Flexible temperature and pressure dual-mode sensor and array equipment

Abstract

The invention belongs to the technical field of flexible sensors, and relates to a flexible temperature and pressure dual-mode sensor and array equipment. The temperature and pressure dual-mode sensor comprises a first flexible substrate, a force-sensitive conductive layer, an interdigital electrode layer, a second flexible substrate, a counter electrode layer and a temperature-sensitive layer which are sequentially stacked; the force-sensitive conductive layer comprises a microstructure layer stacked on the first flexible substrate and a conductive layer stacked on the microstructure layer; wherein the material of the microstructure layer comprises flexible resin and expanded microsphere powder, the interior of the microstructure layer is provided with a microsphere micropore structure formed by expansion of expanded microspheres, and the surface of the microstructure layer is provided with a plurality of protrusions and recesses; the temperature-sensitive layer is connected between the two counter electrodes of the counter electrode layer, and the temperature-sensitive layer is made of graphene.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible sensors, and particularly relates to a flexible temperature-pressure dual-mode sensor and an array device. Background Art

[0002] With the continuous development of the global economy and technology, and the continuous improvement of the requirements for the intelligence, convenience, and comfort of electronic devices, flexible sensors, as an important part of the flexible electronics field, have received extensive attention and research. Flexible sensors include flexible strain sensors, flexible pressure sensors, flexible temperature sensors, and flexible multimodal sensors integrating two or more of the above functions. Among them, multimodal sensors can sense and detect the changes in multiple physical properties exhibited by an object. The data obtained by these sensors can be processed and fused to provide more comprehensive and accurate state information.

[0003] However, most of the existing multimodal sensors are usually in-plane integration of different types of sensing units, resulting in an increase in the volume of the sensor, a decrease in the device integration level, and an increase in the complexity of circuit design; in addition, some sensor devices convert different external excitations into the same type of signal output, making it difficult to decouple the signals between different modes of the sensor.

[0004] Therefore, the development of highly integrated and reliable temperature-pressure dual-mode sensors remains an important research direction for multimodal sensors. Summary of the Invention

[0005] In view of at least one of the technical problems existing in the prior art, the present invention provides a flexible temperature-pressure dual-mode sensor and an array device, which can avoid signal crosstalk between the temperature and pressure sensing units and improve the sensitivity and accuracy of temperature and pressure signal sensing.

[0006] The technical solution adopted in this application is as follows: In a first aspect, this application provides a temperature-pressure dual-mode sensor, including a first flexible substrate, a force-sensitive conductive layer, an interdigital electrode layer, a second flexible substrate, a counter electrode layer, and a temperature-sensitive layer stacked in sequence; The force-sensitive conductive layer includes a microstructural layer stacked on the first flexible substrate and a conductive layer stacked on the microstructural layer; wherein the material of the microstructural layer includes a flexible resin and expandable microsphere powder, and has a microsphere microporous structure formed by the expansion of expandable microspheres inside, and the surface of the microstructural layer has several protrusions and depressions; The temperature-sensitive layer is connected between two counter electrodes located in the counter electrode layer, and the material of the temperature-sensitive layer is graphene.

[0007] In a second aspect, this application provides a preparation method for the above flexible temperature-pressure dual-mode sensor, including the following steps: Prepare a microstructured layer on a first flexible substrate, where the microstructured layer is formed by heating and curing a flexible resin doped with expandable microspheres; Prepare a conductive layer on the microstructured layer to form a force-sensitive conductive layer; Prepare an interdigital electrode layer on the first side of a second flexible substrate, prepare a counter electrode layer on the second side of the second flexible substrate, and prepare a temperature-sensitive layer on the counter electrode layer; Stack and bond the interdigital electrode layer of the second flexible substrate and the force-sensitive conductive layer of the first flexible substrate face to face to obtain the temperature and pressure dual-mode sensor.

[0008] In some embodiments, the microstructured layer, the conductive layer, the interdigital electrode layer, the counter electrode layer, and the temperature-sensitive layer are prepared by a screen printing process.

[0009] In a third aspect, the present application provides a flexible temperature and pressure dual-mode sensor array device, which is composed of a plurality of the temperature and pressure dual-mode sensors electrically connected.

