Telescopic pressure response film and pressure sensor

Abstract

The invention discloses a telescopic pressure response film and application thereof, and belongs to the technical field of sensors. The telescopic pressure response film comprises a first layer and a second layer which are adjacent to each other, the first layer is a telescopic film, and the second layer is a pressure response layer. The telescopic film serving as the substrate layer and the pressure response layer are directly stacked, the telescopic pressure response film has flexibility and irreversible deformation resistance and can be better attached to a test end, so that the pressure sensing layer can better receive a pressure signal, and the pressure response signal can be expanded. Further, the sensitivity of the sensor using the thin film can be improved without the need for a micro-engineering structure of a fine sensing layer. Meanwhile, the sensing layer and the substrate layer can be made into coil samples in advance, so that the subsequent sensor production efficiency can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of stretchable pressure-responsive materials and sensors, and in particular relates to a stretchable pressure-responsive film and a pressure sensor comprising the same. Background Art

[0002] Pressure sensors are widely used in smart wearables, human motion and health monitoring, artificial intelligence, electronic skin, human-computer interaction and other fields, playing an indispensable role. And the research and development of sensors is gradually developing towards flexibility, stretchability, lightness, high sensitivity, and fast response.

[0003] Non-patent document 1 discloses that geometric micro-engineering of the sensing layer has been shown to improve performance parameters such as sensitivity, dynamic range, detection limit, and response and relaxation time. There are a variety of designs that can be implemented, including micro-domes, micro-pyramids, wires or micro-ridges, nipples, micro-spheres, micro-holes, and micro-cylinders, each of which provides different advantages for specific applications. However, flexible pressure sensors with surface microstructures are more susceptible to deformation under pressure, generally reaching 178 kPa in the low pressure range. -1 The sensitivity is high, but the detection range is narrow, only 100-200 Pa. In addition, the geometric micro-engineering structure on the surface of the sensor substrate is usually produced by photolithography, ion etching and other methods that are complex, costly and time-consuming.

[0004] Prior art literature

[0005] Non-patent literature 1: Adv. Funct. Mater. 2020, 30, 2003491 Summary of the invention

[0006] In view of the above problems, an object of the present invention is to provide a stretchable pressure-responsive film having a simple preparation method, a wide pressure detection range and high sensitivity, and a pressure sensor comprising the same.

[0007] In order to achieve the above object, the present invention provides a stretchable pressure-responsive film, which comprises a first layer and a second layer adjacent to each other, wherein the first layer is a stretchable film and the second layer is a pressure-responsive layer.

[0008] The retractable film of the present invention is a polymer material having the ability to rapidly recover to its approximate original shape and size after being significantly deformed by a force and then being removed from the external force.

[0009] The retractable film acts as a supporting layer and is preferably an elastomeric film made of an elastomer in consideration of its flexibility. The elastomeric film may be at least one selected from thermoplastic polyurethane elastomer, polydimethylsiloxane, thermoplastic polyolefin elastomer, thermoplastic vulcanized rubber, polyether ester elastomer, and styrene elastomer. Polyurethane elastomer is preferred due to its wide adjustable flexibility range.

[0010] The Young's modulus of the first layer is preferably in the range of 1-10 MPa, and preferably in the range of 1-5 MPa considering the flexibility of the sensor.

[0011] The thickness of the stretchable film is preferably in the range of 20-100 μm, and more preferably 20-50 μm due to processability and sensor performance.

[0012] The pressure response layer is a layer that can sense pressure signals and convert the pressure signals into usable output electrical signals according to certain rules.

[0013] The pressure response layer acts as a functional layer, and has a pressure response function. The material is preferably selected from at least one of piezoelectric materials and piezoresistive materials. The piezoelectric material is a crystalline material that will generate a voltage between the two end faces when subjected to pressure. The piezoresistive material is a material whose resistivity changes due to the change of carrier mobility when the semiconductor is subjected to stress. The pressure response layer can be selected from at least one of multi-walled carbon nanotubes, graphene, polylactic acid, metal carbon / nitride with a two-dimensional layered structure, polypyrrole, and polyvinylidene fluoride. Graphene is preferred because it still has high sensitivity when the thickness is relatively thin.

