a preparation method of a flexible array type transparent piezoresistive sensor of an embedded electrode, and aims to solve the problem that a conductive path is formed in a substrate by adding a conductive filler into an existing piezoresistive sensor based on PDMS (Polydimethylsiloxane), but the substrate is black and opaque. The preparation method comprises the following steps: S1, mixing a conductive material solution and a PDMS mother solution, dropwise adding a PDMS curing agent into the mixed solution, vacuumizing, defoaming, and baking to obtain a semi-solid flexible conductive substrate material; s2, sequentially depositing a sacrificial layer and a transparent conductive thin film on the transparent substrate to obtain a donor thin film carrier, inversely arranging the donor thin film carrier on the flexible conductive substrate material, and irradiating the sacrificial layer by adopting pulse laser; and S3, adding a liquid PDMS prepolymer on the surface of the flexible conductive substrate, and then carrying out baking, curing and packaging. The flexible array type transparent piezoresistive sensor is simple in preparation process, low in material cost, capable of being automatically prepared on a large scale and long in stability and service life.

Description

Technical Field

[0001] The present invention belongs to the field of flexible optoelectronic devices, and in particular relates to a flexible array-type transparent piezoresistive sensor with embedded electrodes and a preparation method thereof. Background Art

[0002] Flexible pressure sensors have broad application prospects in emerging fields such as wearable devices, human motion and health monitoring, electronic skin, and intelligent robots. Because flexible polymers are used as sensor substrates, they can be completely attached to irregular surfaces such as curved surfaces.

[0003] Piezoresistive sensors are mainly based on the piezoresistive effect of materials. When the material is subjected to forces such as pressure or stretching, the conductive network will change, resulting in changes in the sensor resistivity. The main chain of the polydimethylsiloxane (PDMS) molecule is composed of alternating silicon and oxygen atoms. It has good elasticity, flexibility, ductility, thermal stability and biocompatibility. It is one of the ideal matrix materials for flexible piezoresistive sensors. The rapid development of the field of human body interaction urgently requires the preparation of an array-type transparent sensor. At present, the PDMS-based piezoresistive sensors mainly form a conductive path inside the substrate by adding conductive fillers such as carbon nanotubes and graphene. The application of the above carbon materials will cause most sensors to be black and opaque, which is not suitable for certain special scenarios in the field of human body interaction. Summary of the invention

[0004] The present invention aims to solve the problem that the existing PDMS-based piezoresistive sensor adds conductive fillers to form a conductive path inside the substrate, but the substrate is black and opaque, and provides a method for preparing a flexible array transparent piezoresistive sensor with embedded electrodes to improve the visible transmittance and electrical properties of the flexible conductive substrate.

[0005] The method for preparing the embedded electrode flexible array transparent piezoresistive sensor of the present invention is implemented according to the following steps:

[0006] S1. Preparation of semi-solid flexible conductive substrate materials:

[0007] The conductive material solution and the PDMS mother solution are mixed, stirred evenly, heated to evaporate the solvent in the conductive material solution, cooled to room temperature, and a mixed solution is obtained. The PDMS curing agent is then added dropwise to the stirred mixed solution. After vacuuming and defoaming, the mixed solution is poured into a mold and baked to obtain a semi-solid flexible conductive substrate material.

[0008] S2. Preparation of transparent conductive electrodes:

[0009] a. ultrasonically clean the transparent substrate, and then sequentially deposit a sacrificial layer and a transparent conductive film (electrode) on the cleaned transparent substrate, wherein the transparent conductive film is located on the sacrificial layer and arranged in a rectangular array, and then annealed at high temperature to obtain a donor film carrier;

[0010] b. Inverting the donor film carrier on the flexible conductive substrate material, that is, the transparent conductive film on the donor film carrier is in contact with the flexible conductive substrate material, irradiating the sacrificial layer with a pulsed laser through the transparent substrate of the donor film carrier, removing the transparent substrate, and obtaining a (semi-solid state) flexible conductive substrate with an array of transparent conductive films;

[0011] S3. Preparation and packaging of sensors:

[0012] Leading out a conductive metal wire on a transparent conductive film of a flexible conductive substrate, adding a liquid PDMS prepolymer on the surface of the flexible conductive substrate, and then baking and curing the package to obtain a flexible array-type transparent piezoresistive sensor with embedded electrodes;

[0013] The conductive material described in step S1 is poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), silver nanowires or copper nanowires; the sacrificial layer described in step S2 is a gold film, a titanium film, a platinum film or a carbon film, and the transparent conductive film is indium tin oxide, aluminum-doped zinc oxide or a graphene film.

