Ionic thermoelectric gel material and preparation method thereof, temperature sensor

Abstract

The application discloses an ionic thermoelectric gel material and a preparation method and a temperature sensor thereof, and belongs to the field of ionic thermoelectric sensing materials. The ionic thermoelectric gel material comprises a gel matrix and an ion pair dispersed in the gel matrix, and the chemical structure of the ion pair is shown as formula I. The application finds that by introducing the ion pair with the chemical structure of formula I into the gel matrix, the specific ion pair is hindered from migration in the gel matrix due to the large volume of the cation, while the anion has a small volume and is easy to diffuse in a temperature field and generate a large thermoelectric sensitivity, so that the response time of the material to temperature is shortened, the resolution of the material to temperature is improved, and the defects of the prior art are made up.

Description

Technical Field

[0001] This application belongs to the field of ionic thermoelectric sensing materials, specifically relating to an ionic thermoelectric gel material and its preparation method, and a temperature sensor. Background Technology

[0002] Temperature sensing is a core issue in the field of temperature measurement. Based on whether an external excitation source is required, temperature sensors can be broadly classified into two categories: active (such as resistance temperature detectors, thermistors) and passive (such as thermocouples). Among them, passive thermocouple sensors are one of the most widely used devices in current contact temperature measurement, possessing advantages such as simple structure, convenient manufacturing, wide temperature range, low thermal inertia, and high accuracy. Traditional thermocouples use metals or alloys as the main material, with electrons as the charge carriers. Typical systems include platinum-rhodium-platinum (S-type), nickel-chromium-nickel-silicon (K-type), and copper-constantan (T-type). These materials have a low Seebeck coefficient (also known as the thermoelectric coefficient), typically <0.1 mV / K, therefore their temperature resolution is only about 0.5 K at most. When the temperature difference to be measured is less than 0.5 K, the output voltage is less than 0.1 mV / K × 0.5 K = 0.05 mV, which is easily drowned out by circuit noise and difficult to effectively identify.

[0003] In recent years, ionic thermoelectric materials, which use ions as charge carriers, have attracted widespread attention. Their Seebeck coefficients can reach the order of 1–10 mV / K, an improvement of about one to two orders of magnitude compared to traditional electronic thermoelectric materials, making them highly promising for detecting minute temperature differences near room temperature. Furthermore, compared to electronic thermoelectric materials, ionic thermoelectric materials also possess advantages such as flexibility and wearability, low raw material cost, low toxicity, and simple fabrication processes. However, because the ion migration rate is much lower than that of electrons (about six orders of magnitude lower), the temperature response time of existing ionic thermoelectric materials is typically on the order of minutes to hours, which is insufficient to meet the demands of rapid sensing. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to provide an ionic thermoelectric gel material, its preparation method, and a temperature sensor.

[0005] The first aspect of this application discloses an ionic thermoelectric gel material. According to embodiments of this application, the ionic thermoelectric gel material comprises: Gel matrix; And, ion pairs dispersed within the gel matrix, the chemical structure of the ion pairs being as shown in Formula I; Equation I: R1 is selected from the first straight-chain alkyl group having 6-18 carbon atoms, R2, R3 and R4 are each independently selected from the second straight-chain alkyl group having 1-5 carbon atoms, Y is selected from phosphorus, and X is selected from halogen.

[0006] The ionic thermoelectric gel material of the above embodiments of this application has been found to shorten the material's response time to temperature and improve the material's temperature resolution, thus overcoming the shortcomings of the prior art.

[0007] In addition, the ionic thermoelectric gel material according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the ion pair includes at least one selected from tributylhexylphosphonium bromide, tributylhexylphosphonium bromide, dodecyltributylphosphonium bromide, and tributyl-n-octylphosphonium bromide.

[0008] In some embodiments of this application, the ion pairs account for 0.5%-20% of the mass percentage of the ionic thermogel material.

