Energy harvesting device and method of harvesting

Abstract

The application discloses an energy collecting device and a collecting method thereof. The electrode, dielectric layer, hydrophobic layer and conductive fluid of the device constitute a flat plate capacitor. Under the action of mechanical force, gas flows into the conductive fluid area through the apertures on the lower substrate, electrode, dielectric layer and hydrophobic layer. The gas expands and reduces rapidly in the conductive fluid, changes the contact area between the conductive fluid and the hydrophobic layer, causes the capacitance to change, and thus forms a current in the external circuit. The generated current does work on the load of the external circuit, generates energy, collects the energy through an energy storage device, and achieves the purpose of energy collection. The application converts the low-frequency mechanical movement process in life into the change process of the gas in the device, and achieves the purpose of effectively collecting the energy generated by the low-frequency mechanical movement. The application can convert mechanical energy into electric energy by using extensive mechanical force.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of energy harvesting, and particularly relates to an energy harvesting device and a harvesting method thereof. BACKGROUND

[0002] Energy harvesting is a technology that collects energy from the surrounding environment and converts it into electrical energy. In daily life, there are many forms of energy that can be collected, such as light energy, heat energy, mechanical energy, etc. In many cases, energy can be collected from mechanical motion to power electronic devices.

[0003] For the energy generated by mechanical motion, there are mainly three kinds of existing energy harvesting technologies: electromagnetic energy harvesting technology, piezoelectric energy harvesting technology and triboelectric nanogenerator. Electromagnetic energy harvesting technology is based on Faraday's law of electromagnetic induction. In an electromagnetic energy harvester, when external vibration acts on the device, relative motion occurs between the permanent magnet and the coil, causing the magnetic flux in the coil to change, resulting in an induced electromotive force. Piezoelectric energy harvesting technology uses piezoelectric materials that can generate electric charges and thus generate voltage when the materials are subjected to mechanical strain. Triboelectric nanogenerator is a device that uses the principle of triboelectricity and electrostatic induction to convert mechanical energy into electrical energy. When the device receives mechanical force, contact friction and separation motion occur between the two triboelectric materials, and a potential difference is formed between the two triboelectric materials when they separate. By connecting an external circuit, an electric current can be output, thereby converting mechanical energy into electrical energy. Electromagnetic energy harvesting technology and piezoelectric energy harvesting technology can effectively collect energy generated by high-frequency mechanical motion; but for low-frequency mechanical motion, such as energy generated by human walking, the reliability of these energy harvesting technologies needs to be further improved. Although triboelectric nanogenerator can effectively collect energy generated by low-frequency mechanical motion, it usually requires electrodes to undergo continuous solid-solid friction, which leads to material degradation and directly affects the life and reliability of the generator. Currently, these technologies are still in development. SUMMARY

[0004] The purpose of the present application is to provide an energy harvesting device and a harvesting method thereof, which converts the process of low-frequency mechanical motion into a change process of gas in the energy harvesting device in a conductive liquid. In this change process, the contact area between the conductive liquid and the hydrophobic layer changes, causing the capacitance of the flat-plate capacitor composed of the electrode, the dielectric layer, the hydrophobic layer and the conductive fluid to change. Through REWOD, the energy generated by this process is converted into electrical energy, achieving the purpose of effectively collecting energy generated by low-frequency mechanical motion.

[0005] The technical solution of the present application is as follows: an energy harvesting device, comprising,

[0006] an upper substrate;

[0007] lower substrate;

[0008] electrode arranged on the upper surface of the lower substrate;

[0009] thin film attached to the lower surface of the upper substrate;

[0010] dielectric layer arranged on the upper surface of the electrode;

[0011] hydrophobic layer coated on the upper surface of the dielectric layer;

[0012] electrically conductive fluid filled between the thin film and the hydrophobic layer;

[0013] the lower substrate and the upper substrate are combined and placed between two chambers, which are a top chamber and a bottom chamber, respectively, and the top chamber and the bottom chamber are respectively filled with gas;

[0014] a one-way check valve is arranged between the top chamber and the bottom chamber to realize the flow of gas from the top chamber back to the bottom chamber.