[0010] In some embodiments, the flexible temperature and pressure dual-mode sensor array device includes at least four of the temperature and pressure dual-mode sensors, where the interdigital electrode layer includes a horizontal interdigital electrode array and a vertical interdigital electrode array, and each node of the corresponding horizontal interdigital electrode array and vertical interdigital electrode array is insulated by an insulating material.

[0011] In a third aspect, the present application provides the application of the temperature and pressure dual-mode sensor or the array device in electronic skin or industrial temperature and pressure monitoring.

[0012] Compared with the prior art, the present application has at least the following beneficial effects: In the present invention, due to the temperature-sensitive characteristics of graphene, the resistance of the graphene temperature sensing unit decreases when the temperature rises, thereby reflecting the temperature change. In addition, the patterned design of the temperature sensing unit can increase the conductive path of the sensing unit and the effective contact area of the sensing unit; at the same time, it can make the distribution of heat in the sensing unit more uniform, so that the sensor can respond more quickly and stably in the face of temperature changes.

[0013] In the present invention, expandable microspheres form a microsphere structure with elasticity and compression characteristics inside the force-sensitive layer film, which can make the surface of the film produce uneven microstructures and enhance the compression and rebound ability of the force-sensitive film, thereby improving the sensitivity of the pressure sensing unit and enhancing the response speed of the pressure sensing unit.

[0014] In the present invention, the temperature and pressure sensing units are designed independently, and the signals are transmitted through different interfaces, avoiding the interference problem between different modal signals. In addition, for the sensor array device provided by the present invention, the pressure sensing part integrates the interdigital electrode array on the same side of the thin film by using an insulating thin film, avoiding crosstalk between circuits while reducing the device size and the number of interfaces, and improving the integration degree of the sensor array. Description of the Drawings

[0015] Figure 1 Schematic structural diagram of the temperature-pressure dual-mode sensor according to an embodiment of the present invention; Figure 2 Schematic diagram of the shape of the temperature-sensitive layer in an embodiment of the present invention; Figure 3 Scanning electron microscope image of the microstructure of the force-sensitive conductive layer in an embodiment of the present invention; Figure 4 Schematic diagram of the preparation process of the temperature-pressure dual-mode sensor according to an embodiment of the present invention; Figure 5 Schematic diagram of the pressure detection mechanism in the temperature-pressure dual-mode sensor unit according to an embodiment of the present invention; Figure 6 Schematic diagram of the performance test results of the temperature sensing unit in an embodiment of the present invention; Figure 7 Schematic diagram of the performance test results of the pressure sensing unit in an embodiment of the present invention; Figure 8 Schematic diagram of the test results of the temperature-pressure dual-mode signals of the dual-mode sensor according to an embodiment of the present invention; Figure 9 Schematic structural diagram of the dual-mode sensing array according to an embodiment of the present invention; Figure 10 Schematic structural diagram of the row-column interdigital electrode array of the pressure sensing array according to an embodiment of the present invention.

[0016] In the figure: 1 first flexible substrate, 2 force-sensitive conductive layer, 3 interdigital electrode layer, 4 second flexible substrate, 5 counter electrode layer, 6 temperature-sensitive layer. Detailed Embodiments

[0017] The following further describes the present application in combination with the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present application and cannot be used to limit the protection scope of the present application.

[0018] The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified.

[0019] The reagent materials used in this example can be purchased conventionally. For the quantitative experiments involved in the embodiments, at least three repeated experiments are set, and the results are averaged.

[0020] This embodiment provides a temperature and pressure dual-mode sensor, as Figure 1 shown, which includes a first flexible substrate 1, a force-sensitive conductive layer 2, an interdigital electrode layer 3, a second flexible substrate 4, a counter electrode layer 5, and a temperature-sensitive layer 6 that are sequentially stacked; The force-sensitive conductive layer 2 includes a microstructure layer stacked on the first flexible substrate and a conductive layer stacked on the microstructure layer; wherein the material of the microstructure layer includes a flexible resin and expandable microsphere powder, has a microsphere microporous structure formed by the expansion of expandable microspheres inside, and has a number of protrusions and depressions on the surface of the microstructure layer; The temperature-sensitive layer 6 is connected between two counter electrodes located in the counter electrode layer, and the material of the temperature-sensitive layer is graphene.

