Flexible pressure-temperature dual-mode sensor

Abstract

The invention discloses a flexible pressure-temperature dual-mode sensor, which comprises a pressure sensitive layer, a temperature sensitive layer and a PET substrate, and is characterized in that the two surfaces of the PET substrate are printed with interdigital electrodes, and the two interdigital electrodes are connected through a copper foil; the pressure sensitive layer covers one of the interdigital electrodes to form a pressure sensing circuit, and the temperature sensitive layer covers the other interdigital electrode to form a temperature sensing circuit. According to the invention, the pressure sensitive layer and the temperature sensitive layer are combined together through mutual cooperation of the PET substrate and the interdigital electrode to form a temperature sensing circuit and a pressure sensing circuit, so that simultaneous measurement of temperature and pressure is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and in particular to a flexible pressure-temperature dual-mode sensor. Background Art

[0002] The explosive development of artificial intelligence and Internet of Things technologies has promoted the improvement of people's health awareness and the need for smart life, leading to more and more researchers investing a lot of energy in the research and development of flexible sensor devices. External stimuli are complex and multi-faceted, and multiple stimuli need to be sensed and distinguished at the same time to accurately reflect the shape of the object being measured. Multimodal flexible sensing is an important development trend in the development of future wearable electronic devices or electronic skin. The high precision, high flexibility and easy integration of flexible sensors make them have great application potential in the fields of human-computer interaction, intelligent robots, and intelligent prostheses.

[0003] Temperature and pressure are the most common physical parameters in life, providing us with weight, pressure, and hot and cold information. Most of the current sensors are based on single sensing performance, and can only realize the single detection function of temperature and pressure, that is, temperature sensors or pressure sensors. With the increasing demand for complex scene detection, single sensors need to develop in the direction of multifunctional flexible sensing, and some dual-modal sensors based on heterogeneous working mechanisms have been reported, such as combined piezoelectric and thermoelectric, thermoelectric and piezoresistive effect, ferroelectric and thermoelectric can achieve effective coupling of two signals. However, the two different working mechanisms often involve complex preparation and signal reading equipment, and even signal crosstalk problems. Therefore, there is an urgent need for a flexible pressure-temperature dual-modal sensor. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a flexible pressure-temperature dual-mode sensor.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A flexible pressure-temperature dual-mode sensor comprises a pressure-sensitive layer, a temperature-sensitive layer and a PET substrate. Both sides of the PET substrate are printed with interdigital electrodes. The pressure-sensitive layer covers one of the interdigital electrodes to form a pressure sensing circuit. The temperature-sensitive layer covers the other interdigital electrode to form a temperature sensing circuit. Two interdigital electrodes corresponding to the temperature sensing circuit and the pressure sensing circuit are connected in series through copper foil to form a single signal output circuit.

[0007] The output signal of the signal output circuit is processed through the following steps to avoid crosstalk between the pressure signal and the temperature signal:

[0008] S4.1: Based on the characteristic differences of the temperature signal and the pressure signal fed back by the temperature sensing circuit and the pressure sensing circuit, the output signal is collected by Keithley4200A-SCS parameter analyzer to obtain the current signal, and the obtained Excel current table is exported, the header is removed and only the two columns of time and current data are retained. The output signals include signals with only pressure response, signals with only temperature response, and signals with mixed response of pressure and temperature;

[0009] S4.2: Use the tsfresh library to extract features from the two columns of data. The features extracted by tsfresh include: mean, variance, kurtosis, skewness, zero crossing rate, number of peaks, main frequency, and spectrum energy;

[0010] S4.3: Label the extracted features and convert each feature data after label classification into a standard normal distribution with a mean of 0 and a standard deviation of 1;

[0011] S4.4: Use PCA to reduce the dimension of feature data by finding the direction with the largest variance in the feature data and projecting the feature data to the direction with the largest variance to achieve dimensionality reduction;

[0012] S4.5: The feature data after dimensionality reduction is input into the random forest model for training, so that the random forest model learns the relationship between the classification label and the feature data to distinguish between temperature and pressure signals.