[0014] The present invention provides a flexible array type transparent piezoresistive sensor with embedded electrodes. The flexible array type transparent piezoresistive sensor has a simple preparation process, low material cost, can be automatically prepared in large quantities, and has long stability and service life.

[0015] Compared with the prior art, the method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes of the present invention has the following beneficial effects:

[0016] The present invention does not involve processes such as photolithography and etching during the preparation process, thus avoiding the hazards caused by photoresist, developer and chemical etching solution. By moving the laser according to the trajectory, the transparent conductive electrode is directly written on the surface of the semi-solid flexible transparent conductive material substrate. The operation steps are simple, the shape of the resulting array electrode is more flexible, and the waste of a large number of different mask plates is avoided. At the same time, the transparent conductive electrode prepared on the surface of the semi-solid substrate can be buried in the transparent conductive material, and the two are in close contact and have better conductivity. The most important thing is that the flexible transparent conductive material substrate produced by this method is transparent, which is very suitable for wearable physiological monitoring of the human body or industrial monitoring. Therefore, this sensor preparation method is not only simple in process and suitable for large-scale promotion and application, but also has the characteristics of high flexibility and high response sensitivity, and has broad prospects in wearable electronic devices and industrial detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the flexible array transparent piezoresistive sensor prepared in Example 1, 11 is the encapsulated PDMS, 12 is the transparent conductive film (electrode), and 13 is the mixed flexible substrate of PDMS and transparent conductive material;

[0018] Figure 2 The graph is a response curve of the flexible array piezoresistive sensor prepared in Example 1 to different pressures;

[0019] Figure 3 The cyclic stability diagram of the flexible array piezoresistive sensor prepared in Example 1;

[0020] Figure 4 This is a pressure distribution detection diagram of the flexible array piezoresistive sensor prepared in Example 1;

[0021] Figure 5 A physical picture of the flexible array piezoresistive sensor prepared in Example 1. DETAILED DESCRIPTION

[0022] Specific implementation method 1: The method for preparing a flexible array transparent piezoresistive sensor with embedded electrodes in this implementation method is implemented according to the following steps:

[0023] S1. Preparation of semi-solid flexible conductive substrate materials:

[0024] The conductive material solution and the PDMS mother solution are mixed, stirred evenly, heated to evaporate the solvent in the conductive material solution, cooled to room temperature, and a mixed solution is obtained. The PDMS curing agent is then added dropwise to the stirred mixed solution. After vacuuming and defoaming, the mixed solution is poured into a mold and baked to obtain a semi-solid flexible conductive substrate material.

[0025] S2. Preparation of transparent conductive electrodes:

[0026] a. ultrasonically clean the transparent substrate, and then sequentially deposit a sacrificial layer and a transparent conductive film (electrode) on the cleaned transparent substrate, wherein the transparent conductive film is located on the sacrificial layer and arranged in a rectangular array, and then annealed at high temperature to obtain a donor film carrier;

[0027] b. Inverting the donor film carrier on the flexible conductive substrate material, that is, the transparent conductive film on the donor film carrier is in contact with the flexible conductive substrate material, irradiating the sacrificial layer with a pulsed laser through the transparent substrate of the donor film carrier, removing the transparent substrate, and obtaining a (semi-solid state) flexible conductive substrate with an array of transparent conductive films;

[0028] S3. Preparation and packaging of sensors:

[0029] Leading out a conductive metal wire on a transparent conductive film of a flexible conductive substrate, adding a liquid PDMS prepolymer on the surface of the flexible conductive substrate, and then baking and curing the package to obtain a flexible array-type transparent piezoresistive sensor with embedded electrodes;

[0030] The conductive material described in step S1 is poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), silver nanowires or copper nanowires; the sacrificial layer described in step S2 is a gold film, a titanium film, a platinum film or a carbon film, and the transparent conductive film is indium tin oxide, aluminum-doped zinc oxide or a graphene film.

[0031] The sacrificial layer described in step S2 of this embodiment is a gold film, a titanium film, a platinum film or a carbon film, which is prepared by magnetron sputtering or evaporative deposition. The transparent conductive film is indium tin oxide or aluminum-doped zinc oxide prepared by magnetron sputtering or evaporative deposition, or a graphene film peeled off by mechanical stripping, chemical vapor deposition or chemical oxidation.

