CN110375895B - Multifunctional fully flexible fingerprint-shaped touch sensor - Google Patents
Multifunctional fully flexible fingerprint-shaped touch sensor Download PDFInfo
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- CN110375895B CN110375895B CN201910649993.8A CN201910649993A CN110375895B CN 110375895 B CN110375895 B CN 110375895B CN 201910649993 A CN201910649993 A CN 201910649993A CN 110375895 B CN110375895 B CN 110375895B
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- G—PHYSICS
- 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
- G01K7/22—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 the element being a non-linear resistance, e.g. thermistor
- G01K7/226—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 the element being a non-linear resistance, e.g. thermistor using microstructures, e.g. silicon spreading resistance
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
- G01N27/221—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance by investigating the dielectric properties
Abstract
The invention discloses a multifunctional fully-flexible fingerprint-shaped touch sensor. The sensor is formed by laminating a flexible substrate, a hardened substrate, a stretchable electrode, a temperature measuring unit, a material identification unit, a pressure measuring unit and a beam-shaped boss array from bottom to top; the temperature measuring unit, the material identification unit and the pressure measuring unit are composed of a plurality of groups of concentric circular arc line structures, and a patterned thermistor, an arc-shaped finger insertion capacitor and an arc-shaped pressure-sensitive strain gauge are respectively formed to form the multifunctional tactile sensor capable of realizing the human-finger-print simulation of temperature measurement, object material identification and pressure measurement. The invention utilizes the regional structure design to ensure that the sensor has multiple measurement functions in a small deployment range, and simultaneously, each layer of structure is made of the flexible composite material taking silicon rubber as the matrix, thereby obviously improving the flexibility of the sensor and realizing the fingerprint-shaped design on the structural characteristics and functions.
Description
Technical Field
The invention relates to a flexible touch sensor, in particular to a multifunctional fully-flexible fingerprint touch sensor.
Technical Field
The flexible electronic device has wide application prospect in the aspects of artificial limbs, intelligent robots, wearable equipment and the like. Among them, the flexible tactile sensor has become a research hotspot in the field of intelligent robots. The touch sensor can detect the touch information of the robot in the operation process and feed the touch information back to the motion control system, so that the control of the robot is changed from one-way control, open-loop control to two-way control and closed-loop control, and the complex and fine operation capability of the robot in a non-structural environment is improved. The touch sensor can be widely applied to space robots, deep-sea detection robots, intelligent medical robots and the like.
The fingers of the human hand are the most important parts for human body to perceive the touch information, and can simultaneously perceive various physical information such as the magnitude of the touch force, the temperature, the roughness, the material and the like of a contact object. For the intelligent robot to have autonomous perception and operation ability closer to the human body, a flexible touch sensor having a plurality of touch detection functions such as contact detection, temperature measurement, material identification and the like is indispensable. However, most of the conventional tactile sensors have only a single information detection function, such as pressure and temperature detection. A few sensors with multiple detection functions are difficult to be practically used for the touch detection in the human body capturing process of the intelligent robot due to the large detection area. Meanwhile, the flexibility of the touch sensor is greatly limited due to the use of the traditional metal electrode, the integration degree of the sensor and the robot is reduced, and negative influence is generated on the touch detection accuracy in the grabbing process.
In summary, it is important for the autonomous perception of the intelligent robot to provide a high-flexibility tactile sensor capable of realizing multiple tactile detection functions in a small detection area.
Disclosure of Invention
In order to make up for the deficiency in the prior art, the invention aims to provide a multifunctional fingerprint-shaped touch sensor, which endows the sensor with various touch detection functions such as pressure, temperature, material and the like through regional patterning structural design, improves the detection sensitivity and the overall flexibility of each region of the sensor by adopting a conductive composite material based on flexible silicon rubber, and realizes the fingerprint-shaped design of the sensor on the structural characteristics and the functions.