[0021] In some embodiments, in the material of the microstructure layer, the mass ratio of the flexible resin to the expandable microsphere powder is 100:1 to 100:5. The diameter of the expandable microsphere powder is 8 - 12 microns, and the microsphere diameter expands to 40 - 60 microns after being heated at a high temperature above 120 °C.

[0022] Further, the flexible resin is selected from one or more mixtures of epoxy resin, saturated polyester resin, acrylic resin, and polyurethane resin.

[0023] In some embodiments, the material of the conductive layer is one or more mixtures of carbon-based, MXene, and PEDOT conductive inks.

[0024] In some embodiments, the shape of the temperature-sensitive layer is spiral, serpentine, or linear, preferably spiral.

[0025] In some embodiments, the interdigital electrode layer is stacked on the first side of the second flexible substrate for leading out the pressure signal; the counter electrode layer is stacked on the second side of the second flexible substrate for leading out the temperature signal.

[0026] Further, the materials of the interdigital electrode layer and the counter electrode layer are independently selected from metal pastes such as conductive silver paste, conductive copper paste, and conductive silver-palladium paste; and one or several of conductive polymers such as polypyrrole and polyaniline.

[0027] In some embodiments, the first flexible substrate can be a PET film or a PI film. The second flexible substrate is a PET film.

[0028] It should be noted that in this application, the force-sensitive conductive layer 2, the interdigital electrode layer 3, and the second flexible substrate 4 constitute the pressure sensing unit of the temperature and pressure dual-mode sensor; the second flexible substrate 4, the counter electrode layer 5, and the temperature-sensitive layer 6 constitute the temperature sensing unit of the temperature and pressure dual-mode sensor. The pressure sensing unit is based on the principle of a resistive pressure sensor, and the temperature sensing unit is based on the temperature-resistance effect principle of graphene.

[0029] Specifically, the temperature-sensitive material of the temperature sensing unit in this application is graphene coating. The temperature-resistance response mechanism of graphene is the combined result of four factors: the electro-phonon coupling inside graphene, the thermal expansion of graphene and the substrate material, the intrinsic excitation, and the interaction between electrons and charged particles. Therefore, the graphene-based temperature sensor has a high sensitivity to temperature changes.

[0030] Specifically, the shape and size of the pattern of the temperature-sensitive material of the sensor will directly affect its surface area and the length of the conduction path, thereby affecting the sensitivity and response speed of temperature sensing. A longer conduction path has a larger surface area, which helps to increase the heat exchange with the environment, thus improving the temperature response speed; while a shorter conduction path length can maintain a uniform temperature distribution, making the signal more stable and reliable. Figure 2 The following shows the pattern designs that can be adopted for the temperature-sensitive layer part of the present invention. In the embodiments of the present invention, a spiral pattern is used to fabricate the temperature sensor. Since the sensor sensing area density of the spiral structure is high, it increases the effective contact area of the sensing unit, so the sensitivity and response speed of temperature sensing are also higher.

[0031] Specifically, the force-sensitive conductive layer of the pressure sensing unit in the present invention adopts an expanded microsphere doping process, and a large number of microsphere structures are introduced into the first flexible substrate lining film. As Figure 3 shown in (a) and (b) below, when the microspheres are heated to the thermal expansion trigger temperature, the microsphere shell softens and a large amount of pressure is generated by the internal foaming agent, causing the microspheres to expand. The maximum expansion can reach 40 - 60 μm, which is several times the original microsphere size, and the shell does not shrink after cooling, having good compressibility and rapid rebound characteristics. This microsphere structure will significantly reduce the Young's modulus of the lining film, which can not only improve the compressibility and mechanical properties of the film, but also improve the sensitivity and response range of the pressure sensing unit. At the same time, it can also effectively improve the response speed of the film force sensor and reduce the hysteresis characteristics.