[0014] The thickness of the pressure response layer is preferably in the range of 100-200 μm, and more preferably in the range of 150-200 μm due to processability and sensor performance.

[0015] The so-called film recovery rate refers to the ratio of the length recovered after the film is stretched to a certain proportion and maintained for a certain period of time and the tension is released to the original length.

[0016] In the present invention, the recovery rate of the stretchable pressure-responsive film is preferably 97%-99%, and more preferably 98-99% in consideration of the durability of the composite film.

[0017] After the recovery rate evaluation, the deflection of the stretchable pressure-responsive film is preferably less than 1 cm. The deflection refers to the distance from the highest point of the composite film to the horizontal plane when the convex surface of the composite film with a size of 15 cm × 1 cm is placed on a horizontal plane without external stress. Considering the flexibility of the composite film, the deflection of the stretchable pressure-responsive film is preferably less than 0.5 cm.

[0018] The peel strength between the first layer and the second layer of the stretchable pressure responsive film is preferably 2-15 N / cm. The tighter the combination of the first layer and the second layer, the higher the sensitivity of the sensor using the stretchable pressure responsive film of the present invention, more preferably 10-15 N / cm.

[0019] The stretchable pressure-responsive film can be produced as follows.

[0020] (1) Base

[0021] The raw materials of stretchable films such as elastomers are made into film materials through extrusion casting process.

[0022] (2) Stretchable pressure-responsive film

[0023] The piezoelectric material or the piezoresistive material is dispersed in the ethyl acetate solution of polymethyl acrylate to form a pressure-responsive slurry, which is compounded with the stretchable film substrate obtained in the above (1), and formed by high-temperature drying and curing to prepare a two-layer structure as a stretchable pressure-responsive film.

[0024] The present invention also provides a pressure sensor, which comprises the stretchable pressure-responsive film of the present invention, and the pressure range is 0-200 kPa and the sensitivity reaches 50-200 kPa. -1 The sensitivity of this flexible pressure sensor in the low pressure area (0-1kPa) reaches up to 100kPa -1 , the maximum sensitivity in the pressure range of 1 to 10 kPa is 200 kPa -1 In the high pressure area (10-200 kPa), the sensitivity can be as low as 50 kPa. -1 .

[0025] The pressure sensor can be manufactured by the following method:

[0026] Conductive materials (metal, liquid metal, nanometal, polymer conductive material, etc.) are printed or bonded on the second layer of the stretchable pressure-responsive film of the present invention as electrodes, and then flexible film packaging is performed on the electrodes to prepare pressure sensors.

[0027] Effects of the Invention

[0028] The present invention directly stacks the retractable film as the base layer and the pressure response layer. The retractable pressure response film has flexibility and the ability to resist irreversible deformation, and can better fit the test end, so that the pressure response layer can better receive the pressure change signal, thereby amplifying the pressure response signal. Furthermore, the sensor using the film can improve the sensitivity without the micro-engineering structure of the fine sensing layer. At the same time, the sensing layer and the base layer can be made into a roll sample in advance, which can improve the production efficiency of subsequent sensors. DETAILED DESCRIPTION

[0029] The present invention is described in more detail by the following examples, but the following examples do not constitute a limitation of the present invention.

[0030] 1. Raw materials

[0031] A1: polyurethane elastomer (Lubrizol Pellethane); A2: polydimethylsiloxane (DOW CORNINGSYLGARD 184); A3: polyolefin elastomer (Mitsubishi Chemical ZELAS TM );

[0032] B1: multi-walled carbon nanotube slurry (Merck 901019); B2: graphene (Merck 900561); B3: polylactic acid (Merck 94829); B4: two-dimensional layered titanium carbide (Merck 921408); B5: polypyrrole (Merck 577030) slurry; B6: polyvinylidene fluoride (Merck 182702)

[0033] C1: Polyethylene terephthalate film (Toray Lumirror 50-S10) thickness 20 μm

[0034] D1: Cast polypropylene film (Toray CPP ZK207) thickness 20 μm

[0035] E1: Poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrene sulfonate) (Merck 768618)

[0036] 2. The methods for measuring the relevant properties in the embodiments and comparative examples of the present invention are as follows. For all tests, if the test temperature is not clearly stated, the test is performed at 23°C.