[0015] A collection method of an energy collection device, the method is as follows: when an external mechanical force presses the bottom chamber, the gas flows into the electrically conductive fluid area through the second aperture; the gas rapidly expands and shrinks in the electrically conductive fluid, thereby generating multiple bubbles; in the process of rapid expansion of the gas in the electrically conductive fluid, the gas changes the contact area between the electrically conductive fluid and the hydrophobic layer, resulting in a change in the capacitance of the flat plate capacitor, thereby forming a current in the external circuit; the generated current does work on the load of the external circuit, generating energy, thereby realizing the conversion of mechanical energy to electrical energy; when a bubble is generated, the electrically conductive fluid refills the area until the next bubble is generated; when the bubble contacts the thin film, the gas in the bubble flows into the top chamber through the thin film and the first aperture; after the mechanical force is removed, the gas flows from the top chamber back to the bottom chamber through the one-way check valve, and the electrically conductive fluid refills between the hydrophobic layer and the thin film.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) It can utilize a wide range of mechanical forces.

[0018] (2) It can effectively collect energy generated by low-frequency mechanical motion.

[0019] (3) The device structure is simple, and the application scenarios are wide. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is an exploded view of the energy collection device of the present application.

[0021] Figure 2 is a cross-sectional structure view of the energy collection device of embodiment 1 of the present application when no mechanical force is applied.

[0022] Figure 3 Figure 1 is a cross-sectional view of the energy harvesting device of embodiment 1 of the present application when a mechanical force is applied. DETAILED DESCRIPTION

[0023] The present application will be further described by examples in conjunction with the accompanying drawings.

[0024] The present application proposes a new method of converting mechanical energy into electrical energy related to electrowetting on dielectric (EWOD), which is called reverse electrowetting on dielectric (REWOD). In this method, when a droplet is periodically deformed between two electrodes coated with dielectric under the action of an external mechanical force, the periodic change of the electrode-conductive droplet interface area is caused. This periodic change of the interface area causes the change of the liquid-solid interface capacitance, and forces the current to flow back and forth on the load resistor to generate electrical energy. This method can convert mechanical energy into electrical energy using a wide range of mechanical forces, and effectively collect the energy generated by low-frequency mechanical motion. The energy harvesting device using this method can be placed in the sole to collect the energy generated by people in low-frequency mechanical motion, or to collect the energy generated by other low-frequency mechanical motion.

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] In conjunction with Figure 1 , the energy harvesting device described in the present application comprises: an upper substrate 8; a lower substrate 1; an electrode 2 arranged on the upper surface of the lower substrate 1; a thin film 7 attached to the lower surface of the upper substrate 8; a one-way check valve 5; a dielectric layer 3 arranged on the upper surface of the electrode 2; a hydrophobic layer 4 coated on the upper surface of the dielectric layer 3; a conductive fluid 6 filled between the hydrophobic layer 4 and the thin film 7; the lower substrate 1 and the upper substrate 8 are combined and placed between two chambers, which are a top chamber 10 and a bottom chamber 16 respectively, and a gas 14 is filled in the top chamber 10 and the bottom chamber 16.

[0027] The upper substrate 8 and the lower substrate 1 are made of silicon dioxide, wherein a plurality of first apertures 9 are formed from top to bottom on the upper substrate 8.

[0028] The electrode 2 is made of a material with good electrical conductivity, such as aluminum, indium tin oxide.

[0029] The dielectric layer 3 is a solid dielectric layer, which is a solid material with a relatively high relative dielectric constant, such as one of aluminum oxide, silicon dioxide, and titanium oxide.

[0030] The hydrophobic layer 4 is a fluoropolymer, such as one of Teflon and Cytop. A plurality of second apertures 13 are formed from the lower surface of the lower substrate 1 upward through the electrode 2, the dielectric layer 3, and the hydrophobic layer 4. The diameter of the first apertures 9 is smaller than the diameter of the second apertures 13.

[0031] The conductive fluid 6 is a conductive liquid. The conductive liquid is one of an acid solution, an alkali solution, and a salt solution. The conductive liquid does not wet the film 7 (a tetrafluoroethylene hydrophobic film) and cannot pass through the film 7.

[0032] The gas 14 is one of air and an inert gas. The gas 14 can quickly pass through the film 7.

[0033] The electrode 2, the dielectric layer 3, the hydrophobic layer 4, and the conductive fluid 6 form a flat capacitor. Under the action of an applied mechanical force, the gas 14 flows into the region of the conductive fluid 6 through the second apertures 13, the gas 14 continuously expands in the conductive fluid 6, and the contact area between the conductive fluid 6 and the hydrophobic layer 4 is reduced, resulting in a decrease in the capacitance of the flat capacitor, a decrease in the electric charge that can be stored by the flat capacitor, and a flow of electric charge from the flat capacitor, which forms an electric current in an external circuit, and the electric current does work on the load in the external circuit, thereby achieving the conversion of mechanical energy into electrical energy.