[0013] Preferably, the surface of the pressure sensitive layer in contact with the interdigital electrodes is a convex surface.

[0014] The steps for preparing the temperature sensitive layer are as follows:

[0015] S1.1, pour polyvinyl pyrrolidone powder and cetyl trimethyl ammonium bromide into n-pentanol and fully dissolve them to obtain a mixed solution;

[0016] S1.2, pouring nickel oxide powder into the mixed solution, and obtaining a dispersed nickel oxide raw material by magnetic stirring and ultrasonic treatment;

[0017] S1.3. The dispersed nickel oxide raw material is dried to form a temperature sensitive layer.

[0018] The steps for preparing the pressure sensitive layer are as follows:

[0019] S2.1, ablating polyimide to obtain laser-induced graphene;

[0020] S2.2, using sandpaper as a template for manufacturing the pressure sensitive layer, and cleaning the surface of the template;

[0021] S2.3, evenly applying laser-induced graphene on the surface of the template to form a laser-induced graphene layer, and applying polydimethylsiloxane on the surface of the laser-induced graphene layer;

[0022] S2.4, drying the polydimethylsiloxane attached with laser-induced graphene and removing it from the template to form a pressure-sensitive layer.

[0023] Based on the above steps for preparing the temperature sensitive layer and the pressure sensitive layer, the steps for preparing the flexible pressure-temperature dual-mode sensor are as follows:

[0024] S3.1. Sputtering gold interdigital electrodes on the upper and lower surfaces of the PET substrate by magnetron sputtering using a template, wherein one of the pins of the two interdigital electrodes is connected by copper foil, and a sputtering groove having the same pattern as the interdigital electrodes is provided on the template;

[0025] S3.2, applying the dispersed nickel oxide raw material on the interdigital electrodes on one side of the PET substrate, and drying to form the temperature sensitive layer;

[0026] S3.3, sticking the pressure sensitive layer on the interdigital electrodes on the other side of the PET substrate 3.

[0027] The PET substrate mentioned above is a kind of thermoplastic polyester plastic with excellent toughness, tensile strength, impact strength, wear resistance, and electrical insulation. It has excellent tensile strength and tear resistance, enabling it to withstand mechanical stress. Polydimethylsiloxane is the main material for pressure sensors because of its good elasticity and flexibility, low elastic modulus and high ductility. The purpose of polyvinyl pyrrolidone powder is to bond nickel oxide nanopowder together to form a film. The one used in this experiment is high molecular weight polyvinyl pyrrolidone, which has high viscoelasticity. After being made into a film, it has a certain degree of flexibility and can be bent, which makes the flexible pressure-temperature dual-modal sensor bendable.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The pressure sensitive layer and the temperature sensitive layer provided in the present invention cooperate with each other through the PET substrate and the interdigital electrodes, and are combined together to form a temperature sensing circuit and a pressure sensing circuit, and the simultaneous measurement of temperature and pressure is achieved by utilizing the mechanism that the resistance of the sensing circuit changes due to external signals.

[0030] 2. The present invention utilizes the flexibility of the PET substrate, the pressure sensitive layer, the temperature sensitive layer and the interdigital electrodes so that the manufactured flexible pressure-temperature dual-mode sensor can be bent during use.

[0031] 3. The temperature sensing circuit and the pressure sensing circuit in the present invention are connected by copper foil, so that the same output signal can respectively reflect the temperature and pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 It is a structural schematic diagram of the template of the present invention;

[0034] Figure 3 It is a schematic diagram of the working principle of the pressure sensing circuit of the present invention;

[0035] Figure 4 This is a temperature and pressure performance test diagram of the present invention under 4g, 25°C conditions;

[0036] Figure 5 This is a temperature and pressure performance test diagram of the present invention under 8g, 25°C conditions;

[0037] Figure 6 This is a temperature and pressure performance test diagram of the present invention under 8g and 50°C conditions;

