Method for eliminating water supercooling using non-uniform electric field

Abstract

The present application relates to various fields, including the preservation of biological samples in the biomedical field, the heat storage system based on phase change materials in the field of energy storage, and particularly relates to a method for eliminating water supercooling by using a non-uniform electric field, a controllable non-uniform electric field is constructed by a micro-nano array structure electrode, and the non-supercooled freezing of water is realized. Compared with the uniform electric field and other external field control methods, the method of the present application can adjust the supercooling degree in a wider temperature range, the minimum supercooling degree provided by the method is only 0.3 DEG C, and the supercooling is basically completely eliminated. The method of the present application does not need to add an external source to the supercooled water, and can effectively avoid the pollution of water; the method of the present application adopts a micro-nano structure electrode array, which is beneficial to the formation of a micrometer-thick thin dielectric layer by capillary infiltration of a dielectric layer precursor liquid, which makes it possible to form a larger electric field strength gradient under a smaller voltage to promote the occurrence of the ice formation phenomenon; and can be applied to many industrial occasions.

Description

Technical Field

[0001] This invention relates to multiple fields, including the preservation of biological samples in the biomedical field and the thermal storage system based on phase change materials in the energy storage field, specifically to a method for eliminating water supercooling using a non-uniform electric field. Background Technology

[0002] Water that remains liquid below its freezing point is called supercooled water. Supercooled water is in a metastable state and is highly susceptible to external disturbances, such as foreign substances, vibrations, or temperature fluctuations, leading to sudden ice nucleus formation. During the cryopreservation of biological samples such as cells, tissues, and organs, the uncontrollable formation of ice nuclei in supercooled water can cause structural damage and physiological abnormalities, significantly reducing preservation efficiency. In solid-liquid phase change-based thermal storage processes, such as ice storage technology, the supercooling and instability of the liquid can lead to instability in the energy storage and release processes, reducing the operating efficiency of the energy storage system. Eliminating supercooling has become a significant challenge in these applications.

[0003] Currently, the most widely used method for controlling supercooling in industrial settings is to add nucleating agents, such as silver iodide particles, to supercooled water. However, this method inevitably causes liquid contamination. For example, in the preservation of biological samples, exogenous substances often lack biocompatibility and may cause irreversible damage to the samples. Similarly, in ice storage, added particulate matter can cause blockages in delivery pipelines or corrosion of storage containers. Traditional mechanical methods, such as ultrasonic technology, decompression technology, and vacuum-induced icing technology, are energy-intensive and difficult to scale up in practical applications. Recently, some researchers have used external electric fields to reduce water supercooling. This type of technology does not contaminate supercooled water, consumes less energy, and is simple to operate, making it a highly promising method for controlling water supercooling. However, past research has mostly used flat electrode plates to construct a uniform electrostatic field, which has limited control over water supercooling and cannot completely eliminate it. Summary of the Invention

[0004] The purpose of this invention is to provide a method for eliminating water supercooling using a non-uniform electric field. By constructing a controllable non-uniform electric field through a micro-nano array structure electrode, water of any volume can be frozen without supercooling.

[0005] The solution adopted by the present invention to achieve the objective is: a method for eliminating water supercooling by using a non-uniform electric field, which constructs a controllable non-uniform electric field through a micro-nano array structure electrode to achieve water freezing without supercooling.

[0006] Preferably, it includes the following steps:

[0007] (1) Fabrication of micro / nano array electrodes;

[0008] (2) Connect the power supply to the ordinary electrode and the micro-nano array electrode respectively, wherein the micro-nano array and the ordinary electrode are insulated by a dielectric layer.

[0009] (3) By contacting ordinary electrodes or micro-nano array electrodes with supercooled water and applying a non-uniform electric field, water can be treated without supercooling and freezing.

[0010] Preferably, in step (1), the micro-nano array electrode includes any one of carbon nanotube array, metal microrib array, metal nanowire array, or similar array porous structure; the similar array porous structure includes any one of nanoporous metal, porous graphite, or porous foam metal.

[0011] Preferably, in step (1), when the micro / nano array electrode is a carbon nanotube array, the preparation method is as follows: an adhesion layer and a catalyst layer are sequentially deposited on a Si substrate; secondly, a multi-walled carbon nanotube array is grown on the surface of the catalyst layer using a hydrocarbon as a carbon source and a chemical vapor deposition method is employed; finally, the substrate is inverted and the carbon nanotube array is imprinted onto the surface of the conductive strip and adhered to form the micro / nano array electrode; the hydrocarbon is at least one of ethylene, methane, and acetylene.

[0012] The temperature range for vapor phase chemical deposition is 600-1200℃.

[0013] Preferably, in step (1), the array unit feature size a of the micro-nano array electrode is 0 to 100 micrometers, the unit spacing L>a, and the thickness h>5a.

