Flexible wearable device integrating passive radiation cooling and piezoelectric sensing and preparation method thereof

Abstract

The invention provides a passive radiation cooling and piezoelectric sensing integrated flexible wearable device and a preparation method thereof. The preparation method comprises the following steps: placing high-refractive-index micro-particles and piezoelectric nano-particles in a solvent, and ultrasonically mixing uniformly to obtain a mixture 1; adding a base material into the mixture 1 to obtain a mixture 2; preparing the mixture 2 into a piezoelectric composite film with a micro-nano porous structure; cutting into a required shape to prepare a functional material; mounting conductive electrodes on the upper and lower surfaces of the functional material to form electrode layers; the upper electrode and the lower electrode are connected through a thin copper wire, then insulation packaging is conducted, and the flexible wearable device is obtained. The material source is wide, the process is simple, the method is suitable for large-scale production, an innovative solution is provided for thermal comfort management and environment interaction integrated design of next-generation intelligent wearable electronic equipment, and the method has remarkable market application prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of intelligent thermal management and sensing technology, and specifically discloses a flexible wearable device integrated with passive radiative cooling and piezoelectric sensing and a preparation method thereof. BACKGROUND

[0002] Emerging smart wearable films show great application potential in various fields such as motion detection, wireless communication, and real-time physiological signal monitoring due to the integration of advanced electronic devices and circuits. However, due to the increase in modules, this complex stacked structure increases the thermal and electrical load of the smart wearable film, not only damaging the comfort of the wearer, but also putting higher requirements on the uninterrupted power supply. Therefore, when designing smart wearable films, more attention should be paid to the comfort and lightness of the wearer, and reasonable design and comprehensive optimization should be emphasized.

[0003] Ensuring the best thermal comfort of the user is an essential factor for smart wearable devices, especially when the wearer is exposed to direct sunlight during long outdoor activities, which can easily lead to heat stress disorders and overheating of electronic devices. In cooling technology, passive radiative cooling (PDRC) can transfer heat to the cold universe (3K) through the atmospheric window (8−13 μm) without consuming energy. With the characteristics of environmental protection, lightness, and easy wear, it has shown great application potential and value in a series of applications such as fabrics, buildings, thermoelectric devices, and dew collection.

[0004] Continuous and stable long-term power supply is an important issue for smart wearable films. Traditional power supplies have short service life, high rigidity, and are not easily integrated with fabrics. Therefore, harvesting energy from the environment is an important direction to simplify the process and improve sustainability. Nano generators (PENGs) can collect waste mechanical energy from the surrounding environment and power electronic devices, which have advantages in the design of smart wearable films. Therefore, combining flexible nano generators and radiation greatly simplifies the thermal management and energy supply system in smart wearable films, which is a promising solution. For example, the patent with the application publication number CN119078012 A provides a preparation method of a radiative cooling friction nano generator coating, which effectively realizes cooling and efficient collection of environmental energy. The patent with the application publication number CN 114220905 A discloses a thermoelectric power generation device based on radiative cooling and a preparation method thereof, which is used to solve the technical problems of large volume and low power generation efficiency of the radiative cooling thermoelectric generator in the prior art.

[0005] However, functional integration is usually achieved through complex stacking of different modules, which inevitably compromises the comfort and portability of the wearer and increases the complexity of the preparation process. Integrating these discrete functional modules into a unified design of smart wearable thin films through a simple preparation method is an excellent solution. Here, we propose a rational method of functional integration to address the typical challenges of integrating thermal management and self-powered sensing in smart wearable thin films. SUMMARY

[0006] The present application provides a flexible wearable device integrating passive radiative cooling and piezoelectric sensing and a preparation method thereof. The present application uses an expandable, template-free and non-solvent induced phase separation method to prepare a thin film, and then obtains a smart flexible wearable device with passive radiative cooling and piezoelectric sensing through a series of steps such as electrode installation and packaging.

[0007] To achieve the above-mentioned purpose, the specific technical solution is: A preparation method of a flexible wearable device integrating passive radiative cooling and piezoelectric sensing, comprising the following steps: Step 1: Put high refractive index microparticles and piezoelectric nanoparticles into a solvent, mix uniformly by ultrasonic, and obtain mixture 1; Step 2: Add the base material to the mixture 1 and heat and stir until completely dissolved to obtain mixture 2; Step 3: Form a film by spin coating, blade coating, roll coating or template treatment, immerse in a non-solvent to complete non-solvent induced phase separation, and then dry at room temperature. After the water is completely evaporated, a piezoelectric composite thin film with micro-nano porous structure is obtained; Step 4: Cut the piezoelectric composite thin film into the required shape to prepare a functional material; install conductive electrodes on the upper and lower surfaces of the functional material to form an electrode layer; Step 5: Connect the upper and lower electrodes with fine copper wires, then perform insulation packaging, form a packaging layer on the outer surface of the electrode layer, and obtain a flexible wearable device.

