A porous PDMS film and its preparation method and application

Abstract

This invention discloses a porous PDMS film, its preparation method, and its application. The method involves mixing and stirring an electrospinning material with an electrospinning solvent to prepare an electrospinning material solution. Air bubbles are then removed from the template solution to obtain an electrospinning precursor solution. This precursor solution is then electrospinned to obtain a nanofiber membrane. A PDMS solution composed of a PDMS prepolymer, a crosslinking agent, and an organic solvent is prepared. The prepared PDMS solution is poured onto the nanofiber membrane and crosslinked and cured in a heated environment to obtain a composite material. The composite material is then poured into the electrospinning solvent, and the electrospinning material is dissolved by stirring to obtain a porous PDMS material. The porous PDMS material is then washed and dried to obtain the finished product. The porous PDMS film prepared by this invention has uniform composition, high porosity, and good air permeability. The triboelectric output performance of TENGs assembled from the porous PDMS film is also significantly improved.

Description

Technical Field

[0001] This invention relates to the field of triboelectric nanogenerator technology, and in particular to a porous PDMS thin film, its preparation method, and its application. Background Art

[0002] As electronic devices and systems continue to evolve towards miniaturization, portability, and multifunctionality, individual electronic devices often integrate many different types of sensors, and the construction of the Internet of Things (IoT) is largely based on the network interconnection of a large number of sensor units. Triboelectric nanogenerators (TENGs), as an emerging energy conversion device based on electrostatic induction and triboelectric effects, can be used to directly harvest energy from widely existing but difficult-to-utilize natural sources such as human movement, mechanical vibration, sound waves, and even raindrops and ocean waves. Therefore, they are considered an effective way to achieve green energy and sustainable energy development. Triboelectric nanogenerators have advantages such as biofriendliness, portability, and wide availability of energy sources, providing an excellent solution to the power supply problem of a large number of microelectronic devices and sensors, making TENGs a promising candidate for mobile electronic power supply devices.

[0003] Currently, the optimization and modification methods for triboelectric nanogenerators mainly include the following aspects: (1) Surface roughening: preparing various types of micro-nano structures on the surface; (2) Increasing the amount of charge transferred per unit area: such as finding triboelectric layer materials with better triboelectric performance, injecting charges into the surface, chemical / physical treatment, etc.; (3) Designing special structures: including grid structures, rotating disk structures, roller structures, etc., to improve the electron transfer efficiency; (4) Optimizing the TENG capacitor structure; (5) Constructing series / parallel structures of multiple triboelectric nanogenerators to improve space utilization, thereby increasing the output power per unit area and per unit volume.

[0004] Polydimethylsiloxane (PDMS), with its high electronegativity, good biocompatibility, good flexibility, and low preparation cost, is one of the most commonly used negative friction layers in triboelectric nanogenerators. Current improvements focus on constructing surface micro / nano structures to increase its contact area, using methods such as nanoimprinting, photolithography, and plasma reactive etching. However, these methods are complex and costly, making them unsuitable for large-scale production. Some modifications to the physicochemical properties of PDMS itself employ more complex processes, such as plasma reactive etching, which requires sophisticated equipment and is also relatively expensive, making it unsuitable for industrial production. Summary of the Invention

[0005] The purpose of this invention is to provide a porous PDMS thin film, its preparation method, and its application. The porous PDMS thin film prepared by this invention has uniform composition, high porosity, and good air permeability. The micro-nano structure on the surface increases the contact area of ​​the friction layer during the friction process, which can improve the output electrical performance of the TENG capacitor, while also having better wearable performance.

[0006] The technical solution of this invention: A method for preparing a porous PDMS thin film, comprising the following steps:

[0007] Step 1: Mix and stir the electrospinning material with the electrospinning material solvent to prepare an electrospinning material solution with a mass fraction of 5-20%. Then remove the air bubbles inside the template solution to obtain an electrospinning precursor solution. Then electrospin the electrospinning precursor solution to obtain a nanofiber membrane.

[0008] Step 2: Prepare a PDMS solution consisting of PDMS prepolymer, crosslinking agent and organic solvent. The mass ratio of PDMS prepolymer to crosslinking agent in the PDMS solution is 15:1 to 5:1, and the mass ratio of PDMS prepolymer to organic solvent is 1:2 to 1:10.

[0009] Step 3: The prepared PDMS solution is poured onto the nanofiber membrane and cross-linked and cured in a heated environment to obtain the composite material;

[0010] Step S4: Pour the composite material into the electrospinning material solvent, and dissolve the electrospinning material in the composite material by stirring to obtain a porous PDMS material. Then, wash and dry the porous PDMS material to obtain the finished product.