[0014] Preferably, in step (2), the dielectric layer is made of an insulating material, specifically any one of polydimethylsiloxane, resin, rubber, polyethylene, and polytetrafluoroethylene, and the thickness d of the dielectric layer is 0 < d ≤ 100 micrometers.

[0015] Preferably, when the dielectric layer is polydimethylsiloxane, one method for preparing the dielectric layer is to coat polydimethylsiloxane gel droplets onto the array surface of the micro / nano array electrodes, and then solidify them to form the dielectric layer.

[0016] Preferably, in step (3), the applied electric field strength is greater than 10. 5 V / m, which is less than the breakdown field strength of the dielectric layer.

[0017] The applied electric field strength can be estimated by dividing the applied voltage by the dielectric layer thickness d, and should generally be greater than 10. 5 V / m, which is less than the breakdown field strength of the dielectric layer, such as 2.5 × 10 for PDMS. 8 V / m.

[0018] Preferably, in step (3), the ordinary electrode is brought into contact with supercooled water, and the dielectric layer is located between the supercooled water and the micro / nano array electrode.

[0019] Preferably, in step (3), the micro-nano array electrode is brought into contact with supercooled water, and the dielectric layer is located between the ordinary electrode and the supercooled water.

[0020] The present invention has the following advantages and beneficial effects:

[0021] 1) Compared with uniform electric fields and other external field control methods, the method of the present invention uses a non-uniform electric field to adjust the degree of supercooling over a wider temperature range. The method provided by the present invention has a minimum degree of supercooling of only 0.3℃, which basically completely eliminates supercooling.

[0022] 2) The method of the present invention uses a non-uniform electric field to regulate supercooling, which does not require the addition of external substances to the supercooled water and can effectively avoid water contamination.

[0023] 3) The method of the present invention uses a micro-nano structure electrode array, which is beneficial to the formation of a thin dielectric layer with a micron thickness by utilizing the capillary wetting of the dielectric layer precursor solution. This allows a large electric field intensity gradient to be formed under a small voltage, which promotes the occurrence of icing.

[0024] 4) Because the electrode surface is covered by a dielectric insulating layer, there is no current during the voltage application process, and the voltage is low, making it relatively safe and widely applicable in many industrial settings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the non-uniform electric field control of subcooled water according to the present invention;

[0026] Figure 2 This is a partial schematic diagram of the array electrodes;

[0027] Figure 3 Flowchart of carbon nanotube array electrodes and PDMS dielectric layer fabrication process;

[0028] Figure 4 Scanning electron microscope (SEM) images of carbon nanotube array (a) and PDMS dielectric layer-coated array (b), with a scale bar of 5 micrometers.

[0029] Figure 5 A comparison of the freezing temperature under planar electrodes and micro / nano electrodes as a function of electric field strength;

[0030] Figure 6 These are schematic diagrams illustrating different embodiments of the present invention. Detailed Implementation

[0031] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0032] In this invention, the supercooled water is placed above the dielectric material, separated from the lower electrode, while the upper electrode is in direct contact with the supercooled water, such as... Figure 1 As shown. Traditional electrowetting or icing devices use flat plate electrodes. This invention proposes to construct a non-uniform electric field using micro / nano structured electrodes. In this embodiment, aluminum wire is used as the electrode on the upper side, the dielectric layer is made of composite polydimethylsiloxane (PDMS) material, and a carbon nanotube array is used as the electrode on the lower side, as shown. Figure 2 The image shows a partial schematic diagram of the array electrodes.

[0033] Example 1

[0034] A method for eliminating water supercooling using a non-uniform electric field is proposed. This method constructs a controllable non-uniform electric field through a micro / nano array of electrodes, achieving water freezing without supercooling. The steps include:

[0035] (1) Fabrication of micro / nano array electrodes;

[0036] (2) Connect the power supply to the ordinary electrode and the micro-nano array electrode respectively, wherein the micro-nano array and the ordinary electrode are insulated by a dielectric layer.

[0037] (3) By bringing ordinary electrodes into contact with supercooled water and applying a non-uniform electric field, water can be treated without supercooling and freezing.

[0038] The micro / nano array electrode used is a carbon nanotube electrode, and its fabrication process is as follows: First, a 10 nm thick Al₂O₃ layer and a 2 nm thick Fe layer are deposited on a Si substrate using electron beam evaporation; second, a multi-walled carbon nanotube array is grown in a tube furnace at 770 °C using ethylene as the carbon source. The surface morphology of the carbon nanotube array is as follows. Figure 4 As shown in figure a; finally, the carbon nanotube array is inverted and imprinted onto an aluminum tape to form an aluminum-based micro / nano electrode array, as shown in figure a. Figure 3 As shown.