[0032] In addition, the microsphere structure also makes the surface of the lining film have uneven structural features. As Figure 3As shown in (c), after the conductive layer is printed on the microsphere structure substrate film, the conductive layer also shows a rough surface microstructure. This rough surface microstructure results in fewer conductive paths when the conductive film and the interdigital electrodes are just in contact, and the number of conductive paths increases dramatically when the pressure increases. This rapid change in the conductive loop can improve the sensor's response speed and sensitivity when the pressure changes, thereby improving the sensor's ability to perceive small pressure changes.

[0033] Embodiment 1: A method for preparing a flexible temperature and pressure dual-mode sensor, comprising the following steps: (1) Preparation of expanded microsphere dispersion: 0.5 g of expanded microsphere powder was mixed with 25 g of epoxy resin and 5 g of epoxy resin curing agent, and the mixture was stirred by a planetary mixer for 0.5 hour until the expanded microsphere powder was evenly dispersed in the epoxy resin, thereby obtaining an epoxy resin dispersion doped with expanded microspheres; (2) Preparation of microstructured substrate film: The epoxy resin dispersion doped with expandable microspheres obtained in step (1) is printed on a first flexible substrate (PET, PI film) through a 300-mesh screen printing screen, and the printed film is placed in a vacuum drying oven and dried at 120° C. for 20 minutes to allow the film to solidify and the expandable microspheres to fully expand, thereby generating a microsphere structure inside the film, thereby obtaining a first flexible substrate with a microstructure; (3) Preparation of force-sensitive conductive layer: Using a 300-mesh screen printing plate, print carbon black conductive ink onto the uneven side of the first flexible substrate with microstructure obtained in step (2), and dry the printed film in a vacuum drying oven at 80° C. for 30 minutes to obtain a force-sensitive conductive layer with microstructure; (4) Preparation of the interdigital electrodes of the pressure sensing unit: The conductive silver paste is printed onto another layer of PET film (the second flexible substrate) through a 300-mesh screen printing plate, wherein the interdigital electrode width is 12 mm, the length is 15 mm, the interdigital width is 0.6 mm, the interdigital gap is 0.5 mm, and there are 4 pairs of interdigits. The film with the printed electrode pattern is placed in a vacuum drying oven at 100°C for 0.5 hours to obtain the interdigital electrode layer of the pressure sensing unit in the dual-mode sensor; (5) Flip the PET film (second flexible substrate) printed with the interdigital electrodes in the previous step, and print strip counter electrodes on the other side, with a gap of 1.2 mm between the counter electrodes. The printed film is also vacuum dried in a vacuum oven at 100°C for 0.5 hours to obtain the counter electrode layer of the temperature sensing unit in the dual-mode sensor; (6) Using a silk screen printing stencil with a spiral pattern, print the graphene conductive ink on the counter electrodes of the temperature sensing unit obtained in step (5). The overall width of the spiral pattern is 15 mm, and the line width is 2 mm. Both ends of the graphene spiral coating are connected to the counter electrodes to form a conductive loop. After drying the film in a vacuum at 80 °C for 0.5 hours, a temperature sensing unit is obtained; (7) Finally, face-to-face bond the side of the first flexible substrate printed with the force-sensitive conductive layer and the side of the second flexible substrate printed with the interdigital electrodes to obtain a temperature-pressure dual-mode sensor.

[0034] The working principle of the pressure sensing unit in the temperature-pressure dual-mode sensor prepared by the present invention is as Figure 5 shown. This device can be regarded as a parallel resistance model. In the initial stage, the interdigital electrode layer and the conductive layer are in a separated state, and at this time the device can be regarded as an open circuit; when the pressure reaches the minimum measurable force, contact is generated between the interdigital electrode layer and the conductive layer, and a conductive loop is generated between the counter electrodes of the interdigital electrodes, thereby detecting a change in resistance. At this time, the resistance value is relatively large. As the pressure increases, the contact area between the interdigital electrode layer and the conductive layer increases, and the contact resistance between the conductive layer and the interdigital electrodes decreases significantly; at the same time, more interdigital electrodes also participate in the conductive loop, so the overall resistance value of the device continues to decrease until the resistance change of the device becomes smaller and approaches saturation under the action of pressure.