[0032] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that in step S1, the conductive material solution and the PDMS mother solution are mixed, wherein the mass of the conductive material solution accounts for 5wt% to 15wt% of the PDMS mother solution.

[0033] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that the mass ratio of the PDMS curing agent to the PDMS mother solution in step S1 is 1:10 to 1:30.

[0034] Specific embodiment 4: The difference between this embodiment and specific embodiments 1 to 3 is that the baking treatment described in step S1 is carried out in a vacuum drying oven at a temperature of 40 to 50° C. for 0.5 to 1 hour.

[0035] Specific implementation method five: This implementation method is different from any one of specific implementation methods one to four in that the material of the transparent substrate in step S2 is SiO2, Al2O3, a glass slide, PTFE or PET.

[0036] Specific implementation example 6: This implementation example is different from any one of specific implementation examples 1 to 5 in that in step S2, acetone, alcohol and deionized water are used sequentially to ultrasonically clean the transparent substrate.

[0037] Specific implementation method 7: The difference between this implementation method and any one of specific implementation methods 1 to 6 is that the thickness of the sacrificial layer in step S2 is 50 to 80 nm.

[0038] Specific implementation eight: This implementation is different from any one of specific implementations one to seven in that the thickness of the transparent conductive film in step S2 is 300-1000 nm.

[0039] Specific implementation method 9: The difference between this implementation method and any one of specific implementation methods 1 to 8 is that in step S2, the wavelength of the pulse laser is controlled to be 355 nm, 532 nm or 1064 nm, and the frequency is 1 to 10 kHz.

[0040] In this embodiment, the spot diameter of the pulse laser is adjustable, and the spot diameter is 50 to 500 μm.

[0041] Specific implementation example ten: This implementation example is different from any one of specific implementation examples one to nine in that the conductive metal wire in step S3 is a gold wire or a silver wire, and the diameter of the conductive metal wire is 20 μm to 50 μm.

[0042] Specific implementation eleven: The difference between this implementation and specific implementations one to ten is that the packaging thickness of PDMS in step S3 is 300-500 μm.

[0043] Embodiment 1: The preparation method of the flexible array type transparent piezoresistive sensor with embedded ITO electrodes in this embodiment is implemented according to the following steps:

[0044] S1. Preparation of semi-solid flexible conductive substrate materials:

[0045] PEDOT:PSS aqueous dispersion (1.1wt%) and PDMS mother liquor are placed in a container, the mass of PEDOT:PSS aqueous dispersion accounts for 5% of the mass of PDMS mother liquor, stirred evenly, heated to 100°C to evaporate and remove water, cooled to room temperature to obtain a mixed solution, a curing agent of one tenth of the mass of the PDMS mother liquor is added dropwise to the stirred mixed solution, vacuumed for 30 minutes to ensure the disappearance of bubbles in the mixed solution, added the mixed solution to a mold, and baked in a vacuum drying oven at 40°C for 1 hour to obtain a semi-solid flexible conductive substrate material;

[0046] S2. Preparation of transparent conductive electrodes:

[0047] Acetone, alcohol and deionized water are used to ultrasonically clean the quartz substrate for 15 minutes each, and a 50nm gold film is magnetron sputtered on the surface of the cleaned quartz substrate under the conditions of 0.5Pa gas pressure, 20sccm argon flow rate and 40W radio frequency power, and then a 500nm thick indium tin oxide transparent conductive film is magnetron sputtered under the conditions of 0.5Pa gas pressure, 20sccm argon flow rate and 100W radio frequency power, and then a high-temperature argon annealing is performed at a temperature of 300°C for 0.5h to obtain a donor film carrier with high photoelectric performance; the donor film carrier is inverted on a flexible conductive substrate material, that is, the transparent conductive film on the donor film is in contact with the semi-solid flexible conductive substrate material, and a pulsed laser (wavelength of 355nm, frequency of 1Hz, spot diameter of 500μm) is used to irradiate the donor film in a square array trajectory motion, and after removing the quartz substrate, a semi-solid flexible conductive substrate with an array of transparent conductive electrodes is obtained;

[0048] S3. Preparation and packaging of sensors:

[0049] Conductive gold wires were drawn out from the array-type transparent conductive electrodes on the semi-solid flexible conductive substrate, and liquid PDMS prepolymer was added on the surface with a thickness of 500 μm for baking and curing packaging to obtain a flexible array-type transparent piezoresistive sensor.

