Temperature sensor based on solvent-free nanofluid and preparation method thereof

Abstract

This invention relates to a temperature sensor based on solvent-free nanofluids and its fabrication method. The invention employs a blade coating method to fabricate a temperature sensor. Due to the characteristic that the binding energy of solvent-free nanofluids changes with temperature, as the temperature rises, the solvent-free nanofluids accumulate from the interior of the polymer matrix to the surface. By increasing the content of solvent-free nanofluids on the polymer surface, the polymer conductivity is enhanced, thereby enabling real-time monitoring of temperature changes. This invention provides a new method for applying solvent-free nanofluids as temperature sensors.

Description

Technical Field

[0001] This invention relates to the field of flexible wearable electronic device technology, specifically to a temperature sensor based on solvent-free nanofluids and its fabrication method. Background Technology

[0002] Body temperature is one of the most important physiological parameters of the human body, serving as a reference value for monitoring health-related issues. Therefore, accurate and precise measurement of body temperature is crucial. Temperature sensors can detect various body and environmental temperatures. Traditional temperature sensors are typically made of metals such as gold, silver, aluminum, and copper, or rigid materials such as semiconductors, making them heavy and difficult to use in a portable manner. Several commonly used types of temperature sensors, including thermocouples, resistance temperature detectors (RTDs), and thermally responsive field-effect transistors (TEFETs), usually require complex electronic circuitry to ensure accurate detection, further hindering their convenient use.

[0003] This invention is based on the characteristic that the binding energy of solvent-free nanofluids changes upon heating; as temperature increases, the solvent-free nanofluid accumulates from the interior of the polymer matrix to the surface. By increasing the content of solvent-free nanofluid on the polymer surface, the polymer conductivity is enhanced, thereby enabling real-time monitoring of temperature changes. This invention provides a new method for the application of temperature sensors based on solvent-free nanofluids. Summary of the Invention

[0004] To address the above problems, the purpose of this invention is to provide a temperature sensor based on solvent-free nanofluids and its preparation method.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:

[0006] The fabrication method of a temperature sensor based on solvent-free nanofluids specifically includes the following steps:

[0007] Step 1: Prepare a polymethyl methacrylate solution and then prepare solvent-free nanofluids by ion exchange method;

[0008] Step 2: Add 10-50 wt% of solvent-free nanofluid to the polymethyl methacrylate solution to obtain a mixed solution;

[0009] Step 3: Coat the mixed solution onto a glass slide, pre-dry and set it to obtain a solvent-free nanofluid / polymer matrix solution film;

[0010] Step 4: Place the solvent-free nanofluid / polymer matrix solution film into an oven and dry it thoroughly to obtain a temperature sensor based on solvent-free nanofluid.

[0011] Furthermore, in step 1, the solvent-free nanofluid is obtained by sequentially grafting DC5700 and NPES onto nanoparticles.

[0012] Furthermore, the nanoparticles include any one of SiO2, TiO2, and CNC nanoparticles.

[0013] Furthermore, in step 1, the mass fraction of polymethyl methacrylate in the polymethyl methacrylate solution is 10-30%, and the dissolution temperature when preparing the polymethyl methacrylate solution is 60-70℃.

[0014] Furthermore, in step 3, the pre-drying temperature is 65°C and the pre-drying time is 120–150 minutes.

[0015] Furthermore, in step 4, an oven is used for drying at a temperature of 80°C for a duration of not less than 12 hours, resulting in a temperature sensor based on solvent-free nanofluid with a thickness of 1 mm.

[0016] The temperature sensor based on solvent-free nanofluids was prepared by the above method.

