Flexible electrode with passive radiation cooling performance, preparation method and electronic skin

Abstract

The invention relates to a flexible electrode with passive radiation cooling performance, a preparation method thereof and electronic skin. The flexible electrode with the passive radiation cooling performance sequentially comprises a hydrophilic layer with a micro-nano small aperture, a macroporous hydrophobic layer and a conductive layer, and the aperture of the hydrophilic layer with the micro-nano small aperture is 0.3-25 microns. Compared with the prior art, the flexible electrode with the passive radiation cooling performance, provided by the invention, not only realizes a directional perspiration function through wettability gradient and porosity gradient, but also realizes the passive radiation cooling performance through the micro-nano small-aperture hydrophilic film. The electronic skin prepared by using the flexible electrode disclosed by the invention not only can monitor physiological signals, but also has a passive radiation cooling function, so that the wearing comfort is improved, and the use of the electronic skin in daily wearing is expanded.

Description

Technical Field

[0001] The present invention belongs to the field of electrode technology, and in particular relates to a flexible electrode with passive radiation cooling performance, a preparation method thereof and electronic skin. Background Art

[0002] With people's demand for a comfortable and healthy life, real-time monitoring of physical conditions has attracted widespread attention. Electronic skin provides a real-time, portable, and imperceptible way of physiological monitoring, but its wearing comfort is crucial for long-term daily monitoring. Although some studies have achieved autonomous perspiration function through the design of electronic skin materials, improved the air permeability of electronic skin, avoided the influence of sweat accumulation between electrodes and skin on signal stability, and improved the humidity comfort of wearing, in addition to the influence of sweating, severe solar radiation and the heat emitted by the electronic skin itself will also cause the human skin temperature to rise, seriously affecting the wearing comfort, and the thermal management of electronic skin is also very important for the normal operation of its sensor components. Summary of the invention

[0003] The object of the present invention is to provide a flexible electrode with passive radiation cooling performance, a preparation method thereof and an electronic skin.

[0004] In order to solve the above technical problems, the first aspect of the present invention provides a flexible electrode with passive radiation cooling performance, which comprises: a hydrophilic layer with micro-nano pores, a macroporous hydrophobic layer and a conductive layer, wherein the pore size of the hydrophilic layer with micro-nano pores is 0.3 to 25 μm. Compared with the prior art, the flexible electrode with passive radiation cooling performance provided by the present invention not only realizes the directional perspiration function through the wettability gradient and the pore gradient, but also realizes the passive radiation cooling performance through the micro-nano pore hydrophilic membrane.

[0005] Optionally, in the flexible electrode with passive radiation cooling performance provided by the present invention, the material of the hydrophilic layer with micro-nano small pores is selected from any one of cellulose, cotton, polyvinyl pyrrolidone, polyacrylonitrile or silk.

[0006] Optionally, in the flexible electrode with passive radiation cooling performance provided by the present invention, the material of the macroporous hydrophobic layer is selected from any one of cellulose acetate, polyurethane, fluorinated polyurethane, polyvinylidene fluoride, polystyrene or polymethyl methacrylate, and the pore size of the macroporous hydrophobic layer is 0.3 to 200 μm.

[0007] Optionally, in the flexible electrode with passive radiation cooling performance provided by the present invention, the conductive material is selected from any one of metal nanomaterials, carbon materials or conductive polymers. The metal nanomaterial is selected from any one of metal nanoparticles, metal nanowires or metal nanosheets; the carbon material is selected from any one of carbon nanotubes, carbon black, graphene or Mxene materials; the conductive polymer is selected from any one of polypyrrole, polyaniline, and PEDOT:PSS materials.

[0008] In the flexible electrode with passive radiation cooling performance provided by the present invention, the thickness of the hydrophilic layer with micro-nano pore size is 30-500μm, the thickness of the macroporous hydrophobic layer loaded with phase change material is 5-100μm; the thickness of the conductive material layer is 100nm-500μm. The thickness of each layer in the flexible electrode will affect the sweating effect. If the hydrophilic layer is too thin, the sweat absorption is small, and the sweat cannot be transferred in time, which easily causes sweat accumulation at the interface between the skin and the electrode; if the hydrophilic layer is too thick, the thickness of the electrode will increase, affecting the adhesion to the skin. If the hydrophobic layer is too thin, the sweat absorbed by the hydrophilic layer will reverse osmosis to the water transport layer; if the hydrophobic layer is too thick, the sweat will not be transferred to the hydrophilic layer.