The technical scheme adopted by the invention is as follows:
a multifunctional fully flexible fingerprint-like touch sensor comprises:
the multifunctional fully-flexible fingerprint-shaped touch sensor is mainly formed by closely laminating a flexible substrate, a hardened substrate, a temperature measuring unit, a material identification unit, a pressure measuring unit, a stretchable electrode and a beam-shaped boss array; the hardening substrate is mainly formed by connecting a square area positioned in the center and a pair of fan-shaped areas positioned on a diagonal side of the square area, a through groove matched with the hardening substrate in shape is formed in the flexible substrate, and the hardening substrate is arranged in the through groove; the temperature measuring unit is arranged on the square area of the hardening substrate and mainly comprises a thermistor wire, the thermistor wire is divided into two semicircular parts, each semicircular part is formed by arranging the thermistor wire along a plurality of concentric arcs and then connecting the thermistor wire in series around an S shape to form a complete strip, one ends of the two semicircular parts are connected in series in the square area, and the other ends of the two semicircular parts are led out and connected with the stretchable electrodes; the material identification units are arranged on the fan-shaped areas of the hardened substrate, the two material identification units on the pair of fan-shaped areas are symmetrically arranged in the center of the square area of the hardened substrate, each material identification unit consists of an arc-shaped finger-inserting capacitor, and two electrodes of the arc-shaped finger-inserting capacitor of each material identification unit are led out and connected with the stretchable electrodes; the pressure measurement unit is arranged on the flexible substrate on the diagonal side of the other square region of the hardened substrate, which is not provided with the fan-shaped region, one pressure measurement unit is arranged at each corner, each pressure measurement unit is composed of an arc pressure-sensitive strain line, the arc pressure-sensitive strain lines are formed by arranging the pressure-sensitive strain lines along a plurality of concentric arcs and then connecting the pressure-sensitive strain lines in series in an S shape to form a complete line, and two ends of the arc pressure-sensitive strain line of each pressure measurement unit are led out and connected with stretchable electrodes; each pressure measurement unit is also provided with a beam-shaped boss array, and a plurality of beam-shaped bosses in the beam-shaped boss array are arranged on the arc-shaped area of the arc-shaped pressure-sensitive strain gauge at intervals along the circumferential direction and are contacted with the upper surface of the arc-shaped pressure-sensitive strain line; the temperature measuring unit, the material identification unit and the pressure measuring unit are located on the same plane, and the human finger/object to be measured is in contact with the plane and is used for temperature measurement, material identification and pressure measurement through the temperature measuring unit, the material identification unit and the pressure measuring unit respectively.
According to the invention, the temperature measuring unit, the material identification unit and the pressure measuring unit form a main body sensing part, the main body sensing part adopts a regional patterning structural design, and a plurality of groups of concentric circular arc line structures are connected in series and in parallel to form a patterned thermistor line, an arc pressure sensitive strain line and an arc finger inserting capacitor which are respectively used as the temperature measuring unit, the pressure measuring unit and the material identification unit, and a multifunctional patterned touch sensor simulating a hand fingerprint, which can realize the functions of temperature measurement, pressure measurement and object material identification, is formed together.
The arc-shaped interdigital capacitor of the material identification unit and the arc-shaped pressure-sensitive strain line of the pressure measurement unit occupy a sector area with a central angle of about 1/4.
The input ends of five pairs of stretchable electrodes arranged on the flexible substrate are respectively connected with a thermistor line of a temperature measuring unit, arc-shaped finger inserting capacitors of two material identification units and arc-shaped pressure-sensitive strain lines of two pressure measuring units, and the output ends of the five pairs of stretchable electrodes are converged and arranged into a flexible circuit board flat cable and are connected with a peripheral detection circuit.
The temperature measuring unit, the material identification unit, the pressure measuring unit and the stretchable electrode are all made by blending flexible silicon rubber and silver nano conductive particles, but the mechanical, electrical and thermal characteristics of the four materials are respectively distinguished and controlled by changing the solid content of the silver nano conductive particles, so that the four materials of the temperature measuring unit, the material identification unit, the pressure measuring unit and the stretchable electrode are identical in raw materials and are functionally distinguished.
Wherein the temperature measuring unit has high conductivity and high thermal resistance sensitivity; the pressure measuring unit has low conductivity and high pressure resistance sensitivity; the material identification unit and the stretchable electrode have high conductivity and low resistance sensitivity.
The flexible substrate, the hardened substrate, the temperature measuring unit, the material identification unit, the pressure measuring unit, the stretchable electrode and the beam-shaped boss array are all made of flexible silicon rubber, and full flexibility of the sensor is achieved.
The line widths of the temperature measuring unit, the material identification unit and the pressure measuring unit are about 200-250 mu m, and the thicknesses of the temperature measuring unit, the material identification unit and the pressure measuring unit are about 100 mu m; the stretchable electrode has an electrode line width of about 250 to 300 μm, a lead-out portion having a line width of about 500 μm and a thickness of about 100 μm. The size of the sensing area of the sensor main body is about 12mm multiplied by 14mm, and is similar to the area of the fingerprint of the finger tip of a person, so that the fingerprint-shaped design of the structural characteristics and the functions of the sensor is realized.
The flexible substrate is a film with a patterned through groove and is made of flexible silicon rubber; the hardened substrate is a film with the same pattern shape as the through grooves in the flexible substrate, and is manufactured by blending flexible silicon rubber and nano silicon dioxide particles.