[0038] Figure 7 It is a schematic diagram of the current response and resistance temperature coefficient of the temperature sensing circuit of the present invention at different temperatures;

[0039] Figure 8 It is a linear relationship diagram between the natural logarithm of the resistance ln(R) and 1000 / T of the temperature sensing circuit of the present invention at different temperatures;

[0040] Fig. 9 is a schematic diagram of the current response and pressure sensitivity of the pressure sensing circuit of the present invention under different pressures;

[0041] Fig.10 is a graph showing the current attenuation change of the pressure sensing circuit of the present invention in a continuous cycle test;

[0042] Fig.11 It is the equivalent circuit of the present invention.

[0043] Figure symbols: 1. pressure sensitive layer, 2. temperature sensitive layer, 3. PET substrate, 4. interdigitated electrodes, 5. copper foil, 6. template, 61. sputtering tank. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0045] Example 1

[0046] like Figure 1 A flexible pressure-temperature dual-modal sensor shown includes a pressure sensitive layer 1, a temperature sensitive layer 2 and a PET substrate 3, wherein both sides of the PET substrate 3 are printed with interdigital electrodes 4, the pressure sensitive layer 1 covers one of the interdigital electrodes 4 to form a pressure sensing circuit, the temperature sensitive layer 2 covers the other interdigital electrode 4 to form a temperature sensing circuit, and the two interdigital electrodes 4 corresponding to the temperature sensing circuit and the pressure sensing circuit are connected in series through a copper foil 5 to form a single signal output circuit.

[0047] Specifically, the principle of the above pressure sensing circuit is as follows: Figure 3 As shown, when the pressure sensitive layer 1 is squeezed downward, the contact area between the pressure sensitive layer 1 and the interdigital electrodes 4 in the pressure sensing circuit becomes larger, and the conductive channel of the pressure sensitive layer 1 becomes thicker. According to the resistance law:

[0048]

[0049] In the formula, S is the cross-sectional area of ​​the raised surface of the pressure sensitive layer 1, ρ is the resistivity of the pressure sensitive layer 1, and L is the length of the raised surface of the pressure sensitive layer 1. It can be seen from the above formula (1) that when pressure is applied to the pressure sensitive layer 1, the cross-sectional area of ​​the raised surface of the pressure sensitive layer 1 increases, and the resistance of the pressure sensitive layer 1 decreases. The pressure change can be obtained by the resistance change. Specifically, the surface of the pressure sensitive layer 1 in contact with the interdigital electrode 4 is a raised surface, which ensures that the contact area between the pressure sensitive layer 1 and the interdigital electrode 4 in the pressure sensing circuit changes more significantly when pressure is applied, thereby achieving high-precision detection of pressure.

[0050] The temperature sensitive layer 2 is a semiconductor material whose resistance changes with temperature. This change is manifested as a negative temperature coefficient of resistance characteristic. The resistance decreases with increasing temperature. The reason is that the conductivity of the semiconductor is mainly determined by the carriers. The increase in temperature will increase the carrier concentration or mobility of the semiconductor, thereby resulting in a negative temperature coefficient of resistance behavior. The temperature change can be obtained through the change in resistance.

[0051] During specific implementation, the object to be measured is directly placed on the flexible pressure-temperature dual-modal sensor and in contact with the temperature sensitive layer 2. At this time, the temperature sensing circuit directly senses the temperature of the object to be measured by utilizing the principle that the temperature of the temperature sensitive layer 2 increases and the resistance decreases; then the pressure change of the object to be measured will be transmitted to the pressure sensitive layer 1, and the pressure sensing circuit utilizes the deformation of the convex surface of the pressure sensitive layer 1 under pressure and the increase in the contact area between the interdigital electrodes 4 in the pressure sensing circuit, the coarsening of the conductive channel of the pressure sensitive layer 1, and the deformation of the convex surface of the pressure sensitive layer 1 under pressure, which will also cause the length of the microstructure to shorten and the conductive channel to thicken, so as to directly sense the pressure applied to the pressure sensitive layer 1 by the object to be measured by utilizing the principle of resistance decrease.

