Temperature and strain composite sensor and method for manufacturing the same

Abstract

The application belongs to the field of multifunctional smart materials, and particularly relates to a temperature and strain composite sensor and a preparation method thereof. The composite sensor comprises a flexible substrate layer, a functional material layer and a metal electrode, the functional material layer is deposited on the flexible substrate layer by a magnetron sputtering process, and the metal electrode is deposited at both ends of the flexible substrate layer and electrically connected with the functional material layer; the flexible substrate layer is a polyimide film, and the functional material layer is a highly (000l) textured N-type bismuth telluride film. The composite sensor prepared by the application is extremely sensitive to temperature and strain, and the preparation method is simple and easy to implement. The composite sensor can be used for temperature and strain double-parameter sensing, and has strong application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of multifunctional smart materials, and relates to a temperature and strain composite sensor and a preparation method thereof. BACKGROUND

[0002] With the development of the Internet of Things, artificial intelligence, robots, electronic skin and other industries, the requirements for sensors are becoming higher and higher. For example, as a product simulating human touch, electronic skin needs to respond to various external stimuli such as temperature, strain, humidity, etc. Traditional sensors are often single-function temperature, strain or humidity sensors, and multiple materials or multiple single-function sensors need to be integrated to obtain a multifunctional composite sensor. Not only is a complex process required for preparation, but also the cost is high, the preparation is difficult, and multifunctional integration and miniaturization are difficult. Therefore, it is urgent to develop materials and sensor devices with multiple sensing functions to meet the growing demand in the future. SUMMARY

[0003] To solve the above technical problems, the purpose of the present application is to provide a temperature and strain composite sensor and a preparation method thereof, which is extremely sensitive to temperature and strain, and the preparation method is simple and easy to operate. The composite sensor can be used for temperature and strain double-parameter sensing, and has strong application value.

[0004] The application provides a temperature and strain composite sensor, which comprises a flexible substrate layer, a functional material layer and a metal electrode, the functional material layer is deposited on the flexible substrate layer by a magnetron sputtering process, and the metal electrode is deposited at both ends of the flexible substrate layer and electrically connected with the functional material layer.

[0005] In the temperature and strain composite sensor of the application, the (000l) highly textured N-type bismuth telluride film has a thickness of 300-2000 nm.

[0006] In the temperature and strain composite sensor of the application, the highly textured N-type bismuth telluride film has a piezoresistive effect, and its strain factor is negative, that is, the resistance of the bismuth telluride film decreases under the condition of tensile strain, and the resistance increases under the condition of compressive strain. With the increase of compressive strain or tensile strain, the amplitude of resistance increase or decrease becomes larger. The resistance change law of the bismuth telluride film under tension or compression is reversible.

[0007] In the temperature and strain composite sensor of the application, the metal electrode is an Au, Ag or Pt high-conductivity metal electrode.

[0008] In the temperature and strain composite sensor of the application, the polyimide film has a thickness of 25-175 um.

[0009] In the temperature and strain composite sensor of the application, in the case of simultaneously applying temperature and strain excitation to the bismuth telluride film, the temperature is detected by the thermoelectric effect, the strain is detected by the resistance change, the dual-function detection of temperature and strain is realized, and the signals generated by the two are different to realize signal decoupling.

[0010] The application further provides a preparation method of the temperature and strain composite sensor, and the specific steps comprise:

[0011] Step 1: high-precision magnetron sputtering sample discs and physical mask plates are cut by using femtosecond laser cutting technology;

[0012] Step 2: a polyimide film is taken, and the polyimide film is sequentially ultrasonically cleaned with acetone and anhydrous ethanol for 30 min, and then taken out by using forceps and dried with a dust-free paper after the anhydrous ethanol is dried, and the polyimide film is used for standby;

[0013] Step 3: a bismuth telluride film is deposited on the polyimide film treated in step 2 by using mask film deposition technology and industrial common film deposition technology;

[0014] Step 4: the polyimide film with the deposited bismuth telluride film in step 3 is taken out, the mask plate is replaced, a layer of metal electrode is deposited at both ends of the polyimide film, and finally the metal electrode is bonded with a wire by using silver glue to lead out a signal line.

