Fingerprint biomimetic composite flexible stretchable sensor and preparation method thereof

Abstract

The present application belongs to the technical field of flexible stretchable sensor, and particularly relates to a fingerprint biomimetic composite flexible stretchable sensor and a preparation method thereof. The fingerprint biomimetic composite flexible stretchable sensor comprises a flexible stretchable substrate, a conductive composite layer and an encapsulation layer. The conductive composite layer is composed of a conductive layer composed of metal nanowires and a second conductive substance and a platinum gold conductive layer. The present application also simultaneously provides a preparation method of the fingerprint biomimetic composite flexible stretchable sensor, which comprises the preparation of the flexible stretchable substrate, the preparation of the composite conductive layer, the transfer of the composite conductive layer and the preparation of the sensor device. The present application can effectively broaden the effective working range of the sensor.

Description

Technical Field

[0001] This invention belongs to the field of flexible and stretchable sensor technology, and specifically relates to a fingerprint biomimetic composite flexible and stretchable sensor and its preparation method. Background Technology

[0002] Flexible wearable electronics are constantly developing and integrating into people's daily lives. Among them, flexible sensors have become a highlight of people's lives. Based on their flexible and deformable properties, they can not only collect human physiological signals, such as breathing, movement, pulse, heartbeat, and sweat monitoring, but also avoid the cumbersome and complicated old-fashioned detection tools, bringing great convenience to medical testing and health monitoring of the elderly. These sensors convert human physiological signals into electrical signals through the resistance, capacitance, and inductance of the sensor, and display them in a visual instrument, realizing safe and convenient sensor information transmission. Their future applications will be more widespread.

[0003] Regarding flexible and stretchable sensors, the two most important performance indicators are sensitivity and application range. The former determines the intensity of signal changes that the sensor can reflect in response to changes in movement. Higher sensitivity generally means that the sensor can better and more meticulously reflect changes in physiological signals. The latter determines the application scenarios of the sensor. For some large-amplitude stretching movements of the human body, such as bending the knee or taking big steps, and even in order to be compatible with clothing that is easily stretched and deformed, the sensor needs to be able to meet a larger deformation range to ensure the accuracy and reliability of signals for all movements. Therefore, various studies are constantly exploring ways to improve both performance characteristics simultaneously.

[0004] Patent CN 115143879 A pre-stretches a flexible and stretchable substrate, coats it with conductive material, and allows the substrate to spring back after drying, achieving a 200% working range. This technology can effectively expand the working range of the device, but its preparation steps are relatively complex, its sensitivity is relatively low, and there is still much room for improvement.

[0005] Patent CN 111288885 A) utilizes a mold to first prepare multiple layers of conductive materials, such as conductive carbon material layers and conductive metal particle layers, on its bottom layer, and then covers it with a flexible stretching substrate to form a stretchable conductive sensor. Based on the self-locking effect at the interface of the double-layer conductive sensing layer of conductive carbon material layer and conductive metal material layer, it achieves a wide working range of 120% and a high sensitivity factor of 3990.7692. However, its working range can be further improved, and the signal stability of its repeated stretching also needs to be improved.

[0006] Zhai Heng et al. prepared a stretchable graphene fiber sensor using wet spinning technology. The device achieved a tensile strength of up to 369 MPa, but its operating range (<48.5%) and sensitivity (GF=63) were relatively poor, indicating significant room for improvement (H.Zhai,L.Xu,Z.Liu,L.Jin,Y.Yi,J.Zhang,Y.Fan,D.Cheng,J.Li,X.Liu,Q.Song,P.Yue,Y.Li Twisted graphene fibre based breathable,wettable andwashable anti-jamming strain sensor for underwater motion sensing Chemical engineering journal(Lausanne,Switzerland:1996)439(2022)135502). Zhang Shifeng et al. prepared a biodegradable sensor based on materials such as candle soot, chitosan, and potato starch. Although it achieved good environmental performance, its sensitivity was only 2.71, which is relatively poor (S.Zhang,H.Li,Z.Yang,B.Chen,K.Li,X.Lai,X.Zeng Degradable and stretchable bio-based strain sensor for human motiondetection J.Colloid Interface Sci.626(2022)554-563).