[0052] The signal output by the above signal output circuit is processed by the following steps to avoid crosstalk between the pressure signal and the temperature signal:

[0053] S4.1: The temperature sensing circuit and the pressure sensing circuit have different induction modes to the stimulation signal. The pressure sensing circuit responds to the stimulation signal in real time. When there is pressure, there is a current change. When there is no pressure, the current change disappears immediately. However, the temperature sensing circuit responds to the stimulation signal slowly. When there is stimulation, the current changes slowly until it reaches the highest point. When there is no stimulation, the current change decreases slowly. It does not disappear immediately like the pressure sensing circuit. Therefore, the pressure sensing signal and the temperature sensing signal have huge characteristic differences. Next, signal acquisition is performed. Specifically, based on the characteristic differences of the temperature signal and the pressure signal fed back by the temperature sensing circuit and the pressure sensing circuit, the output signal is acquired by the Keithley 4200A-SCS parameter analyzer to obtain the current signal. Specifically, the output signal includes a signal with only pressure response, a signal with only temperature response, and a signal with mixed pressure and temperature response. 100 groups of each of the signal with only pressure response, the signal with only temperature response, and the signal with mixed pressure and temperature response are collected. The obtained Excel current table is exported, the header is removed, and only the two columns of time and current data are retained;

[0054] S4.2: Use the tsfresh library to perform feature extraction on the two columns of data, wherein the features extracted by tsfresh include: mean, variance, kurtosis, skewness, zero crossing rate, number of peaks, main frequency, and spectrum energy;

[0055] S4.3: Label the extracted features and convert each feature data after label classification into a standard normal distribution with a mean of 0 and a standard deviation of 1;

[0056] S4.4: Use PCA to reduce the dimension of feature data by finding the direction with the largest variance in the feature data and projecting the feature data to the direction with the largest variance to achieve dimensionality reduction;

[0057] S4.5: Input the reduced feature data into the random forest model for training, so that the random forest model can learn the relationship between the classification label and the feature data to distinguish between temperature and pressure signals. The specific steps are as follows:

[0058] Model parameter settings: set the number of decision trees of the random forest, the maximum depth of each tree, the minimum number of samples required to split a node, and the minimum number of samples required for a node. Specifically, set the number of decision trees of the random forest to 50, the maximum depth of each tree to 10, the minimum number of samples required to split a node to 2, and the minimum number of samples required for a node to 1;

[0059] Training model: Input the reduced feature data for training, so that the random forest model can learn the relationship between category labels and features. Next, we input the test signal, and the model will classify the test set we input, so that we can get the type of input signal and distinguish between temperature and pressure signals.

[0060] Example 2

[0061] The temperature sensitive layer 2 and the pressure sensitive layer 1 are made of two different materials, and cooperate with the two interdigital electrodes 4 to sense the temperature and / or pressure of the object being measured simultaneously or separately without input signal crosstalk.

[0062] The steps for preparing the pressure sensitive layer 1 are as follows:

[0063] S2.1, ablation of polyimide by CO2 infrared laser to obtain laser-induced graphene;

[0064] S2.2, using 120-grit sandpaper as a template for manufacturing the pressure-sensitive layer 1, and using a nitrogen gun to purge the surface of the template to remove contaminants;

[0065] S2.3, evenly applying laser-induced graphene on the surface of the template to form a laser-induced graphene layer, applying polydimethylsiloxane on the surface of the laser-induced graphene layer, and scraping away excess polydimethylsiloxane with a scraping rod, finally obtaining a film with a thickness of 0.8 mm;

[0066] S2.4. After drying in an oven for 6 hours, the polydimethylsiloxane attached with laser-induced graphene is removed from the template to form a pressure-sensitive layer 1, and the surface of the pressure-sensitive layer 1 corresponding to the interdigitated electrode 4 is a convex surface. Specifically, the laser-induced graphene has good conductivity, and its sheet shape makes the surface area large. It has a certain flexibility after ablation. The laser-induced graphene and polydimethylsiloxane, that is, PDMS, after ablation cooperate with each other to form a pressure-sensitive layer 1. The low elastic modulus and high ductility (deformation under pressure and recovery to original state under reduced pressure) of PDMS cooperate with the interdigitated electrode 1 to form a pressure sensing circuit. At the same time, the elasticity and flexibility of PDMS cooperate with the flexibility of laser-induced graphene after ablation to allow the pressure sensing circuit to be deformed.