[0015] In the preparation method of the temperature and strain composite sensor of the application, the physical mask plate is divided into a bismuth telluride mask plate and an electrode mask plate.

[0016] In the preparation method of the temperature and strain composite sensor of the application, the magnetron sputtering film deposition parameters in step 3 are as follows: the back vacuum degree is 1x10 -7 -2x10 -7 torr, the Ar gas pressure is 10-20 mT, the sample disc rotation speed is 10-20 r / min, and the film deposition temperature is 300-400 DEG C.

[0017] In the preparation method of the temperature and strain composite sensor of the application, the thickness of the bismuth telluride film is 300-2000 nm, and the bismuth telluride film is a highly ordered (000l) texture film.

[0018] The temperature and strain composite sensor and the preparation method thereof have at least the following beneficial effects:

[0019] 1. The temperature and strain composite sensor of the application adopts a flexible substrate, and combines a highly ordered (000l) texture bismuth telluride film to provide excellent flexibility.

[0020] 2、The composite sensor of the present application utilizes the thermoelectric effect of bismuth telluride itself. If there is a temperature difference between the two sides of the composite sensor, a corresponding thermoelectric voltage U=S*△T (S is the Seebeck coefficient of bismuth telluride material, and △T is the temperature difference between the two sides) will be generated at the two sides. If the temperature of one side is T1, the temperature of the other side can be calculated as T2=U / S-T1.

[0021] 3、The composite sensor of the present application utilizes the piezoresistive effect of the bismuth telluride film. If the composite sensor is deformed, the resistance will change. The strain can be calculated through the relationship between strain and resistance, and the strain sensing function is realized.

[0022] 4、The composite sensor of the present application senses temperature based on the thermoelectric voltage signal and senses strain based on the resistance change. Therefore, the temperature stimulus and strain stimulus of the composite sensor can be determined by detecting the thermoelectric voltage signal and the resistance signal respectively, and the sensing signals of the two functions of temperature and strain of the composite sensor can be highly decoupled.

[0023] 5、The preparation method of the temperature and strain composite sensor of the present application is simple and does not require complex integration process. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a structural schematic diagram of a temperature and strain composite sensor of the present application;

[0025] Figure 2 is a scanning electron microscope image of the bismuth telluride film of the present application;

[0026] Figure 3 is a schematic diagram of a temperature and strain measurement device;

[0027] Figure 4 is a response graph of the output voltage of the sensor when the temperature difference between the two ends of the sensor is 9K, 21K and 36K respectively under no strain;

[0028] Figure 5 is a resistance change response graph of the sensor when the sensor is bent downward and the bending radius is 9mm, 6mm, 5mm and 4mm respectively under no temperature difference between the two ends of the sensor;

[0029] Figure 6 is a resistance change response graph of the sensor when the sensor is bent upward and the bending radius is 13mm, 9mm, 7mm and 6mm respectively under no temperature difference between the two ends of the sensor;

[0030] Figure 7 is a resistance change response graph of the sensor when the sensor is bent upward and the bending radius is 13mm, 9mm, 7mm and 6mm respectively under the condition that the temperature difference between the two ends of the sensor is kept at 9K. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described below in combination with the drawings and examples.

[0032] As shown in the drawings, Figure 1 A temperature and strain composite sensor of the present application comprises a flexible substrate layer 3, a functional material layer 2 and a metal electrode 1. The functional material layer 2 is deposited on the flexible substrate layer 3 by magnetron sputtering process, and the metal electrode 1 is deposited on both ends of the flexible substrate layer 3 and electrically connected with the functional material layer 2. The flexible substrate layer 3 is made of polyimide film or bendable film material with high temperature resistance, and the functional material layer 2 is highly (000l) textured N-type bismuth telluride film.