[0050] Embodiment 2: The preparation method of the flexible array type transparent piezoresistive sensor with embedded AZO electrodes in this embodiment is implemented according to the following steps:

[0051] S1. Preparation of semi-solid flexible conductive substrate materials:

[0052] The silver nanowire ethanol dispersion (1 mg / mL, 2 mL) and PDMS mother liquor are placed in a container, the mass of the silver nanowire ethanol dispersion accounts for 10% of the mass of the PDMS mother liquor, and the mixture is stirred evenly and heated to 75°C to evaporate and remove the ethanol, and then cooled to room temperature. A curing agent with a mass of one twentieth of the PDMS mother liquor is added dropwise to the stirring mixture, and the mixture is vacuumed for 30 minutes to ensure that the bubbles in the mixture disappear. The mixture is added to a mold, and baked in a vacuum drying oven at 50°C for 0.5 hours to obtain a semi-solid flexible conductive substrate material;

[0053] S2. Preparation of transparent conductive electrodes:

[0054] Acetone, alcohol and deionized water are used to ultrasonically clean the sapphire substrate for 15 minutes each, and a 100 nm titanium film is magnetron sputtered on the surface of the cleaned sapphire substrate under the conditions of a gas pressure of 0.5 Pa, an argon flow rate of 20 sccm and a radio frequency power of 60 W. Then, an aluminum-doped zinc oxide transparent conductive film with a thickness of 800 nm is magnetron sputtered under the conditions of a gas pressure of 1 Pa, an argon flow rate of 20 sccm and a radio frequency power of 250 W. Subsequently, a high-temperature vacuum annealing is performed at a temperature of 400° C. for 1 hour to obtain a donor film carrier with high photoelectric performance, and the donor film carrier is inverted on a flexible conductive substrate material, that is, the transparent conductive film on the donor film is in contact with the semi-solid flexible conductive substrate material, and a pulsed laser (wavelength of 1064 nm, frequency of 10 kHz, and spot diameter of 50 μm) is used to irradiate the donor film in a serpentine trajectory, and after removing the sapphire substrate, a semi-solid flexible conductive substrate with an array of transparent conductive electrodes is obtained;

[0055] S3. Preparation and packaging of sensors:

[0056] Conductive silver wires were drawn out from the array-type transparent conductive electrodes on the semi-solid flexible conductive substrate, and liquid PDMS prepolymer with a thickness of 300 μm was added to the surface for baking and curing packaging to obtain a flexible array-type transparent piezoresistive sensor.

[0057] Embodiment 3: The method for preparing the flexible array transparent piezoresistive sensor with embedded graphene electrodes in this embodiment is implemented according to the following steps:

[0058] S1. Preparation of semi-solid flexible conductive substrate materials:

[0059] The isopropanol dispersion of copper nanowires (2 mg / mL, 2 mL) and the PDMS mother liquor are placed in a container, wherein the mass of the isopropanol dispersion of copper nanowires accounts for 10% of the mass of the PDMS mother liquor. After being stirred evenly, the mixture is heated to 80°C to evaporate and remove the isopropanol. The mixture is cooled to room temperature, and a curing agent having a mass of one-thirtieth of the PDMS mother liquor is added dropwise to the stirring mixture. The mixture is vacuumed for 30 minutes to ensure that the bubbles in the mixture disappear. The mixture is added to a mold, and baked in a vacuum drying oven at 50°C for 1 hour to obtain a semi-solid flexible conductive substrate material.

[0060] S2. Preparation of transparent conductive electrodes:

[0061] Acetone, alcohol and deionized water are used to ultrasonically clean the PET substrate for 15 minutes respectively, and an 80nm carbon film is magnetron sputtered on the surface of the cleaned sapphire substrate under the conditions of a gas pressure of 0.5Pa, an argon flow rate of 20sccm and a radio frequency power of 50W, and then a 1mg / mL graphene oxide solution is rotated on the surface of the carbon film at a speed of 2000 rpm for 2 minutes, and then a high-temperature argon-hydrogen mixed gas (hydrogen concentration of 5%) is annealed at a temperature of 280°C for 0.5h to obtain a reduced graphene oxide donor film carrier with high photoelectric performance, and the donor film carrier is inverted on a flexible conductive substrate material, that is, the transparent conductive film on the donor film is in contact with the semi-solid flexible conductive substrate material, and a pulsed laser (wavelength of 1064nm, frequency of 10kHz, spot diameter of 50μm) is used to irradiate the donor film in an interdigitated trajectory motion, and after removing the sapphire substrate, a semi-solid flexible conductive substrate with an array of transparent conductive electrodes is obtained;

[0062] S3. Preparation and packaging of sensors:

[0063] Conductive gold wires were drawn out from the array-type transparent conductive electrodes on the semi-solid flexible conductive substrate, and liquid PDMS prepolymer was added on the surface with a thickness of 500 μm for baking and curing packaging to obtain a flexible array-type transparent piezoresistive sensor.