[0067] The steps for preparing the temperature sensitive layer 2 are as follows:

[0068] S1.1. Pour 0.68 g of polyvinyl pyrrolidone powder with a molecular weight of 40,000 and 0.05 g of hexadecyl trimethyl ammonium bromide with a particle size of 30 nm into 7.5 ml of n-pentanol, and stir them magnetically for 5 hours to fully dissolve them to obtain a mixed solution, wherein the hexadecyl trimethyl ammonium bromide enhances the dispersion stability of polyvinyl pyrrolidone in n-pentanol;

[0069] S1.2, pour 3.1g nickel oxide powder into the above mixed solution, stir magnetically for 2h, and ultrasonically treat for 5min, finally obtain a dispersed nickel oxide raw material for preparing the temperature sensitive layer 2, wherein polyvinyl pyrrolidone ensures the viscosity of the nickel oxide raw material and provides sufficient surface tension so that the nickel oxide can form a film;

[0070] S1.3. Use a rubber-tipped dropper to absorb the dispersed nickel oxide raw material, drop a drop on the PET substrate 3 with the interdigital electrode 4, and dry it in an oven at 60°C for 3 hours to form a nickel oxide film. The nickel oxide film serves as the temperature sensitive layer 2. The flexibility of the film allows the temperature sensing circuit formed by the cooperation between the temperature sensitive layer 2 and the interdigital electrode 4 to be deformed.

[0071] The preparation steps of the above-mentioned flexible pressure-temperature dual-mode sensor are as follows:

[0072] S3.1, if Figure 2 As shown, a template 6 is used to sputter gold interdigital electrodes 4 with a thickness of 20 nm on the upper and lower surfaces of the PET substrate 3 by magnetron sputtering, and one of the pins of the two interdigital electrodes 4 is connected through a copper foil 5, as shown in FIG. Figure 2As shown, the template 6 is provided with a sputtering groove 61 having the same pattern as the interdigital electrode 4, wherein the interdigital electrode 4 is supported by gold, which has the characteristics of high conductivity, high chemical inertness, high stability and low contact resistance, and the copper foil 5 is a copper foil tape, which has good flexibility, can adapt to irregular surfaces, and is easy to be pasted on objects of complex shapes;

[0073] S3.2, applying the dispersed nickel oxide raw material on the interdigital electrode 4 on one side of the PET substrate 3, and drying to form the temperature sensitive layer 2;

[0074] S3.3, pasting the pressure sensitive layer 1 onto the interdigital electrodes 4 on the other side of the PET substrate 3 to form the above-mentioned flexible pressure-temperature dual-mode sensor.

[0075] The above-mentioned PET substrate is made of PET plastic. PET plastic is a thermoplastic polyester with toughness, high tensile and impact strength, electrical insulation, good tensile strength and tear resistance. The flexible pressure-temperature dual-mode sensor formed by cooperating with the deformable temperature sensing circuit and the pressure sensing circuit also has the ability to deform. Since the temperature sensitive layer 2 constituting the temperature sensing circuit is a film, the temperature sensing circuit is almost unaffected by the pressure sensing circuit when it is in operation by utilizing the characteristic that the film has a small elastic deformation when under pressure. In addition, when the temperature sensing circuit is in operation, the heat energy is difficult to be transferred to the pressure sensitive layer 1 due to the barrier of the PET substrate 3, thereby making the operation of the pressure sensing circuit almost unaffected by the operation of the temperature sensing circuit. Therefore, the input signal of the above-mentioned flexible pressure-temperature dual-mode sensor will not be crosstalked when it is in operation.