[0037] (1) Sensitivity

[0038] The calculation formula of pressure sensor sensitivity is as follows:

[0039]

[0040] R0 is the initial resistance when no pressure is applied, ΔR is the change in resistance after pressure is applied, and ΔP is the change in pressure.

[0041] Use a Keithley digital power meter to gradually change the pressure to test the sensing characteristics.

[0042] (2) Response rate

[0043] The stretchable pressure-responsive film was cut into strips with a size of MD×TD: 150 mm×10 mm, stretched along the MD direction to twice the original length, i.e. 300 mm, and maintained for 1 min. This was repeated 10,000 times. The length was measured after the external force was removed for 10 min. The recovery rate was calculated as follows:

[0044]

[0045] Where R g is the recovery rate, L0 is the initial length, L1 is the length after extension by external force (length is 300 mm), and L2 is the straightened length after the external force is removed for 10 minutes.

[0046] (3) Deflection

[0047] After the recovery rate test was completed, the deflection test was performed after the sample was placed for 24 hours. The sample was placed on a horizontal plane with the convex surface facing upward without external stress, and the distance from the highest point of the test piece to the horizontal plane was measured using a ruler with an accuracy of 0.05 cm.

[0048] (4) Peel strength

[0049] When testing the pressure-responsive film between two layers, the first layer was reinforced with TESA7475 test tape and the sample was cut with a cutter to a size of 150 mm × 10 mm. Then a 180° peel strength test was performed using a tensile testing machine at a tensile speed of 200 mm / min. The tear strength τ2 calculation formula is as follows:

[0050]

[0051] In formula (3), the 180-degree peel strength between the first layer and the second layer is τ2 (N / cm); the average load during peeling is the peeling force F2 (N); the width of the peeled sample is L, which is set to 1 cm. Each sample is measured three times in different areas, and the arithmetic average of the three test results is taken as the peel strength result.

[0052] (5) Young's modulus

[0053] The substrate layer was cut into strips of size MD×TD: 150 mm×10 mm. The tensile test was performed in the MD direction. The modulus strain of the tensile curve was read as the average value of the modulus in the range of 0.7-1.0%. The calculation formula is as follows:

[0054] E=σ / ε (Formula 4)

[0055] E is Young's modulus, σ is stress, and ε is strain.

[0056] Embodiment 1:

[0057] (1) Base

[0058] The current production process in the market is adopted: using precision casting technology, the polyurethane elastomer (A1) particles are extruded through a casting process to be made into a thermoplastic polyurethane original film with a uniform thickness of 50 μm and no defects on the surface, and the surface is corona treated.

[0059] (2) Stretchable pressure-responsive film

[0060] High molecular weight polymethyl acrylate is added to ethyl acetate at a mass fraction of 5%, heated at 80°C with magnetic stirring to dissolve it quickly to form a polymethyl acrylate solution, and then multi-walled carbon nanotubes (B1) are dispersed in the 5wt% polymethyl acrylate solution using a high-speed disperser, and the mass fraction of multi-walled carbon nanotubes is 80% to obtain a pressure-responsive slurry. The pressure-responsive slurry is coated on the substrate obtained in step (1), and a second layer with a thickness of 200 μm is obtained by high-temperature drying and curing at 100°C.

[0061] (3) Sensor

[0062] A 2 μm silver electrode is sputtered on the second layer of the stretchable pressure-responsive film prepared in step (2), and a pressure sensor is prepared by flexible membrane encapsulation.

[0063] The performance parameters are listed in Table 1.

