CN115371830A - Temperature-pressure self-decoupling flexible sensor based on microstructure ionic material - Google Patents
Temperature-pressure self-decoupling flexible sensor based on microstructure ionic material Download PDFInfo
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- CN115371830A CN115371830A CN202210818404.6A CN202210818404A CN115371830A CN 115371830 A CN115371830 A CN 115371830A CN 202210818404 A CN202210818404 A CN 202210818404A CN 115371830 A CN115371830 A CN 115371830A
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- G01—MEASURING; TESTING
- G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
- G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
- G01K7/16—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using resistive elements
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- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/12—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor
- G01L9/125—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor with temperature compensating means
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Abstract
The invention discloses a temperature-pressure self-decoupling flexible sensor based on a microstructure ionic material. The flexible electrode array is formed by sequentially laminating a top layer structure, a micro-structure layer and a substrate layer from top to bottom, wherein the upper surface of an ionic gel array in the top layer structure is contacted with the flexible electrode array; the lower surface of an ion gel array in the microstructure layer is in contact with the microstructure ion gel thin layer, the microstructure ion gel thin layer and the conductive metal thin layer are arranged in a stacked mode from top to bottom, the conductive metal thin layer is electrically connected with the signal output interface, the flexible electrode array, the ion gel array, the microstructure ion gel thin layer and the conductive metal thin layer form a capacitive pressure sensor, and the flexible electrode array, the ion gel array and the microstructure ion gel thin layer form a resistive temperature sensor. The multi-mode flexible sensor disclosed by the invention can simultaneously detect the temperature, the pressure and the approaching three sensing modes, the temperature and the approaching sensing modes are realized through partial structures in the pressure sensing modes, the integration level is high, and the space is compact.
Description
Technical Field
The invention relates to a flexible sensor in the technical field of sensors, in particular to a temperature-pressure self-decoupling multi-modal flexible sensor based on a microstructure ionic material.
Background
Human skin is soft, but self-repairing to can the perception slight environmental difference, like breeze, this has amazing a large amount of researches to artificial class skin material, and the machine accomplishes intelligence and snatchs the during operation, need carry out accurate judgement to the dynamics of snatching, guarantees to accomplish under the prerequisite that does not damage the target.
The ionic gel is a solid mixture with ionic conductivity, is usually formed by mixing a high-molecular organic polymer and a salt electrolyte material capable of being electrolyzed into ions, and is called as the ionic gel because polymer molecular chains are connected or intertwined with each other to form a space network structure, and structural gaps are filled with anions and cations serving as dispersion media, and the structure is similar to that of the traditional gel. The high molecules forming the ionic gel are mostly colloidal block copolymers, and the copolymers can form a cross-linked network structure, so that high tensile strength is provided for the ionic gel, and the network structure also provides a channel for the movement of ions. The ionic liquid mixed in the high molecular copolymer is molten strong electrolyte, and the strong electrolyte exists in the ionic gel in the states of anion and cation in the molten state. Since the functional groups of the copolymer have a plurality of coordination sites, under the condition of no external electric field, anions and cations are mostly connected with the functional groups of the copolymer by coordination bonds and are dispersed in the whole ionic gel. Under the action of an external electric field, ions move locally between a polymer chain and an ion coordination site to generate migration of anions and cations, so that uneven charge distribution is generated in the ionic gel, and the anions and the cations are stacked at two ends of an interface respectively to form an electric double layer.
Temperature also changes the distribution of ions. As the temperature increases, the number of ions increases because more ions are pulled out of the polymer network. Furthermore, as the temperature increases, the ions gain more energy and therefore move faster. When a potential difference is applied across the ionic material, more ions will move to the electrode surface (i.e., more polarized). Due to these two phenomena, the capacitance increases with increasing temperature. Therefore, when the pressure generated by the object with the temperature is tested by utilizing the electric double-layer effect, the temperature can be changed due to the contact, and the measured capacitance is changed, so that the measured pressure has errors. Therefore, the dual influence of temperature and pressure needs to be decoupled, capacitance change caused by temperature change is eliminated, and the pressure is accurately measured.
Disclosure of Invention
In order to solve the problems that when the pressure is tested by utilizing the electric double-layer effect, the temperature is changed due to contact, the measured capacitance is changed, the measured pressure has errors, and the function of proximity sensing is realized, the invention provides a temperature-pressure self-decoupling flexible sensor based on a microstructure ionic material.