[0009] In some embodiments of this application, the gel matrix includes at least one of polyacrylamide-based gel, polyacrylic acid-based gel, polymethacrylic acid-based gel, polyvinyl alcohol-based gel, and polyethylene glycol-based gel.

[0010] A second aspect of this application provides a method for preparing the ionic thermoelectric gel material described in the first aspect. According to embodiments of this application, the method for preparing the ionic thermoelectric gel material includes the following steps: The ion pairs are dispersed in a solvent to obtain the first solution; Add gel matrix precursor raw material to the first solution and stir to dissolve to obtain a second solution; The second solution is solidified to obtain the ionic thermoelectric gel material.

[0011] This application provides a method for preparing an ionic thermoelectric gel material. By introducing ion pairs into a gel matrix precursor solution and then performing a curing process to form a gel, a temperature-measuring ionic thermoelectric gel material with characteristics such as fast response and high resolution can be prepared.

[0012] In addition, the preparation method of the ionic thermoelectric gel material according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the gel matrix precursor raw materials include polymer monomers, crosslinking agents, and initiators.

[0013] In some embodiments of this application, the mass ratio of the polymer monomer, the crosslinking agent and the initiator is (10-200):(0.1-5):(0.1-5).

[0014] In some embodiments of this application, the solvent includes water; And / or, the polymer monomer includes acrylamide; And / or, the crosslinking agent includes N,N'-methylenebisacrylamide; And / or, the initiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

[0015] In some embodiments of this application, the curing process includes the following conditions: the light wavelength is 360nm-370nm.

[0016] A third aspect of this application discloses a temperature sensor. According to an embodiment of this application, the temperature sensor comprises the ionic thermogel material described in the first aspect or an ionic thermogel material prepared using the preparation method described in the second aspect. This significantly improves the response speed and temperature resolution of the temperature sensor.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart illustrating the preparation method of the ionic thermogel material provided in the embodiments of this application. Detailed Implementation

[0019] The embodiments of this application are described in detail below by way of example, and are intended to explain this application, but should not be construed as limiting this application.

[0020] The first aspect of this application discloses an ionic thermoelectric gel material. According to embodiments of this application, the ionic thermoelectric gel material comprises: Gel matrix; And, ion pairs dispersed within the gel matrix, the chemical structure of the ion pairs being as shown in Formula I; Equation I: R1 is selected from a first straight-chain alkyl group having 6-18 carbon atoms, for example, the number of carbon atoms can be 6, 8, 12, 14, 15, 16, 17, 18 or any range between the aforementioned values; R2, R3 and R4 are each independently selected from a second straight-chain alkyl group having 1-5 carbon atoms, for example, the number of carbon atoms can be 1, 2, 3, 4, 5 or any range between the aforementioned values; Y is selected from phosphorus, and X is selected from halogens, for example, fluorine, chlorine, bromine, iodine.

[0021] The ionic thermoelectric gel material of the above embodiments of this application has been found to shorten the material's response time to temperature and improve the material's temperature resolution, thus overcoming the shortcomings of the prior art.

[0022] In addition, the ionic thermoelectric gel material according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the ion pair includes at least one selected from tributylhexylphosphonium bromide, tributylhexylphosphonium bromide, dodecyltributylphosphonium bromide, and tributyl-n-octylphosphonium bromide.

[0023] In some embodiments of this application, the mass percentage of the ion pair in the ionic thermoelectric gel material is 0.5%-20%, for example, it can be 0.5%, 1%, 5%, 10%, 15%, 20% or any range between the aforementioned values.

[0024] In some embodiments of this application, the gel matrix includes at least one of polyacrylamide-based gel, polyacrylic acid-based gel, polymethacrylic acid-based gel, polyvinyl alcohol-based gel, and polyethylene glycol-based gel.