[0017] The beneficial effects of this invention are as follows: This invention utilizes a blade coating method to form a uniform and dense film of solvent-free nanofluid and polymer matrix. Because the binding energy of the organic long chains of the solvent-free nanofluid decreases upon heating, it drives the flow of the solvent-free nanofluid. The solvent-free nanofluid is uniformly distributed within the polymer, with no fluid residue on the surface. Heating causes the solvent-free nanofluid to accumulate from the interior of the polymer matrix to the surface, enhancing the polymer's conductivity and enabling real-time monitoring of temperature changes. Existing nanofluids are typically multiphase systems prepared using organic solvents. However, the solvent significantly affects conductivity and has poor temperature responsiveness, making it difficult to quickly and accurately detect temperature changes. By using the method of thermally accumulating solvent-free nanofluid on the polymer surface, a highly sensitive temperature sensor can be formed on the polymer surface, achieving rapid response and accurate measurement of temperature changes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the present invention;

[0019] Figure 2 This is a schematic diagram illustrating the mechanism of the present invention;

[0020] Figure 3 Optical microscope images of polymethyl methacrylate / SiO2 nanofluid films with different SiO2 nanofluid contents in Example 1 before and after heating.

[0021] Figure 4 The binding energy required for SiO2 nanofluid diffusion at different temperatures in Example 1;

[0022] Figure 5 The displacement of SiO2 nanofluid diffusion at different temperatures in Example 1;

[0023] Figure 6 The conductivity of the temperature sensor with different SiO2 nanofluid contents at different temperatures in Example 1;

[0024] Figure 7 This is a displacement distance diagram of different types of solvent-free nanofluids in the polymer matrix at different temperatures in Example 2;

[0025] Figure 8 The conductivity diagrams for temperature sensors of different matrices for SiO2 solvent-free nanofluids at different temperatures are shown in Examples 3 and 4. Detailed Implementation

[0026] The principles and features of the present invention are described below with reference to specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0027] like Figure 1 As shown, the method for fabricating temperature sensors using nanofluids with different concentrations includes the following steps:

[0028] Step 1: Dissolve the polymer matrix with N,N-dimethylformamide and heat and stir until dissolved;

[0029] Step 2: Prepare solvent-free nanofluids by ion exchange method;

[0030] Step 3: Add a certain amount of solvent-free nanofluid to the polymer matrix solution from the previous step;

[0031] Step 4: Coat the polymer matrix solution containing solvent-free nanofluid onto a glass slide and pre-dry for a period of time to set the film.

[0032] Step 5: Place the solvent-free nanofluid / polymer matrix solution film into an oven until the solvent inside the film is completely dried.

[0033] Specifically, the polymer matrix in the dispersion of step 1 can be polymethyl methacrylate, polyethylene terephthalate, or polyimide, with a mass fraction of 30% and a dissolution temperature of around 70°C.

[0034] Specifically, in step 3, the solvent-free nanofluid can be a type of solvent-free nanofluid with nanoparticles as the core, such as SiO2 nanofluid, Al2O3 nanofluid, or Fe3O4 nanofluid, and the content of the solvent-free nanofluid is between 10% and 50%.

[0035] Specifically, in step 4, the size of the glass slide is not limited. The pre-drying temperature is 65°C, and the pre-drying time is 120–150 minutes.

[0036] Specifically, in step 5, the solvent is thoroughly dried in an oven at a temperature of 80°C for a duration of not less than 12 hours, resulting in a film with a thickness of 1 mm.

[0037] A temperature sensor based on solvent-free nanofluids was prepared by the above method.

[0038] Example 1:

[0039] The fabrication method of a temperature sensor based on solvent-free nanofluids specifically includes the following steps:

[0040] Step 1: Dissolve 30% methyl methacrylate in N,N-dimethylformamide and heat at 70°C while stirring until dissolved;

[0041] Step 2: Prepare solvent-free nanofluids by ion exchange method;

[0042] Step 3: Add a certain amount of SiO2 nanofluid to the polymer matrix solution from the previous step; wherein the content of SiO2 nanofluid is 10%, 20%, 30%, 40%, or 50%.

[0043] Step 4: Coat the polymer matrix solution containing solvent-free nanofluid onto a glass slide and pre-dry for a period of time to set the film.

[0044] Step 5: Place the SiO2 nanofluid / polymethyl methacrylate matrix solution film into an oven until the solvent inside the film is completely dried, so that the film thickness is 1 mm.