The technical scheme adopted by the invention is as follows:
the sensor is formed by sequentially stacking a top layer structure, a micro-structural layer and a substrate layer from top to bottom, wherein the top layer structure is provided with a leading-out belt which is bonded on the substrate layer, so that pre-pressure is generated between the top layer structure and the micro-structural layer;
the top layer structure comprises a flexible electrode array and an ionic gel array, wherein the upper surface of the ionic gel array is in contact with the flexible electrode array, and each ionic gel unit in the ionic gel array completely covers a corresponding flexible electrode unit in the flexible electrode array 3; the lower surface of the ionic gel array is contacted with the upper surface of the microstructure layer;
the micro-structure layer comprises a micro-structure ion gel thin layer, a conductive metal thin layer and a signal output interface, the lower surface of the ion gel array is in contact with the upper surface of the micro-structure ion gel thin layer, the micro-structure ion gel thin layer and the conductive metal thin layer are arranged in an up-to-down stacked mode, the conductive metal thin layer is electrically connected with the signal output interface, and the conductive metal thin layer is arranged on the substrate layer;
the flexible electrode array and the conductive metal thin layer are respectively used as two electrode plates of the capacitive pressure sensor, and the ion gel array and the microstructure ion gel thin layer are used as dielectric layers of the capacitive pressure sensor;
the flexible electrode array and the ionic gel array form a resistance type temperature sensor; the flexible electrode array is used as an electrode of the resistance temperature sensor, and the ionic gel array is used as a conductive medium of the resistance temperature sensor.
The flexible electrode array is composed of a plurality of flexible electrode units which are arranged into an N multiplied by M array, each electrode unit has the same structure and comprises a central wafer type electrode and a semi-closed ring type electrode, the central wafer type electrode is placed in the ring type electrode, and the central wafer type electrode and the ring type electrode are arranged at intervals.
The substrate layer is a flexible PI film.
The ion gel array consists of a plurality of ion gel units which are arranged into an N multiplied by M array; the mass ratio of each component material in the ionic gel array is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =8:1:1 to 12:1: 1.
The micro-structure ionic gel thin layer is provided with a micro-protrusion structure array on one side in contact with the ionic gel array, and the side, in contact with the conductive metal thin layer, of the micro-structure ionic gel thin layer is smooth.
The mass ratio of each component material in the microstructure ionic gel thin layer is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =10:1:1.
the conductive metal thin layer is made of copper foil.
The preparation method of the ionic gel solution of the ionic gel array comprises the following steps:
firstly, adding Dimethylacetamide (DMAC) into a beaker to serve as a solvent, and then adding a thermoplastic polyurethane elastomer (TPU) and [ EMIM ] [ TFSi ] ionic liquid, wherein the mass ratio of the DMAC to the TPU to the [ EMIM ] [ TFSi ] ionic liquid is 10:1:1; stirring the mixture on a magnetic stirrer for 12 hours to uniformly mix the three components; then placing the stirred ionic gel solution in a vacuum defoaming machine for defoaming for 20 minutes to remove bubbles in the ionic gel solution; heating the defoamed solution at 70 ℃ for 10 minutes, and removing water in the solution to obtain an ionic gel solution;
the top layer structure is prepared by the following method:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; pouring the mixed Ecoflex solution into a mold, heating at 60 ℃ for 2 hours to prepare a separation curing mold, placing the separation curing mold on the flexible electrode array, wherein each flexible electrode unit corresponds to a blank on the mold, and ensuring that no gap exists between the mold and the flexible electrode array in a bonding way; dripping 20ul of ionic gel solution into blank spaces in the mould by using a pipette gun; heating at the constant temperature of 60 ℃ for 24h for curing to form the ionic gel array with the thickness of 100um, and obtaining the top layer structure.
The microstructure layer is prepared by the following method:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; coating the mixed Ecoflex solution with the thickness of 2mm on the surface of sand paper with a preset mesh number by using a coating machine, and heating for 2 hours at 60 ℃ for curing; removing the sand paper to obtain a silica gel mold with a microstructure; coating ionic gel solution with the thickness of 3mm on a silica gel mold in a scraping way; heating at the constant temperature of 60 ℃ for 24h for curing to form the microstructure ion gel thin layer with the thickness of 300um; and adsorbing the microstructure ion gel thin layer on a conductive metal thin layer to obtain the microstructure layer.
The invention has the beneficial effects that:
when the pressure generated by an object with temperature is measured, the temperature can be measured through the resistance measured by the top layer structure, the common influence of the temperature and the pressure is measured through the capacitance change, the pressure borne by the sensor is deduced, the self-decoupling of the temperature and the pressure is realized, the pressure and the temperature are accurately measured, and the device has a wide application prospect in the aspects of artificial skin, intelligent robot grabbing and the like.
The robot has the function of proximity sensing, can measure the proximity condition of an object by utilizing the change of the capacitance value, and can position the relative position of the mechanical claw and the target when the robot intelligently grabs.