[0009] The second aspect of the present invention provides a method for preparing a flexible electrode with passive radiation cooling performance as described in the first aspect, comprising the following steps: S1: preparing a hydrophilic layer with micro-nano small pores by any one of electrospinning, solvent evaporation, template sacrificial method or phase separation method, wherein the pore size of the hydrophilic layer with micro-nano small pores is 0.3 to 25 μm; S2: sequentially preparing a macroporous hydrophobic layer and a conductive layer on the surface of the hydrophilic layer with micro-nano small pores: the macroporous hydrophobic layer is prepared by any one of electrospinning or electrostatic spraying; the conductive layer is prepared by any one of magnetron sputtering, vacuum evaporation, electrostatic spraying or impregnation; a flexible electrode with passive radiation cooling performance is obtained, and the flexible electrode with passive radiation cooling performance sequentially comprises: a hydrophilic layer with micro-nano small pores, a macroporous hydrophobic layer and a conductive layer.

[0010] The third aspect of the present invention provides an electronic skin, which includes the flexible electrode with passive radiation cooling performance described in the first aspect of the present invention. The electronic skin prepared using the flexible electrode with passive radiation cooling performance described in the first aspect of the invention can not only monitor physiological signals, but also has the function of passive radiation cooling, which increases the wearing comfort and expands the use of electronic skin in daily wear. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 11 are SEM photos of the layers of the flexible electrode in Example 1, wherein (a) is a SEM photo of a hydrophilic layer having micro-nano pores, (b) is a SEM photo of a macroporous hydrophobic layer, and (c) is a SEM photo of a conductive layer;

[0012] Figure 2 is the pore size distribution of each layer of the flexible electrode in Example 1, wherein (a) is the pore size distribution of the hydrophilic layer with micro-nano small pores, and (b) is the pore size distribution of the macroporous hydrophobic layer;

[0013] Figure 3 1 is an optical picture of the wettability of the flexible electrode in Example 1, wherein (a) shows the wettability of the hydrophilic layer with micro-nano pores, and (b) shows the wettability of the macroporous hydrophobic layer;

[0014] Figure 4 These are optical pictures of the directional water transport performance of the flexible electrode in Example 1, wherein (a) shows the diffusion of water when it is dripped from the hydrophobic layer of the electrode; (b) shows the diffusion of water when it is dripped from the hydrophilic layer;

[0015] Figure 5 1 is a graph showing the passive radiation cooling performance of the flexible electrode in Example 1, wherein (a) is a solar reflectivity curve graph, and (b) is a mid-infrared emissivity curve graph;

[0016] Figure 6 This is a graph showing the skin surface temperature changes when the flexible electrode in Example 1 is exposed to solar radiation. DETAILED DESCRIPTION

[0017] In order to more clearly understand the purpose, characteristics and advantages of the present invention, the advantages of the present application are further illustrated in conjunction with specific examples and comparative examples. The materials used without indicating the manufacturer are all conventional products that can be purchased commercially. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0018] The embodiment of the present invention provides a flexible electrode with passive radiation cooling performance, which comprises: a hydrophilic layer with micro-nano pores, a macroporous hydrophobic layer and a conductive layer, wherein the pore size of the hydrophilic layer with micro-nano pores is 0.3 to 25 μm. Compared with the prior art, the flexible electrode with passive radiation cooling performance provided by the present invention not only realizes the directional perspiration function through the wettability gradient and the pore gradient, but also realizes the passive radiation cooling performance through the micro-nano pore hydrophilic membrane.

