Telescopic temperature response film and temperature sensor

Abstract

The invention discloses a telescopic temperature response film and application thereof, and belongs to the technical field of sensors. The telescopic temperature response film comprises a first layer and a second layer which are adjacent to each other, the first layer is a telescopic film, and the second layer is a temperature response layer. According to the invention, the telescopic film as the substrate layer and the temperature response layer are directly laminated, and the telescopic temperature response film has flexibility and irreversible deformation resistance and can be better attached to a test end, so that the temperature sensing layer can better receive a temperature signal, and the temperature response signal can be expanded. Further, the sensitivity of the sensor using the film can be improved. Meanwhile, the sensing layer and the substrate layer can be made into coil samples in advance, so that the subsequent sensor production efficiency can be improved. And the method is environment-friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of stretchable temperature responsive materials and sensors, and in particular relates to a stretchable temperature responsive film and a temperature sensor comprising the same. Background Art

[0002] Accurately monitoring and controlling local temperature is essential for assessing health status, early detection and diagnosis of diseases, and providing the possibility of building smart medical systems. Flexible temperature sensors can conform to human skin and achieve stable and continuous measurements, so they have attracted widespread attention in recent years.

[0003] In this regard, Patent Document 1 proposes a thin film temperature sensor, a preparation method and application thereof, including a thin film hydrogel, an insulating elastomer film and an electrode, wherein the insulating elastomer film is wrapped on both sides of the thin film hydrogel, and the thin film hydrogel is a double network hydrogel containing an electrolyte salt and propylene glycol, which has two working modes. In the external power supply mode, the sensitivity of the thin film temperature sensing is significantly improved by molecular exchange between propylene glycol and the solvent in the hydrogel, and the thin film temperature sensor has a wide temperature measurement range, but there is residual solvent in the prepared hydrogel and cannot be used in practice. In addition, its temperature measurement range is 50-90°C, and the maximum sensitivity is 34.52%°C, but its temperature response range and response sensitivity need to be further improved.

[0004] Prior art literature

[0005] Patent document 1: CN 114838843 A Summary of the invention

[0006] In view of the above problems, the present invention provides a stretchable temperature-responsive film with no solvent residue and a simple preparation method, and has excellent performance, a wide temperature detection range and higher sensitivity, and a temperature sensor containing the same.

[0007] In order to achieve the above object, the present invention provides a stretchable temperature-responsive film, which comprises a first layer and a second layer adjacent to each other, wherein the first layer is a stretchable film and the second layer is a temperature-responsive layer.

[0008] The retractable film of the present invention is a polymer material having the ability to rapidly recover to its approximate original shape and size after being significantly deformed by a force and then being removed from the external force.

[0009] The retractable film acts as a supporting layer. Considering its flexibility, it is preferably an elastomeric film made of an elastomer. The elastomeric film can be a thermoplastic elastomer. The thermoplastic elastomer includes but is not limited to polyurethane elastomer, polydimethylsiloxane, thermoplastic polyolefin elastomer, thermoplastic vulcanized rubber, polyether ester elastomer, styrene elastomer or one or more. Thermoplastic polyurethane elastomer is preferred due to its wide adjustable flexibility range.

[0010] The Young's modulus of the first layer is preferably in the range of 1-10 MPa, and preferably in the range of 1-5 MPa considering the flexibility of the sensor.

[0011] The thickness of the stretchable film is preferably in the range of 20-100 μm, and more preferably 20-50 μm due to processability and sensor performance.

[0012] The temperature response layer is a layer that can sense temperature signals and convert the temperature signals into usable output electrical signals according to certain rules.

[0013] The temperature responsive layer acts as a functional layer, which has a temperature responsive function, and its material is preferably a natural high molecular polymer. It can be at least one of pectin and its derivatives, chitosan and its derivatives, alginic acid and its derivatives, hyaluronic acid and its derivatives, carboxymethyl cellulose and its derivatives. Considering the content of cross-linkable groups, steric hindrance and cross-linking structure, pectin and its derivatives are preferred.