[0064] Embodiment 2-14:

[0065] (1) Basal layer

[0066] The base layer was prepared according to the materials and parameters listed in Table 1 and the same method as in Example 1.

[0067] (2) Stretchable pressure-responsive film

[0068] The stretchable pressure-responsive film was prepared according to the materials and parameters listed in Table 1 and the same method as in Example 1.

[0069] (3) Sensor

[0070] The sensor was prepared by referring to the method of Example 1.

[0071] The performance parameters are listed in Table 1.

[0072] Comparative Example 1:

[0073] Different from Example 1, the second layer in step (2) is replaced by sputtering of Ag electrode, and then the pressure response layer is prepared and packaged.

[0074] The performance parameters are listed in Table 1.

[0075] Comparative Example 2:

[0076] A stretchable pressure-responsive film and a sensor were prepared in the same manner as in Example 1 except that the base layer was made of polyethylene terephthalate (PET film).

[0077] The performance parameters are listed in Table 1.

[0078] By comparing Examples 1, 2, and 10, it can be seen that the lower the thickness of the first layer, the higher the sensitivity; by comparing Example 1 with Comparative Example 1, it can be seen that exchanging the order of the sensing layer and the electrode layer can improve the sensitivity of the sensor.

[0079] By comparing Example 2 with Examples 3, 8, 9, and 13, it can be seen that the sensor made with the stretchable film as the first layer has higher sensitivity, and the sensor made with the recovery rate of the pressure-responsive film in the range of 97-99% and the Young's modulus of the first layer in the range of 1-10 MPa has higher sensitivity.

[0080] In combination with Examples 3, 4, 5, 6, 7, 10, 13, and 14, it can be seen that the sensor made of the stretchable pressure-responsive film has high sensitivity, graphene is the most preferred pressure-responsive layer, and the sensor made of the stretchable pressure-responsive film with a deflection less than 1 cm is the preferred solution, among which less than 0.5 cm is the most preferred.

[0081] It can be seen from Examples 10, 11 and 12 that the thicker the second layer is, the higher the sensitivity of the sensor is.

[0082] Table 1

[0083]

Claims

1. A stretchable pressure-responsive film, characterized in that: The stretchable pressure-responsive film comprises a first layer and a second layer adjacent to each other, wherein the first layer is a stretchable film and the second layer is a pressure-responsive layer.

2. The stretchable pressure-responsive film according to claim 1, characterized in that: The recovery rate of the film is 97%-99%.

3. The stretchable pressure-responsive film according to claim 2, characterized in that: After the recovery rate of the film is evaluated, the deflection of the stretchable pressure-responsive film is less than 1 cm.

4. The stretchable pressure-responsive film according to claim 1, characterized in that: The peeling strength between the first layer and the second layer of the film is 2-15 N / cm.

5. The stretchable pressure-responsive film according to claim 1, characterized in that: The Young's modulus of the first layer is in the range of 1-10 MPa.

6. The stretchable pressure-responsive film according to claim 1, characterized in that: The stretchable membrane is an elastomeric membrane.

7. The stretchable pressure-responsive film according to claim 6, characterized in that: The retractable film is at least one selected from thermoplastic polyurethane elastomer, polydimethylsiloxane, thermoplastic polyolefin elastomer, thermoplastic vulcanized rubber, polyether ester elastomer, and styrene elastomer.

8. The stretchable pressure-responsive film according to claim 1, characterized in that: The pressure response layer of the second layer is at least one selected from piezoelectric materials and piezoresistive materials.

9. The stretchable pressure-responsive film according to claim 8, characterized in that: The second pressure-responsive layer is at least one selected from multi-walled carbon nanotubes, graphene, polylactic acid, metal carbon / nitride with a two-dimensional layered structure, polypyrrole, and polyvinylidene fluoride.

10. A pressure sensor comprising the stretchable pressure-responsive film according to any one of claims 1 to 9, wherein the pressure range is 0-200 kPa and the sensitivity reaches 50-200 kPa -1 .

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