[0019] The directional perspiration function is achieved through the wettability gradient and the pore gradient: the wettability gradient is achieved through the setting of the hydrophilic membrane and the hydrophobic membrane, and the pore size gradient is achieved through the setting of the macroporous membrane and the microporous membrane; water is easily diffused from the hydrophobic layer to the hydrophilic layer, and from the macroporous layer to the microporous layer. The side of the electrode close to the skin is a macroporous hydrophobic layer, and the side away from the skin is a microporous hydrophilic layer. The sweat will be transferred to the outer hydrophilic layer under the action of the strong capillary force of the hydrophilic layer, and the sweat in the hydrophilic layer will not return to the skin through the hydrophobic layer, so as to achieve directional perspiration. In addition, the passive radiation cooling performance is also achieved through the micro-nano small-pore hydrophilic membrane. The inventor believes that under normal circumstances, the human body can maintain thermal homeostasis through the synergistic effect of four different heat dissipation methods: radiation, evaporation, conduction and convection. When the outside temperature is lower than the human skin temperature, the human body mainly dissipates heat through radiation, conduction and convection; when the outside temperature is close to or higher than the skin temperature, the human body mainly dissipates heat through evaporation. When the human body is exposed to the outdoor environment, solar radiation, strenuous exercise and hot / humid environment are not conducive to the heat dissipation of the human body through evaporation. Moreover, the hot and humid air hinders the skin from dissipating heat through conduction, and the air circulation rate seriously affects the rate of convective heat dissipation. Therefore, radiative cooling, which is less affected by the environment, passive, and does not require external energy, becomes an effective heat dissipation method at this time. Furthermore, radiative cooling includes spontaneous reflection of sunlight (wavelength of 0.3-2.5 μm) and mid-infrared emission (wavelength of 8-13 μm). The present invention introduces radiative cooling technology into electronic skin, effectively realizing the thermal management of electronic skin and further improving the wearing comfort of electronic skin. In the flexible electrode of the present invention, the material of the hydrophilic layer with micro-nano small pores is selected from any one of cellulose, cotton, polyvinyl pyrrolidone, polyacrylonitrile or silk. The chemical bonds contained in the molecular structures of these materials are in the infrared region, and their vibrations can emit the heat of the material itself into outer space, and have good passive radiation cooling performance. Therefore, the flexible electrode provided by the present invention is breathable and sweat-wicking, and can also reflect sunlight and emit mid-infrared rays, effectively solving the problem of moisture and heat comfort of electronic skin in outdoor environments and avoiding the increase of skin surface temperature.

[0020] In some embodiments of the present invention, the material of the hydrophilic layer having micro-nano pores is selected from any one of cellulose, cotton, polyvinyl pyrrolidone, polyacrylonitrile or silk.

[0021] In some embodiments of the present invention, the material of the macroporous hydrophobic layer is selected from any one of cellulose acetate, polyurethane, fluorinated polyurethane, polyvinylidene fluoride, polystyrene or polymethyl methacrylate, and the pore size of the macroporous hydrophobic layer is 0.3-200 μm.

[0022] In some embodiments of the present invention, the conductive material is selected from any one of metal nanomaterials, carbon materials or conductive polymers. The metal nanomaterial is selected from any one of metal nanoparticles, metal nanowires or metal nanosheets; the carbon material is selected from any one of carbon nanotubes, carbon black, graphene or Mxene materials; the conductive polymer is selected from any one of polypyrrole, polyaniline and PEDOT:PSS materials.

[0023] In some embodiments of the present invention, the thickness of the hydrophilic layer with micro-nano pores is 30-500 μm, the thickness of the macroporous hydrophobic layer loaded with phase change material is 5-100 μm; the thickness of the conductive material layer is 100 nm-500 μm. The thickness of each layer in the flexible electrode will affect the perspiration effect. If the hydrophilic layer is too thin, the amount of sweat absorbed is small, and the sweat cannot be transferred in time, which easily causes sweat to accumulate at the interface between the skin and the electrode; if the hydrophilic layer is too thick, the thickness of the electrode will increase, affecting the adhesion to the skin. If the hydrophobic layer is too thin, the sweat absorbed by the hydrophilic layer will reverse osmosis to the water transport layer; if the hydrophobic layer is too thick, the sweat will not be transferred to the hydrophilic layer.