[0007] Therefore, based on existing research, simplifying the sensor fabrication method and fabricating tensile-resistant resistive sensors with a wider working range and higher sensitivity is of greater significance for the development of their display applications. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a fingerprint biomimetic composite flexible stretchable sensor and its preparation method.

[0009] To address the aforementioned technical problems, this invention provides a fingerprint biomimetic composite flexible stretchable sensor, comprising a flexible stretchable substrate, a conductive composite layer, and an encapsulation layer; the conductive composite layer is composed of a conductive layer made of metal nanowires and a second conductive material, as well as a platinum conductive layer.

[0010] This invention also provides a method for fabricating a fingerprint biomimetic composite flexible stretchable sensor, comprising the following steps:

[0011] 1) Fabrication of flexible and stretchable substrates:

[0012] After cleaning and drying the template, the precursor of the flexible stretchable substrate is uniformly coated on the template and cured by heating (heated to 50-70℃ and cured for 3-7 hours) to obtain the flexible stretchable substrate attached to the template.

[0013] 2) Preparation of the composite conductive layer:

[0014] Metal nanowires were cut into 50×10 -3 mg·mL -1 The concentration was dispersed in ethanol and ultrasonically treated (1±0.5h) to obtain uniformly dispersed ink I; the second conductive material was added at a concentration of 0.1mg·mL⁻¹. -1 The concentration was dispersed in ethanol and ultrasonically treated (4±1h) to obtain uniformly dispersed ink II;

[0015] Ink I and ink II are mixed at a volume ratio of 25-150:50-100, and then deposited on textured filter paper (deposited on filter paper with specific texture using a vacuum filtration method), and dried (heated at 50±10℃ for 1±0.1h) to obtain a textured composite conductive layer attached to the filter paper.

[0016] 3) Transfer of the composite conductive layer:

[0017] The flexible stretchable substrate precursor is coated onto the flexible stretchable substrate obtained in step 1) to form a precursor layer; the material obtained in step 2) is pressed onto the precursor layer so that the textured composite conductive layer is in contact with the precursor layer; after curing (heating at 50±10℃ for 3~7h), the filter paper is removed to obtain a conductive layer with filter paper texture on the flexible stretchable substrate.

[0018] 4) Fabrication of sensor devices

[0019] Cut the conductive layer with filter paper texture obtained in step 3) on the flexible stretchable substrate, and place a platinum conductive layer (with a thickness of about 5 to 10 nanometers) on the surface of the conductive layer with filter paper texture; thus forming a conductive composite layer.

[0020] Two copper electrodes are attached to both ends of the conductive composite layer with silver paste, and then the encapsulation layer is attached. The ends of the copper electrodes are located outside the encapsulation layer, thus obtaining a flexible and stretchable sensor.

[0021] Note: Platinum conductive layer (thickness of about 5-10 nanometers) can be formed on the surface of the conductive layer with filter paper texture by spraying using an ion sputtering vapor deposition coating machine (spraying time is about 30-70s); thus forming a conductive composite layer.

[0022] An improvement to the fabrication method of the fingerprint biomimetic composite flexible stretchable sensor of the present invention:

[0023] The flexible and stretchable substrate is made of Ecoflex, thermoplastic polyurethane, rubber, or polydimethylsiloxane.

[0024] The metal nanowires are silver nanowires, copper nanowires, or gold nanowires, with diameters ranging from 20 to 100 nm.

[0025] The second conductive material is graphite sheet, graphene, graphene oxide, reduced graphene oxide, carbon nanotube, carbon fiber, or MXene.

[0026] The encapsulation layer is made of Ecoflex, thermoplastic polyurethane, rubber, and polydimethylsiloxane.

[0027] The templates are polyethylene terephthalate, polycarbonate, colorless transparent polyimide, polymethyl methacrylate, polydimethylsiloxane, and polyurethane.

[0028] As a further improvement to the preparation method of the fingerprint biomimetic composite flexible stretchable sensor of the present invention:

[0029] On a circular corrugated nylon filter paper (5μm pore size) with a diameter of 50mm, the total volume of ink I and ink II is 125-300ml.

[0030] As a further improvement to the preparation method of the fingerprint biomimetic composite flexible stretchable sensor of the present invention: step 1):

[0031] The template is ultrasonically cleaned in acetone, deionized water and ethanol sequentially (30 min each time), and then dried in an oven. The precursor of the flexible stretchable substrate is uniformly coated on the template using techniques such as scraping, spin coating, dip coating and slot coating. After curing at 50-70℃ for 3-7 h, a uniform flexible stretchable substrate attached to the template is obtained.