The thickness of the flexible substrate and the thickness of the hardened substrate are both about 100 μm, and the hardened substrate is completely embedded into the patterned through grooves of the flexible substrate and is located in the same plane. The beam-shaped boss array is manufactured by blending flexible silicon rubber and nano silicon dioxide particles, the thickness is about 100 micrometers, and the width is 150-550 micrometers. The overall thickness of the sensor is about 300 μm.
The temperature measuring unit is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (1.5-1.75), coating the mixture on a hardening substrate according to a required pattern shape, and heating and curing the mixture; the material identification unit is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles according to the proportion of 1:0.1 (2.5-3), coating the mixture on a hardening substrate according to the shape of a required pattern and heating and curing the mixture; the pressure measurement unit is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (1-1.25), coating the mixture on a hardening substrate according to a required pattern shape, and heating and curing the mixture; the stretchable electrode is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (3.5-4), coating the mixture on a hardening substrate according to a required pattern shape, and heating and curing the mixture.
The preparation process of the invention is that a layer of polyimide film is closely covered on a glass substrate, and the glass substrate is cleaned in an ultrasonic cleaning machine after being immersed in alcohol, and then taken out and placed on a heating table for drying; uniformly mixing base rubber of silicon rubber (PDMS, polydimethylsiloxane), a curing agent and nano silicon dioxide particles according to a proportion; adding the materials into an organic solvent, stirring until the materials are completely dissolved, dispersing by an ultrasonic crusher, then placing on a stirring table, stirring and completely evaporating the organic solvent; and after cooling, placing the steel mesh mask plate in a vacuum drying oven for defoaming, covering the steel mesh mask plate on a glass substrate adhered with a polyimide film, coating a layer of silicone rubber film in a pattern shape on the steel mesh mask plate in a scraping way, and after removing the mask plate, heating and curing to obtain the hardened substrate. And then respectively manufacturing the flexible substrate, the temperature measuring unit, the material identification unit, the pressure measuring unit, the stretchable electrode and the beam-shaped boss array by using the same method.
The invention utilizes the regional structure design to ensure that the sensor has multiple measurement functions in a small deployment range, and simultaneously, each layer of structure is made of the flexible composite material taking silicon rubber as the matrix, thereby obviously improving the flexibility of the sensor and realizing the fingerprint-shaped design on the structural characteristics and functions.
Secondly, a manufacturing method of the multifunctional fully-flexible fingerprint-shaped touch sensor comprises the following steps:
1) closely coating a polyimide film on a glass substrate, soaking the glass substrate in alcohol, then cleaning the glass substrate in an ultrasonic cleaning machine, and then taking out and drying the glass substrate;
2) uniformly mixing base rubber of silicon rubber, a curing agent and nano silicon dioxide particles, coating a layer of patterned silicon rubber film on a glass substrate stuck with a polyimide film by using a steel mesh mask after vacuum defoaming, and heating and curing to obtain a hardened substrate;
3) uniformly mixing base rubber of silicon rubber and a curing agent, coating a layer of silicon rubber film on the periphery of a hardened substrate by using a film coating device after vacuum defoaming, and heating and curing to obtain a flexible substrate;
4) uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles according to different proportions, respectively coating multiple groups of concentric arc line structures connected in series and in parallel on a hardened substrate and a flexible substrate by using a steel mesh mask, and respectively obtaining a temperature measuring unit, a pressure measuring unit and a material identification unit after heating and curing;
5) uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles, aligning a steel mesh mask plate with the measurement units in the step 4) under an optical microscope, coating electrode leads with high conductivity on a flexible substrate by using the steel mesh mask plate to respectively connect the units and form a closed loop, and heating and curing to obtain a stretchable electrode;
6) uniformly mixing base rubber of silicon rubber, a curing agent and nano silicon dioxide particles, coating a beam-shaped boss structure on a pressure measurement unit by using a steel mesh mask after vacuum defoaming, heating and curing to obtain a beam-shaped boss array, and finishing the manufacturing of the multifunctional fully-flexible fingerprint-shaped touch sensor.
The invention has the beneficial effects that:
(1) the temperature measuring unit, the pressure measuring unit and the material identification unit are all made of silicon rubber and silver nanoparticles, the force, electricity and thermal characteristics required by each unit are regulated and controlled by changing the proportion of materials, and the manufacturing complexity of the sensor is reduced.
(2) The sensitivity of the temperature measuring unit and the material identification unit to external force is reduced by using the hardened substrate, and the influence of the external force on temperature measurement and material identification is reduced; the sensitivity of the pressure measuring unit to external force is improved by utilizing the flexible substrate and the beam-shaped boss array, so that the coupling effect among different detection functional units can be reduced.
