Resistance-type flexible pressure sensing array only with single pair of electrodes and preparation method of resistance-type flexible pressure sensing array

Abstract

A resistive flexible pressure sensing array only with a single pair of electrodes and a preparation method thereof belong to the technical field of sensors, the resistive flexible pressure sensing array comprises a flexible sensing layer and a flexible electrode layer, the flexible sensing layer and the flexible electrode layer form an integral structure in a superposition combination mode, and the two layers are respectively connected with a positive electrode and a negative electrode of a power supply through electrode leads. The flexible sensing layer is formed by alternately connecting a substrate, and a pressure sensitive module and a connecting resistor module which are laid on the substrate in series; the flexible electrode layer is composed of a substrate and an electrode module laid on the substrate. On the basis of an up-down series circuit which is formed after an array is pressed and is connected by a single pair of electrode leads, the resistance value range of connected resistors in the circuit is changed through the difference of the number of connected resistor modules in the circuit, and the purpose of identifying the pressure sensing position is achieved; the purpose of detecting the pressure is achieved through the resistance change condition when the pressure sensitive module is subjected to pressure. The invention has the advantages of simple preparation process, high sensitivity and strong stability, and can be applied to intelligent wearable equipment, electronic skin and other pressure sensing equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of sensors and relates to a resistive flexible pressure sensing array having only a single pair of electrodes and a preparation method thereof. Background Art

[0002] With the continuous development of the field of flexible electronics and the growing demand for tactile sensing technology, flexible sensor arrays that can simultaneously detect pressure location and pressure magnitude have attracted much attention in the fields of electronic skin, smart wearable devices, etc.

[0003] At present, most pressure sensor arrays use multiple circuits to test separately to identify the pressure position and detect the pressure size. However, the design of such sensor array circuits is often complex, and as the number of unit modules inside the array increases, the difficulty of circuit design and electrode lead arrangement will increase significantly, which largely limits the further expansion of the sensor array scale.

[0004] In terms of the number of electrodes, each sensing unit in most pressure sensing arrays requires two electrodes for signal output, that is, for a sensing array with N internal units, a total of 2N electrodes are required to achieve the transmission of all signals. This greatly increases the complexity and cost of the circuit, and is also difficult to implement in large-scale practical applications.

[0005] In terms of testing, the positive and negative electrodes of different sensor units inside most pressure sensor arrays often need to be connected to the test instruments in sequence. Only by repeatedly switching the circuits of different sensor units can the signals of the pressure position and pressure size reflected by different sensor units be obtained, or each sensor unit is equipped with a test instrument to measure the internal signals of different sensor units, which causes great inconvenience to actual operations.

[0006] In the context of the current high demand for pressure sensor arrays and the need to further expand the array scale, a design scheme and sensor array preparation method with a simple circuit structure, a small number of electrodes and convenient testing has become an urgent need in the sensing field. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a pressure sensing array having a simple circuit structure and capable of realizing pressure position identification and pressure magnitude detection by relying on only a single pair of electrodes, and a preparation method thereof.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A resistive flexible pressure sensing array having only a single pair of electrodes, the resistive flexible pressure sensing array comprising a flexible sensing layer and a flexible electrode layer, which are stacked and combined to form an overall unified structure; the flexible sensing layer and the flexible electrode layer are respectively provided with an electrode lead for connecting the positive and negative electrodes of a power supply.

[0010] The flexible sensing layer is composed of a substrate and a pressure sensitive module and a connecting resistor module laid flat on the substrate. The pressure sensitive modules and the connecting resistor modules are alternately connected in series, and each component is connected to each other through an electrode lead. The flexible electrode layer is composed of a substrate and an electrode module laid flat on the substrate, and each component is connected to each other through an electrode lead.