[0008] Preferably, the mass percentage of high refractive index microparticles in the mixture 1 is 0-30%; the mass percentage of piezoelectric nanoparticles is 0-5%.

[0009] Preferably, the high refractive index microparticles are metal or non-metal oxide particles with a size of 0.3-10 μm.

[0010] Preferably, the high refractive index microparticles are one or more of SiO2, TiO2, ZnO, Si3N4 and Al2O3.

[0011] Preferably, the piezoelectric nanoparticles are one or more of BaTiO3, PbTiO3, ZnO, LiGaO2, LiTaO3, GaN, with a diameter of 1-500 nm. Preferably, the solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, tetrahydrofuran.

[0012] Preferably, the base material is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene.

[0013] Preferably, the electrode in step 4 is a flexible and breathable electrode, including but not limited to one or more of conductive fiber cloth, conductive polyurethane sponge, conductive foam.

[0014] Preferably, the encapsulation material in step 4 is at least one of polyimide film, polyamide-imide film, polybenzimidazole film, polyethylene terephthalate.

[0015] Compared with the prior art, the present application has the following beneficial effects: (1) The functional layer of the flexible wearable device of the present application is a porous film with high infrared emissivity, high solar reflectivity and excellent piezoelectric performance, which realizes cooling all day by reflecting visible light and emitting infrared radiation, and realizes mechanical energy-electric energy conversion by the rotation of dipoles. At the same time, the microparticles with high solar spectrum refractive index and high dielectric constant are used to improve the solar reflectivity of the substrate and increase the piezoelectric output signal.

[0016] (2) The present application has a simple structure and is soft, providing comfort and portability to the wearer, so that it can be applied to most sports scenes. When exercising outdoors, the device not only realizes passive cooling by radiative cooling, but also monitors the human body movement state through the piezoelectric effect.

[0017] (3) The present application not only has a simple manufacturing process and low cost, but also is suitable for large-scale production, and has a significant market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic diagram of the flexible wearable device of the present application; Figure 2 is a schematic diagram of the working principle of the flexible wearable device of the present application; Figure 3 is a representation of the cooling performance of the flexible wearable device of Example 1 of the present application in outdoor testing; Figure 4 is the output voltage of the flexible wearable device of Example 1 of the present application under different driving forces at a fixed driving frequency; Figure 5The output voltage of the flexible wearable device of Example 1 of the present application under different driving frequencies and fixed driving force.

[0019] Figure 6 The radiation cooling performance of the flexible wearable device of Example 2 of the present application under different hollow silica contents.

[0020] Figure 7 The piezoelectric performance of the flexible wearable device of Example 3 of the present application under different barium titanate contents. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present application clearer, the preferred embodiments of the present application will be further described in detail below in combination with examples. All other examples obtained by those skilled in the art on the basis of the examples in the present application without creative labor shall fall within the scope of protection of the present application.

[0022] Example 1

[0023] Step 1: Hollow silica (HSiO2) with a diameter of 1 μm-2.5 μm and barium titanate (BTO) particles with a diameter of 200 nm are uniformly dispersed in N,N-dimethylformamide (DMF) by ultrasonic wave to obtain a mixture 1, wherein the mass fraction of the hollow silica in the mixture 1 is 15 wt%, and the mass fraction of the barium titanate particles is 2 wt%. Step 2: Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) matrix material is added to the mixture 1, and the solution is completely dissolved and uniformly mixed by magnetic stirring at 50℃ to obtain a mixture 2, wherein the mass fraction of the matrix material in the mixture 2 is 15 wt%. Step 3: The mixture 2 is uniformly scraped and coated on a glass substrate by a glass rod, immersed in water at 30℃ for 0.5 h to complete the non-solvent induced phase separation, and then dried at room temperature, and the radiation cooling piezoelectric composite film PTSB is obtained after the water is completely evaporated, and the film thickness is about 200 μm.

[0024] As Figure 2 The working mechanism of the radiation cooling piezoelectric composite film (PTSB) can realize passive radiation cooling and air permeability at the same time, and obtain human mechanical energy through piezoelectric effect, and is expected to realize self-powered intelligent sensing application. Figure 3 The radiation cooling performance of the radiation cooling piezoelectric composite film PTSB.