[0014] From the viewpoint of sensor sensitivity and easy availability, pectin having a galacturonic acid content of more than 65 wt % is preferred.

[0015] In the present invention, from the perspective of steric hindrance, the temperature responsive layer is preferably a cross-linked product of a natural high molecular polymer and a divalent metal cation. The divalent metal cation may be one or more of calcium ions, magnesium ions, cobalt ions, copper ions, iron ions, barium ions, and zinc ions, wherein calcium ions are preferred in view of ion size and hydrolysis.

[0016] The temperature response layer preferably has a thickness ranging from 100 to 200 μm, and more preferably from 150 to 200 μm in consideration of processability and sensor performance.

[0017] In the present invention, the recovery rate of the retractable temperature-responsive film is preferably in the range of 97%-99%, so that the film has the ability to resist irreversible deformation, and considering the durability of the composite film, it is more preferably 98-99%.

[0018] After the recovery rate evaluation, the deflection of the stretchable temperature-responsive film is preferably less than 1 cm. The deflection refers to the distance from the highest point of the composite film to the horizontal plane when the film with a size of 15 cm × 1 cm is placed on a horizontal plane with the convex surface facing upward under the condition of no external stress. Considering the flexibility of the composite film, the deflection of the stretchable temperature-responsive film is preferably less than 0.5 cm.

[0019] The peel strength between the first layer and the second layer of the stretchable temperature responsive film is preferably 2-15 N / cm. The tighter the combination of the first layer and the second layer, the higher the sensitivity of the sensor using the stretchable temperature responsive film of the present invention, more preferably 10-15 N / cm.

[0020] The stretchable temperature-responsive film can be produced as follows.

[0021] (1) Base

[0022] The raw materials of stretchable films such as elastomers are made into film materials through extrusion casting process.

[0023] (2) Stretchable temperature-responsive film

[0024] On a substrate, a temperature-responsive slurry is compounded with a stretchable film by coating, and a two-layer structure is prepared as a stretchable temperature-responsive film by dehydration forming.

[0025] The present invention also provides a temperature sensor, which comprises the stretchable temperature responsive film of the present invention, and the sensitivity in the temperature range of 15-100°C can reach up to 46.32%°C. -1 .

[0026] The temperature sensor can be manufactured by the following method:

[0027] Conductive materials (metal, liquid metal, nano-metal, polymer conductive materials, etc.) are printed or bonded on the second layer of the stretchable temperature responsive film of the present invention as electrodes, and then flexible film packaging is performed on the electrodes to prepare temperature sensors.

[0028] Effects of the Invention

[0029] The present invention directly stacks the retractable film as the base layer and the temperature response layer. The retractable temperature response film has flexibility and the ability to resist irreversible deformation, can better fit the test end, so that the temperature sensing layer can better receive the temperature signal, thereby amplifying the temperature response signal. Furthermore, the sensor using the film can improve sensitivity. At the same time, the sensing layer and the base layer can be made into a roll sample in advance, which can improve the production efficiency of subsequent sensors and is environmentally friendly. DETAILED DESCRIPTION

[0030] The present invention is described in more detail by the following examples, but the following examples do not constitute a limitation of the present invention.

[0031] 1. Raw materials

[0032] A1 polyurethane elastomer (Lubrizol Pellethane); A2 polydimethylsiloxane (DOW CORNINGSYLGARD 184); A3 polyolefin elastomer (Mitsubishi Chemical ZELAS TM )

[0033] B1 pectin (Herbstreith & Fox AB902); B12 pectin (Merck P9135); B13 pectin (Andre APC310SC); B2 alginic acid (Merck A7003); B3 hyaluronic acid (Merck924474)

[0034] C1: Polyethylene terephthalate film (Toray Lumirror 50-S10) thickness 20 μm

[0035] D1: Cast polypropylene film (Toray CPP ZK207) thickness 20 μm

[0036] E1: CaCl2 (Merck C5670)

[0037] E2: MgCl2 (Merck M8266)

[0038] E3: ZnCl2 (Merck 208086)

[0039] 2. The methods for measuring the relevant properties in the embodiments and comparative examples of the present invention are as follows. For all tests, if the test temperature is not clearly stated, the test is performed at 23°C.