[0011] The electrode leads of the flexible sensing layer are arranged in a serpentine shape, the electrode leads of the flexible electrode layer are arranged in a field shape, and the pressure sensitive module on the flexible sensing layer corresponds to the electrode module on the flexible electrode layer. The two electrode leads are relatively connected up and down to form a pair of electrodes, and the electrode module in the electrode layer and the pressure sensitive module in the sensing layer and the connection resistor module are connected to form a series circuit.

[0012] Furthermore, the base material of the flexible sensing layer includes but is not limited to polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), polyimide (PI) or other polymer materials; the pressure sensitive module constitutes a pressure sensitive array, and its sensitive material includes but is not limited to carbon nanomaterials, transition metal carbides or other pressure sensitive materials; the material of the connecting resistor module includes but is not limited to carbon nanomaterials, transition metal carbides or other conductive materials; the electrode lead material includes but is not limited to gold, silver, copper or other materials with excellent conductive properties.

[0013] Furthermore, the base material of the flexible electrode layer includes but is not limited to polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), polyimide (PI) or other polymer materials; the electrode module material includes but is not limited to gold, silver, copper or other materials with excellent conductive properties; the electrode lead material includes but is not limited to gold, silver, copper or other materials with excellent conductive properties, wherein the electrode module material and the electrode lead material may be the same or different.

[0014] Furthermore, the shape of the pressure sensitive module of the flexible sensing layer includes but is not limited to a triangle, a quadrilateral, or other polygons, or a circle. The shape of the electrode module of the flexible electrode layer includes but is not limited to a triangle, a quadrilateral, or other polygons, or a circle. When forming a resistive flexible pressure sensing array, the shapes of the two may be the same or different, and the center of the pressure sensitive module and the center of the electrode module are required to be aligned.

[0015] Furthermore, the connection resistor module of the flexible sensing layer is located between two adjacent pressure sensitive modules, and is alternately connected in series with the pressure sensitive modules by serpentine electrode leads, and its shape includes but is not limited to triangle, quadrilateral, or other polygons, or circles.

[0016] Furthermore, the stacking and combining methods of the flexible sensing layer and the flexible electrode layer include but are not limited to adhesion, suturing, and hot pressing.

[0017] Furthermore, the preparation methods of the pressure sensitive module in the flexible sensing layer, the connection resistance module and the electrode module in the flexible electrode layer include but are not limited to printing method, drop coating method and deposition method.

[0018] A method for preparing a resistive flexible pressure sensing array having only a single pair of electrodes, based on the upper and lower series circuits connected by a single pair of electrode leads formed after pressing the array, changes the resistance range of the resistors connected in the circuit by the difference in the number of resistor modules connected in the circuit, and achieves the purpose of identifying the pressure sensing position; and detects the pressure magnitude by the change in resistance of the pressure sensitive module when it is subjected to pressure. The invention comprises the following steps:

[0019] Step 1: Prepare two polymer films of the same size as the substrates of the flexible sensing layer and the flexible conductive layer, and ensure that the substrate surface is flat and clean;

[0020] Step 2: Making pressure sensitive modules, connection resistor modules and serpentine electrode leads on the surface of the flexible sensing layer, ensuring that the pressure sensitive modules and the connection resistor modules are alternately arranged to form an array structure, and the electrode leads connect the pressure sensitive modules and the connection resistor modules in a serpentine series in sequence;

[0021] Step 3: Make electrode modules and electrode leads arranged in a field shape on the surface of the flexible electrode layer. The electrode leads connect the electrode modules and ensure that the positions of the electrode modules in the flexible electrode layer correspond to the positions of the pressure sensitive modules in the flexible sensing layer.

[0022] Step 4: Overlay and fix the flexible sensitive layer and the flexible electrode layer laid flat on the two substrates, ensuring that the pressure sensitive module and the electrode module are opposite and aligned in the center, and the flexible pressure sensing array can be obtained. Connect the serpentine electrode lead terminal of the flexible sensitive layer and the field-shaped electrode lead terminal of the flexible electronic layer to the digital source meter to test the resistance value of the pressure sensing array under the current situation. The specific test process is as follows:

[0023] When a certain position of the pressure sensing array is subjected to pressure, the pressure sensitive module and the electrode module at the corresponding position will contact each other, so that all the pressure sensitive modules and connecting resistance modules between the pressed position in the flexible sensing layer and the serpentine electrode lead terminals are connected to the circuit at the same time, so that the information of the pressure position and pressure magnitude can be obtained according to the resistance value measured by the digital source meter.