[0039] The dielectric layer used is PDMS dielectric material, and its preparation method is as follows: PDMS gel droplets are spin-coated onto a carbon nanotube array and cured at 70℃ for 24 hours. Its surface morphology is as follows. Figure 4As shown in b, the PDMS gel was prepared by hydrosilylation of vinyl-terminated PDMS (v-PDMS, molecular weight 95 kg / mol) and hydrogen-terminated PDMS (h-PDMS, molecular weight 1.3 kg / mol), with ordinary t-PDMS added as a viscosity modifier. Specifically, v-PDMS, h-PDMS, and t-PDMS were ultrasonically mixed at a mass ratio of 10:1:11 for 10 minutes (or mechanically stirred for 30 minutes), and then the mixture was degassed in a vacuum oven for at least 30 minutes. The thickness d of the dielectric layer could be adjusted by changing the spin-coating time, speed, and t-PDMS content.

[0040] In this embodiment, when the spin coating speed is 2000 rpm, the running time is 1 minute, and the t-PDMS mass fraction is 50%, the resulting PDMS dielectric layer thickness is 1.5 micrometers. Using this dielectric layer as an example, the role of a non-uniform electric field in controlling supercooling is illustrated. The specific verification method is as follows: different voltages are applied between the aluminum wire and carbon nanotube electrodes, and the freezing temperature of water is measured during a slow cooling process. Figure 5 The freezing temperatures of water were compared under uniform (PDMS spin-coated directly onto aluminum tape electrodes) and non-uniform electric fields. It can be seen that the freezing temperature of water increases with increasing electric field strength (E=U / d) in both cases. Under a uniform electric field, the freezing temperature gradually reaches saturation at -4.9℃ and then stops increasing. However, a non-uniform electric field does not have this limitation, allowing for adjustment of supercooling over a wider range, up to 3×10⁻⁶. 7 Under an electric field strength of V / m (applied voltage of 45V), the freezing temperature reaches -0.3℃, which basically eliminates supercooling.

[0041] Example 2

[0042] The difference between this embodiment and Embodiment 1 is that the supercooled water is in the form of droplets, not a macroscopic water body, such as... Figure 6 As shown in a.

[0043] Example 3

[0044] The difference between this embodiment and Embodiment 1 is that the ordinary electrode is a common flat plate electrode, such as... Figure 6 As shown in b.

[0045] Example 4

[0046] The difference between this embodiment and Embodiment 1 is that: the ordinary electrode is a standard flat electrode, and the supercooled water is in contact with the micro / nano array electrode, with the dielectric layer located between the ordinary electrode and the supercooled water, such as... Figure 6 As shown in c.

[0047] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for eliminating water supercooling using a non-uniform electric field, characterized in that: A controllable, non-uniform electric field is constructed using micro / nano array electrodes to achieve water freezing without supercooling; this includes the following steps: (1) Fabrication of micro / nano array electrodes; (2) Connect the power supply to the ordinary electrode and the micro / nano array electrode respectively, wherein the micro / nano array and the ordinary electrode are insulated by a dielectric layer; (3) By contacting ordinary electrodes or micro-nano array electrodes with supercooled water and applying a non-uniform electric field, water can be frozen without supercooling.

2. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (1), the micro-nano array electrode includes any one of carbon nanotube array, metal microrib array, metal nanowire array, or similar array porous structure; the similar array porous structure includes any one of nanoporous metal, porous graphite, or porous foam metal.

3. The method for eliminating water supercooling using a non-uniform electric field according to claim 2, characterized in that: In step (1), when the micro-nano array electrode is a carbon nanotube array, the preparation method is as follows: an adhesion layer and a catalyst layer are deposited sequentially on a Si substrate; secondly, a multi-walled carbon nanotube array is grown on the surface of the catalyst layer using a chemical vapor deposition method with hydrocarbons as the carbon source; finally, the carbon nanotube array is inverted and imprinted onto the surface of the conductive strip and adhered to form the micro-nano array electrode. The hydrocarbon is at least one of ethylene, methane, and acetylene.

4. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (1), the array unit feature size of the micro / nano array electrode a The range is 0 to 100 micrometers, with a cell spacing of [missing information]. L > a ,thickness h >5 a .

5. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (2), the dielectric layer is made of an insulating material, specifically any one of polydimethylsiloxane, resin, rubber, polyethylene, or polytetrafluoroethylene, and the thickness of the dielectric layer is... d The value is 0 < d ≤ 100 micrometers.

6. The method for eliminating water supercooling using a non-uniform electric field according to claim 5, characterized in that: When the dielectric layer is polydimethylsiloxane, one method for preparing the dielectric layer is to coat polydimethylsiloxane gel droplets onto the array surface of the micro / nano array electrodes, and then solidify them to form the dielectric layer.

7. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (3), the applied electric field strength is greater than 10. 5 V / m, which is less than the breakdown field strength of the dielectric layer.

8. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (3), the ordinary electrode is brought into contact with supercooled water, and the dielectric layer is located between the supercooled water and the micro / nano array electrode.

9. The method for eliminating water supercooling using a non-uniform electric field according to claim 1, characterized in that: In step (3), the micro-nano array electrode is brought into contact with supercooled water, and the dielectric layer is located between the ordinary electrode and the supercooled water.

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