A flexible multifunctional electronic skin and a preparation method thereof

Abstract

The present application relates to flexible multifunctional electronic skin and its preparation method, belong to flexible wearable electronic field and new material technical field.The flexible multifunctional electronic skin is composed of multiple flexible multifunctional electronic skin sensing units;The sensing unit includes: first sensitive film, second sensitive film, third sensitive film, electrode material and wire;The first sensitive film includes: sensitive material A, flexible substrate A loaded with sensitive material A, flexible substrate C adhered to the outer surface of the flexible substrate A;The second sensitive film includes: sensitive material A, flexible substrate A loaded with sensitive material A;The first sensitive film and the second sensitive film are electrically connected;The third sensitive film includes: sensitive material B, flexible substrate B loaded with sensitive material B, flexible substrate C adhered to the outer surface of the flexible substrate B;The second sensitive film and the third sensitive film are electrically connected.

Description

TECHNICAL FIELD

[0001] The present application relates to a flexible multifunctional electronic skin and a preparation method thereof, and belongs to the field of flexible wearable electronics and the field of new materials. BACKGROUND

[0002] Flexible wearable electronics have a strong application prospect in the fields of motion monitoring, healthcare, human-computer interaction, etc. As an important component of wearable electronics, flexible electronic skin has been widely concerned by academia and industry. Flexible electronic skin is a kind of multifunctional sensor array that can perceive various stimuli, which is similar to human skin. The most important perception function of human skin is pressure perception and temperature perception (Reference 1), and flexible electronic skin can also perceive pressure and temperature. Moreover, the two perception functions do not interfere with each other, and are also not disturbed by tensile strain (Reference 2).

[0003] There are currently three methods to construct flexible multifunctional electronic skin that can perceive pressure and temperature. The first method is to integrate a single pressure sensing unit and a temperature sensing unit. This method of constructing electronic skin is relatively complex, and it is easily disturbed by tensile strain (Reference 3). The second method is to construct a single sensing unit that has both pressure and temperature perception functions, and to use mathematical model algorithms to distinguish pressure and temperature perception signals. This kind of mathematical model algorithm is complex, and the distinguishing process is tedious. In addition, the mathematical model established does not exclude the disturbance signal of tensile strain, resulting in inaccurate results of distinguishing pressure and temperature perception signals (Reference 4). The third method is to use the piezoresistive effect and thermoelectric effect of functional materials to construct a single sensing unit that has both pressure and temperature perception functions. Although the electronic skin constructed by this method does not interfere with the perception functions, its sensing performance is low, and it cannot exclude the disturbance of tensile strain. In addition, it uses the thermoelectric effect of materials to perceive temperature, and needs to construct a complex temperature gradient in the perception process, and can only directly perceive relative temperature difference, but cannot directly perceive absolute temperature, which is not convenient in practical application (Reference 5, 6).

[0004] Therefore, it has important application prospects to construct flexible multifunctional electronic skin that can directly perceive absolute pressure and absolute temperature, two perception functions do not interfere with each other, and can avoid the disturbance of tensile strain. However, there is currently no report on flexible multifunctional electronic skin that meets the above requirements.

[0005] Reference:

[0006] (1) Khatib M, Zohar O, Saliba W, et al. A Multifunctional Electronic Skin Empowered with Damage Mapping and Autonomic Acceleration of Self-Healing in Designated Locations [J]. Advanced Materials, 2020, 32(17): 2000246.

[0007] (2) Lim H R, Kim H S, Qazi R, et al. Wearable Flexible Hybrid Electronics: Advanced Soft Materials, Sensor Integrations, and Applications of Wearable Flexible Hybrid Electronics in Healthcare, Energy, and Environment [J]. Advanced Materials, 2020, 32(15): 1901924.

[0008] (3) Hua Q, Sun J, Liu H, et al. Skin-Inspired Highly Stretchable and Conformable Matrix Networks for Multifunctional Sensing [J]. Nature Communications, 2018, 9(1): 244.

[0009] (4) You I, Mackanic D G, Matsuhisa N, et al. Artificial Multimodal Receptors Based on Ion Relaxation Dynamics [J]. Science, 2020, 370(6519): 961-965.

[0010] (5) Han S, Alvi N, L et al. A Multiparameter Pressure–Temperature–Humidity Sensor Based on Mixed Ionic–Electronic Cellulose Aerogels[J]. Advanced Science, 2019, 6(8): 1802128.

[0011] (6) Sun Jing, Li Yuxiang, Wang Ranran. A flexible dual-function electronic skin and its preparation method, 202110244056.1[P]. 2022-09-06. SUMMARY

[0012] The present application provides a kind of flexible multifunctional electronic skin and its preparation method, to solve the problems such as the signal distinguishing process of existing flexible multifunctional electronic skin that can perceive pressure and temperature is cumbersome, easily interfered by tensile strain signal, to realize that flexible multifunctional electronic skin can directly and accurately perceive absolute pressure and absolute temperature.