[0024] Furthermore, during the pressing process, different pressing positions will cause differences in the number of pressure-sensitive modules and connection resistor modules in the connected circuit, that is, when different pressure-sensitive modules are pressed sequentially along the serpentine circuit of the flexible sensing layer, the connection circuit at the latter pressing position always has one more pressure-sensitive resistor and one more connection resistor connected to it than the connection circuit at the previous pressing position, so that the resistance change caused by pressing different positions sequentially along the serpentine circuit will change in a step-like manner with the difference in the sum of the resistance values ​​of one pressure-sensitive resistor and one connection resistor.

[0025] Furthermore, in step 2, the resistance change range of the pressure sensitive module when subjected to pressure is smaller than the resistance value of a single connected resistance module, so that the resistance value generated after pressing uniquely corresponds to the pressure value at a certain position, thereby avoiding the situation where the resistance value of a pressure sensitive module pressed with a small pressure coincides with the resistance value of the next pressure sensitive module pressed with a large pressure, making it impossible to accurately determine the pressure position and pressure magnitude.

[0026] Furthermore, the method for reading the resistance output signal in step 4 is as follows: pressing a certain position of the flexible sensing layer will cause the circuit resistance to change in a step-like manner. The sudden increase in resistance is caused by the pressing behavior causing a number of pressure-sensitive resistors and connection resistors to be suddenly connected to the circuit, so the resistance value can be used to determine the number of pressure-sensitive resistors and connection resistors connected to the circuit, thereby determining the pressure position. The resistance change after the sudden increase in resistance is caused by the pressure sensing phenomenon generated by the pressure-sensitive material after pressing the pressure-sensitive module, so it can be used to test the magnitude of the pressure.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention can complete the production of a flexible pressure sensor array through a simple structure and circuit design, and the number of module units of the sensor array can be expanded using the same array arrangement scheme, effectively solving the problem that the sensor array is difficult to expand due to complex circuits and structures.

[0029] (2) The present invention can simultaneously realize the functions of identifying the pressure position and detecting the pressure magnitude by only using a single pair of electrodes connected to a test instrument to measure the array resistance. Moreover, the number of electrodes in the sensor array does not depend on the number of sensor unit modules in the array, that is, the expansion of the sensor array scale does not increase the number of electrodes required.

[0030] The present invention has the advantages of simple circuit and preparation process, low cost, high sensitivity and strong stability, and easy expansion of the sensor array scale, and can be applied to smart wearable devices, electronic skin and other pressure sensing devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A structural model diagram of a flexible pressure sensing array in an embodiment of the present invention;

[0032] Figure 2 1 is a perspective view and a plan view of a flexible pressure sensing array according to an embodiment of the present invention. Figure 2 (a) is a perspective view of the flexible electrode layer. Figure 2 (b) is a plan view of the flexible electrode layer. Figure 2 (c) is a perspective view of the flexible sensing layer. Figure 2 (d) is a plan view of the flexible sensing layer;

[0033] Figure 3 The resistance gradient diagram and position comparison diagram of the flexible pressure sensing array when different positions are pressurized in the embodiment of the present invention are shown in FIG. Figure 3 (a) is the resistance gradient diagram of the flexible pressure sensing array when different positions are compressed. Figure 3 (b) is a schematic diagram of the position comparison of the flexible pressure sensing array;