[0040] (1) Sensitivity

[0041] The calculation formula of temperature sensor sensitivity is as follows:

[0042]

[0043] R0 is the initial resistance when there is no temperature change, ΔR is the resistance change after the temperature change, and ΔT is the temperature change.

[0044] The sensing characteristics were tested by gradually changing the temperature using a Keithley digital power meter.

[0045] (2) Response rate

[0046] The stretchable temperature-responsive film was cut into strips with a size of MD×TD: 150mm×10mm, stretched along the MD direction to twice the original length, i.e. 300mm, and maintained for 1min. This was repeated 10,000 times. The length was measured after the external force was removed for 10min. The recovery rate was calculated as follows:

[0047]

[0048] Where R g is the recovery rate, L0 is the initial length, L1 is the length after extension by external force, and L2 is the straightened length 10 minutes after the external force is removed.

[0049] (3) Deflection

[0050] After the recovery rate test is completed, the deflection test is performed after the sample is placed for 24 hours. The sample is placed on a horizontal plane with the convex surface facing upward without external stress, and the distance from the highest point of the test piece to the horizontal plane is measured using a ruler with an accuracy of 0.05 cm.

[0051] (4) Peel strength

[0052] When testing the two layers of the stretchable temperature-responsive film, the first layer was reinforced with TESA7475 test tape and the sample was cut with a cutter to a size of 150 mm × 10 mm. Then a 180° peel strength test was performed using a tensile testing machine at a tensile speed of 200 mm / min. The tear strength τ2 calculation formula is as follows

[0053]

[0054] In formula (3), the 180-degree peel strength between the first layer and the second layer is τ2 (N / cm); the average load during peeling is the peeling force F2 (N); the width of the peeled sample is L, which is set to 1 cm. Each sample is measured three times in different areas, and the arithmetic average of the three test results is taken as the peel strength result.

[0055] (5) Young's modulus

[0056] The test specimen size is 10mm×150mm. The tensile test is carried out in the MD and TD directions. The modulus strain range of the tensile curve is 0.7-1.0%, and the average value of the modulus is calculated as follows:

[0057] E=σ / ε (Formula 4)

[0058] E is Young's modulus, σ is stress, and ε is strain

[0059] Embodiment 1:

[0060] (1) Base layer 1

[0061] The current production process in the market is adopted: using precision casting technology, thermoplastic polyurethane elastomer (A1) particles are extruded through a casting process to produce a thermoplastic polyurethane original film with a uniform thickness of 50 μm and no defects on the surface, and the surface is corona treated.

[0062] (2) Stretchable temperature-responsive film

[0063] Pectin (B1) powder was dissolved in deionized water at 80°C to a mass content of 2wt%, and stirred at 1400rpm until a uniform solution was obtained. A 32mM CaCl2 (E1) solution was prepared separately, and the calcium chloride solution was added dropwise to the pectin solution by titration, and stirred at 1200rpm to form a uniform mixed system sol. The sol system was applied to the substrate obtained in step (1) by spin coating, and vacuum dehydrated and dried at a temperature of 70-80°C to obtain a second layer with a thickness of 200μm.

[0064] (3) Sensor

[0065] An Ag electrode is sputtered on the second layer of the stretchable temperature-responsive film obtained in step (2), and a flexible packaging layer is then attached to the electrode layer to finally obtain a temperature sensor.

[0066] The performance parameters are listed in Table 1.

[0067] Embodiment 2-15:

[0068] (1) Basal layer

[0069] The base layer was prepared according to the materials and parameters listed in Table 1 and the same method as in Example 1.

[0070] (2) Stretchable temperature-responsive film

[0071] The stretchable temperature-responsive film was prepared according to the materials and parameters listed in Table 1 and the same method as in Example 1.

[0072] (3) Sensor

[0073] The sensor was prepared by referring to the method of Example 1.

[0074] The performance parameters are listed in Table 1.

[0075] Comparative Example 1:

[0076] Different from Example 1, the second layer in step (2) is replaced by sputtering of Ag electrode, and then the temperature response layer is prepared and packaged.