[0013] In the first aspect, the present application provides a kind of flexible multifunctional electronic skin.The flexible multifunctional electronic skin is composed of multiple flexible multifunctional electronic skin sensing units;The sensing unit includes: first sensitive film, second sensitive film, third sensitive film, electrode material and wire;

[0014] The first sensitive film includes: sensitive material A, flexible substrate A loaded with sensitive material A, flexible substrate C adhered to the outer surface of the flexible substrate A;

[0015] The second sensitive film includes: sensitive material A, flexible substrate A loaded with sensitive material A;

[0016] The sensitive material A of the first sensitive film and the sensitive material A of the second sensitive film are arranged closely;

[0017] The first sensitive film and the second sensitive film are electrically connected;

[0018] The third sensitive film includes: sensitive material B, flexible substrate B loaded with sensitive material B, flexible substrate C adhered to the outer surface of the flexible substrate B;

[0019] The flexible substrate A of the second sensitive film and the flexible substrate B of the third sensitive film are arranged closely;

[0020] The second sensitive film and the third sensitive film are electrically connected;

[0021] The sensitive material A is a flexible conductive material, preferably one or more of a conductive metal organic framework (MOF) material, a transition metal carbide (MXene) material, and a carbon nanomaterial; the sensitive material B is a flexible semiconductor material, and the sensitive material B and the sensitive material A form a p-n junction or a Schottky junction after being connected; preferably, the sensitive material B is a lead-based superlattice material (Pb-SLs).

[0022] Preferably, the flexible multifunctional electronic skin has the functions of directly sensing absolute pressure and directly sensing absolute temperature, and the two sensing functions do not interfere with each other.

[0023] Preferably, the sensing of pressure and temperature by the flexible multifunctional electronic skin is not disturbed by stretching.

[0024] Preferably, the flexible multifunctional electronic skin is composed of a plurality of flexible multifunctional electronic skin sensing units arranged in a specific manner, and preferably, the specific arrangement is a periodic array arrangement.

[0025] Preferably, the Young's modulus of the flexible substrate A and the flexible substrate B is not less than 2 times that of the flexible substrate C.

[0026] Preferably, the flexible substrate A and the flexible substrate B are independently selected from a polyvinylidene fluoride film, a polytetrafluoroethylene film, a cotton cellulose film, a nylon film, or a polyether sulfone film; and the flexible substrate C is a silicone rubber film, a styrene-based thermoplastic elastomer film, or a polyurethane film.

[0027] Preferably, the electrode material is silver, copper, copper-nickel alloy, or magnesium-aluminum alloy; and the wire is a silver wire, a copper wire, or a copper-nickel alloy wire.

[0028] In a second aspect, the present application provides a preparation method of a flexible multifunctional electronic skin. The preparation method comprises: attaching a sensitive material A to a flexible substrate A, coating an electrode material on the end of the flexible substrate A and fixing a wire, then directly adhering or adhering in a specific arrangement manner a plurality of the flexible substrate A loaded with the sensitive material A to the surface of a pre-polymerized flexible substrate C, and then fully curing to obtain an upper part of the flexible multifunctional electronic skin.

[0029] Attaching a sensitive material A to a flexible substrate A, coating an electrode material on the end of the flexible substrate A and fixing a wire; attaching a sensitive material B to a flexible substrate B, coating an electrode material on the end of the flexible substrate B and fixing a wire; adhering the flexible substrate A loaded with the sensitive material A and the flexible substrate B loaded with the sensitive material B, then coating an electrode material on the end side of the flexible substrate to connect the sensitive material A and the sensitive material B to obtain a composite unit; directly adhering or adhering in a specific arrangement manner a plurality of the composite units to the surface of a pre-polymerized flexible substrate C, and then fully curing to obtain a lower part of the flexible multifunctional electronic skin.

[0030] The upper part of the flexible multifunctional electronic skin is attached to the lower part of the flexible multifunctional electronic skin face to face to obtain the flexible multifunctional electronic skin.

[0031] Preferably, the method for attaching the sensitive material on the flexible substrate comprises any one of an interface in-situ growth method, an immersion coating method, a drop coating method, an infiltration method, and a printing method.

[0032] Preferably, the pre-polymerization temperature is 60-150 DEG C, and the pre-polymerization time is 10-20 minutes; the curing temperature is 60-150 DEG C, and the curing time is 2-6 hours.

[0033] Beneficial effects:

[0034] 1. The present application utilizes the feature that the contact potential between the sensitive material A and the sensitive material B changes with temperature, and realizes the function of directly sensing absolute temperature of the flexible multifunctional electronic skin based on the potential difference mechanism; in combination with the high deformation potential of the Pb-SLs and the feature that the Fermi level abnormally moves downward with the increase of temperature, the flexible multifunctional electronic skin has an ultra-high temperature sensing sensitivity coefficient; based on the interface piezoresistance and the potential difference two different sensing principles, the pressure sensing and temperature sensing functions of the flexible multifunctional electronic skin do not interfere with each other. This is because, on the one hand, the interface piezoresistance effect has a high pressure sensing sensitivity, and the pressure response mainly depends on the change of the interface contact resistance, and the change of the self-resistance of the two layers of sensitive material A with temperature has a negligible influence on the pressure response of the device. On the other hand, the junction potential of the sensitive material A-B p-n junction only depends on the band movement of the sensitive material A and B, and the conventional pressure does not cause the band change of the sensitive material A and B, so the potential difference is only affected by temperature.

[0035] 2. The present application utilizes the feature that the flexible substrate A and the flexible substrate B are not less than 2 times of the flexible substrate C, and realizes that the pressure sensing and temperature sensing functions of the flexible multifunctional electronic skin are not disturbed by tensile strain.

[0036] 3. The preparation method of the present application is simple, can be mass-produced, and realizes integration and commercial mass production.