The invention simulates the flexible characteristic and the multi-modal perception function of the skin of an organism and can independently measure a plurality of variables in the human-computer interaction process. The same layer of electrodes are multiplexed to multiple sensing functions, the number of layers of the sensing device is reduced, the thickness of each layer is optimized, the total thickness is guaranteed to be 500 microns, the characteristics of lightness and thinness are achieved, and the limitation of the robot to the movement of the robot by the robot skin is reduced to the maximum extent.
The invention utilizes the microstructure ionic gel to ensure that the pressure sensing function of the sensor has higher sensitivity and linearity.
The invention has simple processing technology, all steps can be accurately quantified, the die can be recycled, and the equipment manufacturing repeatability is better.
The invention integrates a signal output port, and can be quickly integrated on the surface of a robot body, an end effector, an intelligent artificial hand and other equipment during application.
Drawings
FIG. 1 is an exploded view of an ionic gel sensor according to the present invention;
FIG. 2 is a schematic view of the structure of an ionic gel sensor according to the present invention
FIG. 3 is a top level structure circuit diagram;
FIG. 4 is a schematic diagram of the circuit of the present invention;
FIG. 5 is a flow chart for the preparation of the top layer structure;
FIG. 6 is a flow chart of the preparation of the microstructure layer;
FIG. 7 is a partitioned curing mold;
FIG. 8 is a pressure cycle applied to an ionic gel;
FIG. 9 shows the corresponding resistance change of the ionic gel;
FIG. 10 is a temperature-resistance calibration curve;
FIG. 11 is a temperature-capacitance calibration curve;
fig. 12 is a pressure-capacitance calibration curve.
In the figure: the device comprises a top layer structure 1, a microstructure layer 2, a substrate layer 3, a flexible electrode array 4, an ionic gel array 5, a microstructure ionic gel thin layer 6, a conductive metal thin layer 7, a signal output interface 8, a central wafer type electrode 41, a circular ring type electrode 42 and a separation curing mold 9.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1 and 2, the invention is formed by sequentially stacking a top layer structure 1, a micro-structure layer 2 and a substrate layer 3 from top to bottom, wherein the top layer structure 1 (i.e. a flexible electrode array 4) is provided with a lead-out tape which is adhered to the substrate layer 3, so that pre-pressure is generated between the top layer structure 1 and the micro-structure layer 2, and higher sensitivity is achieved; the top layer structure is used for detecting the temperature of a contact point, and the influence of pressure on the resistance of the material needs to be avoided as much as possible. Since the capacitance needs to be tested by using the electrical double layer effect, the contact resistance between the top layer structure and the microstructure layer is inevitable. By controlling the ionic concentration of the ionic gel, the sheet resistance can be increased, thereby reducing the contact resistance effect. The basal layer 3 is formed by cutting a flexible PI film, so that the flexibility of the sensor is ensured.
The top layer structure 1 comprises a flexible electrode array 4 and a smooth ionic gel array 5, wherein the upper surface of the ionic gel array 5 is arranged opposite to and in close contact with the flexible electrode array 3, and each ionic gel unit in the ionic gel array 5 completely covers the corresponding flexible electrode unit in the flexible electrode array 3; the lower surface of the ionic gel array 5 is tightly contacted with the upper surface of the microstructure layer 2;
the microstructure layer 2 comprises a microstructure ion gel thin layer 6, a conductive metal thin layer 7 and a signal output interface 8, the lower surface of the ion gel array 5 is tightly contacted with the upper surface of the microstructure ion gel thin layer 6, the microstructure ion gel thin layer 6 and the conductive metal thin layer 7 are arranged in a stacking manner from top to bottom, the conductive metal thin layer 7 is electrically connected with the signal output interface 8, and the conductive metal thin layer 7 is arranged on the substrate layer 3;
the microstructure layer is combined with the top layer structure, and the two layers of ionic gel are mutually contacted to generate an electric double-layer effect. When two polymers are brought into contact with each other and a potential difference is applied across the two layers, the ions will redistribute according to their polarity. The electric field is formed by the combined action of positive ions and negative ions. As the contact area increases, the capacitance increases due to the increase of the electric field. The microstructure ion gel thin layer is smooth on one side, a microstructure is prepared by using sand paper on the other side, the microstructure with better consistency can be prepared after the mesh number of the sand paper is determined, and the sensor has good repeatability; because the microstructure prepared by the sand paper shows consistency and uniformity on a macroscopic level, the contact area of two layers of ionic gel can be uniformly increased along with the increase of pressure in the process of pressurizing the sensor, and the sensor has higher sensitivity and linearity; the thickness of the microstructure ionic gel thin layer needs to ensure that the microstructure on the sand paper is completely covered, but the capacitance and resistance characteristics of the sensor are not influenced, and the minimum thickness can reach 300 mu m.