[0011] In the above-mentioned method for preparing porous PDMS films, the electrospinning material is PVA, PVB, or PVC.

[0012] In the aforementioned method for preparing porous PDMS films, the electrospinning solvent is water or ethanol.

[0013] In the aforementioned method for preparing porous PDMS films, in step S1, the electrospinning involves drawing an electrospinning precursor solution with a syringe, connecting the syringe needle to the positive electrode of a static high voltage, and connecting the receiving substrate to the negative electrode; then adjusting the electrospinning voltage and the syringe injection speed until a stable Taylor cone is formed at the tip of the syringe, thereby synthesizing a nanofiber membrane.

[0014] In the aforementioned method for preparing porous PDMS films, the electrospinning voltage is 6–16 kV, the syringe injection speed is 0.06–0.08 mm / min, and the receiving substrate is aluminum foil or release paper.

[0015] In the aforementioned method for preparing porous PDMS films, in step S2, the organic solvent is ethyl acetate or n-hexane.

[0016] In the aforementioned method for preparing porous PDMS films, step 3 involves heating at a temperature of 60–80°C and crosslinking curing for 3–6 hours.

[0017] A porous PDMS film is prepared using the aforementioned method for preparing porous PDMS films.

[0018] An application of a porous PDMS film is described, in which the porous PDMS film is applied to a triboelectric nanogenerator.

[0019] In the aforementioned application, the porous PDMS film is attached to the permeable electrode of a triboelectric nanogenerator; the permeable electrode is made of conductive fiber material.

[0020] Compared to existing technologies, current methods for modifying the porosity of PDMS often focus on selecting solid particles to construct a template framework and then eliminating it. However, when applied to the TENG (Temperature Encapsulation) field, the preparation of porous PDMS often fails to effectively control the porous structure of the material, resulting in a breathable and transparent material. This invention employs a simple template elimination method to prepare a porous PDMS film suitable for TENG capacitors. The resulting porous PDMS film has uniform composition, high porosity, and excellent breathability. The micro / nano structures on the surface increase the contact area of ​​the friction layer during friction, thereby improving the electrical performance of the TENG and enhancing its wearability. This invention provides a simple, low-cost, and mass-producible method for preparing porous PDMS films for TENG friction layers, offering a new preparation method and approach for achieving high-performance TENGs. Attached Figure Description

[0021] Figure 1 This is a scanning electron microscope image of the porous PDMS thin film prepared in this invention.

[0022] Figure 2 A graph showing the transmittance of the porous PDMS film prepared in this invention;

[0023] Figure 3 A comparison of the hydrophobic angles of the porous PDMS film prepared in this invention with those of pure PDMS film and PVA film;

[0024] Figure 4 A comparison of the air permeability of the porous PDMS prepared in this invention and the plastic wrap.

[0025] Figure 5A comparison of the output voltages of TENGs assembled from the porous PDMS films prepared in this invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0027] Example 1: A method for preparing a porous PDMS thin film, comprising the following steps:

[0028] Step 1: Mix and stir the electrospinning material and the electrospinning material solvent to prepare an electrospinning material solution with a mass fraction of 12%. Then, remove air bubbles from the template solution to obtain an electrospinning precursor solution. The electrospinning precursor solution is then electrospinned to obtain a nanofiber membrane. In this step, the electrospinning material is PVA, and the electrospinning material solvent is water. In other embodiments, the electrospinning material can be PVB or PVC, and the electrospinning material solvent can be a volatile solvent such as ethanol. The selected solvents have the following advantages for the materials chosen in this invention: First, they can dissolve the electrospinning material, thereby preparing a solution of a certain concentration and viscosity for the electrospinning process; second, they are bio-friendly materials and are harmless to the human body.

[0029] In this step, the electrospinning involves drawing the electrospinning precursor solution with a syringe, connecting the syringe needle to the positive electrode of a static high voltage, and connecting the receiving substrate to the negative electrode. The electrospinning voltage and syringe injection speed are then adjusted until a stable Taylor cone forms at the syringe tip, thereby synthesizing the nanofiber membrane. The spinning voltage is 10kV, and the spinning distance is 15cm. The electrospinning receiving substrate is aluminum foil or release paper. In this embodiment, aluminum foil is used because it has a smooth surface, is easy to peel off from the sample, and reduces costs.