[0037] In summary, the flexible multifunctional electronic skin sensing unit of the present application can directly sense absolute pressure based on the interface piezoresistance mechanism, and can directly sense absolute temperature based on the potential difference mechanism; the two sensing functions of the flexible multifunctional electronic skin sensing unit do not interfere with each other, and are not disturbed by tensile strain. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 is a schematic diagram of the flexible multifunctional electronic skin of the present application;

[0039] Figure 2This is a schematic diagram of the flexible multifunctional electronic skin sensing unit described in this invention;

[0040] Figure 3 Voltage-temperature curve of the flexible multifunctional electronic skin prepared in Example 1;

[0041] Figure 4 The relative current change-pressure curve of the flexible multifunctional electronic skin prepared in Example 1;

[0042] Figure 5 Relative current-pressure curves of the flexible multifunctional electronic skin prepared in Example 1 at 26°C and 38°C;

[0043] Figure 6 The relative voltage change-pressure curve of the flexible multifunctional electronic skin prepared in Example 1 at 38°C;

[0044] Figure 7 The relative resistance change-strain curve of the flexible multifunctional electronic skin prepared in Example 1;

[0045] Figure 8 The relative voltage change-strain curve of the flexible multifunctional electronic skin prepared in Example 1 at 38°C. Detailed Implementation

[0046] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0047] The flexible multifunctional electronic skin of this invention is composed of multiple flexible multifunctional electronic skin sensing units. For example, it is composed of multiple flexible multifunctional electronic skin sensing units arranged in a specific pattern. The preferred specific arrangement is a periodic array arrangement.

[0048] More preferably, the periodic array arrangement is as follows: Figure 1 As shown. The size of the flexible multifunctional electronic skin sensing unit can be (5-10)mm × (5-10)mm, and the interval between two adjacent flexible multifunctional electronic skin sensing units can be 5-15mm.

[0049] The sensing unit includes: a first sensitive film, a second sensitive film, a third sensitive film, an electrode material, and a wire.

[0050] The first sensitive film includes: a sensitive material A, a flexible substrate A on which the sensitive material A is loaded, and a flexible substrate C attached to the outer surface of the flexible substrate A. The sensitive material A is a flexible conductive material. The sensitive material A includes, but is not limited to, one or more of conductive metal-organic framework (MOF) materials, transition metal carbide (MXene) materials, and carbon nanomaterials.

[0051] The flexible substrate C includes, but is not limited to, silicone rubber, styrene thermoplastic elastomer or polyurethane. Preferably, the flexible substrate C is silicone rubber. More preferably, the flexible substrate C is polydimethylsiloxane.

[0052] The Young's modulus of the flexible substrate A is not less than 2 times that of the flexible substrate C. The flexible substrate A includes, but is not limited to, polyvinylidene fluoride film, polytetrafluoroethylene film or nylon film. Preferably, the flexible substrate A is polyvinylidene fluoride film.

[0053] The flexible substrate A has excellent surface structure properties. Preferably, the flexible substrate A has a high-low relief microstructure, so that the sensitive material A thin film (i.e. the first sensitive thin film and the second sensitive thin film) also has a high-low relief microstructure. For example, the polyvinylidene fluoride film used in the embodiments is formed by random lapping arrangement of tubular fibers, with a high-low relief surface, which is beneficial for the adhesion of the sensitive material A, and the prepared sensitive material A thin film also has a high-low relief microstructure. That is, the present application utilizes the high-low relief microstructure of the sensitive material A thin film, based on the interface piezoresistive mechanism, to realize the function of directly sensing absolute pressure of the flexible multifunctional electronic skin, and has a wide sensing range and high sensitivity coefficient.

[0054] The flexible substrate A used in the present application not only facilitates the conformal adhesion of the sensitive material A, such as conductive MOF material, but also facilitates the adhesion of other sensitive materials A, such as transition metal carbide (MXene) material and carbon nanomaterial, to realize the piezoresistive pressure sensing function.

[0055] The flexible substrate A (such as polyvinylidene fluoride film) also has excellent mechanical properties. Under tensile strain, the tensile strain acting on the flexible substrate C causes the flexible substrate C to deform, while the morphology of the flexible substrate A loaded with the sensitive material A remains almost unchanged, which ensures that the thin film resistance and Fermi level of the sensitive material A remain almost unchanged. Therefore, the flexible multifunctional electronic skin is not disturbed by tensile strain when sensing pressure.

[0056] The flexible substrate A of Chinese patent 202110244056.1 can be a hybrid cellulose film, and the designed flexible dual-functional electronic skin has pressure sensing performance in the range of 0-300 kPa, with a sensitivity of up to 61.61 kPa -1(0-32.02 kPa). The preferred flexible substrate A of the present application is a polyvinylidene fluoride film, which not only satisfies the conformal attachment of the sensitive material A, but also has a roughness in the range of 500-2000 nm (measured by atomic force microscopy), which is higher than the preferred mixed cellulose film (10-400 nm, measured by atomic force microscopy) in Chinese patent 202110244056.1. Therefore, the pressure sensing range of the flexible multifunctional electronic skin preferably designed by the present application can be widened to 1025 kPa, and the sensitivity is improved to 220.70 kPa -1 (0-40.75 kPa).

[0057] The second sensitive film comprises: a sensitive material A, a flexible substrate A loaded with the sensitive material A. Similarly, the sensitive material A comprises but is not limited to one or more of conductive metal organic framework (MOF) material, transition metal carbide (MXene) material and carbon nanomaterial. Similarly, the Young's modulus of the flexible substrate A is not less than 2 times that of the flexible substrate C, including but not limited to a polyvinylidene fluoride film, a polytetrafluoroethylene film or a nylon film. Preferably, the flexible substrate A is a polyvinylidene fluoride film.