(3) Each layer of structure in the touch sensor is made of flexible silicon rubber as a substrate, so that the use of a traditional metal electrode is avoided, and the overall flexibility of the sensor is improved; meanwhile, each layer takes flexible silicon rubber as a substrate, so that stable bonding effect can be generated between the layers due to the hydrosilation reaction of the silicon rubber during layered manufacturing, and the assembly strength and stability of each layer of the sensor are improved.
Drawings
FIG. 1 is a disassembled perspective view of the layered structure of the sensor of the present invention.
Fig. 2 is a top view of the overall structure of the sensor of the present invention.
FIG. 3 is a schematic view of a sensor temperature measurement unit of the present invention.
FIG. 4 is a schematic diagram of a sensor material identification unit according to the present invention.
FIG. 5 is a schematic view of a sensor pressure measurement unit of the present invention.
FIG. 6 is a schematic view of a stretchable electrode of the sensor of the present invention.
FIG. 7 is a schematic diagram of a sensor steel mesh mask according to the present invention.
Fig. 8 is a graph comparing the compression modulus of the flexible substrate 1 and the hardened substrate 2 in the examples.
Fig. 9 is a graph showing the results of the change in the resistance value of the pressure measuring cell 5 according to the tensile deformation in the example.
FIG. 10 is a graph showing the results of the change in conductivity of the material with respect to the solid content of silver nanoparticles in examples.
FIG. 11 is a graph showing the results of the tensile rate of the material in examples as a function of the solid content of silver nanoparticles.
In the figure: 1. the flexible substrate, 2, the hardening substrate, 3, the temperature measuring unit, 4, the material identification unit, 5, the pressure measuring unit, 6, the stretchable electrode and 7, the beam-shaped boss array.
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 1 and 2, the multifunctional fully-flexible fingerprint-shaped touch sensor is mainly formed by tightly laminating a flexible substrate 1, a hardened substrate 2, a temperature measuring unit 3, a material identification unit 4, a pressure measuring unit 5, a stretchable electrode 6 and a beam-shaped boss array 7; the hardening substrate 2 is mainly formed by connecting a square area with round corners at the center and a pair of fan-shaped areas on a diagonal side of the square area, namely, the pair of fan-shaped areas are symmetrically connected at two symmetrical diagonal positions of the square area by the center of the square area and are connected into a whole; a through groove matched with the shape of the hardened substrate 2 is formed in the flexible substrate 1, and the hardened substrate 2 is arranged in the through groove; the temperature measuring unit, the material identification unit and the pressure measuring unit are composed of a plurality of groups of concentric circular arc line structures, and are respectively provided with a patterned thermistor line, an arc-shaped finger insertion capacitor and an arc-shaped pressure-sensitive strain line, so that the multifunctional tactile sensor capable of realizing temperature measurement, object material identification and pressure measurement and simulating finger prints of a human finger is formed.
The single sensor comprises a temperature measuring unit 3, two material identification units 4 and two pressure measuring units 5.
As shown in fig. 3, a temperature measuring unit 3 is arranged on a square area of a hardened substrate 2, the temperature measuring unit 3 is mainly composed of a patterned thermistor wire, the thermistor wire is divided into two semicircular parts connected in series, each semicircular part is formed by arranging the thermistor wire along a plurality of concentric arcs and then connecting the thermistor wire in series around an S shape to form a complete strip, one end of each semicircular part is connected in series in the square area, and the other end of each semicircular part is led out and connected with a stretchable electrode 6; the temperature measuring unit 3 generates different resistance changes when contacting with objects with different surface temperatures under the structural arrangement, so as to realize temperature measurement.
As shown in fig. 2 and 4, a material identification unit 4 is arranged on a sector region of the hardened substrate 2, two material identification units 4 on a pair of sector regions are arranged in a central symmetry manner in a square region of the hardened substrate 2, each material identification unit 4 is composed of arc-shaped finger-inserted capacitors, namely, the finger-inserted capacitors are arranged in concentric arcs, the capacitors are exposed in the air, and two poles of the arc-shaped finger-inserted capacitors of each material identification unit 4 are led out and connected with the stretchable electrodes 6; the material identification unit 4 is structurally arranged in an initial state, air is used as a dielectric medium, when the material identification unit is in contact with an object, the dielectric medium of the capacitor changes, the dielectric constant changes, the capacitance value of the finger insertion capacitor is changed, and the material identification of the object is realized.