[0034] The energy harvesting device further includes a bias voltage source 12 and an energy storage device 11. The bias voltage source 12 is a direct current voltage source, and the bias voltage source 12 is connected to the electrode 2 and the conductive fluid 6 to apply a bias voltage. The energy storage device 11 is connected to the electrode 2, the conductive fluid 6, and the bias voltage source 12 to collect the electrical energy converted from mechanical energy, thereby achieving energy harvesting.

[0035] Example 1

[0036] In combination Figure 2This diagram shows a cross-sectional view of the energy harvesting device according to Embodiment 1 of the present invention when no mechanical force is applied. The energy harvesting device and its harvesting method include a lower substrate 1 and an upper substrate 8 disposed opposite each other. The upper substrate 8 has a plurality of first pores 9 formed from top to bottom. A plurality of second pores 13 are formed from the lower surface of the lower substrate 1 upwards, passing through an electrode 2, a dielectric layer 3, and a hydrophobic layer 4. The electrode 2 is arranged on the upper surface of the lower substrate 1. The dielectric layer 3 is disposed on the upper surface of the electrode 2, and the hydrophobic layer 4 is coated on the upper surface of the dielectric layer 3. A thin film 7 is attached to the lower surface of the upper substrate 8. A conductive liquid 6 is filled between the hydrophobic layer 4 and the thin film 7. The lower substrate 1 and the upper substrate 8 are combined and placed between two chambers, a top chamber 10 and a bottom chamber 16. Gas 14 is filled in the top chamber 10 and the bottom chamber 16. Gas 14 can flow from the top chamber 10 back to the bottom chamber 16 through a one-way check valve 5. The conductive liquid 6 and the electrode 2 are connected via an external circuit, which also includes an energy storage device 11 (such as a load) and a bias power supply 12. When the bias voltage source 12 of the external circuit applies a voltage between the conductive liquid 6 and the electrode 2, the electrode 2, the dielectric layer 3, the hydrophobic layer 4, and the conductive droplet 6 form a parallel plate capacitor. At this time, the contact area between the conductive droplet 6 and the hydrophobic layer 4 is the largest, the capacitance of the parallel plate capacitor is also the largest, and the charge stored in the parallel plate capacitor is the largest.

[0037] Combination Figure 3 The diagram shows a cross-sectional view of the energy harvesting device of Embodiment 1 of the present invention under the influence of mechanical force. Combined with... Figure 2 and Figure 3 When a mechanical force is applied to the bottom chamber 16, gas 14 enters the area containing the conductive liquid 6 through the second pore 13. Gas 14 replaces a portion of the conductive liquid 6, reducing the contact area between the conductive liquid 6 and the hydrophobic layer 4. At this time, the capacitance of the parallel plate capacitor formed by the electrode 2, dielectric layer 3, hydrophobic layer 4, and conductive droplet 6 decreases, reducing the charge that the parallel plate capacitor can store. Charge flows out of the parallel plate capacitor, generating current in the external circuit. This generated current performs work on the energy storage device 11 in the external circuit, producing energy.

[0038] In this embodiment, the lower substrate 1 and the upper substrate 8 are made of a robust, insulating material such as silicon dioxide. The electrode 2 is made of a material with good conductivity, such as aluminum. The dielectric layer 3 is made of a material with a relatively high dielectric constant, such as alumina. The hydrophobic layer 4 is made of Teflon. The conductive droplet 6 is made of a salt solution. The thin film 7 is made of polytetrafluoroethylene hydrophobic film. The energy storage device 11 is a load used to generate and store energy. The bias voltage source 12 is a DC voltage source. The top chamber 10 and the bottom chamber 16 are made of a material with good sealing properties, such as butyl rubber. The gas 14 is air.

[0039] In this embodiment, after the mechanical force is applied to the bottom chamber 16, the gas 14 flows into the area where the conductive liquid 6 is located, and the gas 14 expands and shrinks in the conductive liquid 6 continuously, thereby generating a plurality of bubbles 15. In the process of the rapid expansion of the gas 14 in the conductive liquid 6, the gas 14 changes the contact area between the conductive liquid 6 and the hydrophobic layer 4, resulting in a change in the capacitance of the plate capacitor, thereby forming a current in the external circuit. When a bubble 15 is generated, the conductive liquid 6 refills the area until the next bubble 15 is generated. When the bubble 15 contacts the membrane 7, the gas 14 in the bubble 15 flows into the top chamber through the membrane 7 and the upper substrate aperture 9. After the mechanical force is removed, the gas 14 flows back from the top chamber 10 to the bottom chamber 16 through the one-way check valve 5, and the conductive liquid 6 refills between the upper substrate 8 and the lower substrate 1. When the mechanical force is applied again, the process is repeated, and the mechanical energy is converted into electrical energy, which is collected by the energy storage device 11, achieving the purpose of energy collection.