[0030] Step 2: Mix PDMS prepolymer, crosslinking agent and n-hexane to prepare PDMS solution, wherein the mass ratio of PDMS prepolymer to n-hexane is 1:4, and the amount of crosslinking agent added is 5% of the mass of PDMS prepolymer;

[0031] Step 3: The prepared PDMS solution is poured onto the nanofiber membrane and further cross-linked and cured at 60°C for 6 hours to obtain the composite material;

[0032] Step 4: Pour the composite material into water and dissolve the electrospinning material by stirring to obtain porous PDMS material. Then wash and dry the porous PDMS material to obtain the finished PDMS film.

[0033] Example 2: A method for preparing a porous PDMS film. PVA, an electrospinning material, is mixed with ethanol, an electrospinning solvent, and stirred to prepare an electrospinning solution with a concentration of 6% by mass. Air bubbles are removed from the solution to obtain an electrospinning precursor solution. The precursor solution is then electrospinned at a voltage of 15 kV and a spinning distance of 20 cm. Release paper is used as the electrospinning substrate to obtain a nanofiber membrane. A PDMS solution is prepared by mixing PDMS prepolymer, a crosslinking agent, and n-hexane, with a PDMS prepolymer to n-hexane mass ratio of 1:8 and the crosslinking agent added at 8% of the PDMS prepolymer mass. The prepared PDMS solution is poured onto the nanofiber membrane and further crosslinked and cured at 90°C for 3 hours to obtain a composite material. The composite material is poured into water, and the electrospinning material is dissolved by stirring to obtain a porous PDMS material. The porous PDMS material is then washed and dried to obtain the finished PDMS film.

[0034] Example 3: A method for preparing a porous PDMS film. PVB, an electrospinning material, is mixed with ethanol, an electrospinning solvent, and stirred to prepare an electrospinning solution with a mass fraction of 10%. Air bubbles are removed from the solution to obtain an electrospinning precursor solution. The precursor solution is then electrospinned at a voltage of 6 kV and a spinning distance of 10 cm. The electrospinning substrate is aluminum foil, resulting in a nanofiber membrane. A PDMS solution is prepared by mixing PDMS prepolymer, a crosslinking agent, and ethyl acetate, with a PDMS to ethyl acetate mass ratio of 1:10. The amount of crosslinking agent added is 10% of the mass of the PDMS prepolymer. The prepared PDMS solution is poured onto the nanofiber membrane and further crosslinked and cured at 80°C for 4 hours to obtain a composite material. The composite material is poured into water, and the electrospinning material is dissolved by stirring to obtain a porous PDMS material. The porous PDMS material is then washed and dried to obtain the finished PDMS film.

[0035] Example 4: A method for preparing a porous PDMS film. The method involves mixing and stirring PVC (a PVC electrospinning material) with ethanol (an ethanol solvent) to prepare an electrospinning solution with a concentration of 15% by mass. Air bubbles are removed from the solution to obtain an electrospinning precursor solution. The precursor solution is then electrospinned at a voltage of 15 kV and a distance of 15 cm. The substrate used for electrospinning is aluminum foil or release paper, resulting in PVC nanofibers as the electrospinning template material. A PDMS solution is prepared by mixing PDMS prepolymer, a crosslinking agent, and ethyl acetate at a mass ratio of 1:6. The amount of crosslinking agent added is 15% of the mass of the PDMS prepolymer. The prepared PDMS solution is poured onto a nanofiber membrane and further crosslinked and cured at 80°C for 4 hours to obtain a composite material. The composite material is then poured into water, and the electrospinning material is dissolved by stirring to obtain a porous PDMS material. The porous PDMS material is then washed and dried to obtain the finished PDMS film.

[0036] Example 5: A method for preparing a porous PDMS film. The method involves mixing and stirring PVC (a PVC electrospinning material) with ethanol (an ethanol solvent) to prepare an electrospinning solution with a concentration of 15% by mass. Air bubbles are removed from the solution to obtain an electrospinning precursor solution. The precursor solution is then electrospinned at a voltage of 15 kV and a distance of 15 cm. The substrate used for electrospinning is aluminum foil or release paper, resulting in PVC nanofibers as the electrospinning template material. A PDMS solution is prepared by mixing PDMS prepolymer, a crosslinking agent, and ethyl acetate, with a PDMS to ethyl acetate mass ratio of 1:2. The amount of crosslinking agent added is 20% of the mass of the PDMS prepolymer. The prepared PDMS solution is poured onto a nanofiber membrane and further crosslinked and cured at 80°C for 4 hours to obtain a composite material. The composite material is then poured into water, and the electrospinning material is dissolved by stirring to obtain a porous PDMS material. The porous PDMS material is then washed and dried to obtain the finished PDMS film.