[0033] In specific implementation, the metal electrode is Au, Ag or Pt high-conductivity metal electrode. In specific implementation, the thickness of the polyimide film is 25 um. The thickness of the (000l) highly textured N-type bismuth telluride film is 300 nm. The thickness of the metal electrode 1 is 100 nm. Figure 2 is a scanning electron microscope image of the bismuth telluride film of the present application.

[0034] The highly (000l) textured N-type bismuth telluride film has obvious piezoresistive effect, and its strain factor is negative, i.e. the resistance of the bismuth telluride film decreases under tensile strain, and the resistance increases under compressive strain. Moreover, the amplitude of the resistance increase or decrease becomes larger with the increase of the compressive or tensile strain. The resistance change rule of the bismuth telluride film under tension or compression is reversible.

[0035] In the case of simultaneously applying temperature and strain excitation to the bismuth telluride film, the temperature can be detected by thermoelectric effect, and the strain can be detected by resistance change, so as to realize dual-function detection of temperature and strain and signal decoupling.

[0036] The preparation method of the temperature and strain composite sensor in this embodiment includes the following specific steps:

[0037] Step 1: cut high-precision magnetron sputtering sample disc and physical mask plate by femtosecond laser cutting technology;

[0038] In specific implementation, the physical mask plate is divided into bismuth telluride mask plate and electrode mask plate.

[0039] Step 2: take polyimide film, and sequentially ultrasonically clean with acetone and anhydrous ethanol for 30 min. Then, take out the polyimide film with tweezers, and then dry the anhydrous ethanol with dust-free paper for standby. The width of the polyimide film is 15-30 mm, the length is 15-50 mm, and the thickness is 25 um-175 um.

[0040] In specific implementation, the width of the polyimide film is 20 mm, the length is 40 mm, and the thickness is 25 um.

[0041] Step 3: Using the magnetron sputtering coating technology, using the industrial common coating process, in the back vacuum degree is 2x10 - 7 torr, the Ar gas pressure is 15mT, the sample disc rotation speed is 10r / min, the coating temperature is 340℃, using the bismuth telluride mask prepared in step 1, a 300nm thick bismuth telluride film is deposited on the polyimide film treated in step 2;

[0042] Step 4: Take out the polyimide film deposited with bismuth telluride film in step 3, replace it with a metal mask, and deposit a 100nm thick metal electrode on both ends of the polyimide film. Finally, the metal electrode is bonded with a wire by silver glue to lead out the signal line.

[0043] In actual application, first, the Seebeck coefficient of the sensor is measured to be -197uV / K using a commercial Seebeck coefficient instrument. Then, the strain factor GF of the sensor is measured to be -15 using a strain factor GF measurement device. Finally, as shown in Figure 3 , the sensor 6 prepared above is clamped at both ends on the clamp 4, the two ends of which can move horizontally, and the first end 7 of the clamp can be heated to facilitate temperature and strain measurement.

[0044] Temperature detection: In the absence of strain, the first end 7 of the clamp is heated, and the second end 5 is maintained at room temperature. When the temperature difference between the two ends is 9K, 21K and 36K respectively, the response of the output voltage of the sensor is as shown in Figure 4 .

[0045] A temperature stimulus T is applied to one end of the sensor 6, and the other end is kept at room temperature T0. Due to the Seebeck effect, a voltage will be generated across the sensor. The output voltage V across the two ends is measured using a multimeter, and the temperature T = V / S-T0 can be calculated. S is the Seebeck coefficient of bismuth telluride material. As shown in Figure 4 , it can be seen that when the temperature difference is 9K, the output voltage is 1.77mV, when the temperature difference is 21K, the output voltage is 4.13mV, and when the temperature difference is 36K, the output voltage is 7.08mV. According to the voltage and the Seebeck coefficient, T can be calculated.