[0025] The second aspect of this application discloses a method for preparing the ionic thermoelectric gel material described in the first aspect. According to embodiments of this application, such as... Figure 1 As shown, the preparation method of the ionic thermoelectric gel material includes the following steps: The ion pairs are dispersed in a solvent to obtain the first solution; Add gel matrix precursor raw material to the first solution and stir to dissolve to obtain a second solution; The second solution is solidified to obtain the ionic thermoelectric gel material.

[0026] This application provides a method for preparing an ionic thermoelectric gel material. By introducing ion pairs into a gel matrix precursor solution and then performing a curing process to form a gel, a temperature-measuring ionic thermoelectric gel material with characteristics such as fast response and high resolution can be prepared.

[0027] In addition, the preparation method of the ionic thermoelectric gel material according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the gel matrix precursor raw materials include polymer monomers, crosslinking agents, and initiators.

[0028] In some embodiments of this application, the mass ratio of the polymer monomer, the crosslinking agent, and the initiator is (10-200):(0.1-5):(0.1-5), for example, it can be 70:1:1, 100:0.1:1, 50:1:0.1, or any of the aforementioned values.

[0029] In some embodiments of this application, the solvent includes water; And / or, the polymer monomer includes acrylamide; And / or, the crosslinking agent includes N,N'-methylenebisacrylamide; And / or, the initiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

[0030] In some embodiments of this application, the curing process parameters include: a light wavelength of 360nm-370nm, such as 360nm, 365nm, 370nm, or any of the aforementioned values. Furthermore, the light power and illumination time are only required to be sufficient to initiate the polymerization reaction; for example, the light power is 10W-120W, such as 10W, 30W, 70W, 110W, 120W, or any of the aforementioned values; and the illumination time is 3min-20min, such as 3min, 10min, 12min, 15min, or any of the aforementioned values.

[0031] As an example, taking polyacrylamide-based gel as an example, the specific steps for preparing a fast-response, high-resolution thermoelectric ionotropic gel material are as follows: (1) Purchase the required raw materials: Tributylhexadecanylphosphonium bromide (ion source, CAS No.: 14937-45-2), Acrylamide (polymer monomer, CAS: 79-06-1), N,N'-methylenebisacrylamide (crosslinking agent, CAS: 110-26-9), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone (photoinitiator, CAS: 106797-53-9), and deionized water.

[0032] (2) Dissolve the ion source in deionized water. The mass ratio of tributylhexylphosphonium bromide to water is 1~20:100, preferably 1:50. Stir the mixture at room temperature for 20 minutes to allow the ions to dissolve completely until a transparent and colorless solution is formed.

[0033] (3) Weigh 0.7g of acrylamide powder, add it to the solution after stirring in (2), and continue stirring for 15 minutes until most or all of it is dissolved.

[0034] (4) Weigh 0.01g of crosslinking agent N,N'-methylenebisacrylamide and put it into the solution after stirring in (3). Continue stirring for 15 minutes until most or all of it is dissolved.

[0035] (5) Weigh 0.01g of the photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and put it into the solution after stirring in (4). Continue stirring for 15 minutes until most or all of it is dissolved.

[0036] (6) Transfer the solution from (5) into a silicone mold and place it in a UV light box for curing. In this example, an 80W, 365nm UV light box was used, and the material was cured into a gel after ten minutes. Thus, the preparation of the fast-response, high-resolution thermoelectric ionotropic gel material is complete.

[0037] A third aspect of this application discloses a temperature sensor. According to an embodiment of this application, the temperature sensor comprises the ionic thermogel material described in the first aspect or an ionic thermogel material prepared using the preparation method described in the second aspect. This significantly improves the response speed and temperature resolution of the temperature sensor.

[0038] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0039] Example 1 This embodiment provides an ionic thermoelectric gel material, comprising: a gel matrix, wherein the gel matrix is ​​a polyacrylamide-based gel; and an ion pair dispersed in the gel matrix, wherein the ion pair is tributylhexadecanylphosphonium bromide; the ion pair accounts for 1.72% of the mass percentage of the ionic thermoelectric gel material by mass percentage.