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the PDMS thin film product prepared by the present invention will be briefly described below. Figure 1 This is a scanning electron microscope (SEM) image of the porous PDMS thin film prepared in Example 5 of this invention; from Figure 1 As can be seen from the above, the porous PDMS film prepared by the present invention has good porosity, uniform composition and high porosity, which shows that the method of the present invention can achieve good control of porous structure. Figure 2 This is a transmittance diagram of the porous PDMS film prepared in this invention. Figure 2 As can be seen from the above, the porous PDMS film prepared by this invention has a light transmittance of over 80%. Figure 3A comparison of the hydrophobic angles of the porous PDMS film prepared in Example 5 of this invention and a conventional pure PDMS planar film; from Figure 3 As can be seen from the above, the porous PDMS film prepared by this invention has a good hydrophobic angle and can achieve a good waterproof effect. Figure 4 This is a comparison diagram of the air permeability of the porous PDMS film prepared in Example 5 of the present invention and the plastic wrap. Figure 4 Figure a shows the air permeability of the porous PDMS film. Figure 4 Figure b shows the breathability of the plastic wrap; from Figure 4 As can be seen from the paper, the porous PDMS film prepared by the present invention has good air permeability, which is due to the porous structure of the PDMS film. Figure 5 This is a comparison graph showing the output voltage of the TENG assembled from the porous PDMS film prepared in Example 5 of the present invention, and the output voltage of the TENG assembled from the pure PDMS film. As can be seen from the graph, the output voltage of the TENG assembled from the porous PDMS film prepared in this invention is significantly increased, indicating that the porous structure can significantly increase the amount of triboelectric charge transferred by the TENG.

[0038] In summary, this invention employs a simple template elimination method to prepare a porous PDMS film suitable for TENG capacitors. The resulting porous PDMS material exhibits uniform composition, high porosity, and excellent air permeability. The micro / nano structures on its surface increase the contact area of ​​the friction layer during the friction process, thereby improving the output electrical performance of the TENG and enhancing its wearable performance. This invention provides a simple, low-cost, and mass-producible method for preparing porous PDMS films for TENG friction layers, offering a new preparation method and approach for achieving high-performance TENGs.

Claims

1. An application of a porous PDMS thin film in a triboelectric nanogenerator, characterized in that: The method for preparing the porous PDMS thin film includes the following steps: Step 1: Mix and stir the electrospinning material with the electrospinning material solvent to prepare an electrospinning material solution with a mass fraction of 5-20%. Then remove the air bubbles inside the template solution to obtain an electrospinning precursor solution. Then electrospin the electrospinning precursor solution to obtain a nanofiber membrane. Step 2: Prepare a PDMS solution consisting of PDMS prepolymer, crosslinking agent and organic solvent. The mass ratio of PDMS prepolymer to crosslinking agent in the PDMS solution is 15:1 to 5:1, and the mass ratio of PDMS prepolymer to organic solvent is 1:2 to 1:

10. Step 3: The prepared PDMS solution is poured onto the nanofiber membrane and cross-linked and cured in a heated environment to obtain the composite material; Step 4: Pour the composite material into the electrospinning material solvent, and dissolve the electrospinning material in the composite material by stirring to obtain porous PDMS material. Then wash and dry the porous PDMS material to obtain the finished product. The electrospinning material is PVA or PVB. The solvent for the electrospinning material is water or ethanol; The electrospinning voltage is 6–16 kV, the syringe injection speed is 0.06–0.08 mm / min, and the receiving substrate is aluminum foil or release paper. In step 3, the temperature of the heating environment is 60-80 ℃, and the cross-linking curing time is 3-6 hours; In step 1, the electrospinning involves drawing an electrospinning precursor solution with a syringe, connecting the syringe needle to the positive electrode of a static high voltage, and connecting the receiving substrate to the negative electrode. Then, the electrospinning voltage and the syringe injection speed are adjusted until a stable Taylor cone is formed at the tip of the syringe, thereby obtaining a nanofiber membrane.

2. The application according to claim 1, characterized in that: In step 2, the organic solvent is ethyl acetate or n-hexane.

3. The application according to claim 1, characterized in that: The porous PDMS film is attached to the permeable electrode of the triboelectric nanogenerator; the permeable electrode is made of conductive fiber material.

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