[0045] Example 2:

[0046] The method for fabricating temperature sensors using different types of nanofluids specifically includes the following steps:

[0047] Step 1: Dissolve 30% methyl methacrylate in N,N-dimethylformamide and heat at 70°C while stirring until dissolved;

[0048] Step 2: Prepare solvent-free nanofluids by ion exchange method;

[0049] Step 3: Add a certain amount of solvent-free nanofluid to the polymer matrix solution from the previous step; wherein the types of solvent-free nanofluid are SiO2 nanofluid, Al2O3 nanofluid, and Fe3O4 nanofluid, and the content of solvent-free nanofluid is 50%.

[0050] Step 4: Coat the polymer matrix solution containing solvent-free nanofluid onto a glass slide and pre-dry for a period of time to set the film.

[0051] Step 5: Place the solvent-free nanofluid / polymethyl methacrylate matrix solution film into an oven until the solvent inside the film is completely dried, and the thickness of the film is 1 mm.

[0052] Example 3:

[0053] The method for fabricating a flexible temperature sensor based on polyethylene terephthalate using SiO2 nanofluids specifically includes the following steps:

[0054] Step 1: Dissolve 30% polyethylene terephthalate in N,N-dimethylformamide and heat at 70°C while stirring until dissolved;

[0055] Step 2: Prepare solvent-free nanofluids by ion exchange method;

[0056] Step 3: Add a certain amount of SiO2 nanofluid to the polymer matrix solution from the previous step; wherein the content of SiO2 nanofluid is 50%;

[0057] Step 4: Coat the polymer matrix solution containing solvent-free nanofluid onto a glass slide and pre-dry for a period of time to set the film.

[0058] Step 5: Place the SiO2 nanofluid / polyethylene terephthalate matrix solution film into an oven until the solvent inside the film is completely dried, so that the film thickness is 1 mm.

[0059] Example 4:

[0060] The method for fabricating a flexible wearable temperature sensor based on polyimide using SiO2 nanofluids specifically includes the following steps:

[0061] Step 1: Dissolve 30% polyimide by N,N-dimethylformamide and heat at 70°C while stirring until dissolved;

[0062] Step 2: Prepare solvent-free nanofluids by ion exchange method;

[0063] Step 3: Add a certain amount of SiO2 nanofluid to the polymer matrix solution from the previous step; wherein the content of SiO2 nanofluid is 50%;

[0064] Step 4: Coat the polymer matrix solution containing solvent-free nanofluid onto a glass slide and pre-dry for a period of time to set the film.

[0065] Step 5: Place the SiO2 nanofluid / polyimide matrix solution film into an oven until the solvent inside the film is completely dried, and the thickness of the film is 1 mm.

[0066] like Figure 1As shown, polymethyl methacrylate was dissolved in N,N-dimethylformamide, and a solvent-free nanofluid prepared by ion exchange was added to the solution. The solvent-free nanofluid / polymer matrix solution was mixed evenly by mechanical stirring, coated by a blade coating method, pre-dried and shaped into a film, and then placed in an oven for a period of time to completely dry the solvent, obtaining the finished product.

[0067] like Figure 2 As shown, based on the change in the thermal binding energy of solvent-free nanofluids, the Brownian motion of the nanofluids is accelerated, causing the solvent-free nanofluids to accumulate from the interior of the polymer matrix to the surface of the polymer matrix. The displacement of the solvent-free nanofluids was monitored every 200 picoseconds at temperatures of 298, 313, and 333 Kelvin, respectively, to determine the content of solvent-free nanofluids on the polymer surface, and thus to monitor temperature changes in real time.

[0068] like Figure 3 As shown, with increasing temperature, SiO2 nanofluid diffuses more on polymethyl methacrylate (PMMA), resulting in a smoother surface. The porosity of pure PMMA is approximately 30%, the porosity of 10% SiO2 nanofluid / PMMA is approximately 15%, and the PMMA matrix of 50% SiO2 nanofluid has almost no porosity.

[0069] like Figure 4 As shown, the binding energy required for SiO2 nanofluid diffusion increases with increasing temperature. The binding energy at 298 Kelvin is -15.6 kcal / mol, at 313 Kelvin it is -15.2 kcal / mol, and at 333 Kelvin it is -14.6 kcal / mol.