[0032] This invention aims to solve the problems of narrow working range, low sensitivity, and complex preparation steps of common sensors. By using filter paper as a template, this invention can prepare a raised and recessed shape that mimics fingerprints, effectively expanding the effective working range of the sensor.

[0033] The technical advantages of this invention are:

[0034] 1. Comprehensively utilize the advantages of various materials (including metal nanowires, secondary conductive materials, flexible stretchable substrates, etc.) in terms of conductivity and stretchability.

[0035] 2. Effectively combining metal nanowires and a second conductive material (second conductive substance), the second conductive material acts as an improver of the conductivity of metal nanowires, enabling the entire network to achieve higher conductivity.

[0036] 3. The conductivity of the second conductive material is slightly inferior to that of the metal nanowire, but its stretchability is stronger, which effectively expands the stretchability range of the device and improves the device performance.

[0037] 4. By using filter paper as a template, it is possible to prepare a raised and recessed shape that mimics fingerprints, effectively expanding the effective working range of the sensor.

[0038] 5. This invention uses textured filter paper as the filtration filter paper and employs a transfer method to give the conductive layer a specific shape (fingerprint pattern). In contrast, the existing technology results in a planar conductive layer after transfer, lacking a fingerprint pattern.

[0039] This invention utilizes a concave-convex shape to delay the breakage of the conductive layer during the stretching process, thereby expanding the stretchable range. Attached Figure Description

[0040] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0041] Figure 1 This is a photograph of the actual product before packaging in Example 1.

[0042] That is, in step 4), two copper electrodes are attached to both ends of the conductive composite layer with silver paste.

[0043] Figure 2 This is a scanning electron microscope image of the final product obtained in Example 1.

[0044] Figure 3 This is a scanning electron microscope image of the filter paper used in Example 1.

[0045] Figure 4 The graph shows the change in relative resistance as a function of strain in Example 3.

[0046] Figure 5 This is a relative resistance test graph for Example 3 after 5000 cyclic stretching cycles. Detailed Implementation

[0047] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0048] Example 1: A method for fabricating a fingerprint biomimetic composite flexible stretchable sensor, comprising the following steps:

[0049] 1) A polyethylene terephthalate film (125 μm thick) used as a flexible stretchable substrate template was ultrasonically cleaned in acetone, deionized water and ethanol for 30 min each, and then dried in an oven (60℃ for 0.5 h); the precursor of the flexible stretchable substrate Ecoflex (liquid, commercially available) was uniformly coated on the template substrate using a blade coating technique, with a wet film thickness of 400 μm. After curing at 50℃ for 7 h, a uniform flexible stretchable substrate Ecoflex (approximately 300 μm thick) attached to the template was obtained.

[0050] 2) Silver nanowires with a diameter of 20 nm (approximately 5 μm in length) are shaped into 50 × 10⁻⁶ nanometers. -3 mg·mL -1 The metal nanowire ink I was obtained by dispersing the ink in ethanol at a concentration of 0.1 mg / mL and then sonicating it for 1 hour. -1 The ink was dispersed in ethanol and ultrasonically treated for 4 hours to obtain well-dispersed ink II.

[0051] Ink I and Ink II were mixed at a ratio of 150 mL: 50 mL and deposited on corrugated woven nylon filter paper using a vacuum filtration method. After drying at 50°C for 1 hour, a composite conductive layer with a specific texture was obtained and attached to the filter paper.

[0052] The corrugated woven nylon filter paper (with a height difference of 20μm) is a circle with a diameter of 50mm, a pore size of 5μm, and a fiber coarseness of about 50μm.

[0053] 3) Coating the Ecoflex flexible stretchable substrate precursor obtained in step 1) onto the Ecoflex flexible stretchable substrate to form a precursor layer with a wet film thickness of 400 μm.

[0054] The composite conductive layer with a specific texture, which is attached to the filter paper and prepared in step 2), is pressed onto the precursor layer (i.e., the composite conductive layer is in contact with the precursor layer). The precursor layer is heated at 50°C for 4 hours to solidify it. The filter paper is then peeled off, and the composite conductive layer is transferred to a flexible stretchable substrate to obtain a conductive layer with the filter paper texture located on the flexible stretchable substrate.