[0058] The sensitive material A of the first sensitive film and the sensitive material A of the second sensitive film are arranged in close proximity. Here, "close proximity" can also be understood as "adjacent" or "face-to-face".

[0059] The first sensitive film and the second sensitive film are electrically connected. For example, an electrical contact is formed by conductive silver paste.

[0060] The flexible substrate A of the first sensitive film and the flexible substrate A of the second sensitive film can be independently arranged. Preferably, the flexible substrate A of the first sensitive film and the flexible substrate A of the second sensitive film are the same material.

[0061] The third sensitive film comprises: a sensitive material B, a flexible substrate B loaded with the sensitive material B, and a flexible substrate C attached to the outer surface of the flexible substrate B.

[0062] The sensitive material B is a flexible semiconductor material, and forms a p-n junction or a Schottky junction after being (electrically) connected with the sensitive material A. Preferably, the sensitive material B is a lead-based superlattice material (Pb-SLs). The Pb-SLs has excellent properties. First, it can be conformally attached and grown on the surface of a flexible substrate with different microstructures; second, the Pb-SLs is a semiconductor material with high lattice deformation potential, and its Fermi level abnormally decreases with temperature rise. By using the high lattice deformation potential of the Pb-SLs and the characteristic of abnormal decrease of the Fermi level with temperature rise, the flexible multifunctional electronic skin has a temperature sensing sensitivity coefficient as high as millivolts.

[0063] The Pb-SLs material is composed of a lead-containing inorganic phase and an organic phase. The lead-containing inorganic phase is a single lead salt, including but not limited to lead iodide, lead chloride, lead sulfate or lead acetate. Preferably, the lead-containing inorganic phase is lead iodide. The organic phase is a single organic compound, including but not limited to 3,3',5,5'-tetraethylbenzidine, 3,3',5,5'-tetramethylbenzidine or N,N,N',N'-tetramethyl-p-phenylenediamine. Preferably, the lead-containing inorganic phase is 3,3',5,5'-tetraethylbenzidine.

[0064] The Young's modulus of the flexible substrate B is not less than 2 times of that of the flexible substrate C, including but not limited to cotton cellulose film, nylon film or polyether sulfone film. Preferably, the flexible substrate B is a nylon film.

[0065] The flexible substrate B (e.g. nylon film) has excellent properties. First, the flexible substrate B is beneficial to the adhesion of the sensitive material B, realizing the large-area thin film preparation of the sensitive material B. Second, the Young's modulus of the flexible substrate B is not less than 2 times of that of the flexible substrate C. Under the action of tensile strain, the tensile strain acting on the flexible substrate C causes the deformation of the flexible substrate C, while the morphology of the flexible substrate B loaded with the thin film of the sensitive material B is almost unchanged, which ensures that the thin film resistance and Fermi level of the sensitive material B are almost unchanged. Therefore, the prepared flexible multifunctional electronic skin is not disturbed by the tensile strain when sensing temperature.

[0066] The flexible substrate C includes but is not limited to silicone rubber, styrene thermoplastic elastomer or polyurethane. Preferably, the flexible substrate C is silicone rubber. More preferably, the flexible substrate C is polydimethylsiloxane.

[0067] The flexible substrate A of the second sensitive thin film and the flexible substrate B of the third sensitive thin film are arranged in close proximity. Similarly, "close proximity" here can also be understood as "adjacent arrangement" or "face-to-face arrangement".

[0068] The second sensitive thin film and the third sensitive thin film are electrically connected. For example, the (one) end side of the flexible substrate A loaded with the sensitive material A and the flexible substrate B loaded with the sensitive material B is connected by an electrode material.

[0069] Therefore, in the flexible multifunctional electronic skin, the sensitive material A and the sensitive material B are connected to form a p-n junction or a Schottky junction. There is a contact potential between the two, which changes with temperature. Based on this potential difference mechanism, the flexible multifunctional electronic skin can directly sense the absolute temperature. The potential difference depends on the energy band structure of the material, and is generally not affected by pressure, excluding the energy band bending caused by extreme pressure. Therefore, the temperature sensing function of the flexible multifunctional electronic skin is almost not disturbed by pressure.

[0070] Chinese patent 201910343050.2 cannot realize the decoupling of temperature and pressure. This is because the temperature change and pressure sensing of the electronic skin are both based on the resistance mechanism, so whether it is temperature change or pressure, it will cause a change in the resistance of the film, resulting in the inability to realize decoupling.

[0071] Chinese patent 202110244056.1 realizes the pressure and temperature dual-sensing functions that do not interfere with each other by using the piezoresistive effect and thermoelectric effect of the conductive MOF material. However, when Chinese patent 202110244056.1 senses temperature by using the thermoelectric effect of the conductive MOF material, a complex temperature gradient needs to be constructed, and only the relative temperature difference can be sensed, but the absolute temperature cannot be directly sensed, which is not convenient in actual application. Unlike this, the present application realizes the pressure and temperature dual-sensing functions that do not interfere with each other by using the piezoresistive effect of the sensitive material A and the contact potential difference mechanism between the sensitive material A and the sensitive material B. In the present application, the sensitive material A and the sensitive material B are connected to form a p-n junction or a Schottky junction. There is a contact potential between the two, which changes with temperature. Therefore, based on this potential difference mechanism, the flexible multifunctional electronic skin described in the present application can directly sense the absolute temperature. Therefore, compared with Chinese patent 202110244056.1, the present application can directly sense the absolute temperature without the need to construct a complex temperature gradient, which is more convenient in actual application.