As shown in fig. 2 and 5, a pressure measurement unit 5 is arranged on the flexible substrate 1 on the diagonal side of the other square region of the hardened substrate 2 without the fan-shaped region, one pressure measurement unit 5 is arranged at each corner, each pressure measurement unit 5 is composed of arc-shaped pressure-sensitive strain lines, each arc-shaped pressure-sensitive strain line is composed of pressure-sensitive strain lines which are arranged along a plurality of concentric arcs and then connected in series in an S-shape to form a complete line, and two ends of each arc-shaped pressure-sensitive strain line of each pressure measurement unit 5 are led out and connected with stretchable electrodes 6; each pressure measurement unit 5 is also provided with a beam-shaped boss array 7, a plurality of beam-shaped bosses in the beam-shaped boss arrays 7 are arranged on the arc-shaped area of the arc-shaped pressure-sensitive strain gauge at intervals along the circumferential direction and are contacted with the upper surface of the arc-shaped pressure-sensitive strain gauge, and the beam-shaped boss arrays 7 on the two pressure measurement units 5 are arranged in a central symmetry manner in the square area of the hardened substrate 2; the pressure measuring unit 5 is structurally arranged so that the linear structure in the pressure-sensitive strain line is stretched and deformed after being acted by external force, so that the resistance of the strain line is increased, and pressure measurement is realized;
the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5 are located on the same plane, a human finger/an object to be measured contacts the plane, and temperature measurement, material identification and pressure measurement are carried out through the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5 respectively.
In the invention, a temperature measuring unit 3, a material identification unit 4 and a pressure measuring unit 5 form a main sensing part, the main sensing part adopts a regional patterning structural design, and utilizes a plurality of groups of concentric circular arc line structures to be connected in series and in parallel to form a patterned thermistor line, an arc pressure sensitive strain line and an arc finger inserting capacitor which are respectively used as the temperature measuring unit 3, the pressure measuring unit 5 and the material identification unit 4, and a multifunctional patterned touch sensor simulating a hand fingerprint, which can realize the functions of temperature measurement, pressure measurement and object material identification, is formed together.
In the specific implementation, the arc-shaped interdigital capacitor of the material identification unit 4 and the arc-shaped pressure-sensitive strain line of the pressure measurement unit 5 both occupy a sector area with a central angle of about 1/4.
As shown in fig. 1, 2 and 6, the specific implementation includes five pairs of stretchable electrodes 6 disposed on the flexible substrate 1, input ends of the five pairs of stretchable electrodes 6 are respectively connected to a thermistor line of one temperature measuring unit 3, arc-shaped finger insertion capacitors of two material identification units 4, and arc-shaped pressure-sensitive strain lines of two pressure measuring units 5, and output ends of the five pairs of stretchable electrodes 6 are converged and disposed into a flexible printed circuit board (fpc) line and connected to a peripheral detection circuit. Two ends of the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5 are connected by the stretchable electrode 6 to form a closed loop, and meanwhile, all electrode leads in the stretchable electrode 6 are led out to the same side of the flexible substrate 1 to form a flexible circuit board flat cable connected with a peripheral detection circuit.
As shown in fig. 2, 3 and 4, the temperature measuring unit 3 and the material identification unit 4 are arranged on the hardening substrate 2, and when the temperature measuring unit 3 and the material identification unit 4 are in contact with an object, the hardening substrate 2 is difficult to compress, so that the temperature measuring unit 3 and the material identification unit 4 are not deformed obviously, and the influence of an external force on the temperature measurement and the material identification performance is reduced.
As shown in fig. 2 and 5, the pressure measurement units 5 are arranged on the flexible substrate 1, the beam-shaped boss array 7 is arranged at the top of the flexible substrate, when the sensor is acted by an external force, the beam-shaped boss array 7 generates stress concentration and transmits the stress concentration to the pressure measurement units 5, so that the pressure measurement units 5 generate tensile deformation and generate resistance change, and the unit pressure measurement sensitivity is improved.
As shown in fig. 1 and 2, the flexible substrate 1, the hardened substrate 2, the temperature measurement unit 3, the material identification unit 4, the pressure measurement unit 5, the stretchable electrode 6 and the beam-shaped boss array 7 are all made of flexible silicon rubber, so that the fully flexible design of the sensor is realized. The line width of the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5 is about 200-250 μm, and the thickness is about 100 μm; the stretchable electrode 6 has an electrode line width of about 250 to 300 μm, a lead-out portion length of 5mm, a line width of about 500 μm, a line pitch of about 500 μm, and a thickness of about 100 μm. The size of the sensing area of the sensor main body is about 12mm multiplied by 14mm, and is similar to the area of the fingerprint of the finger tip of a person, so that the fingerprint-shaped design of the structural characteristics and the functions of the sensor is realized.
As shown in fig. 3, 4, 5 and 6, the temperature measuring unit 3, the material identification unit 4, the pressure measuring unit 5 and the stretchable electrode 6 are all made by blending flexible silicone rubber and silver nano conductive particles, and the regulation and control of mechanical, electrical and thermal properties of the material are realized by changing the solid content of the silver nano conductive particles. Wherein the temperature measuring unit 3 has high electric conductivity and high thermal resistance sensitivity (electric conductivity sigma-10)2S/cm); the pressure measuring unit 4 has low conductivity and high pressure resistance sensitivity (conductivity sigma-0.1S/cm, strain coefficient GF-10)6) (ii) a The material discriminating unit 5 and the stretchable electrode 6 have high conductivity and low resistance sensitivity (conductivity sigma-10)3S/cm, strain coefficient GF-10).