[0055] 4) Cut the conductive layer with filter paper texture obtained in step 3) onto the flexible stretchable substrate, and then spray it for 30-70 seconds using an ion sputtering vapor deposition apparatus to prepare a platinum conductive layer (approximately 5-10 nanometers thick) on the surface of the conductive layer with filter paper texture. This completes the formation of the conductive composite layer.

[0056] Two copper electrodes are attached to both ends of the conductive composite layer with silver paste and then bonded to the encapsulation layer. The ends of the copper electrodes are located outside the encapsulation layer, thus obtaining a flexible and stretchable sensor. Except for the ends of the copper electrodes, which are located outside the encapsulation layer, the rest of the sensor is encapsulated by the encapsulation layer.

[0057] The encapsulation layer is a conventional technique, typically using the same material as the flexible, stretchable substrate. For example, Ecoflex is used in this embodiment.

[0058] The sensor ultimately achieved a sensitivity factor of GF = 941.4, with an operating range of 140%. It remained stable after 5000 cycles of cyclic stretching in relative resistance testing.

[0059] Test method: The sensor is placed on a tensile instrument with adjustable stretching length and rate. The copper wires at both ends are connected to a current source meter. A DC voltage of 0.1V is applied across the sensor using the current source meter, and the resistance change curve of the sensor during uniform stretching is recorded. The sensitivity factor is calculated according to GF = ΔR / R0 / ε (ΔR is the difference between the changed resistance and the initial resistance, R0 is the initial resistance of the sensor, and ε is the strain rate of the sensor length). The working range is defined as the maximum deformation reached by the sensor from the start of stretching while recording the signal until the signal becomes discontinuous. Within this range, the sensor signal changes stably and continuously.

[0060] Example 2: A method for fabricating a fingerprint biomimetic composite flexible stretchable sensor, comprising the following steps:

[0061] 1) The polycarbonate film (125 μm thick) used as a flexible stretchable substrate template was ultrasonically cleaned in acetone, deionized water and ethanol for 30 min in sequence, and then dried in an oven (60℃ for 0.5 h); the Ecoflex precursor of the flexible stretchable substrate was uniformly coated on the template substrate using a blade coating technique, with a wet film thickness of 400 μm. After curing at 50℃ for 7 h, a uniform flexible stretchable substrate (approximately 300 μm thick) attached to the template was obtained.

[0062] 2) Silver nanowires with a diameter of 110 nm (approximately 45 μm in length) are shaped into 50 × 10⁻⁶ nanometers. -3 mg·mL -1 The concentration was dispersed in ethanol and sonicated for 1 hour to obtain uniformly dispersed metal nanowire ink I; graphite sheets (approximately 10 layers of graphene sheets) were prepared at a concentration of 0.1 mg / mL. -1 The ink was dispersed in ethanol and ultrasonically treated for 4 hours to obtain well-dispersed ink II.

[0063] Ink I and II were mixed at a ratio of 25 mL: 100 mL and deposited on corrugated woven nylon filter paper using a vacuum filtration method. After drying at 50°C for 1 hour, a composite conductive layer with a specific texture was obtained and attached to the filter paper.

[0064] The corrugated woven nylon filter paper described above is the same as in Example 1.

[0065] 3) Coating the Ecoflex flexible stretchable substrate precursor obtained in step 1) onto the Ecoflex flexible stretchable substrate to form a precursor layer with a wet film thickness of 400 μm.

[0066] The composite conductive layer with a specific texture, which is attached to the filter paper and prepared in step 2), is pressed onto the precursor layer (i.e., the composite conductive layer is in contact with the precursor layer). The precursor layer is heated at 50°C for 7 hours to solidify. The filter paper is then peeled off, and the composite conductive layer is transferred to a flexible stretchable substrate to obtain a conductive layer with the filter paper texture located on the flexible stretchable substrate.

[0067] 4) Cut the conductive layer with filter paper texture obtained in step 3) on the flexible stretchable substrate, and use an ion sputtering evaporation coating machine to spray for 30-70 seconds to prepare a platinum conductive layer on the surface of the conductive layer with filter paper texture; thus forming a conductive composite layer.