[0034] Figure 4 is a pressure sensing performance diagram of a single pressure sensing module of a flexible pressure sensing array in an embodiment of the present invention, Figure 4 (a) is the pressure sensing performance diagram when the first position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (b) is the pressure sensing performance diagram when the second position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (c) is the pressure sensing performance diagram when the third position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (d) is the pressure sensing performance diagram when the fourth position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (e) is the pressure sensing performance diagram when the 5th position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4(f) is the pressure sensing performance diagram when the 6th position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (g) is the pressure sensing performance diagram when the 7th position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (h) is the pressure sensing performance diagram when the 8th position starting from the serpentine electrode lead terminal is subjected to increasing pressure. Figure 4 (i) is a pressure sensing performance diagram when the 9th position starting from the serpentine electrode lead terminal is subjected to increasing pressure;

[0035] Figure 5 This is a pressure sensor response time test in an embodiment of the present invention;

[0036] Figure 6 This is a pressure sensor cycle stability test in an embodiment of the present invention. Figure 6 (a) is the overall cycle test diagram. Figure 6 (b) in Figure 6 (a) A local enlarged view of point A; Figure 6 (c) in Figure 6 A local enlarged view of point B in (a). DETAILED DESCRIPTION

[0037] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. It should be understood that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by ordinary technicians in the field according to the content of the present invention belong to the scope of protection of the present invention. The specific process parameters in the following embodiments are also only an example in a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description of the present invention, and are not limited to the specific parameter values ​​in the following embodiments.

[0038] Embodiment 1:

[0039] like Figure 1 , Figure 2 As shown, a resistive flexible pressure sensing array having only a single pair of electrodes provided by the present invention comprises a flexible sensing layer and a flexible electrode layer, and the edge portion between the two substrate layers is fixed with a double-sided tape.

[0040] The method for preparing the above-mentioned resistive flexible pressure sensing array having only a single pair of electrodes comprises the following steps:

[0041] Step 1: Clean the PET film as the substrate material with alcohol to remove impurities on its surface. Subsequently, the PET substrate is treated with a plasma cleaner for 30 seconds to make it hydrophilic, so as to enhance the adhesion between the material and the surface of the PET substrate in subsequent operations. Use a high-precision printer to print the required electrode layer pattern on the PET substrate. Among them, the electrode layer is composed of 3×3 silver modules, each module is 0.9cm×0.9cm in size, and the modules are connected by 0.1cm wide silver electrode leads in a field shape. The electrode layer substrate with the printed pattern is placed on a heating table at 120°C for 30 minutes of heating treatment to ensure that the silver ink is completely dried and fixed, and a silver electrode layer with a corresponding pattern is formed on the surface of the substrate.

[0042] Step 2: Print serpentine silver electrode leads on the surface of the PET film as the base material of the flexible sensing layer. The process is the same as the method of the silver electrode leads in the flexible electrode layer in step 1. Subsequently, print the pressure sensitive module on the PET base of the flexible sensing layer. The pressure sensitive material in this embodiment is MXene. The MXene ink used is an aqueous solution with a concentration of 10 mg / mL. The pressure sensitive array is composed of 3×3 arranged MXene module units. The size of each module unit is 1cm×1cm. The relative position of each MXene unit module in the sensing layer corresponds to each silver electrode module in the electrode layer. After printing, place the sensing layer base in an oven at 60°C for 30 minutes to ensure that the MXene pressure sensitive unit is completely dried and formed, and a pressure sensitive module with a corresponding pattern is formed on the surface of the base.

[0043] Subsequently, a connection resistor module is printed on the surface of the PET substrate. In this embodiment, the material used for the connection resistor module is MXene, and the MXene ink used is an aqueous solution with a concentration of 10 mg / mL. A high-precision printer is used to print the MXene connection resistor module on the silver electrode wire between adjacent pressure-sensitive modules. The size of each module is 0.4 cm × 0.2 cm. According to the requirements of the resistance value of the connection resistor module in the circuit, each connection resistor can be repeatedly printed at the same position to adjust its resistance value to an appropriate size. After the connection resistor module is printed, the sensing layer substrate is placed in an oven at 60°C for 30 minutes to ensure that the MXene connection resistor is completely dried and formed, and a connection resistor module with a corresponding pattern is formed on the surface of the substrate.