As shown in fig. 1, the flexible substrate 1 is a film with patterned through grooves, and is made of flexible silicon rubber; the hardened substrate 2 is a thin film with the same pattern as the through grooves in the flexible substrate and is manufactured by blending flexible silicon rubber and nano silicon dioxide particles. The thickness of the flexible substrate 1 and the thickness of the hardened substrate 2 are both about 100 μm, and the hardened substrate 2 is completely embedded in the patterned through grooves of the flexible substrate 1 and is located in the same plane. The beam-shaped boss array 7 is manufactured by blending flexible silicon rubber and nano silicon dioxide particles, the thickness is about 100 micrometers, and the width is 150-550 micrometers. The overall thickness of the sensor is about 300 μm.
The manufacturing method provided by the invention mainly comprises the following steps of manufacturing the hardened substrate 2, manufacturing the flexible substrate 1, manufacturing the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5, manufacturing the stretchable electrode 6, manufacturing the beam-shaped boss array 7 and the like.
The embodiment of the invention and the implementation process thereof are as follows:
1) production of the hardened substrate 2:
a polyimide film having a thickness of 100 μm was closely attached to a glass substrate of 5cm × 5cm, immersed in alcohol, cleaned in an ultrasonic cleaner for 15 minutes, then taken out and dried on a heating table at 80 ℃.
Uniformly mixing base rubber of silicon rubber (PDMS, polydimethylsiloxane), a curing agent and nano silicon dioxide particles according to a ratio of 1:0.1: 0.1. The above materials were added to an organic solvent and stirred until completely dissolved, dispersed by a sonicator at a power of 100W for 1 hour, then placed on a stirring table at 80 ℃ and stirred and the organic solvent was completely evaporated. And cooling, placing the steel mesh mask 8 in the figure 7 in a vacuum drying oven for defoaming, then blade-coating a layer of patterned silicon rubber film on the steel mesh mask 8 on a glass substrate stuck with a polyimide film, removing the mask, and heating and curing at 80 ℃ for two hours to obtain the hardened substrate 2. The thickness of the steel mesh mask was 100 μm, and thus the thickness of the hardened substrate 2 was also 100 μm.
2) Production of the flexible substrate 1:
uniformly mixing base rubber of silicon rubber and a curing agent according to the proportion of 1:0.1, coating a layer of silicon rubber film on the periphery of a hardened substrate 2 by using a film coating device after defoaming in a vacuum drying oven, and heating and curing for two hours at 80 ℃ to obtain a flexible substrate 1. The flexible substrate 1 and the hardened substrate 2 compression modulus pair is shown in fig. 8.
3) Production of temperature measuring unit 3, material identification unit 4, and pressure measuring unit 5:
uniformly mixing the base rubber of the silicon rubber, the curing agent and the silver nanoparticles according to the method in the step 1) in a ratio of 1:0.1: 1.75. Attaching a steel mesh mask 8 on the hardened substrate 2 and aligning, coating the mixed material on the hardened substrate 2, removing the mask, and heating and curing at 80 ℃ for two hours to obtain a temperature measurement unit 3 (sigma-10)2S/cm)。
Uniformly mixing the base rubber of the silicon rubber, the curing agent and the silver nanoparticles according to the method in the step 1) in a ratio of 1:0.1:3. Attaching the steel mesh mask 8 on the hardening substrate 2 and aligning, coating the mixed material on the hardening substrate 2, removing the mask, and heating and curing at 80 ℃ for two hours to obtain the material quality identificationDifferential unit 4 (sigma-10)3S/cm，GF～10)。
Uniformly mixing the base rubber of the silicon rubber, the curing agent and the silver nanoparticles according to the method in the step 1) in a ratio of 1:0.1: 1.25. Attaching a steel mesh mask 8 on the flexible substrate 1 and aligning, coating the mixed material on the flexible substrate 1, removing the mask, and heating and curing at 80 ℃ for two hours to obtain a pressure measurement unit 5 (sigma-0.1S/cm, GF-10)6)。
The resistance value of the pressure measuring cell 5 as a function of the tensile deformation is shown in fig. 9.