[0076] Verification Example

[0077] The PET substrate 3 of the flexible pressure-temperature dual-mode sensor is made of a PET transparent plastic film with a thickness of 0.4 mm and a size of 20 mm*20 mm.

[0078] Perform temperature and pressure performance measurements:

[0079] Water with different masses and temperatures is placed in a transparent glass bottle, and then the bottle is placed on the temperature-pressure dual-modal sensor. As the bottle is picked up and put down, the temperature and pressure sensing performance can be measured.

[0080] Specifically, when the bottle is filled with 4g of water at 25°C, the temperature and pressure performance test graphs are as follows: Figure 4 As shown, it can be seen that the current change of the temperature signal has hardly changed, but the current change of the pressure signal has been huge.

[0081] When the bottle is filled with 8g of water at 25℃, the temperature and pressure performance test graph is as follows Figure 5As shown, the current change of the temperature signal still does not change significantly, but the current change of the pressure signal almost doubles.

[0082] When the bottle is filled with 8g of water at 50℃, the temperature and pressure performance test graph is as follows Figure 6 As shown in Figure 2, the current of the temperature signal has changed significantly, but the current change of the pressure signal is Figure 5 resemblance.

[0083] In summary, the temperature-pressure dual-mode sensor disclosed in the present invention can detect both the change in pressure signal and the change in temperature signal.

[0084] Specifically, the room temperature during the measurement is about 27°C, and the glass sample bottle used contains tap water at a temperature of about 25°C. When they touch, the temperature sensor will feel the cold temperature, and the current will decrease slightly, but it is also visible, similar to a downward jitter. The same pressure, different temperature, the pressure signal is not affected by the temperature, the peak of the pressure signal has jitter, but their current change values ​​are about 10,000, which is the same in order of magnitude and the values ​​are similar.

[0085] Its circuit equivalent diagram is as follows Fig.11 As shown, the temperature sensor and pressure sensor are actually two components. Because they are based on different materials, they are just connected in series and will only respond to a single signal, so they have no crosstalk.

[0086] When measuring temperature performance:

[0087] The current response of the temperature sensing circuit at different temperatures and the temperature coefficient of resistance (TCR) at different temperature ranges are as follows: Figure 7 As shown in the figure, the resistance of the temperature sensing circuit gradually decreases as the temperature increases, and has the largest TCR coefficient in the low temperature range of 25-45℃, reaching -4.70%℃ -1 , then as the temperature increases, the resistance change trend gradually slows down.

[0088] By fitting the curve, the excellent thermal sensitivity constant of the temperature sensitive layer 2 in the temperature range (25-45° C.) is obtained as 13015K, which far exceeds the standard of commercial thermistors (3500K).

[0089] To perform pressure performance measurements:

[0090] The current response of the pressure sensing circuit under different pressures and the pressure sensitivity (S) under different pressure ranges are as follows: Fig. 9 As shown, within the pressure range of 0.12-1.86kPa, the sensitivity is 1592kPa -1; In the pressure range of 1.86-19.85kPa, the sensitivity is 28086kPa -1 ; In the pressure range of 19.52-49kPa, the sensitivity is 7062kPa -1 .

[0091] In summary, the pressure sensing circuit exhibits excellent sensing performance.

[0092] Cyclic durability measurement of the pressure sensing part:

[0093] The linear motor is used to apply pressure to the pressure sensitive layer 1. Specifically, when the pressure sensitive layer 1 is pressed and released for more than 10 cycles, 4 In this test, the current signal of the pressure sensing circuit decays as follows Fig.10 As shown, there is no obvious current decay in continuous cycles, indicating that the pressure sensing circuit has excellent durability.