[0024] Some embodiments of the present invention also provide a method for preparing the flexible electrode with passive radiation cooling performance, comprising the following steps: S1: preparing a hydrophilic layer with micro-nano small pores by any one of electrospinning, solvent evaporation, template sacrificial method or phase separation method, wherein the pore size of the hydrophilic layer with micro-nano small pores is 0.3 to 25 μm; S2: sequentially preparing a macroporous hydrophobic layer and a conductive layer on the surface of the hydrophilic layer with micro-nano small pores: the macroporous hydrophobic layer is prepared by any one of electrospinning or electrostatic spraying; the conductive layer is prepared by any one of magnetron sputtering, vacuum evaporation, electrostatic spraying or impregnation; and obtaining a flexible electrode with passive radiation cooling performance, wherein the flexible electrode with passive radiation cooling performance sequentially comprises: a hydrophilic layer with micro-nano small pores, a macroporous hydrophobic layer and a conductive layer.

[0025] Some embodiments of the present invention also provide an electronic skin, which includes the flexible electrode with passive radiation cooling performance. The electronic skin prepared using the flexible electrode with passive radiation cooling performance can monitor physiological signals and also has the function of passive radiation cooling, which increases wearing comfort and expands the use of electronic skin in daily wear.

[0026] The following is an example of an implementation of the present invention.

[0027] Example 1

[0028] First, a hydrophobic cellulose acetate membrane is prepared by electrospinning technology, and the cellulose acetate membrane is hydrolyzed in an ethanol solution of potassium hydroxide to obtain a hydrophilic cellulose membrane. Then, a layer of hydrophobic cellulose acetate with a larger diameter is electrospun on the cellulose membrane to obtain a cellulose acetate / cellulose membrane. Finally, an oxidant of ferric chloride is sprayed on the cellulose acetate side of the cellulose acetate / cellulose membrane by electrostatic spraying, and the fiber membrane sprayed with ferric chloride is placed in a closed oven containing pyrrole monomers, and conductive polypyrrole is polymerized in situ to obtain a flexible electrode with passive radiation cooling performance. When the electrode prepared in this embodiment is applied to human skin, it can not only be breathable and perspire, but also reflect sunlight and emit mid-infrared rays; avoid the increase in skin surface temperature, and effectively solve the problem of heat and humidity comfort of electronic skin in outdoor environments.

[0029] The flexible electrode prepared in this embodiment was tested as follows:

[0030] 1. Observe the morphology of each layer of the flexible electrode using an electron microscope:

[0031] Figure 1 : are SEM photos of the flexible electrode in this embodiment, wherein (a) is a SEM photo of a hydrophilic layer with micro-nano pores, which is a porous fiber membrane with a smooth surface; (b) is a SEM photo of a macroporous hydrophobic layer, which is a porous fiber membrane with a smooth surface; (c) is a SEM photo of a conductive layer, which is a porous fiber membrane with a rough surface, and the preparation process of the conductive layer does not change the fiber morphology of the hydrophobic layer.

[0032] 2. Detect the aperture of each layer of the flexible electrode:

[0033] Figure 2 It is the pore size distribution of each layer of the flexible electrode in this embodiment, wherein (a) is the pore size distribution of the hydrophilic layer with micro-nano small pores, and the hydrophilic layer with micro-nano small pores contains nano- and micron-sized pores; (b) is the pore size distribution of the macroporous hydrophobic layer, and the macroporous hydrophobic layer contains micron-sized pores, and the pore size of the hydrophobic layer is larger than that of the hydrophilic layer.

[0034] 3. Detect the wettability of each layer of the flexible electrode:

[0035] Detection method: Add 5 μL of water on the fiber membrane, test the contact angle of the fiber membrane with an optical contact angle meter, and take the average value at 5 random locations.

[0036] Test results: Figure 3 These are electron micrographs of the wettability of the flexible electrode in this embodiment, wherein (a) shows the wettability of the hydrophilic layer with micro-nano pores, which exhibits super-hydrophilicity; and (b) shows the wettability of the macroporous hydrophobic layer, which exhibits hydrophobicity.

[0037] 4. Detect the directional water transport performance of flexible electrodes:

[0038] Detection method: 10 μL of ink was dropped from the hydrophobic layer and the hydrophilic layer of the electrode respectively, and the optical image of the fiber membrane and the transport process of the liquid on the membrane were recorded with a digital camera.

[0039] Test results: Figure 4 These are test diagrams of the directional water transport performance of the flexible electrode of this embodiment, wherein (a) shows that when water is dripped from the hydrophobic layer of the electrode, it quickly penetrates into the hydrophilic layer and diffuses in the hydrophilic layer; (b) shows that when water is dripped from the hydrophilic layer, the water only quickly diffuses in the hydrophilic layer and does not penetrate into the hydrophobic layer, indicating that the flexible electrode of this embodiment has directional water transport performance.