4) Fabrication of stretchable electrode 6:
uniformly mixing the base rubber of the silicon rubber, the curing agent and the silver nanoparticles according to the method in the step 1) in a ratio of 1:0.1: 3.5. Attaching a steel mesh mask 8 on the flexible substrate 1, aligning the hollowed part of the electrode of the mask with the two ends of the temperature measuring unit 3, the material identification unit 4 and the pressure measuring unit 5 under an optical microscope, coating the mixed material on the flexible substrate 1, removing the mask, and heating and curing at 80 ℃ for two hours to obtain the stretchable electrode 6 (sigma-10)3S/cm，GF～10)。
The following graph shows the relationship between the conductivity of the material and the tensile rate as a function of the solid content of the silver nanoparticles:
5) manufacturing of the beam-shaped boss array 7:
uniformly mixing the base rubber of the silicon rubber, the curing agent and the nano silicon dioxide particles according to the proportion of 1:0.1:0.1 by the method in the step 1). And attaching the steel mesh mask 8 to the pressure measurement unit 5 and aligning, coating the mixed material on the pressure measurement unit 5, removing the mask, heating and curing at 80 ℃ for two hours to obtain the beam-shaped boss array 7, and finishing the manufacture of the multifunctional fully-flexible fingerprint-shaped touch sensor.
In specific implementation, SYLGARD 184 silicone rubber from Dow Corning is adopted as the silicone rubber; silver nanoparticles from Sigma-Aldrich were used as the conductive silver nanoparticles.
Therefore, the sensor has multiple measuring functions in a small deployment range by utilizing the regional structure design, and each layer of structure is made of the flexible composite material taking the silicon rubber as the matrix, so that the flexibility of the sensor is obviously improved, and the fingerprint-shaped design is realized on the structural characteristics and the functions.
Claims (5)
1. The utility model provides a multi-functional full flexible fingerprint form tactile sensor which characterized in that: the multifunctional fully-flexible fingerprint-shaped touch sensor is mainly formed by tightly laminating a flexible substrate (1), a hardened substrate (2), a temperature measuring unit (3), a material identification unit (4), a pressure measuring unit (5), a stretchable electrode (6) and a beam-shaped boss array (7); the hardening substrate (2) is mainly formed by connecting a square area positioned in the center and a pair of fan-shaped areas positioned on a diagonal side of the square area, a through groove matched with the hardening substrate (2) in shape is formed in the flexible substrate (1), and the hardening substrate (2) is arranged in the through groove;
a temperature measuring unit (3) is arranged on a square area of the hardening substrate (2), the temperature measuring unit (3) mainly comprises a thermistor wire, the thermistor wire is divided into two semicircular parts, each semicircular part is formed by arranging the thermistor wire along a plurality of concentric arcs and then connecting the thermistor wire in series around an S shape to form a complete strip, one ends of the two semicircular parts are connected in series in the square area, and the other ends of the two semicircular parts are led out and connected with stretchable electrodes (6);
a material identification unit (4) is arranged on a fan-shaped area of the hardening substrate (2), two material identification units (4) on a pair of fan-shaped areas are symmetrically arranged by taking the square area of the hardening substrate (2) as the center, each material identification unit (4) is composed of an arc-shaped finger insertion capacitor, and two electrodes of the arc-shaped finger insertion capacitor of each material identification unit (4) are led out and connected with a stretchable electrode (6);
a pressure measurement unit (5) is arranged on the flexible substrate (1) on the diagonal side of the other square region of the hardened substrate (2) without the fan-shaped region, one pressure measurement unit (5) is arranged at each corner, each pressure measurement unit (5) is composed of arc-shaped pressure-sensitive strain lines, each arc-shaped pressure-sensitive strain line is composed of pressure-sensitive strain lines which are arranged along a plurality of concentric arcs and then connected in series in an S-shaped manner to form a whole line, and two ends of each arc-shaped pressure-sensitive strain line of each pressure measurement unit (5) are led out and connected with a stretchable electrode (6);
each pressure measurement unit (5) is also provided with a beam-shaped boss array (7), and a plurality of beam-shaped bosses in the beam-shaped boss array (7) are arranged on an arc-shaped area of the arc-shaped pressure-sensitive strain sheet at intervals along the circumferential direction and are contacted with the upper surface of the arc-shaped pressure-sensitive strain line; the temperature measuring unit (3), the material identification unit (4) and the pressure measuring unit (5) are positioned on the same plane, and the fingers/the object to be measured contact the plane and respectively carry out temperature measurement, material identification and pressure measurement through the temperature measuring unit (3), the material identification unit (4) and the pressure measuring unit (5);
the temperature measuring unit (3), the material identification unit (4), the pressure measuring unit (5) and the stretchable electrode (6) are all made by blending flexible silicon rubber and silver nano conductive particles, but the mechanical, electrical and thermal characteristics of the four materials are respectively distinguished and controlled by changing the solid content of the silver nano conductive particles, so that the four materials of the temperature measuring unit (3), the material identification unit (4), the pressure measuring unit (5) and the stretchable electrode (6) are distinguished in function;
the flexible substrate (1), the hardened substrate (2), the temperature measuring unit (3), the material identification unit (4), the pressure measuring unit (5), the stretchable electrode (6) and the beam-shaped boss array (7) are all made of flexible silicon rubber, and full flexibility of the sensor is achieved.