[0072] In addition, the temperature sensing mechanism of Chinese patent 202110244056.1 is different from that of the present application. Chinese patent 202110244056.1 adopts a thermoelectric mechanism and can only give a temperature difference, but cannot directly give the actual temperature of the object to be measured, which needs to be corrected. The present application adopts a potential difference mechanism, which is innovative in itself, and in addition, the actual temperature of the object to be measured can be directly given by using this potential difference mechanism.

[0073] The electrodes and wires are arranged at the end of the first sensitive film, the second sensitive film and the third sensitive film. The electrode material includes but is not limited to silver, copper, copper-nickel alloy or magnesium-aluminum alloy. The electrode material is preferably silver.

[0074] The wires include but are not limited to silver wire, copper wire or copper-nickel alloy wire. The wire is preferably a copper-nickel alloy wire.

[0075] The following will be described in combination with Figure 2 The preparation method of the flexible multifunctional electronic skin described in the present application will be described.

[0076] Preparation of the upper part of the flexible multifunctional electronic skin. Attach sensitive material A to flexible substrate A, coat electrode material on its (one) end side and fix the wire. Then directly adhere or adhere in a specific arrangement a plurality of flexible substrates A loaded with sensitive material A to the surface of the pre-polymerized flexible substrate C, and then fully cure to obtain the upper part of the flexible multifunctional electronic skin.

[0077] Preparation of the lower part of the flexible multifunctional electronic skin. Attach sensitive material A to flexible substrate A, coat electrode material on its end and fix the wire. Attach sensitive material B to flexible substrate B, coat electrode material on its end and fix the wire. Adhere flexible substrate A loaded with sensitive material A and flexible substrate B loaded with sensitive material B (this adhesion means that flexible substrate A and flexible substrate B are arranged face to face, so that sensitive material A and sensitive material B are arranged back to back), then coat electrode material on its end side to connect sensitive material A and sensitive material B to obtain a composite unit. Directly adhere or adhere in a specific arrangement a plurality of composite units to the surface of the pre-polymerized flexible substrate C, and then fully cure to obtain the lower part of the flexible multifunctional electronic skin. That is, adhere the flexible substrate A loaded with the thin film of sensitive material A and the flexible substrate B loaded with the thin film of sensitive material B to the surface of the pre-polymerized flexible substrate C, and then fully cure to obtain the lower part of the flexible multifunctional electronic skin. Among them, the flexible substrate B loaded with the thin film of sensitive material B is close to the surface of the flexible substrate C.

[0078] Adhere the upper part of the flexible multifunctional electronic skin to the lower part of the flexible multifunctional electronic skin face to face (this face-to-face adhesion means that the sensitive material A of the upper part and the sensitive material A of the lower part are arranged face to face), to obtain the flexible multifunctional electronic skin.

[0079] The method of attaching to form a thin film of sensitive material A or sensitive material B includes but is not limited to interface in-situ growth method, dip coating method, drop coating method, infiltration method or printing method, etc.

[0080] The pre-polymerization means that the flexible substrate C has undergone a polymerization reaction to increase its viscosity, but has not been further polymerized to a fully cured state. The pre-polymerization temperature is 60-150°C, preferably 100-120°C. The pre-polymerization time is 10-20 minutes, preferably 12-17 minutes.

[0081] The fully cured temperature is 60-150°C, preferably 100-120°C. The fully cured time is 2-6 hours, preferably 3-5 hours.

[0082] In summary, the flexible multifunctional electronic skin based on the upper and lower interface pressure resistance mechanism realizes direct and high sensitive sensing of a wide range of absolute pressure. On the one hand, the flexible multifunctional electronic skin has a large deformable space between the upper and lower sensitive material A films when being pressed, so that it has a pressure sensing range of up to the order of megapascal. On the other hand, the flexible multifunctional electronic skin has few contact points between the upper and lower sensitive material A films when not being pressed, and the initial resistance is much larger than the resistance after being pressed, so that it has a high pressure sensing sensitivity coefficient. The deformable space and the contact points between the upper and lower sensitive material A films are almost not affected by temperature. Therefore, the pressure sensing function of the flexible multifunctional electronic skin is almost not disturbed by temperature. Moreover, the pressure and temperature sensing functions of the flexible multifunctional electronic skin do not interfere with each other.

[0083] The following examples are further listed to illustrate the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e. those skilled in the art can select within the appropriate range through the description herein, and are not limited to the specific values in the following examples.