The flexible electrode array 4, the ionic gel array 5, the microstructure ionic gel thin layer 6 and the conductive metal thin layer 7 form a capacitance type pressure sensor, wherein the flexible electrode array 4 and the conductive metal thin layer 7 are used as the capacitance type pressure sensor, a central disc type electrode 41 in each flexible electrode unit in the flexible electrode array, an ionic gel unit attached to the central disc type electrode 41, the microstructure ionic gel thin layer and the conductive metal thin layer can be regarded as a capacitance type pressure sensing unit, and capacitance signals of the capacitance type pressure sensing unit are jointly led out by the central disc type electrode 41 and the conductive metal thin layer. The flexible electrode array 4 and the conductive metal thin layer 7 are respectively used as two electrode plates which are parallel to each other of the capacitive pressure sensor, the ionic gel array 5 and the microstructure ionic gel thin layer 6 are used as dielectric layers of the capacitive pressure sensor, the conductive metal thin layer 7 can sense the approach of an external conductive object by measuring the capacitance change to the ground generated when a conductor approaches, and the measurement of the capacitance of the capacitive pressure sensor reflects the pressure applied by the external environment and the distribution;
the flexible electrode array 4 and the ionic gel array 5 form a resistance type temperature sensor, and temperature change is detected through resistance change. Each flexible electrode unit and the ion gel unit attached to the flexible electrode unit can be regarded as a resistance type temperature sensor, and resistance signals are led out together by a central circular sheet type electrode 41 and a semi-closed circular ring type electrode 42; the flexible electrode array 3 is used as an electrode of the resistance temperature sensor, and the ionic gel array 5 is used as a conductive medium of the resistance temperature sensor.
In the temperature sensing module, the resistance of the ionic gel corresponding to a detection point is measured through the central wafer type electrode and the ring type electrode, so that the temperature of the detection point can be calculated; in the pressure sensing module, the central disc-type electrode is used as one electrode of capacitance measurement; for a plate capacitor, the electric field intensity between two plates determines the size of the capacitor, the electrode area determines the electric field intensity, and the sensitivity of the sensor can be improved by adopting the larger central wafer type electrode. The ionic gel needs to be prepared in proportion. The electric double-layer effect can be enhanced by adding more ionic liquid into the sample, so that the sensitivity of the sensor is improved, but the mechanical property and the transparency of the sample are influenced. A trade-off between electrical and mechanical properties is therefore required.
In conclusion, the multi-mode flexible sensor disclosed by the invention can simultaneously detect the temperature, the pressure and the approaching sensing mode, the temperature and the approaching sensing mode are realized through partial structures in the pressure sensing mode, the integration level is high, and the space is compact.
The multi-mode flexible sensor disclosed by the invention utilizes the characteristic that the self resistance value of an ionic material is insensitive to an external force to decouple the double influences of temperature and pressure on the capacitance value in a capacitance type pressure sensing mode, eliminates the capacitance change caused by the temperature change and accurately measures the pressure applied to the sensor. When the pressure generated by an object with temperature is measured, the multipoint temperature distribution can be calculated through the resistance measured by the ionic gel array in the top layer structure, the relation curve of the common influence of the capacitance change measured in the pressure sensing mode and the temperature, the capacitance change and the pressure is calibrated, the pressure borne by the sensor is deduced according to the temperature value calculated by using the resistance at present, the self-decoupling of the temperature and the pressure is realized, the pressure and the temperature are accurately measured, the decoupling process only relates to the ionic material of the capacitive pressure sensor, other materials are not needed, other temperature sensors are not needed to be arranged outside the sensor, the self-decoupling in the sense of the ionic material and the self-decoupling in the sense of a sensing device are realized, and when a proximity sensing module is used, the central circular sheet type electrodes on the flexible electrode array can be connected in series to form a large ground capacitance; the approach condition of the object can be measured by using the capacitance value change caused by the approach of the object.