[0044] Step 3: Stick an appropriate amount of double-sided tape on the edges of the printed flexible electrode layer PET film and the flexible sensor layer PET film, and then stack and bond the two layers of PET film. During the bonding process, ensure that the electrode module in the flexible electrode layer and the pressure sensitive module in the flexible sensor layer are relative and centrally aligned, and the positions correspond one to one.

[0045] Embodiment 2:

[0046] Starting from the first pressure-sensitive module counting from the serpentine electrode lead terminal in the flexible sensing layer to the ninth pressure-sensitive module at the end of the serpentine electrode lead, a pressure of 8 kPa is applied to each pressure-sensitive module in turn, and the resistance change of the sensor array during the entire pressing process is tested in real time. The resistance change is shown in the figure below. Figure 3 As shown in the figure, it can be seen that pressing along the path of the serpentine electrode leads will cause the contact resistance and pressure sensitive resistor in front of each pressing position to be connected to the circuit in sequence, resulting in the resistance change caused by pressing at different positions showing a step-like monotonous upward trend. Therefore, the pressing position of the sensor array can be determined from the step-like rising resistance value of the sensor array.

[0047] Embodiment 3:

[0048] A pressure gradually increasing from 2 kPa to 32 kPa is applied to each pressure sensing unit of the flexible pressure sensing array, and its resistance change is tested in real time. The pressure sensing performance is shown in the following figure. Figure 4 As shown. It can be seen that for each individual pressing position, as the pressure gradually increases, the resistance gradually decreases. Moreover, the resistance change ranges when different positions are subjected to pressure do not overlap with each other. Therefore, for each individual pressing position, the magnitude of the pressure can be determined by observing the resistance value.

[0049] Embodiment 4:

[0050] Apply a momentary pressure to one of the sensing units in the flexible pressure sensing array and then remove the pressure immediately. The resistance change caused by this operation is as follows: Figure 5 As shown in the figure, it can be seen that instantaneous pressure can produce a sharp resistance change, and its response time and recovery time are both within 100ms.

[0051] Embodiment 5:

[0052] A universal material testing machine was used to perform a 1000-cycle pressure test on one of the sensing units in the flexible pressure sensing array. The resistance change caused by this operation is shown in Figure 2. Figure 6 As shown. It can be seen that during the process of applying multiple cycles of pressure, its resistance has been changing within a fixed range, reflecting its excellent stability and reliability.

[0053] The above-described embodiments merely express the implementation methods of the present invention, but they cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A resistive flexible pressure sensing array having only a single pair of electrodes, characterized in that: The resistive flexible pressure sensing array comprises a flexible sensing layer and a flexible electrode layer, which are stacked and combined to form an overall structure; the flexible sensing layer and the flexible electrode layer are respectively provided with an electrode lead for connecting the positive electrode and the negative electrode of the power supply; The flexible sensing layer consists of a substrate and a pressure sensitive module and a connecting resistor module laid flat on the substrate. The pressure sensitive modules and the connecting resistor modules are alternately connected in series, and the components are interconnected through an electrode lead; the flexible electrode layer consists of a substrate and an electrode module laid flat on the substrate, and the components are interconnected through an electrode lead.

2. A resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The electrode leads of the flexible sensing layer are arranged in a serpentine shape, the electrode leads of the flexible electrode layer are arranged in a field shape, and the pressure sensitive module on the flexible sensing layer corresponds to the electrode module on the flexible electrode layer in one-to-one position; the two electrode leads are relatively connected up and down to form a pair of electrodes, and the electrode module in the electrode layer and the pressure sensitive module in the sensing layer and the connecting resistor module are connected to form a series circuit.