[0025] Step 4: The radiation cooling piezoelectric composite film is cut into a required shape to obtain a functional layer, as shown in Figure 1 A conductive Cu-Ni fabric is mounted on the upper and lower surfaces of the film as an electrode, and a nano generator is integrated, as shown in Figure 1 the electrode layer.

[0026] Step 5: The upper and lower electrodes are connected by using thin copper wire, and the flexible thermal comfort piezoelectric sensor prepared in step 4 is packaged with a polyimide (PI) film, as shown in the packaging layer, to prevent external signal interference, multiple rubs, and humid environments from affecting the sensor. Figure 1

[0027] As shown in Figure 4 , the open-circuit voltage of the nanogenerator based on the PTSB film under different driving conditions (force: 1 ~ 15 N, frequency: 2 Hz), in which the output voltage increases with the driving force. Figure 5 The effect of different driving frequencies (0.4-1.6 Hz) on the output signal of the PTSB film nanogenerator under a fixed driving force of 1 N. As the strain rate increases, the charge accumulation increases.

[0028] The following examples are based on Example 1 by adjusting the mass ratio of scattering particles or piezoelectric micro-nanoparticles to regulate the radiative cooling and piezoelectric properties of the sensor.

[0029] Example 2

[0030] Step 1: Different amounts of hollow silica HSiO2 are placed in N,N-dimethylformamide (DMF) and ultrasonically mixed to obtain a mixture 1; the mass fraction of HSiO2 microparticles in the mixture 1 is 0wt%, 5wt%, 10wt%, 15wt%, 20wt%, and 25wt%, respectively; Step 2: Add polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) matrix material to mixture 1 and stir magnetically at 50°C until the solution is completely dissolved and uniformly mixed to obtain mixture 2, the mass fraction of the matrix material in the mixture 2 is 15wt%; Step 3: The mixture 2 is uniformly scraped on a glass substrate with a glass rod, immersed in water at 30°C for 0.5h to complete the non-solvent induced phase separation; then dried at room temperature, and the radiative cooling piezoelectric composite film PTSB is obtained after the water is completely evaporated, the film thickness is about 200μm.

[0031] As shown in Figure 2 , the working mechanism of the radiative cooling piezoelectric composite film (PTSB), which can simultaneously achieve passive radiative cooling and air permeability, and obtain human mechanical energy through piezoelectric effect, is expected to realize self-powered intelligent sensing application. Figure 3 The radiative cooling performance of the radiative cooling piezoelectric composite film PTSB.

[0032] Step 4: The radiative cooling piezoelectric composite film is cut into the required shape to obtain a functional layer, as shown in Figure 1 ​as shown; install conductive Cu-Ni fabric as electrodes on the upper and lower surfaces of the film, integrate the nanogenerator, and the electrode layer is as shown. Figure 1

[0033] Step 5: connect the upper and lower electrodes using thin copper wires, and encapsulate the flexible thermal comfort piezoelectric sensor prepared in step 4 with a polyimide (PI) film, as shown in the encapsulation layer, to prevent external signal interference, multiple rubbing, and humid environment from affecting the sensor. Figure 1

[0034] Figure 6 As shown, the temperature difference between the surface temperature of the radiation cooling piezoelectric composite film PTSB and the ambient temperature under different hollow silica content, the increase of HSiO2 content can effectively improve the cooling effect.

[0035] Example 3

[0036] The preparation method of the radiation cooling piezoelectric sensor of this example is basically the same as that of example 1, and the difference between the two is the difference in the mass fraction of the nano piezoelectric particles in step 1. Specifically, it can be: Step 1: ultrasonically mix HSiO2 and barium titanate in N,N-dimethylformamide (DMF) according to a certain mass ratio to obtain a mixture 1. In the mixture 1, the mass fraction of HSiO2 microparticles is 15wt%; the mass fraction of barium titanate nanoparticles is 0wt%, 1wt%, 2wt%, and 3wt%, respectively, and the particles are not dissolved and uniformly dispersed in the solvent.

[0037] Step 2: add polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) matrix material to the above mixture 1, respectively, and stir magnetically at 50°C until the solution is completely dissolved and uniformly mixed to obtain a mixture 2, and the mass fraction of the matrix material in the mixture 2 is 15wt%.

[0038] Step 3: uniformly scrape the mixture 2 on a glass substrate with a glass rod, immerse it in water at 30°C for 0.5h, complete the non-solvent induced phase separation, and then dry at room temperature. After the water is completely evaporated, a radiation cooling piezoelectric composite film with different BTO nanoparticle contents is obtained, and the film thickness is about 200μm.