[0040] In this embodiment, after the mechanical force is applied to the bottom chamber 16, the gas 14 expands and shrinks in the conductive liquid 6 continuously. The energy collection device converts the low-frequency mechanical movement process into a change process of the gas 14 in the conductive liquid 6 inside the device, in which the contact area between the conductive liquid 6 and the hydrophobic layer 4 changes, resulting in a change in the capacitance of the plate capacitor composed of the electrode 2, the dielectric layer 3, the hydrophobic layer 4, and the conductive liquid 6. Through the REWOD, the energy generated in the process is converted into electrical energy, achieving the purpose of effectively collecting the energy generated by the low-frequency mechanical movement. This method can convert mechanical energy into electrical energy using a wide range of mechanical forces.

Claims

1. An energy harvesting device, characterized in that: include, Upper substrate (8); Lower substrate (1); Electrodes (2) arranged on the upper surface of the lower substrate (1); A thin film (7) is attached to the lower surface of the upper substrate (8); A dielectric layer (3) is disposed on the upper surface of the electrode (2); A hydrophobic layer (4) is coated on the upper surface of the dielectric layer (3); Conductive fluid (6) is filled between the thin film (7) and the hydrophobic layer (4); After the lower substrate (1) and the upper substrate (8) are combined, they are placed between two chambers, namely the top chamber (10) and the bottom chamber (16), which are filled with gas (14). A one-way check valve (5) is provided between the top chamber (10) and the bottom chamber (16) to allow gas (14) to flow from the top chamber (10) back to the bottom chamber (16). The upper substrate (8) and the lower substrate (1) are made of silicon dioxide, wherein the upper substrate (8) has a number of first pores (9) from top to bottom. The thin film (7) is a hydrophobic polytetrafluoroethylene film. The thin film (7) is not porous, and the dielectric layer (3) is a solid dielectric layer. The hydrophobic layer (4) is a fluoropolymer, and several second pores (13) are formed from the lower surface of the substrate (1) upward through the electrode (2), dielectric layer (3) and hydrophobic layer (4).

2. The energy harvesting device according to claim 1, characterized in that: The conductive fluid (6) is a conductive liquid that does not wet the film (7) or pass through the film (7).

3. The energy harvesting device according to claim 2, characterized in that: The gas (14) is either air or an inert gas.

4. The energy harvesting device according to claim 3, characterized in that: An electrode (2), a dielectric layer (3), a hydrophobic layer (4), and a conductive fluid (6) form a parallel plate capacitor.

5. The energy harvesting device according to claim 4, characterized in that: It also includes a bias voltage source (12), which is a DC voltage source and is connected to the electrode (2) and the conductive fluid (6) to apply a bias voltage.

6. The energy harvesting device according to claim 5, characterized in that: It also includes an energy storage device (11), which is connected to an electrode (2), a conductive fluid (6) and a bias voltage source (12) to collect electrical energy converted from mechanical energy, thereby achieving the purpose of energy collection.

7. A method for collecting energy using the energy harvesting device as described in any one of claims 1-6, characterized in that, The method is as follows: When external mechanical force squeezes the bottom chamber, gas (14) flows into the conductive fluid (6) region through the second pore (13); gas (14) expands and contracts rapidly in the conductive fluid (6), thereby generating multiple bubbles (15); during the rapid expansion of gas (14) in the conductive fluid (6), gas (14) changes the contact area between the conductive fluid (6) and the hydrophobic layer (4), causing the capacitance of the parallel plate capacitor to change, thereby forming a current in the external circuit; The generated current does work on the load of the external circuit, generating energy, thereby realizing the conversion of mechanical energy into electrical energy; When a bubble (15) is generated, the conductive fluid (6) refills the area until the next bubble (15) is generated; when the bubble (15) comes into contact with the membrane (7), the gas (14) in the bubble (15) flows into the top chamber (10) through the membrane (7) and the first pore (9); after the mechanical force is removed, the gas (14) flows from the top chamber (10) back to the bottom chamber (16) through the one-way check valve (5), and the conductive fluid (6) refills between the hydrophobic layer (4) and the membrane (7).

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