As shown in fig. 3, the flexible electrode array 4 is composed of a plurality of flexible electrode units arranged in a coplanar manner to form an N × M array, each electrode unit has the same structure and includes a central circular sheet type electrode 41 and a semi-closed circular ring type electrode 42, the central circular sheet type electrode 41 is disposed in the circular ring type electrode 42, and the central circular sheet type electrode 41 and the circular ring type electrode 42 are arranged at intervals. The center wafer type electrode 41 of each flexible electrode unit independently outputs signals using a signal output interface, such as the signal output interfaces 1_1-1_9 of fig. 3 and 4; the circular ring type electrodes 42 are connected in series and share one signal output interface, such as the signal output interface 1_0 in fig. 3 and 4; the resistance between each group of electrodes can be measured through the signal output port 1 _0and the signal output ports 1_1-1_9, and the temperature of the contact point can be obtained by comparing with a calibration result. The capacitance between each group of electrodes can be measured through the signal output port 8 and the signal output ports 1 \/9, and the result under the joint influence of temperature and pressure can be obtained through comparison with a calibration result. And then the pressure applied on the contact point can be obtained through self-decoupling calculation. Simultaneous measurement of the contact point temperature and pressure is thus achieved. In the temperature sensing module, the resistance of the ionic gel corresponding to a detection point is measured by each central wafer type electrode 41 and each ring type electrode 42, so that the temperature of the detection point can be calculated; in the pressure sensing module, the center wafer-type electrode 41 serves as one electrode for capacitance measurement; for a plate capacitor, the electric field intensity between two plates determines the size of the capacitor, the electrode area determines the electric field intensity, and the central circular sheet type electrode 41 can improve the sensitivity of the sensor.
The substrate layer 3 is a flexible PI film, the thickness of the flexible PI film is 50 microns, the whole thickness of the sensor is favorably reduced, and the sensor is favorably applied to the aspects of intelligent robot grabbing, artificial skin and the like.
The ionic gel array 5 consists of a plurality of ionic gel units which are arranged in a coplanar manner to form an NxM array; the thickness of the ionic gel array 5 does not influence the capacitance and resistance performance of the sensor, and the thickness of the gel can be reduced to the greatest extent to reach about 100 mu m on the premise of ensuring complete coverage of the electrodes; each ionic gel unit of the ionic gel array 5 does not contact with each other, so that mutual insulation is realized, and data are independently provided in the working process; the resistance of the ionic gel array 5 is insensitive to pressure, and the temperature of the ionic gel unit can be calculated by measuring the resistance value of the ionic gel in the temperature sensing module; in the pressure sensing module, the ionic gel array 5 is used as one layer of an electric double-layer structure; organic solvents including Dimethylacetamide (DMAC) are required for the preparation of the ionic gel used by the ionic gel array 5; there is a need for elastomeric polymers, including thermoplastic polyurethane elastomers TPU; ionic liquids IL are required, including [ EMIM ] [ TFSi ]; the mass ratio of each component material in the ionic gel array 5 is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =8:1: 1. The prepared solution is ensured to have lower viscosity, and the requirement of subsequent operation is met.
The micro-structure ion gel thin layer 6 is provided with a micro-protrusion structure array on the surface contacted with the ion gel array 5, in the specific implementation, the micro-structure is prepared by using sand paper, and after the mesh number of the sand paper is determined, the micro-structure with better consistency can be prepared, and the sensor has good repeatability; due to the consistency and uniformity of the microstructure prepared by using the sand paper, the contact area of two layers of ion gel can be uniformly increased along with the increase of pressure in the process of pressing the sensor, so that the sensitivity and the linearity of the capacitive pressure sensor are increased. The surface of the microstructure ion gel thin layer 6, which is in contact with the conductive metal thin layer 7, is smooth; the thickness of the microstructure ion gel thin layer 6 needs to ensure that the microstructure on the sand paper is completely covered, but the capacitance and resistance characteristics of the sensor are not influenced, and the minimum thickness can reach 300um; the microstructure ion gel thin layer 6 is used as one layer of an electric double layer in the pressure sensing module; the capacitance of the electric double layer depends on the contact area, when the sensor is pressed, the microstructure ion gel thin layer 6 is deformed, the contact area with the ion gel array 5 is increased, and the capacitance of the sensor is increased;
organic solvents including Dimethylacetamide (DMAC) are required for the preparation of the ionic gel used by the microstructure ionic gel thin layer 6; there is a need for elastomeric polymers, including thermoplastic polyurethane elastomer TPUs; ionic liquids are required, including [ EMIM ] [ TFSi ]; the mass ratio of the materials of the components is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =10:1:1.
the thin conductive metal layer 7 is made of copper foil, typically several tens of microns thick, and serves as one pole in a parallel plate capacitor, contributing to reducing the overall thickness of the sensor; the adhesive surface of the conductive metal thin layer 7 is adhered to the substrate 3, so that the adhesion is ensured to be stable, and the relative positions of all layers are fixed in the process of pressing the sensor; the metal surface of the conductive metal thin layer 7 is bonded with the microstructure ionic gel thin layer 6 through the self adhesion of the ionic gel; the conductive metal thin layer 7 has high fatigue resistance and flexibility, and can keep stable performance in a long-term use process.