[0077] The performance parameters are listed in Table 1.

[0078] Comparative Example 2:

[0079] A stretchable temperature-responsive film and a sensor were prepared in the same manner as in Example 1 except that the substrate layer was made of polyethylene terephthalate (PET film). The performance parameters are shown in Table 1.

[0080] By comparing Examples 1, 2, and 3, it can be seen that the lower the thickness of the first layer, the higher the sensitivity; by comparing Example 1 with Comparative Example 1, it can be seen that exchanging the order of the sensing layer and the electrode layer can improve the sensitivity of the sensor.

[0081] By comparing Examples 2 with 3, 9, 10, and 13, it can be seen that the sensor made with the stretchable film as the first layer has higher sensitivity, and the sensor made with the recovery rate of the temperature-responsive film in the range of 97-99% and the Young's modulus of the first layer in the range of 1-10 MPa has higher sensitivity.

[0082] In combination with Examples 4, 5, 6, 7, and 8, it can be seen that the sensor made of a stretchable temperature-responsive film has high sensitivity, and the sensor made of a temperature-responsive layer made of pectin and a calcium ion crosslinker has higher sensitivity. At the same time, the sensor made of a stretchable temperature-responsive film with a deflection of less than 1 cm is a preferred option, among which less than 0.5 cm is the most preferred option.

[0083] It can be seen from Examples 3, 11 and 12 that the thicker the second layer is, the higher the sensitivity of the sensor is.

[0084] By comparing Examples 1, 14, and 15, it can be seen that the sensor made with the calcium ion crosslinked material as the temperature response layer has higher sensitivity. By comparing Examples 4, 5, and 6, it can be seen that the higher the pectin galacturonic acid content, the higher the sensitivity.

[0085] Table 1

[0086]

Claims

1. A stretchable temperature-responsive film, characterized in that: The stretchable temperature-responsive film comprises a first layer and a second layer adjacent to each other, wherein the first layer is a stretchable film and the second layer is a temperature-responsive layer.

2. The stretchable temperature-responsive film according to claim 1, characterized in that: The recovery rate of the film is 97%-99%.

3. The stretchable temperature responsive film according to claim 2, characterized in that: After the film is evaluated for recovery rate, the deflection of the stretchable temperature-responsive film is less than 1 cm.

4. The stretchable temperature-responsive film according to claim 1, characterized in that: The peeling strength between the first layer and the second layer of the film is 2-15 N / cm.

5. The stretchable temperature-responsive film according to claim 1, characterized in that: The Young's modulus of the stretchable film is in the range of 1-10 MPa.

6. The stretchable temperature-responsive film according to claim 1, characterized in that: The stretchable membrane is an elastomeric membrane.

7. The stretchable temperature-responsive film according to claim 6, characterized in that: The retractable film is at least one selected from thermoplastic polyurethane elastomer, polydimethylsiloxane, thermoplastic polyolefin elastomer, thermoplastic vulcanized rubber, polyether ester elastomer, and styrene elastomer.

8. The stretchable temperature-responsive film according to claim 1, characterized in that: The second temperature responsive layer is a natural high molecular polymer.

9. The stretchable temperature-responsive film according to claim 8, characterized in that: The second temperature response layer is a cross-linked product of a natural high molecular polymer and a divalent metal cation.

10. The stretchable temperature-responsive film according to claim 8, characterized in that: The natural high molecular polymer in the second layer is at least one of pectin and its derivatives, chitosan and its derivatives, alginate and its derivatives, hyaluronic acid and its derivatives, carboxymethyl cellulose and its derivatives.

11. The stretchable temperature-responsive film according to claim 9, characterized in that: The divalent metal cations in the second layer are at least one of calcium ions, magnesium ions, cobalt ions, copper ions, iron ions, barium ions, and zinc ions.

12. A temperature sensor comprising the stretchable temperature responsive film according to any one of claims 1 to 11, wherein the sensitivity range of the temperature sensor in the range of 15 to 100°C is 10.54 to 46.32%°C. -1 .

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