[0040] The preparation method of the above-mentioned ionic thermogel material includes the following steps: Step (1): Dissolve the ion source in deionized water. The mass ratio of tributylhexylphosphonium bromide to water is 1:50 (specifically, 0.1g of tributylhexylphosphonium bromide to 5g of water). Stir at room temperature for 20 minutes to obtain the first solution.

[0041] Step (2): Weigh 0.7g of acrylamide powder, a polymer monomer, and add it to the first solution after stirring in step (1). Continue stirring for 15 minutes. Then weigh 0.01g of N,N'-methylenebisacrylamide, a crosslinking agent, and add it to the solution system. Continue stirring for 15 minutes. Then weigh 0.01g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone, a photoinitiator, and add it to the solution system. Continue stirring for 15 minutes to obtain the second solution.

[0042] Step (3): Transfer the second solution obtained in step (2) into a silicone mold and place it in an ultraviolet light box for photocuring. The light wavelength is 365nm, the light power is 80W, and the light time is 10min to obtain the ionic thermoelectric gel material.

[0043] Example 2 This embodiment provides an ionic thermoelectric gel material and its preparation method, which differs from Example 1 only in that: (1) The mass percentage of the ion pair in the ionic thermoelectric gel material is adjusted to 8.04% by mass.

[0044] Example 3 This embodiment provides an ionic thermoelectric gel material and its preparation method, which differs from Example 1 only in that: (1) The ion pair was adjusted to tributylhexylphosphonium bromide.

[0045] Comparative Example 1 This comparative example provides an ionic thermoelectric gel material and its preparation method, which differs from Example 1 only in that: (1) The ion pair was adjusted to sodium chloride (NaCl).

[0046] Comparative Example 2 This comparative example provides an ionic thermoelectric gel material and its preparation method, which differs from Example 1 only in that: (1) The ion pair was adjusted to 1-allyl-3-methylimidazolium dicyandiamide salt (CAS No.: 917956-73-1).

[0047] Comparative Example 3 This comparative example provides a conventional electronic thermocouple - the K-type thermocouple.

[0048] Test case This test case examines the temperature response time and resolution of the ionic thermogel materials obtained in the above embodiments and comparative examples.

[0049] The testing method is as follows: (1) Temperature response time test: The test was conducted using a self-built dynamic temperature response testing platform. The ionic thermoelectric gel material to be tested was cut into samples measuring 10mm × 10mm × 5mm. Both sides of the sample were placed in contact with nickel foam electrodes coated with capacitive carbon. The entire sample was then sealed in a plastic bag, exposing the electrodes to form the test device. The device was placed on the surface of a temperature control platform and electrically connected to a data acquisition system (Keithley 2002, Keithley Instruments, USA) via wires. The temperature of the programmable heat source was increased stepwise from 25℃ to 26℃, while the thermoelectric voltage signal output by the thermoelectric gel material was recorded. The time required for the thermoelectric voltage signal to rise from 10% to 90% of its steady-state value was defined as the temperature response time. Each sample was tested three times, and the average value was taken.

[0050] (2) Temperature resolution test: The above-mentioned test device is placed in a constant temperature bath, and the constant temperature bath is controlled to achieve a temperature step change of 0.001K / time (each time held for 10s). The voltage signal is read. If the temperature change cannot be effectively distinguished each time, the temperature change amplitude is increased (e.g., increased to 0.005K / time) until the temperature step change can be distinguished by the collected voltage signal.

[0051] The test results are shown in Table 1.

[0052] Table 1

[0053] As shown in Table 1: As can be seen from the test results in Table 1, the ionic thermoelectric gel materials provided in Examples 1-3 of this application are significantly better than the comparative examples in terms of both temperature response time and temperature resolution, which are two key performance indicators.