The preparation method of the ionic gel solution of the ionic gel array 5 is as follows:
firstly, adding Dimethylacetamide (DMAC) as a solvent into a clean and dry beaker, and then adding a thermoplastic polyurethane elastomer (TPU) and an [ EMIM ] [ TFSi ] ionic liquid, wherein the mass ratio of the dimethylacetamide to the DMAC to the thermoplastic polyurethane elastomer to the [ EMIM ] [ TFSi ] ionic liquid is 10:1:1; stirring the mixture on a magnetic stirrer for 12 hours to uniformly mix the three components; then placing the stirred ionic gel solution in a vacuum defoaming machine for defoaming for 20 minutes to remove bubbles in the ionic gel solution; heating the defoamed solution at 70 ℃ for 10 minutes to remove water in the solution; pouring the solution into a dry and clean glass container, and sealing and storing to obtain an ionic gel solution; the amount of free ions in unit volume can be increased by adding more ionic liquid into a sample, so that the sensitivity of the sensor is improved, but the mechanical property and the transparency of the sample are influenced; therefore, a trade-off between electrical performance and mechanical performance is required according to the requirements of application scenarios; organic solvents including Dimethylacetamide (DMAC) are needed for preparing the ionic gel used by the microstructure ionic gel thin layer; there is a need for elastomeric polymers, including thermoplastic polyurethane elastomers TPU; ionic liquids IL are required, including EMIM [ TFSi ]; the mass ratio during configuration is DMAC: TPU: IL =10:1:1. the prepared solution is ensured to have certain viscosity, and the requirements of subsequent operation are met.
As shown in fig. 5, the top layer structure 1 is prepared by the following method:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; pouring the mixed Ecoflex solution into a mold, heating at 60 ℃ for 2 hours to prepare a separation curing mold 9, as shown in fig. 6, carefully placing the separation curing mold 9 on the flexible electrode array 4, wherein each flexible electrode unit corresponds to a blank on the mold, and ensuring that the mold is attached to the flexible electrode array 4 without any gap; dripping 20ul of ionic gel solution into the blank in the mould by using a liquid-transfering gun; heating at the constant temperature of 60 ℃ for 24h for curing to form an ionic gel array 5 with the thickness of 100 um; carefully taking down the separation curing mold to obtain a top layer structure 1; the separated curing mold 9 can be repeatedly used, all the steps can be accurately quantified, and the manufacturing repeatability of the equipment is better.
As shown in fig. 6, the microstructure layer 2 is prepared by the following method:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; coating the mixed Ecoflex solution with the thickness of 2mm on the surface of sand paper with a preset mesh number by using a coating machine, and heating for 2 hours at 60 ℃ for curing; removing the sand paper to obtain a silica gel mold with a microstructure; coating ionic gel solution with the thickness of 3mm on a silica gel mold in a scraping way; heating at the constant temperature of 60 ℃ for 24h for curing to form a microstructure ion gel thin layer 6 with the thickness of 300um; adsorbing the microstructure ionic gel thin layer 6 on a conductive metal thin layer 7 (the side of the copper foil without the glue) by utilizing the inherent adsorption capacity of the smooth surface of the ionic gel to obtain a microstructure layer 2; the silica gel mold with the microstructure can be recycled, all steps can be accurately quantified, and the repeatability of the performance of the microstructure layer prepared each time is ensured.
The signal output interface 8 is adhered on the substrate layer 3 by using a conductive adhesive; the signal output interface 8 is wrapped by an insulating tape, so that the corrosion of the electrode and the change of the conductivity caused by the change of the external environment are prevented; and outputting the electric signals measured by the conductive metal thin layer 7 as a common electrode of each detection point in the pressure sensing module through a signal output interface 8.
The sensor can decouple the dual influences of temperature and pressure in a decoupling pressure sensing mode by utilizing the characteristic that the resistance value of the ionic material is insensitive to an external force, eliminate the capacitance change caused by the temperature change and accurately measure the pressure applied to the sensor; when the pressure generated by an object with temperature is measured, the multipoint temperature distribution can be calculated through the resistance measured by the ionic gel array 5 in the top layer structure 1, the capacitance change caused by the temperature is deduced and eliminated by calibrating the relation curve of the capacitance and the temperature and the capacitance and the pressure in a pressure sensing mode according to the temperature value calculated by using the resistance at present and further using the relation curve of the capacitance and the temperature, the pressure born by the sensor is obtained, the self-decoupling of the temperature and the pressure is realized, and the pressure and the temperature are accurately measured; the decoupling process only relates to the ionic material of the capacitive pressure sensor, does not need other materials, does not need to arrange other temperature sensors outside the sensor, and realizes the self-decoupling of the ionic material and the self-decoupling of the sensing device.