[0040] 5. Detect the solar reflectivity and mid-infrared emissivity of the flexible electrode:

[0041] Test results: Figure 5 It is a passive radiation cooling performance test diagram of the flexible electrode in this embodiment, wherein (a) is a solar reflectivity curve diagram, and the average solar reflectivity of the flexible electrode in this embodiment is 95%; (b) is a mid-infrared emissivity curve diagram, and the average mid-infrared emissivity is 93%.

[0042] 6. Detection electrodes are exposed to solar radiation to monitor changes in skin surface temperature:

[0043] (1) Detection method: When using electrodes to monitor the surface temperature of human skin, it is necessary to first test the relationship curve between temperature and resistance change. When monitoring the hydration level in real time, first test the resistance change, and then convert the tested resistance into temperature according to the temperature-resistance relationship curve to obtain a real-time temperature change curve.

[0044] (2) Test results: Figure 6 This is a graph of the skin surface temperature changes monitored when the flexible electrode in this embodiment is exposed to solar radiation, showing that the electrode can monitor the temperature of the human skin surface as a temperature sensor.

[0045] The above examples are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A flexible electrode with passive radiation cooling performance, characterized in that: Including: A hydrophilic layer with micro-nano pores, a macroporous hydrophobic layer and a conductive layer are provided, wherein the pore size of the hydrophilic layer with micro-nano pores is 0.3-25 μm.

2. The flexible electrode with passive radiation cooling performance according to claim 1, characterized in that: The material of the hydrophilic layer with micro-nano pores is selected from any one of cellulose, cotton, polyvinyl pyrrolidone, polyacrylonitrile or silk.

3. The flexible electrode with passive radiation cooling performance according to claim 1, characterized in that: The material of the macroporous hydrophobic layer is selected from any one of cellulose acetate, polyurethane, fluorinated polyurethane, polyvinylidene fluoride, polystyrene or polymethyl methacrylate, and the pore size of the macroporous hydrophobic layer is 0.3-200 μm.

4. The flexible electrode with passive radiation cooling performance according to claim 1, characterized in that: The material of the conductive layer is selected from any one of metal nanomaterials, carbon materials or conductive polymers.

5. The flexible electrode with passive radiation cooling performance according to claim 4, characterized in that: The metal nanomaterial is selected from any one of metal nanoparticles, metal nanowires or metal nanosheets.

6. The flexible electrode with passive radiation cooling performance according to claim 4, characterized in that: The carbon material is selected from any one of carbon nanotubes, carbon black, graphene or Mxene materials.

7. The flexible electrode with passive radiation cooling performance according to claim 4, characterized in that: The conductive polymer is selected from any one of polypyrrole, polyaniline and PEDOT:PSS materials.

8. The flexible electrode with passive radiation cooling performance according to claim 1, characterized in that: The thickness of the hydrophilic layer with micro-nano pores is 30-500 μm, the thickness of the macroporous hydrophobic layer is 5-100 μm; the thickness of the conductive layer is 100 nm-500 μm.

9. The method for preparing a flexible electrode with passive radiation cooling performance according to any one of claims 1 to 8, characterized in that: The steps include: S1: preparing a hydrophilic layer with micro-nano pores by any one of electrospinning, solvent evaporation, template sacrificial method or phase separation method, wherein the hydrophilic layer with micro-nano pores has a pore size of 0.3 to 25 μm; S2: preparing a macroporous hydrophobic layer and a conductive layer in sequence on the surface of the hydrophilic layer with micro-nano pores: the macroporous hydrophobic layer is prepared by any one of electrospinning or electrostatic spraying; the conductive layer is prepared by any one of magnetron sputtering, vacuum evaporation, electrostatic spraying or dipping; A flexible electrode with passive radiation cooling performance is obtained, which comprises in sequence: a hydrophilic layer with micro-nano pores, a macroporous hydrophobic layer and a conductive layer.

10. An electronic skin, characterized in that: The flexible electrode having passive radiation cooling performance comprises any one of claims 1 to 8.

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