[0046] Strain detection: In the absence of temperature difference, the relative movement of the two ends of the clamp 4 causes the sensor to bend downward, corresponding to the tensile strain experienced by the sensor. When the sensor is bent, the resistance change rate ΔR / R0 is measured by connecting a multimeter across the two ends, where ΔR is the absolute change in resistance when bent, and R0 is the initial resistance of the sensor when it is horizontal. The strain of the sensor can be obtained according to the strain e = ΔR / R0 x GF.

[0047] The resistance response of the sensor is shown in the following table when the bending radius R is 9mm, 6mm, 5mm and 4mm respectively. Figure 5 When the sensor is bent upward by the relative movement of the clamp 4, the sensor generates a compressive strain, and the response of the sensor is shown in the following table when the bending radius R is 13mm, 9mm, 7mm and 6mm respectively. Figure 6 According to the amplitude of the resistance change, the strain value of the sensor can be calculated.

[0048] The response of the sensor to temperature and resistance under the condition of constant 9K is shown in the following table. Figure 7

[0049] When the temperature difference between the two ends of the sensor is kept at 9K, the thermoelectric voltage between the two ends of the sensor is 1.77mV and remains constant. Under this condition, the bending radius of the sensor is adjusted to 13mm, 9mm, 7mm and 6mm, and the resistance changes, but the thermoelectric voltage value remains stable, indicating that the sensor is accurate in sensing temperature and strain and has signal decoupling property.

[0050] The above examples prove that the thin film sensitive to temperature and strain prepared by the present application can simultaneously realize effective detection of temperature and strain, and is suitable for the field of flexible electronic devices.

[0051] The above description is only the preferred embodiment of the present application, and is not intended to limit the idea of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for fabricating a temperature-strain composite sensor, characterized in that, The sensor comprises: a flexible substrate, a functional material layer, and metal electrodes. The functional material layer is deposited on the flexible substrate using magnetron sputtering. The metal electrodes are deposited at both ends of the flexible substrate and electrically connected to the functional material layer. The flexible substrate is a polyimide film, and the functional material layer is a highly textured N-type bismuth telluride film. The thickness of the highly textured N-type bismuth telluride film is 300 nm-2000 nm. The highly textured N-type bismuth telluride film exhibits a piezoresistive effect, and its strain factor is negative, meaning that the bismuth telluride film exhibits piezoresistive effect under tensile strain conditions. The resistance decreases under pressure; under compressive strain, the resistance increases; and the magnitude of the increase or decrease in resistance increases with the increase of compressive or tensile strain; and the resistance change of the bismuth telluride film under tension or compression is reversible; the metal electrode is a highly conductive metal electrode of Au, Ag, or Pt; the thickness of the polyimide film is 25um-175um; when temperature and strain excitation are applied to the bismuth telluride film simultaneously, temperature is detected by thermoelectric effect, and strain is detected by resistance change, realizing dual-function detection of temperature and strain, and the signals generated by the two are different, so as to achieve signal decoupling; The specific steps of the sensor fabrication method include: Step 1: Use femtosecond laser cutting technology to cut a high-precision magnetron sputtering sample disk and physical mask; Step 2: Take the polyimide film, and ultrasonically clean it with acetone and anhydrous ethanol for 30 minutes in sequence. Take it out with tweezers and then blot it dry with lint-free paper for later use. Step 3: Using magnetron sputtering and masking techniques, a bismuth telluride film is deposited on the polyimide film treated in Step 2. Step 4: Remove the polyimide film with bismuth telluride film deposited in Step 3, replace the mask, deposit another layer of metal electrodes at both ends of the polyimide film, and finally bond the metal electrodes to the wires with silver paste to lead out the signal lines. Physical masks are divided into bismuth telluride masks and electrode masks; The magnetron sputtering coating parameters in step 3 are: back vacuum level of 1×10⁻⁶. -7 -2×10 -7 The Ar gas pressure was 10-20 mT, the sample disk rotation speed was 10-20 r / min, and the coating temperature was 300-400℃.

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