[0068] Two copper electrodes are attached to both ends of the conductive composite layer with silver paste and then bonded to the encapsulation layer. The ends of the copper electrodes are located outside the encapsulation layer, thus obtaining a flexible and stretchable sensor. Except for the ends of the copper electrodes, which are located outside the encapsulation layer, the rest of the sensor is encapsulated by the encapsulation layer.

[0069] The encapsulation layer is a conventional technique, typically using the same material as the flexible, stretchable substrate. For example, Ecoflex is used in this embodiment.

[0070] The sensor sensitivity factor GF was ultimately obtained as 1855.5, with an operating range of 100%. It remained stable after 5000 cycles of cyclic stretching in a relative resistance test.

[0071] Example 3: A method for fabricating a fingerprint biomimetic composite flexible stretchable sensor, comprising the following steps:

[0072] 1) A polyethylene terephthalate film (125 μm thick) serving as a flexible stretchable substrate template was ultrasonically cleaned in acetone, deionized water, and ethanol for 30 min each, and then dried in an oven (60 °C for 0.5 h). The Ecoflex precursor for the flexible stretchable substrate was uniformly coated onto the template substrate using a blade coating technique, with a wet film thickness of 400 μm. After curing at 50 °C for 6 h, a uniform flexible stretchable substrate (approximately 300 μm thick) attached to the template was obtained.

[0073] 2) Silver nanowires with a diameter of 45 nm (approximately 50 μm in length) are shaped into 50 × 10⁻⁶ nanometers. -3 mg·mL -1 The metal nanowire ink I was dispersed in ethanol at a concentration of 0.1 mg / mL and sonicated for 1 hour. -1 The concentration was dispersed in ethanol and ultrasonically treated for 4 hours to obtain well-dispersed ink II.

[0074] Ink I and II were mixed at a ratio of 75 mL: 75 mL and deposited onto corrugated woven nylon filter paper using a vacuum filtration method. After drying at 50°C for 1 hour, a composite conductive layer with a specific texture was obtained adhering to the filter paper.

[0075] The corrugated woven nylon filter paper described above is the same as in Example 1.

[0076] 3) Coating the Ecoflex flexible stretchable substrate precursor onto the Ecoflex flexible stretchable substrate prepared in step 1) to form a precursor layer with a wet film thickness of 400 μm.

[0077] The composite conductive layer with a specific texture, which is attached to the filter paper and prepared in step 2), is pressed onto the precursor layer (i.e., the composite conductive layer is in contact with the precursor layer). The precursor layer is heated at 50°C for 4 hours to solidify it. The filter paper is then peeled off, and the composite conductive layer is transferred to a flexible stretchable substrate to obtain a conductive layer with the filter paper texture located on the flexible stretchable substrate.

[0078] 4) Cut the conductive layer with filter paper texture obtained in step 3) on the flexible stretchable substrate, and use an ion sputtering evaporation coating machine to spray for 30-70 seconds to prepare a platinum conductive layer on the surface of the conductive layer with filter paper texture; thus forming a conductive composite layer.

[0079] Two copper electrodes are attached to both ends of the conductive composite layer with silver paste and then bonded to the encapsulation layer. The ends of the copper electrodes are located outside the encapsulation layer, thus obtaining a flexible and stretchable sensor. Except for the ends of the copper electrodes, which are located outside the encapsulation layer, the rest of the sensor is encapsulated by the encapsulation layer.

[0080] The encapsulation layer is a conventional technique, typically using the same material as the flexible, stretchable substrate. For example, Ecoflex is used in this embodiment.

[0081] The final sensor sensitivity factor was GF = 2064.1, with an operating range of 150%. It remained stable after 5000 cyclic stretching tests of relative resistance. Figure 4 , which represents the sensor's sensitivity value within different strain ranges.

[0082] Comparative Example 1: The “stretchable flexible substrate” in Example 3 is replaced with the following: PDMS substrate, rubber substrate, thermoplastic polyurethane substrate; that is, the Ecoflex precursor in steps 1) and 3) of Example 3 is replaced with the precursor of the above substrate; and the encapsulation layer in step 4) is also replaced with the above substrate accordingly.

[0083] The rest is the same as in Example 3.