[0035] The test results of the temperature sensing performance of the dual-mode sensor provided in Embodiment 1 of the present invention are as Figure 6 shown. The temperature coefficient is calculated to be -0.6% / °C by linear fitting between 20 °C and 40 °C -1 , and the temperature coefficient result is -0.1% / °C in the temperature range of 40 °C to 70 °C -1 , indicating that the sensor has a high sensitivity to temperature changes, as shown in Figure 6 (a); and the temperature sensing unit also shows good stability during the temperature cycle of 25 °C - 50 °C, as shown in Figure 6 (b).

[0036] The test results of the pressure sensing performance of the dual-mode sensor provided in Embodiment 1 of the present invention are as Figure 7 shown. The sensitivity reaches 35.76 kPa in the range of 0 - 0.7 kPa -1 , and when the pressure increases, the sensitivity decreases to saturation, indicating that the pressure sensing unit has a high pressure sensitivity, as shown in Figure 7 (a); the response time and recovery time of the sensor are 143 ms and 91 ms respectively, with a fast response speed, capable of real-time monitoring of pressure changes, as shown in Figure 7In (b); in addition, during the 3000-cycle test, the signal response of the sensor was relatively stable, and the signal response curves were basically the same at the initial and final cycles, indicating that the sensor device had good repeatability and durability, as shown in Figure 7 in (c).

[0037] The dual-mode sensing test results of the dual-mode sensor provided in Embodiment 1 of the present invention are as shown in Figure 8 shown, where Stage S1: Without applying pressure and without changing the temperature, the sensor reading remains unchanged; Stage S2: When pressure is applied and the temperature remains unchanged, the pressure signal of the sensor increases and the temperature signal remains unchanged; Stage S3: When the pressure is maintained and the temperature is increased, the pressure signal of the sensor remains unchanged and the temperature signal increases; Stage S4: When the pressure is further increased and the temperature remains unchanged, the pressure signal of the sensor increases and the temperature signal remains unchanged.

[0038] During this process, when the dual-mode sensor is only affected by pressure, the pressure signal changes with the change of pressure and the temperature signal remains unchanged; when the dual-mode sensor is only affected by temperature, the temperature signal changes with the contact temperature and the pressure signal remains unchanged; when the temperature and pressure signals act simultaneously, both the temperature and pressure signals change accordingly. The above results show that the dual-mode sensor provided in Embodiment 1 of the present invention has the ability to detect temperature and pressure signals simultaneously, and there is no signal interference between the two.

[0039] On the other hand, the embodiment of the present invention also provides a flexible temperature-pressure dual-mode sensor array device, which is composed of a plurality of temperature-pressure dual-mode sensors described in Embodiment 1 electrically connected.

[0040] In some embodiments, the flexible temperature-pressure dual-mode sensor array device includes at least four of the temperature-pressure dual-mode sensors, wherein the interdigital electrode layer includes a horizontal interdigital electrode array and a vertical interdigital electrode array, and each node of the corresponding horizontal interdigital electrode array and vertical interdigital electrode array is insulated by an insulating material.

[0041] A flexible temperature-pressure dual-mode sensor array device is provided in this embodiment, and the structure diagram is as shown in Figure 9 shown. From top to bottom, they are a graphene temperature-sensitive layer, a temperature-sensitive electrode layer, a second flexible substrate, a horizontal interdigital electrode array, a vertical interdigital electrode array, and 16 force-sensitive conductive layers with microstructures at the bottom layer. The graphene temperature-sensitive layer and the temperature-sensitive electrode layer constitute a temperature-sensing array with 7 temperature-sensing units, and the horizontal interdigital electrode array, the vertical interdigital electrode, and the microstructured force-sensitive conductive layer constitute a pressure-sensing array with 16 pressure-sensing units.

[0042] Specifically, the horizontal and vertical interdigital electrodes of the pressure sensing module are prepared on the same side of the second flexible substrate by screen printing. And as Figure 10 shown, an insulating film is printed between the horizontal and vertical electrodes, so that insulation between the electrodes can be ensured at the nodes, without affecting the signal transmission between the interdigital electrodes. When a certain pressure sensing unit is under pressure, the force-sensitive conductive layer of this unit will contact the horizontal and vertical interdigital electrodes where it is located to form a connected circuit, and the pressure signal is transmitted and read into the external system through the horizontal and vertical interdigital electrodes, thereby realizing the acquisition of the pressure signal of the dual-mode sensor array device.