[0039] Step 4: cut the radiation cooling piezoelectric composite film to the desired shape to obtain a functional layer, as shown. Figure 1 as shown; install conductive Cu-Ni fabric as electrodes on the upper and lower surfaces of the film, integrate the nanogenerator, and the electrode layer is as shown. Figure 1

[0040] ​​​Step 5: The upper and lower electrodes were connected by thin copper wire, and the flexible thermal comfort piezoelectric sensor prepared in step 4 was packaged with a polyimide (PI) film, as shown in the packaging layer in order to prevent external signal interference, multiple rubbing and humid environment from affecting the sensor. Figure 1

[0041] As shown in Figure 7 , the piezoelectric properties of PTSB under a periodic pressure of 2N and 1.5Hz with different barium titanate particle contents. The increase of barium titanate loading effectively improves the piezoelectric output.

[0042] Obviously, the embodiments described are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0043] The above described embodiments are part of the embodiments of the present application, rather than all the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.​

Claims

1. A method for fabricating a flexible wearable device integrating passive radiative cooling and piezoelectric sensing, characterized in that, The method comprises the following steps: Step 1: placing high-refractive microparticles and piezoelectric nanoparticles in a solvent, uniformly mixing by ultrasonic, and obtaining a mixture 1; Step 2: adding a matrix material to the mixture 1, heating and stirring until completely dissolved, and obtaining a mixture 2; Step 3: forming a film from the mixture 2 by spin coating, blade coating, roll coating or stencil processing, immersing in a non-solvent to complete non-solvent induced phase separation, and then drying at room temperature, and obtaining a piezoelectric composite film with micro-nano porous structure after complete evaporation of water; Step 4: cutting the piezoelectric composite film into a desired shape to prepare a functional material, and mounting a conductive electrode on the upper and lower surfaces of the functional material to form an electrode layer; Step 5: connecting the upper and lower electrodes with a thin copper wire, then performing insulation packaging, forming a packaging layer on the outer surface of the electrode layer, and obtaining a flexible wearable device.

2. The method of claim 1, wherein the flexible wearable device is prepared by the steps of: a) providing a flexible substrate; b) depositing a piezoelectric material on the flexible substrate; c) depositing a passive radiative cooling material on the piezoelectric material; and d) depositing a top layer on the passive radiative cooling material. The mass percentage of the high-refractive microparticles in the mixture 1 is 0-30%; the mass percentage of the piezoelectric nanoparticles is 0-5%.

3. The method of claim 1, wherein the flexible wearable device is prepared by the steps of: a) providing a flexible substrate; b) forming a passive radiative cooling layer on the flexible substrate; c) forming a piezoelectric sensor layer on the flexible substrate; d) forming a flexible display layer on the flexible substrate; and e) forming a flexible housing layer on the flexible substrate. The high-refractive microparticles are metal or non-metal oxide particles with a size of 0.3-10 μm.

4. The method of claim 3, wherein the flexible wearable device is prepared by the steps of: a) providing a flexible substrate; b) forming a passive radiative cooling layer on the flexible substrate; c) forming a piezoelectric sensor layer on the flexible substrate; d) forming a flexible display layer on the flexible substrate; and e) forming a flexible housing layer on the flexible substrate. The high-refractive microparticles are one or more of SiO2, TiO2, ZnO, Si3N4 and Al2O3.

5. The method of claim 1, wherein the flexible wearable device is prepared by the steps of: a) providing a flexible substrate; b) forming a passive radiative cooling layer on the flexible substrate; c) forming a piezoelectric sensor layer on the flexible substrate; d) forming a flexible display layer on the flexible substrate; and e) forming a flexible housing layer on the flexible substrate. The piezoelectric nanoparticles are one or more of BaTiO3, PbTiO3, ZnO, LiGaO2, LiTaO3 and GaN, with a diameter of 1-500 nm.

6. The method for fabricating a flexible wearable device integrating passive radiative cooling and piezoelectric sensing as described in claim 1, characterized in that, The solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone and tetrahydrofuran.

7. The method for fabricating a flexible wearable device integrating passive radiative cooling and piezoelectric sensing as described in claim 1, characterized in that, The matrix material is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and polyvinylidene fluoride-trifluoroethylene.

8. The method for fabricating a flexible wearable device integrating passive radiative cooling and piezoelectric sensing as described in claim 1, characterized in that, The electrode in step 4 is a flexible breathable electrode, including but not limited to one or more of conductive fiber cloth, polyurethane conductive sponge and conductive foam.

9. The method of claim 1, wherein the method further comprises: The packaging material in step 4 is at least one of polyimide film, polyamide-imide film, polybenzimidazole film and polyethylene terephthalate.

10. A flexible wearable device integrating passive radiative cooling and piezoelectric sensing, characterized in that, Prepared by any one of the methods of claims 1-9.

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