[0084] Example 1

[0085] A polyvinylidene fluoride film is placed on the surface of a conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL), and after the conductive MOF Ni3(HiTP)2 is grown in situ on the surface interface of the polyvinylidene fluoride film, it is taken out to realize the preparation of a conductive MOF Ni3(HiTP)2 film on the surface of the polyvinylidene fluoride film. Silver paste is coated on one end of the film, and a copper-nickel alloy wire is fixed. Unsolidified polydimethylsiloxane is poured into a mold and pre-polymerized at 110°C for 15 minutes. Then, a plurality of polyvinylidene fluoride films loaded with conductive MOF Ni3(HiTP)2 are arranged in a periodic array as shown in the drawing, and after being cured at 110°C for 4 hours, the upper part of the flexible multifunctional electronic skin is obtained. Figure 1

[0086] ​A polyvinylidene fluoride film was placed on the surface of a conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL), and after the in-situ growth of the conductive MOF Ni3(HiTP)2 on the surface interface of the polyvinylidene fluoride film was completed, it was taken out, realizing the preparation of a conductive MOF Ni3(HiTP)2 film on the surface of the polyvinylidene fluoride film, and silver paste was coated on one end of the film to fix the copper-nickel alloy wire. The nylon film was placed on the surface of the Pb-SLs dispersion liquid containing lead iodide and 3,3',5,5'-tetraethyl benzidine (dispersion liquid solvent: N,N-dimethylformamide, lead iodide concentration: 3 mg / mL, 3,3',5,5'-tetraethyl benzidine concentration: 3 mg / mL), and after the Pb-SLs infiltrated the surface of the nylon film was completed, it was taken out, realizing the preparation of a Pb-SLs film on the surface of the nylon film, and silver paste was coated on one end of the film to fix the copper-nickel alloy wire. The polyvinylidene fluoride film loaded with conductive MOF Ni3(HiTP)2 was attached to the back of the Pb-SLs-loaded nylon film (i.e. the polyvinylidene fluoride film and the nylon film were arranged face to face), and silver paste was coated on one side to connect the conductive MOF Ni3(HiTP)2 film and the Pb-SLs film. Unsolidified polydimethylsiloxane was poured into a mold and pre-polymerized at 110°C for 15 minutes. The polyvinylidene fluoride film loaded with conductive MOF Ni3(HiTP)2 and the nylon film loaded with Pb-SLs were attached together and placed on the surface of the pre-polymerized polydimethylsiloxane, and after being cured at 110°C for 4 hours, the lower part of the flexible multifunctional electronic skin was obtained.

[0087] The upper part of the flexible multifunctional electronic skin was attached to the lower part of the flexible multifunctional electronic skin face to face to obtain the flexible multifunctional electronic skin.

[0088] Figure 3 The voltage-temperature curve of the flexible multifunctional electronic skin of Example 1 is shown. It can be seen that the flexible multifunctional electronic skin has a voltage change response in the temperature range of 25-125°C, and the sensitivity coefficient is as high as 7.08 mV / K in the temperature range of 25-80°C, and the temperature sensing sensitivity coefficient is as high as 20.3 mV / K in the temperature range of 80-125°C.

[0089] Figure 4 The relative current change-pressure curve of the flexible multifunctional electronic skin of Example 1 is shown. It can be seen that the pressure sensing range of the flexible multifunctional electronic skin is as wide as 1.025 MPa, and the sensitivity coefficient is as high as 220.70 kPa in the range of 0-40.75 kPa -1 .

[0090] Figure 5The relative current change-pressure curve of the flexible multifunctional electronic skin of Example 1 at 26°C and 38°C is shown. It can be seen that the pressure response of the flexible multifunctional electronic skin is hardly affected by temperature.

[0091] Figure 6 The relative voltage change-pressure curve of the flexible multifunctional electronic skin of Example 1 at 38°C is shown. It can be seen that the temperature response of the flexible multifunctional electronic skin is hardly affected by pressure.

[0092] Figure 7 The relative resistance change-strain curve of the flexible multifunctional electronic skin of Example 1 is shown. It can be seen that the resistance of the flexible multifunctional electronic skin hardly changes under tensile strain, ensuring that the pressure sensing function of the flexible multifunctional electronic skin is not affected by tensile strain.

[0093] Figure 8 The relative voltage change-strain curve of the flexible multifunctional electronic skin of Example 1 at 38°C is shown. It can be seen that the voltage of the flexible multifunctional electronic skin hardly changes under tensile strain, ensuring that the temperature sensing function of the flexible multifunctional electronic skin is not affected by tensile strain.

[0094] Example 2

[0095] A MXene Ti3C2 dispersion solution (dispersion solution solvent: deionized water, concentration: 3 mg / mL) was drop-coated on the surface of a polyvinylidene fluoride film and dried to prepare a MXene Ti3C2 film on the surface of the polyvinylidene fluoride film. Silver paste was coated on one end of the film, and a copper-nickel alloy wire was fixed. Figure 1 The upper part of the flexible multifunctional electronic skin was obtained after the multiple polyvinylidene fluoride films loaded with MXene Ti3C2 were attached to the surface of the pre-polymerized polydimethylsiloxane in a periodic array arrangement as shown, and completely cured at 110°C for 4 hours.

[0096] A MXene Ti3C2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL) was dropped on the surface of a polyvinylidene fluoride film and dried to prepare a MXene Ti3C2 film on the surface of the polyvinylidene fluoride film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. A nylon film was placed on the surface of a Pb-SLs dispersion liquid containing lead iodide and 3,3',5,5'-tetraethyl benzidine (dispersion liquid solvent: N,N-dimethylformamide, lead iodide concentration: 3 mg / mL, 3,3',5,5'-tetraethyl benzidine concentration: 3 mg / mL). After the Pb-SLs infiltrated the surface of the nylon film, the nylon film was removed, and a Pb-SLs film was prepared on the surface of the nylon film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. Then, the polyvinylidene fluoride film loaded with the MXene Ti3C2 was attached to the back of the nylon film loaded with the Pb-SLs (i.e., the polyvinylidene fluoride film and the nylon film were arranged face to face), and silver paste was applied to one side to connect the MXene Ti3C2 film and the Pb-SLs film. Uncured polydimethylsiloxane was poured into a mold and pre-polymerized at 110°C for 15 minutes. Then, the polyvinylidene fluoride film loaded with the MXene Ti3C2 and the nylon film loaded with the Pb-SLs were attached to the surface of the pre-polymerized polydimethylsiloxane, and after being cured at 110°C for 4 hours, the lower part of the flexible multifunctional electronic skin was obtained.