2. The multifunctional fully flexible fingerprint-like tactile sensor according to claim 1, wherein: the arc-shaped interdigital capacitor of the material identification unit (4) and the arc-shaped pressure-sensitive strain line of the pressure measurement unit (5) both occupy a sector area with the central angle of about 1/4.
3. The multifunctional fully flexible fingerprint-like tactile sensor according to claim 1, wherein: the input ends of five pairs of stretchable electrodes (6) arranged on the flexible substrate (1) are respectively connected with a thermistor line of one temperature measuring unit (3), arc-shaped finger inserting capacitors of two material identification units (4) and arc-shaped pressure-sensitive strain lines of two pressure measuring units (5), and the output ends of the five pairs of stretchable electrodes (6) are converged and arranged into a flexible circuit board flat cable and are connected with a peripheral detection circuit.
4. The multifunctional fully flexible fingerprint-like tactile sensor according to claim 1, wherein: the flexible substrate (1) is a film with a patterned through groove and is made of flexible silicon rubber; the hardened substrate (2) is a film with the same pattern shape as the through grooves in the flexible substrate (1) and is manufactured by blending flexible silicon rubber and nano silicon dioxide particles.
5. The multifunctional fully flexible fingerprint-like tactile sensor according to claim 1, wherein: the temperature measuring unit (3) is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (1.5-1.75) and coating the mixture on a hardening substrate (2) according to a required pattern shape by heating and curing; the material identification unit (4) is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles according to the proportion of 1:0.1 (2.5-3), and coating the mixture on a hardening substrate (2) according to the shape of a required pattern for heating and curing; the pressure measurement unit (5) is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (1-1.25), and coating the mixture on a hardening substrate (2) according to a required pattern shape for heating and curing; the stretchable electrode (6) is prepared by uniformly mixing base rubber of silicon rubber, a curing agent and silver nanoparticles in a ratio of 1:0.1 (3.5-4), and coating the mixture on a hardening substrate (2) according to a required pattern shape for heating and curing.
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| CN110763378B (en) * | 2019-11-01 | 2020-09-22 | 浙江大学 | Wearable flexible touch force sensor |
| CN111006802B (en) * | 2019-12-17 | 2021-07-27 | 华中科技大学 | Multi-mode metamorphic flexible sensor and signal acquisition system |
| CN110987029B (en) * | 2019-12-17 | 2020-11-24 | 华中科技大学 | Multifunctional flexible sensor and preparation method and application thereof |
| CN111551294B (en) * | 2020-05-21 | 2021-03-30 | 浙江大学 | Flexible pressure sensor based on liquid metal photocuring printing technology |
| CN112179410B (en) * | 2020-09-24 | 2022-03-01 | 之江实验室 | Multifunctional flexible touch sensor and preparation method thereof |
| CN112720538B (en) * | 2020-12-23 | 2022-06-07 | 西安交通大学 | Touch sensor system applied to fingers of mechanical dexterous hand |
| CN113567038A (en) * | 2021-07-13 | 2021-10-29 | 中山市富茂密封科技有限公司 | Pressure sensing metal diaphragm, pressure sensing diaphragm group and pressure gauge |
| CN113834418B (en) * | 2021-09-06 | 2023-04-18 | 电子科技大学 | Flexible strain sensor with adjustable Poisson ratio |
| CN113776702B (en) * | 2021-11-15 | 2022-03-18 | 北京石墨烯技术研究院有限公司 | Flexible pressure sensor, preparation method thereof and wearable device |
| CN114932568B (en) * | 2022-05-07 | 2023-07-21 | 之江实验室 | Flexible electronic skin capable of sensing dynamic and static pressure and preparation method thereof |
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| CN105136369B (en) * | 2015-05-28 | 2017-11-28 | 合肥工业大学 | A kind of Grazing condition resistance-type touch-pressure sensation detecting sensor and preparation method thereof |
| CN106568539A (en) * | 2016-10-20 | 2017-04-19 | 上海交通大学 | Polymer substrate-based monolithic integrated temperature and humidity flexible sensor and preparation method |
| CN109323784B (en) * | 2018-09-21 | 2020-07-10 | 浙江大学 | Piezoresistive flexible touch sensor with double-layer buckle type micro-boss |
| CN109781315B (en) * | 2019-02-02 | 2020-08-25 | 五邑大学 | Touch sensor |
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