[0054] First, regarding temperature response time, the temperature response times of Examples 1-3 are 1.2 seconds, 1.3 seconds, and 1.5 seconds, respectively, all within 1.5 seconds. In contrast, Comparative Example 1, using sodium chloride as the ion pair, has a temperature response time as long as 212 seconds, significantly longer than the examples in this application; Comparative Example 2, using 1-allyl-3-methylimidazolium dicyandiamide salt ionic liquid as the ion pair, has a temperature response time as long as 387 seconds; while the temperature response time of a traditional K-type thermocouple is 2.5 seconds. These results indicate that the specific ion pair selected in this application synergistically interacts with the polyacrylamide gel matrix, enabling the material to respond rapidly to temperature changes, with a response speed significantly superior to traditional inorganic salts, ionic liquids, and commercial thermocouples.

[0055] Secondly, regarding temperature resolution, the temperature resolutions of Examples 1-3 are 0.005K, 0.005K, and 0.01K, respectively, all reaching the 0.01K level or even higher (0.005K). In contrast, Comparative Example 1 has a temperature resolution of 1.23K, Comparative Example 2 has a temperature resolution of 0.89K, and the K-type thermocouple has a temperature resolution of 0.523K. Therefore, the temperature resolution of the embodiments of this application is more than two orders of magnitude higher than Comparative Example 1, and more than one order of magnitude higher than Comparative Example 2 and the K-type thermocouple. This fully demonstrates that the ionic thermogel material provided in this application can accurately distinguish extremely small temperature changes and has extremely high temperature detection sensitivity.

[0056] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0057] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. An ionic thermoelectric gel material, characterized in that, include: Gel matrix; And, ion pairs dispersed within the gel matrix, the chemical structure of the ion pairs being as shown in Formula I; Equation I: R1 is selected from the first straight-chain alkyl group having 6-18 carbon atoms, R2, R3 and R4 are each independently selected from the second straight-chain alkyl group having 1-5 carbon atoms, Y is selected from phosphorus, and X is selected from halogen.

2. The ionic thermoelectric gel material according to claim 1, characterized in that, The ion pair includes at least one selected from tributylhexylphosphonium bromide, tributylhexylphosphonium bromide, dodecyltributylphosphonium bromide, and tributyl-n-octylphosphonium bromide.

3. The ionic thermoelectric gel material according to claim 1, characterized in that, The ion pairs account for 0.5%-20% of the mass percentage of the ionic thermoelectric gel material.

4. The ionic thermoelectric gel material according to any one of claims 1-3, characterized in that, The gel matrix includes at least one of polyacrylamide-based gel, polyacrylic acid-based gel, polymethacrylic acid-based gel, polyvinyl alcohol-based gel, and polyethylene glycol-based gel.

5. A method for preparing the ionic thermoelectric gel material according to any one of claims 1-4, characterized in that, Its characteristic is that it includes the following steps: The ion pairs are dispersed in a solvent to obtain the first solution; Add gel matrix precursor raw material to the first solution and stir to dissolve to obtain a second solution; The second solution is solidified to obtain the ionic thermoelectric gel material.

6. The method for preparing the ionic thermoelectric gel material according to claim 5, characterized in that, The precursor materials for gel matrix include polymer monomers, crosslinking agents, and initiators.

7. The method for preparing the ionic thermoelectric gel material according to claim 6, characterized in that, The mass ratio of the polymer monomer, the crosslinking agent and the initiator is (10-200):(0.1-5):(0.1-5).

8. The method for preparing the ionic thermoelectric gel material according to claim 7, characterized in that, The solvent includes water; And / or, the polymer monomer includes acrylamide; And / or, the crosslinking agent includes N,N'-methylenebisacrylamide; And / or, the initiator includes 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone.

9. The method for preparing the ionic thermoelectric gel material according to claim 8, characterized in that, The curing process conditions include: light wavelength of 360nm-370nm.

10. A temperature sensor, characterized in that, This includes the ionic thermoelectric gel material according to any one of claims 1-4 or the ionic thermoelectric gel material prepared by the preparation method of the ionic thermoelectric gel material according to any one of claims 5-9.

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