3. A resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The base material of the flexible sensing layer includes polyethylene terephthalate PET, polydimethylsiloxane PDMS, polyimide PI or other polymer materials; the pressure sensitive module constitutes a pressure sensitive array, and its sensitive material includes carbon nanomaterials, transition metal carbides or other pressure sensitive materials; the material of the connecting resistor module includes carbon nanomaterials, transition metal carbides or other conductive materials; the electrode lead material includes gold, silver, copper or other conductive materials.

4. A resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The base material of the flexible electrode layer includes polyethylene terephthalate PET, polydimethylsiloxane PDMS, polyimide PI or other polymer materials; the electrode module material includes gold, silver, copper or other conductive materials; the electrode lead material includes gold, silver, copper or other conductive materials, wherein the electrode module material and the electrode lead material may be the same or different.

5. The resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The shapes of the pressure sensitive module of the flexible sensing layer and the electrode module of the flexible electrode layer may be the same or different, and the center of the pressure sensitive module is required to be aligned with the center of the electrode module.

6. A resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The connection resistance module of the flexible sensing layer is located between two adjacent pressure sensitive modules, and is alternately connected in series with the pressure sensitive modules by serpentine-arranged electrode leads.

7. A resistive flexible pressure sensing array having only a single pair of electrodes according to claim 1, characterized in that: The stacking and combination methods of the flexible sensing layer and the flexible electrode layer include adhesion method, suturing method, and hot pressing method; the preparation methods of the pressure sensitive module, the connection resistance module in the flexible sensing layer and the electrode module in the flexible electrode layer include printing method, drip coating method, and deposition method.

8. A method for preparing a resistive flexible pressure sensing array having only a single pair of electrodes, characterized in that: The following steps are involved: Step 1: Prepare two polymer films of the same size as the substrates of the flexible sensing layer and the flexible conductive layer, and ensure that the substrate surface is flat and clean; Step 2: Making pressure sensitive modules, connection resistor modules and serpentine electrode leads on the surface of the flexible sensing layer, ensuring that the pressure sensitive modules and the connection resistor modules are alternately arranged to form an array structure, and the electrode leads connect the pressure sensitive modules and the connection resistor modules in a serpentine series in sequence; Step 3: Make electrode modules and electrode leads arranged in a field shape on the surface of the flexible electrode layer. The electrode leads connect the electrode modules and ensure that the positions of the electrode modules in the flexible electrode layer correspond to the positions of the pressure sensitive modules in the flexible sensing layer. Step 4: Overlay and fix the flexible sensitive layer and the flexible electrode layer laid flat on the two substrates, ensure that the pressure sensitive module and the electrode module are opposite and center-aligned, and obtain a flexible pressure sensing array; connect the serpentine electrode lead terminal of the flexible sensitive layer and the field-shaped electrode lead terminal of the flexible electronic layer to the digital source meter. When a certain position of the pressure sensing array is subjected to pressure, the information of the pressure position and pressure magnitude can be obtained based on the resistance value measured by the digital source meter.

9. The method for preparing a resistive flexible pressure sensing array having only a single pair of electrodes according to claim 8, characterized in that: The process of obtaining the pressure position and pressure magnitude through the resistance value measured by the digital source meter is as follows: In step 4, during the pressing process, pressing a certain position of the flexible sensing layer causes the circuit resistance to change in a step-like manner; wherein, the sudden increase in resistance is caused by the sudden connection of a number of pressure-sensitive resistors and connection resistors to the circuit due to the pressing behavior, and the resistance value can be used to judge the number of pressure-sensitive resistors and connection resistors connected to the circuit, and then determine the pressure position; the resistance change generated after the sudden increase in resistance is caused by the pressure sensing phenomenon generated by the pressure-sensitive material after pressing the pressure-sensitive module, and can be used to test the pressure size.

10. The method for preparing a resistive flexible pressure sensing array having only a single pair of electrodes according to claim 8, characterized in that: The resistance variation range of the pressure sensitive module when subjected to pressure is smaller than the resistance value of a single connected resistance module, and the resistance value generated after pressing uniquely corresponds to the pressure value at a certain position.

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