[0097] The upper part of the flexible multifunctional electronic skin was attached to the lower part of the flexible multifunctional electronic skin face to face to obtain the flexible multifunctional electronic skin.

[0098] Example 3

[0099] A polytetrafluoroethylene film was placed on the surface of a conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL). After the conductive MOF Ni3(HiTP)2 grew in situ on the interface of the polytetrafluoroethylene film surface, the film was removed, and a conductive MOF Ni3(HiTP)2 film was prepared on the surface of the polytetrafluoroethylene film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. Then, multiple polytetrafluoroethylene films loaded with the conductive MOF Ni3(HiTP)2 were arranged in a periodic array as shown in FIG. 6A and attached to the surface of the pre-polymerized polydimethylsiloxane. After being cured at 110°C for 4 hours, the upper part of the flexible multifunctional electronic skin was obtained. Figure 1

[0100] ​A polytetrafluoroethylene film was placed on the surface of a conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL), and after the in-situ growth of the conductive MOF Ni3(HiTP)2 on the surface interface of the polytetrafluoroethylene film was completed, the film was removed, thereby preparing a conductive MOF Ni3(HiTP)2 film on the surface of the polytetrafluoroethylene film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. A polyethersulfone film was placed on the surface of a Pb-SLs dispersion liquid containing lead iodide and 3,3',5,5'-tetraethyl benzidine (dispersion liquid solvent: N,N-dimethylformamide, lead iodide concentration: 3 mg / mL, 3,3',5,5'-tetraethyl benzidine concentration: 3 mg / mL), and after the Pb-SLs infiltrated the surface of the polyethersulfone film, the film was removed, thereby preparing a Pb-SLs film on the surface of the polyethersulfone film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. Subsequently, the polytetrafluoroethylene film loaded with the conductive MOF Ni3(HiTP)2 was attached to the back of the polyethersulfone film loaded with the Pb-SLs (i.e., the polyvinylidene fluoride film and the polyethersulfone film were arranged face to face), and silver paste was applied to one side to connect the conductive MOF Ni3(HiTP)2 film and the Pb-SLs film. Uncured polydimethylsiloxane was poured into a mold, and pre-polymerized at 110°C for 15 minutes. Then, the polytetrafluoroethylene film loaded with the conductive MOF Ni3(HiTP)2 and the polyethersulfone film loaded with the Pb-SLs were attached to the surface of the pre-polymerized polydimethylsiloxane, and after curing at 110°C for 4 hours, the lower part of the flexible multifunctional electronic skin was obtained.

[0101] The upper part of the flexible multifunctional electronic skin was attached to the lower part of the flexible multifunctional electronic skin face to face, and the flexible multifunctional electronic skin was obtained.

[0102] Comparative Example 1

[0103] A polyvinylidene fluoride film was placed on the surface of a conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL), and after the in-situ growth of the conductive MOF Ni3(HiTP)2 on the surface interface of the polyvinylidene fluoride film was completed, the film was removed, thereby preparing a conductive MOF Ni3(HiTP)2 film on the surface of the polyvinylidene fluoride film. Silver paste was applied to one end of the film, and a copper-nickel alloy wire was fixed. Uncured polydimethylsiloxane was poured into a mold, and pre-polymerized at 110°C for 15 minutes. Then, the polyvinylidene fluoride film loaded with the conductive MOF Ni3(HiTP)2 was attached to the surface of the pre-polymerized polydimethylsiloxane in a periodic array arrangement as shown in FIG. 1, and after curing at 110°C for 4 hours, the upper part of the flexible multifunctional electronic skin was obtained. Figure 1

[0104] ​The polyvinylidene fluoride film was placed on the surface of the conductive MOF Ni3(HiTP)2 dispersion liquid (dispersion liquid solvent: deionized water, concentration: 3 mg / mL), and after the in-situ growth of the conductive MOF Ni3(HiTP)2 on the surface interface of the polyvinylidene fluoride film was completed, it was taken out, realizing the preparation of a conductive MOF Ni3(HiTP)2 film on the surface of the polyvinylidene fluoride film, and silver paste was coated on one end of the film to fix the copper-nickel alloy wire. The nylon film was placed on the surface of the lead iodide dispersion liquid (dispersion liquid solvent: N,N-dimethylformamide, lead iodide concentration: 3 mg / mL), and after the lead iodide infiltrated the surface of the nylon film was completed, it was taken out, realizing the preparation of a lead iodide film on the surface of the nylon film, and silver paste was coated on one end of the film to fix the copper-nickel alloy wire. The polyvinylidene fluoride film loaded with conductive MOF Ni3(HiTP)2 was attached to the back of the nylon film loaded with lead iodide (i.e., the polyvinylidene fluoride film and the nylon film were arranged face to face), and silver paste was coated on one side to connect the conductive MOF Ni3(HiTP)2 film and the lead iodide film. Unsolidified polydimethylsiloxane was poured into a mold and pre-polymerized at 110°C for 15 minutes. The polyvinylidene fluoride film loaded with conductive MOF Ni3(HiTP)2 and the nylon film loaded with lead iodide were attached together and attached to the surface of the pre-polymerized polydimethylsiloxane, and after curing at 110°C for 4 hours, the lower part of the flexible multifunctional electronic skin was obtained.