[0084] The final sensor performance data are as follows:

[0085] PDMS substrate: Sensitivity factor GF = 588.2, operating range 40%; stable relative resistance after 5000 cycles of tensile testing;

[0086] Rubber substrate: Sensitivity factor GF = 1045.3, operating range 105%; stable relative resistance after 5000 cycles of tensile testing;

[0087] The thermoplastic polyurethane substrate has a sensitivity factor GF of 622.2 and an operating range of 60%. It remains stable in relative resistance tests after 5000 cyclic tensile cycles.

[0088] Comparative Example 2, compared to Example 3, changed the volume of ink I and II in step 2), as shown in Table 1 below. The rest remained the same as in Example 3. The results are shown in Table 1. The relative resistance remained stable after 5000 cycles of cyclic stretching.

[0089] Table 1

[0090] 50mL:75mL 309.1 100％ 50mL:100mL 402.3 140％ 50mL:125mL 736.3 60％ 75mL:50mL 169.6 170％ 100mL:50mL 775.1 190％ 125mL:50mL 1430.1 175％

[0091] Comparative Example 3: The "corrugated woven nylon filter paper" in Example 3 was replaced with conventional "flat filter paper", and the rest was the same as in Example 3.

[0092] The final sensor performance data obtained is as follows:

[0093] Sensitivity factor GF = 1245.65, operating range 150%.

[0094] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating a fingerprint biomimetic composite flexible stretchable sensor, characterized in that, Includes the following steps: 1) Fabrication of flexible and stretchable substrates: The template is cleaned and dried; the precursor of the flexible stretchable substrate is uniformly coated on the template, and after heating and curing, a flexible stretchable substrate attached to the template is obtained. 2) Preparation of the composite conductive layer: Metal nanowires were cut into 50×10 -3 mg·mL -1 The concentration was dispersed in ethanol and ultrasonically treated to obtain uniformly dispersed ink I; the second conductive material was added at a concentration of 0.1 mg / mL. -1 The ink was dispersed in ethanol and ultrasonically treated to obtain a uniformly dispersed ink II. Ink I and ink II are mixed in a volume ratio of 25~150:50~100, then deposited on textured filter paper and dried to obtain a textured composite conductive layer attached to the filter paper. 3) Transfer of the composite conductive layer: A precursor of a flexible stretchable substrate is coated onto the flexible stretchable substrate obtained in step 1) to form a precursor layer; the material obtained in step 2) is pressed onto the precursor layer so that the textured composite conductive layer is in contact with the precursor layer; after curing, the filter paper is removed to obtain a conductive layer with filter paper texture on the flexible stretchable substrate. 4) Fabrication of sensor devices: Cut the conductive layer with filter paper texture obtained in step 3) on the flexible stretchable substrate, and deposit a platinum conductive layer on the surface of the conductive layer with filter paper texture; to form a conductive composite layer. Two copper electrodes are attached to both ends of the conductive composite layer with silver paste, and then the encapsulation layer is attached. The ends of the copper electrodes are located outside the encapsulation layer, thus obtaining a flexible and stretchable sensor.

2. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to claim 1, characterized in that: The flexible and stretchable substrate is Ecoflex, thermoplastic polyurethane, rubber, or polydimethylsiloxane.

3. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to claim 2, characterized in that: The metal nanowires are silver nanowires, copper nanowires, or gold nanowires, with a diameter of 20~100 nm.

4. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to claim 3, characterized in that: The second conductive material is graphite sheet, graphene oxide, reduced graphene oxide, carbon nanotubes, carbon fiber, or MXene.

5. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to claim 4, characterized in that: The encapsulation layer is made of Ecoflex, thermoplastic polyurethane, rubber, or polydimethylsiloxane.

6. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to claim 5, characterized in that: The template is ethylene terephthalate, polycarbonate, colorless transparent polyimide, polymethyl methacrylate, polydimethylsiloxane, or polyurethane.

7. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to any one of claims 1 to 6, characterized in that: On a circular corrugated nylon filter paper with a diameter of 50mm, the combined volume of ink I and ink II is 125~300ml.

8. The method for fabricating a fingerprint biomimetic composite flexible stretchable sensor according to any one of claims 1 to 6, characterized in that: Step 1): The template is ultrasonically cleaned in acetone, deionized water and ethanol in sequence, and then dried in an oven. The precursor of the flexible stretchable substrate is uniformly coated on the template by scraping, spin coating, dip coating or slot coating. After heating to 50~70 ℃ and curing for 3~7 h, a uniform flexible stretchable substrate attached to the template is obtained.

Images