Through the design of the signal acquisition circuit, when the approach induction module is used, the central circular sheet type electrodes 41 on the flexible electrode array 4 can be connected in series to form a larger capacitance to ground, and the approach condition of an object can be measured by utilizing the change of capacitance values caused by the approach of the object; the conductive metal thin layer 7 can also be regarded as a larger electrode, and the approaching condition of the object can be measured by utilizing the capacitance change of the electrode to the ground caused by the approach of the object; the central disc type electrodes 41 can also be connected in series to form a larger electrode, and a mutual capacitance is formed between the larger electrode and the conductive metal thin layer 7, and the approaching condition of an object can be measured by utilizing the change of the mutual capacitance value of the electrode pair caused by the approach of the object.
As shown in fig. 8, the ionic gel is applied with a pressure of 0-1N cycle, and the corresponding resistance change of the ionic gel is shown in fig. 9; under the pressure circulation effect, the resistance change rate of the ionic gel is less than 1%, which indicates that the ionic gel is a material insensitive to pressure, the temperature of a contact point can be accurately measured through the resistance in the pressure process, and the reliability and the accuracy of the temperature sensing module are ensured.
As shown in FIG. 10, the holding pressure is 0.01N, the temperature is changed at 10-60 deg.C, the resistance is changed in the range of 2.3-0.22M Ω, the change rate is 1000%, and the measured resistance can be used to calculate the temperature of the detecting point of the sensor in combination with the calibration result.
As shown in fig. 11, the guaranteed pressure is 2N, and the sensor pressure sensing module can reach the maximum range. The temperature is changed at 10-60 ℃, the capacitance is correspondingly changed in the range of 580-3650pF, and the change rate is 5300 percent. Because the capacitance value of the electric double layer is determined by the contact area and the ion concentration together, the ion concentration is only changed by the temperature change, the contact area is not changed, and the capacitance value change proportion of the sensor caused by the temperature change can be calculated by utilizing the temperature capacitance calibration curve. The equivalent capacitance value at 20 c can be estimated in combination with the measured temperature value.
As shown in fig. 12, the sensor capacitance correspondingly changes from 40pF to 1000pF with 2500% change as the pressure increases from 0 to 0.5N at room temperature of 20 ℃. The equivalent capacitance value calculated in the earlier stage can be used for calculating the pressure borne by the sensor, and the accurate measurement of the temperature and the pressure can be completed.
Claims (10)
1. A temperature-pressure self-decoupling flexible sensor based on a microstructure ionic material is characterized by being formed by sequentially stacking a top layer structure (1), a microstructure layer (2) and a substrate layer (3) from top to bottom, wherein the top layer structure (1) is provided with a leading-out belt which is adhered to the substrate layer (3) so that pre-pressure is generated between the top layer structure (1) and the microstructure layer (2);
the top layer structure (1) comprises a flexible electrode array (4) and an ionic gel array (5), the upper surface of the ionic gel array (5) is in contact with the flexible electrode array (3), and each ionic gel unit in the ionic gel array (5) completely covers the corresponding flexible electrode unit in the flexible electrode array (3); the lower surface of the ionic gel array (5) is in contact with the upper surface of the microstructure layer (2);
the microstructure layer (2) comprises a microstructure ion gel thin layer (6), a conductive metal thin layer (7) and a signal output interface (8), the lower surface of the ion gel array (5) is in contact with the upper surface of the microstructure ion gel thin layer (6), the microstructure ion gel thin layer (6) and the conductive metal thin layer (7) are arranged in a stacking mode from top to bottom, the conductive metal thin layer (7) is electrically connected with the signal output interface (8), and the conductive metal thin layer (7) is arranged on the substrate layer (3);
the flexible electrode array (4), the ion gel array (5), the microstructure ion gel thin layer (6) and the conductive metal thin layer (7) form a capacitive pressure sensor, wherein the flexible electrode array (4) and the conductive metal thin layer (7) are used as the capacitive pressure sensor, the flexible electrode array (4) and the conductive metal thin layer (7) are respectively used as two electrode plates of the capacitive pressure sensor, and the ion gel array (5) and the microstructure ion gel thin layer (6) are used as dielectric layers of the capacitive pressure sensor;
the flexible electrode array (4) and the ionic gel array (5) form a resistance type temperature sensor; the flexible electrode array (3) is used as an electrode of the resistance temperature sensor, and the ionic gel array (5) is used as a conductive medium of the resistance temperature sensor.