[0094] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A flexible pressure-temperature dual-mode sensor, characterized in that: The invention comprises a pressure sensitive layer (1), a temperature sensitive layer (2) and a PET substrate (3), wherein both sides of the PET substrate (3) are printed with interdigital electrodes (4), the pressure sensitive layer (1) covers one of the interdigital electrodes (4) to form a pressure sensing circuit, the temperature sensitive layer (2) covers the other interdigital electrode (4) to form a temperature sensing circuit, and the two interdigital electrodes (4) corresponding to the temperature sensing circuit and the pressure sensing circuit are connected in series through copper foil (5) to form a single signal output circuit; The output signal of the signal output circuit is processed by the following steps to avoid crosstalk between the pressure signal and the temperature signal: S4.1: Based on the characteristic differences of the temperature signal and the pressure signal fed back by the temperature sensing circuit and the pressure sensing circuit, the output signal is collected by a Keithley 4200A-SCS parameter analyzer to obtain a current signal, and the obtained Excel current table is exported, the table header is removed, and only the two columns of time and current data are retained; S4.2: Use the tsfresh library to perform feature extraction on the two columns of data, wherein the features extracted by tsfresh include: mean, variance, kurtosis, skewness, zero crossing rate, number of peaks, main frequency, and spectrum energy; S4.3: Label the extracted features and convert each feature data after label classification into a standard normal distribution with a mean of 0 and a standard deviation of 1; S4.4: Use PCA to reduce the dimension of feature data by finding the direction with the largest variance in the feature data and projecting the feature data to the direction with the largest variance to achieve dimensionality reduction; S4.5: The feature data after dimensionality reduction is input into the random forest model for training, so that the random forest model learns the relationship between the classification label and the feature data to distinguish between temperature and pressure signals.

2. The flexible pressure-temperature dual-mode sensor according to claim 1, characterized in that: The output signals include signals that respond only to pressure, signals that respond only to temperature, and signals that respond in combination with pressure and temperature.

3. The flexible pressure-temperature dual-mode sensor according to claim 2, characterized in that: The surface of the pressure sensitive layer (1) in contact with the interdigital electrodes (4) is a convex surface.

4. The flexible pressure-temperature dual-mode sensor according to claim 3, characterized in that: The steps for preparing the temperature sensitive layer (2) are as follows: S1.1, pour polyvinyl pyrrolidone powder and cetyl trimethyl ammonium bromide into n-pentanol and fully dissolve them to obtain a mixed solution; S1.2, pouring nickel oxide powder into the mixed solution, and obtaining a dispersed nickel oxide raw material by magnetic stirring and ultrasonic treatment; S1.3, the dispersed nickel oxide raw material is dried to form the temperature sensitive layer (2).

5. The flexible pressure-temperature dual-mode sensor according to any one of claims 2 to 4, characterized in that: The steps for preparing the pressure sensitive layer (1) are as follows: S2.1, ablating polyimide to obtain laser-induced graphene; S2.2, using sandpaper as a template for manufacturing the pressure sensitive layer (1), and cleaning the surface of the template; S2.3, applying the laser induced graphene uniformly on the surface of the template to form a laser induced graphene layer, and applying polydimethylsiloxane on the surface of the laser induced graphene layer; S2.4, drying the polydimethylsiloxane attached with laser-induced graphene and removing it from the template to form the pressure-sensitive layer (1).

6. The flexible pressure-temperature dual-mode sensor according to claim 5, characterized in that: The preparation steps of the flexible pressure-temperature dual-mode sensor are as follows: S3.1, using a template (6) to sputter gold interdigital electrodes (4) on the upper and lower surfaces of the PET substrate (3) by magnetron sputtering, and one of the pins of the two interdigital electrodes (4) is connected by a copper foil (5); S3.2, applying the dispersed nickel oxide raw material on the interdigital electrode (4) on one side of the PET substrate (3), and drying to form the temperature sensitive layer (2); S3.3, pasting the pressure sensitive layer (1) onto the interdigital electrodes (4) on the other side of the PET substrate 3.

7. The flexible pressure-temperature dual-mode sensor according to claim 6, characterized in that: The template (6) is provided with a sputtering groove (61) having the same pattern as the interdigital electrode (4).

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