[0105] The upper part of the flexible multifunctional electronic skin was attached to the lower part of the flexible multifunctional electronic skin face to face to obtain the flexible multifunctional electronic skin. The temperature response sensitivity of the electronic skin of this example was lower. This is because: the superlattice material Pb-SLs material such as PbI2 SL is formed by regularly intercalating organic molecules between inorganic PbI2, and has a higher thermal expansion coefficient. Compared with PbI2 SL, the linear thermal expansion coefficient of pure PbI2 film is lower, resulting in a smaller degree of downward movement of the material valence band with temperature rise, a smaller potential difference produced, and a lower response sensitivity of the electronic skin.

Claims

1. A flexible multifunctional electronic skin, characterized by, The flexible multifunctional electronic skin is composed of a plurality of flexible multifunctional electronic skin sensing units; the sensing unit comprises a first sensitive film, a second sensitive film, a third sensitive film, an electrode material and a wire; The first sensitive film comprises a sensitive material A, a flexible substrate A loaded with the sensitive material A, and a flexible substrate C attached to the outer surface of the flexible substrate A; The second sensitive film comprises a sensitive material A and a flexible substrate A loaded with the sensitive material A; The sensitive material A of the first sensitive film and the sensitive material A of the second sensitive film are arranged in close proximity; The first sensitive film and the second sensitive film are electrically connected; The third sensitive film comprises a sensitive material B, a flexible substrate B loaded with the sensitive material B, and a flexible substrate C attached to the outer surface of the flexible substrate B; The flexible substrate A of the second sensitive film and the flexible substrate B of the third sensitive film are arranged in close proximity; The second sensitive film and the third sensitive film are electrically connected; The sensitive material A is a flexible conductive material, preferably one or more of a conductive metal organic framework (MOF) material, a transition metal carbide (MXene) material and a carbon nanomaterial; the sensitive material B is a flexible semiconductor material, and the sensitive material B forms a p-n junction or a Schottky junction after being connected with the sensitive material A; preferably, the sensitive material B is a lead-based superlattice material (Pb-SLs). 2.The flexible multi-functional electronic skin of claim 1, wherein, The flexible multifunctional electronic skin has the functions of directly sensing absolute pressure and directly sensing absolute temperature, and the two sensing functions do not interfere with each other. 3.The flexible multi-functional electronic skin according to claim 1 or 2, characterized in that, The sensing of pressure and temperature by the flexible multifunctional electronic skin is not disturbed by stretching. 4.The flexible multi-functional electronic skin according to any one of claims 1 to 3, wherein, The flexible multifunctional electronic skin is composed of a plurality of flexible multifunctional electronic skin sensing units arranged in a specific manner, preferably a periodic array arrangement.

5. The flexible multi-functional electronic skin according to any one of claims 1-4, wherein, The Young's modulus of the flexible substrate A and the flexible substrate B is not less than 2 times that of the flexible substrate C. 6.The flexible multi-functional electronic skin of any one of claims 1-5, wherein, The flexible substrate A and the flexible substrate B are independently selected from a polyvinylidene fluoride film, a polytetrafluoroethylene film, a cotton cellulose film, a nylon film or a polyether sulfone film; the flexible substrate C is a silicone rubber film, a styrene thermoplastic elastomer film or a polyurethane film.

7. The flexible multi-functional electronic skin according to any one of claims 1-6, wherein, The electrode material is silver, copper, copper-nickel alloy or magnesium-aluminum alloy; the wire is silver wire, copper wire or copper-nickel alloy wire.

8. A method of preparing the flexible multifunctional e-skin according to any one of claims 1-7, characterized by, The method comprises: attaching the sensitive material A to the flexible substrate A, coating the electrode material at the end of the flexible substrate A and fixing the wire, then directly attaching or attaching in a specific arrangement manner a plurality of flexible substrates A loaded with the sensitive material A to the surface of the pre-polymerized flexible substrate C, and then fully curing to obtain the upper part of the flexible multifunctional electronic skin; attaching the sensitive material A to the flexible substrate A, coating the electrode material at the end of the flexible substrate A and fixing the wire, and attaching the sensitive material B to the flexible substrate B, coating the electrode material at the end of the flexible substrate B and fixing the wire; The flexible substrate A loaded with the sensitive material A and the flexible substrate B loaded with the sensitive material B are attached, and then electrode materials are coated on the end sides of the flexible substrates to connect the sensitive material A and the sensitive material B to obtain a composite unit; a plurality of composite units are directly attached or attached in a specific arrangement mode on the surface of a pre-polymerized flexible substrate C, and then completely cured to obtain the lower part of the flexible multifunctional electronic skin; The upper part of the flexible multifunctional electronic skin is attached to the lower part of the flexible multifunctional electronic skin in a face-to-face manner to obtain the flexible multifunctional electronic skin.

9. The production method according to claim 8, characterized by, The method for attaching the sensitive material on the flexible substrate includes any one of an interface in-situ growth method, an immersion coating method, a drop coating method, an infiltration method and a printing method.

10. The production method according to claim 8 or 9, characterized by, The pre-polymerization temperature is 60-150 DEG C, and the pre-polymerization time is 10-20 minutes; the curing temperature is 60-150 DEG C, and the curing time is 2-6 hours.

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