2. The flexible temperature-pressure self-decoupling sensor based on microstructured ionic materials as claimed in claim 1, wherein the flexible electrode array (4) is composed of a plurality of flexible electrode units arranged in an N × M array, each electrode unit has the same structure and comprises a central circular-disc-type electrode (41) and a semi-closed circular-ring-type electrode (42), the central circular-disc-type electrode (41) is disposed inside the circular-ring-type electrode (42), and the central circular-disc-type electrode (41) and the circular-ring-type electrode (42) are spaced apart from each other.
3. A temperature-pressure self-decoupling flexible sensor based on microstructured ionic material according to claim 1, characterized in that the substrate layer (3) is a flexible PI film.
4. A temperature-pressure self-decoupling flexible sensor based on microstructured ionic material according to claim 1, characterized in that the ionic gel array (5) is composed of a plurality of ionic gel units arranged in an N x M array; the mass ratio of each component material in the ionic gel array (5) is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =8:1:1 to 12:1: 1.
5. The temperature-pressure self-decoupling flexible sensor based on the microstructure ionic material as claimed in claim 1, wherein the microstructure ionic gel thin layer (6) is provided with a micro-protrusion structure array on the side in contact with the ionic gel array (5), and the microstructure ionic gel thin layer (6) is smooth on the side in contact with the conductive metal thin layer (7).
6. The temperature-pressure self-decoupling flexible sensor based on the microstructure ionic material as claimed in claim 1, wherein the mass ratio of each component material in the microstructure ionic gel thin layer (6) is Dimethylacetamide (DMAC): thermoplastic polyurethane elastomer TPU: ionic liquid IL =10:1:1.
7. a temperature-pressure self-decoupling flexible sensor based on microstructured ionic materials according to claim 1, characterized in that the thin conductive metal layer (7) is made of copper foil.
8. A temperature-pressure self-decoupling flexible sensor based on microstructured ionic material according to claim 1, characterized in that the ionic gel solution of the ionic gel array (5) is prepared as follows:
firstly, adding Dimethylacetamide (DMAC) into a beaker as a solvent, and then adding thermoplastic polyurethane elastomer (TPU) and [ EMIM ] [ TFSi ] ionic liquid, wherein the mass ratio of the DMAC to the TPU to the [ EMIM ] [ TFSi ] ionic liquid is 10:1:1; stirring the mixture on a magnetic stirrer for 12 hours to uniformly mix the three components; then placing the stirred ionic gel solution in a vacuum defoaming machine for defoaming for 20 minutes to remove bubbles in the ionic gel solution; the defoamed solution was heated at 70 ℃ for 10 minutes, and water in the solution was removed to obtain an ionic gel solution.
9. A temperature-pressure self-decoupling flexible sensor based on microstructured ionic material according to claim 8, characterized in that the top layer structure (1) is prepared by the following method:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; pouring the mixed Ecoflex solution into a mold, heating at 60 ℃ for 2 hours to prepare a separation curing mold (9), placing the separation curing mold (9) on the flexible electrode array (4), wherein each flexible electrode unit corresponds to a blank on the mold, and ensuring that no gap exists between the mold and the flexible electrode array (4); dripping 20ul of ionic gel solution into the blank in the mould by using a liquid-transfering gun; heating at the constant temperature of 60 ℃ for 24h for curing to form the ionic gel array (5) with the thickness of 100um, and obtaining the top layer structure (1).
10. The temperature-pressure self-decoupling flexible sensor based on microstructured ionic material of claim 8, wherein the microstructured layer (2) is prepared by:
pouring the A and B glue of aliphatic aromatic random copolyester Ecoflex into a container, uniformly mixing, and vacuumizing; coating the mixed Ecoflex solution with the thickness of 2mm on the surface of sand paper with a preset mesh number by using a coating machine, and heating for 2 hours at 60 ℃ for curing; removing the sand paper to obtain a silica gel mold with a microstructure; coating ionic gel solution with the thickness of 3mm on a silica gel mold in a scraping way; heating at the constant temperature of 60 ℃ for 24h for curing to form the microstructure ionic gel thin layer (6) with the thickness of 300um; and adsorbing the microstructure ionic gel thin layer (6) on a conductive metal thin layer (7) to obtain the microstructure layer (2).
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| CN116026372A (en) * | 2022-12-06 | 2023-04-28 | 西安交通大学 | Broadband based on preloading design Flexible dynamic sensor and preparation method thereof |
| CN116026372B (en) * | 2022-12-06 | 2024-07-09 | 西安交通大学 | Broadband flexible dynamic sensor based on preloaded design and preparation method thereof |
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