[0070] like Figure 5 As shown, the displacement of SiO2 nanofluid diffusion increases with increasing temperature; the displacement at 298 Kelvin is 9 Å. 2 The displacement at 313 Kelvin is 11.5 Å. 2 The displacement at Kelvin temperature is 12.5A. 2 .

[0071] like Figure 6 As shown, the conductivity of the temperature sensor increases with increasing temperature. At the same temperature, the temperature sensor prepared with 50% SiO2 nanofluid has the highest conductivity. The conductivity of pure polymethyl methacrylate remains unchanged at 20, 40, and 60 °C, all being 7 × 10⁻⁶. -4 The electrical conductivity of 10% SiO2 nanofluid / polymethyl methacrylate matrix at 20, 40, and 60 °C is 9 × 10⁻⁶. -4 1×10 -3 1.3×10 -3The electrical conductivity of 50% SiO2 nanofluid / polymethyl methacrylate matrix at 20, 40, and 60 °C is 1×10⁻⁶. -3 1.4×10 -3 2×10 -3 .

[0072] like Figure 7 As shown, at the same temperature, the SiO2 solvent-free nanofluid exhibits the highest displacement distance in the polymer matrix. With increasing temperature, the displacement distance of various types of solvent-free nanofluids in the polymer matrix increases. The displacements of the SiO2 solvent-free nanofluid at 20, 40, and 60℃ are 5 Å, respectively. 2 10A 2 14A 2 The displacements of the solvent-free Al2O3 nanofluid at 20, 40, and 60 °C were 3 Å, respectively. 2 4A 2 8A 2 The displacement of the solvent-free Fe3O4 nanofluid at 20, 40, and 60 °C was 2.8 Å, respectively. 2 6A 2 8.5A 2 .

[0073] like Figure 8 As shown, the conductivity of the temperature sensor increases with increasing temperature. At the same temperature, the polymethyl methacrylate (PMMA) matrix temperature sensor exhibits the highest conductivity, while the conductivity of the polyimide matrix remains unchanged at 20, 40, and 60°C, all at 1×10⁻⁶. -3 Siemens / meter, the electrical conductivity of the polyethylene terephthalate matrix at 20, 40, and 60°C is 1×10⁻⁶. -2 1.2×10 -2 1.3×10 -2 Siemens / meter, the electrical conductivity of the polymethyl methacrylate matrix at 20, 40, and 60°C is 1.5 × 10⁻⁶. -2 2.8×10 -2 3×10 -2 .

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a temperature sensor based on solvent-free nanofluids, characterized in that, Specifically, the following steps are included: Step 1: A polymethyl methacrylate solution is prepared, and a solvent-free nanofluid is prepared by ion exchange. In Step 1, the solvent-free nanofluid is obtained by grafting onto nanoparticles. Step 2: Add 10-50 wt% of solvent-free nanofluid to the polymethyl methacrylate solution to obtain a mixed solution; Step 3: Coat the mixed solution onto a glass slide, pre-dry and set it to obtain a solvent-free nanofluid / polymer matrix solution film; Step 4: Place the solvent-free nanofluid / polymer matrix solution film into an oven and dry it thoroughly to obtain a temperature sensor based on solvent-free nanofluid.

2. The method for fabricating a temperature sensor based on solvent-free nanofluids according to claim 1, characterized in that, The nanoparticles include any one of SiO2, TiO2, and CNC nanoparticles.

3. The method for fabricating a temperature sensor based on solvent-free nanofluids according to claim 1, characterized in that, In step 1, the mass fraction of polymethyl methacrylate in the polymethyl methacrylate solution is 10-30%, and the dissolution temperature when preparing the polymethyl methacrylate solution is 60-70℃.

4. The method for fabricating a temperature sensor based on solvent-free nanofluids according to claim 1, characterized in that, In step 3, the pre-drying temperature is 65°C and the pre-drying time is 120-150 minutes.

5. The method for fabricating a temperature sensor based on solvent-free nanofluids according to claim 1, characterized in that, In step 4, an oven is used for drying at a temperature of 80°C for a duration of no less than 12 hours. The resulting temperature sensor based on solvent-free nanofluid has a thickness of 1 mm.

6. A temperature sensor based on solvent-free nanofluids, characterized in that, Prepared by the method described in any one of claims 1-5.

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