[0043] Specifically, the signals of the pressure sensing units are collected by row-column scanning, and the signals of each sensor are obtained by row-by-row scanning and column-by-column scanning; the signals of the temperature sensing units are collected by the common cathode method, and the common cathode interface of the temperature sensing array and the individual interfaces of each temperature sensing unit are respectively connected for collection.

[0044] The above are the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A temperature and pressure dual-mode sensor, characterized in that: It includes a first flexible substrate, a force-sensitive conductive layer, an interdigital electrode layer, a second flexible substrate, a counter electrode layer and a temperature-sensitive layer which are stacked in sequence; The force-sensitive conductive layer comprises a microstructure layer stacked on a first flexible substrate and a conductive layer stacked on the microstructure layer; wherein the material of the microstructure layer comprises a flexible resin and expanded microsphere powder, the interior of the microstructure layer has a microsphere microporous structure formed by the expansion of expanded microspheres, and the surface of the microstructure layer has a plurality of protrusions and depressions; The temperature-sensitive layer is connected between two counter electrodes of the counter electrode layer, and the material of the temperature-sensitive layer is graphene.

2. The temperature and pressure dual-mode sensor according to claim 1, characterized in that: In the material of the microstructure layer, the mass ratio of the flexible resin to the expanded microsphere powder is 100:1 to 100:5; And / or, the flexible resin is selected from one or more mixtures of epoxy resin, saturated polyester resin, acrylic resin and polyurethane resin; And / or, the diameter of the expanded microspheres in the microstructure layer after expansion is 40-60 microns.

3. The temperature and pressure dual-mode sensor according to claim 1, characterized in that: The material of the conductive layer is a mixture of one or more of carbon-based, MXene, and PEDOT conductive ink.

4. The temperature and pressure dual-mode sensor according to claim 1, characterized in that: The shape of the temperature-sensitive layer is spiral, serpentine or linear, preferably spiral.

5. The temperature and pressure dual-mode sensor according to claim 1, characterized in that: The interdigital electrode layer is stacked on the first side of the second flexible substrate to extract the pressure signal; The counter electrode layer is stacked on the second side of the second flexible substrate and is used to extract a temperature signal.

6. The method for preparing the temperature and pressure dual-mode sensor according to any one of claims 1 to 5, characterized in that: The steps include: Preparing a microstructure layer on a first flexible substrate, wherein the microstructure layer is formed by heating and curing a flexible resin doped with expanded microspheres; preparing a conductive layer on the microstructure layer to form a force-sensitive conductive layer; preparing an interdigitated electrode layer on a first side of the second flexible substrate, preparing a counter electrode layer on a second side of the second flexible substrate, and preparing a temperature-sensitive layer on the counter electrode layer; The interdigital electrode layer of the second flexible substrate and the force-sensitive conductive layer of the first flexible substrate are laminated face to face to obtain the temperature-pressure dual-mode sensor.

7. The method for preparing the temperature and pressure dual-mode sensor according to claim 6, characterized in that: The microstructure layer, the conductive layer, the interdigital electrode layer, the counter electrode layer and the temperature-sensitive layer are prepared by a screen printing process.

8. A flexible temperature and pressure dual-mode sensor array device, characterized in that: The invention is composed of several temperature and pressure dual-mode sensors as described in claims 1 to 4 which are electrically connected.

9. The flexible temperature and pressure dual-mode sensor array device according to claim 8, characterized in that: It comprises at least four of the temperature and pressure dual-mode sensors, wherein the interdigitated electrode layer comprises a transverse interdigitated electrode array and a longitudinal interdigitated electrode array, and each node of the corresponding transverse interdigitated electrode array and longitudinal interdigitated electrode array is insulated by insulating material.

10. Application of the temperature-pressure dual-mode sensor according to any one of claims 1 to 5 or the array device according to claim 8 or 9 in electronic skin or industrial temperature and pressure monitoring.

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