[0064] The flexible array transparent piezoresistive sensor prepared in the above embodiment 1 was tested for its response under different pressures. Figure 2 As shown, from Figure 3 It can be seen that the cyclic stability of the sensor is good. Figure 4 The figure shows the pressure distribution detection diagram of the flexible array piezoresistive sensor, which shows excellent response performance and can be used in the field of wearable physiological monitoring of the human body. Figure 5 The figure shows a real picture of the flexible array transparent piezoresistive sensor of the first embodiment, and it can be seen that the light transmission effect is good.

Claims

1. A method for preparing a flexible array transparent piezoresistive sensor with embedded electrodes, characterized in that The preparation method of the embedded electrode flexible array transparent piezoresistive sensor is implemented according to the following steps: S1. Preparation of semi-solid flexible conductive substrate materials: The conductive material solution and the PDMS mother solution are mixed, stirred evenly, heated to evaporate the solvent in the conductive material solution, cooled to room temperature, and a mixed solution is obtained. The PDMS curing agent is then added dropwise to the stirred mixed solution. After vacuuming and defoaming, the mixed solution is poured into a mold and baked to obtain a semi-solid flexible conductive substrate material. S2. Preparation of transparent conductive electrodes: a. ultrasonically clean the transparent substrate, and then sequentially deposit a sacrificial layer and a transparent conductive film on the cleaned transparent substrate, wherein the transparent conductive film is located on the sacrificial layer and arranged in a rectangular array, and then annealed at a high temperature to obtain a donor film carrier; b. Inverting the donor film carrier on the flexible conductive substrate material, that is, the transparent conductive film on the donor film carrier is in contact with the flexible conductive substrate material, irradiating the sacrificial layer through the transparent substrate of the donor film carrier with a pulsed laser, removing the transparent substrate, and obtaining a flexible conductive substrate with an array of transparent conductive films; S3. Preparation and packaging of sensors: Leading out a conductive metal wire on a transparent conductive film of a flexible conductive substrate, adding a liquid PDMS prepolymer on the surface of the flexible conductive substrate, and then baking and curing the package to obtain a flexible array-type transparent piezoresistive sensor with embedded electrodes; The conductive material described in step S1 is poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, silver nanowires or copper nanowires; the sacrificial layer described in step S2 is a gold film, a titanium film, a platinum film or a carbon film, and the transparent conductive film is indium tin oxide, aluminum-doped zinc oxide or a graphene film.

2. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that In step S1, a conductive material solution and a PDMS mother solution are mixed, wherein the mass of the conductive material solution accounts for 5wt% to 15wt% of the PDMS mother solution.

3. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that In step S1, the mass ratio of the PDMS curing agent to the PDMS mother solution is 1:10 to 1:

30.

4. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that The baking treatment in step S1 is carried out in a vacuum drying oven at a temperature of 40 to 50° C. for 0.5 to 1 hour.

5. The method for preparing the embedded electrode flexible array transparent piezoresistive sensor according to claim 1, characterized in that In step S2, the material of the transparent substrate is SiO2, Al2O3, a glass slide, PTFE or PET.

6. The method for preparing the embedded electrode flexible array transparent piezoresistive sensor according to claim 1, characterized in that The thickness of the sacrificial layer in step S2 is 50-80 nm.

7. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that The thickness of the transparent conductive film in step S2 is 300-1000 nm.

8. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that In step S2, the wavelength of the pulse laser is controlled to be 355 nm, 532 nm or 1064 nm, and the frequency is 1 to 10 kHz.

9. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that In step S3, the conductive metal wire is a gold wire or a silver wire, and the diameter of the conductive metal wire is 20 μm to 50 μm.

10. The method for preparing the flexible array transparent piezoresistive sensor with embedded electrodes according to claim 1, characterized in that The packaging thickness of PDMS in step S3 is 300-500 μm.

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