CN114440759A - Flexible tensile strain sensor based on packaging material structure - Google Patents
Flexible tensile strain sensor based on packaging material structure Download PDFInfo
- Publication number
- CN114440759A CN114440759A CN202210093766.3A CN202210093766A CN114440759A CN 114440759 A CN114440759 A CN 114440759A CN 202210093766 A CN202210093766 A CN 202210093766A CN 114440759 A CN114440759 A CN 114440759A
- Authority
- CN
- China
- Prior art keywords
- strain sensor
- flexible
- main body
- strain
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
-
- 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
- G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
- G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
- G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges
Abstract
The invention discloses a flexible tensile strain sensor based on a packaging material structure. The flexible tensile strain sensor is symmetrically arranged and comprises a strain sensor main body and a strain signal reading interface; the two ends of the strain sensor main body are respectively provided with a strain signal reading interface, and the strain signal reading interfaces at the two ends of the strain sensor main body are respectively and electrically connected with the two ends of the strain sensor main body; the strain sensor main body is composed of a strain sensor substrate, a conducting layer and a main body packaging layer, the conducting layer is attached to the outer surface of the strain sensor substrate, the strain sensor substrate attached with the conducting layer is embedded in the main body packaging layer, and strain signal reading interfaces at two ends of the strain sensor main body penetrate through the corresponding ends of the main body packaging layer respectively and then are arranged at two ends of the strain sensor substrate. The strain sensor has the characteristics of good tensile property, large measurement range and the like, and can adjust the structure of the sensor according to requirements, adjust the stress distribution of the flexible tensile strain sensor in the working process, control the mechanical property of the sensor and improve the adaptability of the sensor.
Description
Technical Field
The invention relates to a tensile strain sensor in the technical field of sensors, in particular to a flexible tensile strain sensor based on a packaging material structure.
Background
With the rapid development of artificial intelligence and robot technology and the popularization of intelligent terminals, the development of modern science and technology and the improvement of automation level, the fields of robots, wearable devices and the like present huge market prospects, and will have great influence on the future development of the human society. The flexible tensile strain sensor has wide application value in the fields of robots, wearable equipment and the like. The method is generally used in the fields of wearable human-computer interaction interfaces, wearable health monitoring equipment, soft robot flexible skin and the like. The flexible tensile strain sensor can reflect the deformation amount of the flexible tensile strain sensor through the collected electric signal data, and can be used as a wearable human-computer interaction interface, such as a data glove, for collecting the human body motion data of a user and controlling the operation of a robot or other equipment; the wearable health monitoring device can be used as a wearable health monitoring device, such as a wearable health monitoring device arranged at a knee joint and an elbow joint, and is used for collecting and monitoring joint angle data of a body of a wearer and estimating the limb movement health state of the wearer; the embedded soft robot body or the soft robot body surface is covered, the driving state of the soft robot is monitored in real time, for example, the bending state of the crawling soft robot body driven by positive pressure is fed back, and the crawling of the soft robot is controlled.
The traditional flexible strain sensor substrate material is an elastic film with a smooth surface, the conductive sensitive layer embedded or covered on the surface of the traditional flexible strain sensor substrate material is also of a planar structure, and a crack mechanism is introduced into the conductive sensitive layer, namely, the conductive sensitive layer cracks along with the tensile deformation of the strain sensor, so that the number of conductive paths is suddenly changed, and the detection sensitivity of the flexible strain sensor to micro stress can be improved. The flexible strain sensor is limited by a plane structure, the deformation capacity of the flexible strain sensor in a micro-stress state is limited, and the flexible porous substrate material with a three-dimensional skeleton structure is adopted, so that the deformation capacity of the flexible strain sensor in the micro-stress state can be remarkably improved, and the detection sensitivity of the flexible strain sensor to the micro-stress is enhanced. But the physical property of the flexible porous substrate material is limited, the stretching deformation quantity is determined by the material property, and the flexible stretching strain sensor based on the flexible porous substrate material generally has the defect of poor stretching mechanical property; and the pore distribution of the flexible porous material as the substrate material is not completely uniform, and the flexible porous material is stressed in the stretching process, so that the problems that the crack forming position is difficult to control, the reproducibility is low, the crack propagation degree is low, and the larger stretching deformation detection range is difficult to cover exist.
Disclosure of Invention
In order to solve the problems that a conductive layer of an existing flexible strain sensor is easy to fall off, low in stability, small in measurement range, uncontrollable in sensing performance, poor in repeatability and the like, the invention provides a flexible tensile strain sensor based on a packaging material structure, which can be applied to a human-computer interaction interface, wearable health monitoring equipment and flexible electronic skin of a soft robot, and the strain range, performance, sensitivity and stability of the strain sensor are improved.
The technical scheme adopted by the invention for solving the problems is as follows:
the flexible tensile strain sensors are symmetrically arranged and comprise strain sensor bodies and strain signal reading interfaces;
the two ends of the strain sensor main body are respectively provided with a strain signal reading interface, and the strain signal reading interfaces at the two ends of the strain sensor main body are respectively and electrically connected with the two ends of the strain sensor main body;
the strain sensor comprises a strain sensor main body, a strain sensor substrate, a conductive layer and a main body packaging layer, wherein the conductive layer is attached to the outer surface of the strain sensor substrate, the strain sensor substrate attached with the conductive layer is embedded in the main body packaging layer, and strain signal reading interfaces at two ends respectively penetrate through the corresponding ends of the main body packaging layer and are arranged at two ends of the strain sensor substrate.
At least one side of four sides of a main body packaging layer of the strain sensor main body is provided with a protruding structure, the protruding structure is composed of a plurality of protruding units which are arranged in parallel and at intervals along the stretching direction of the strain sensor, and each protruding unit is arranged on the current side.
The protruding units have the same or different sizes, and the intervals between the adjacent protruding units are the same or different.
At least one side of four sides of a main body packaging layer of the strain sensor main body is provided with a concave structure, the concave structure is composed of a plurality of concave units which are arranged in parallel along the stretching direction of the strain sensor at intervals, and each concave unit is arranged on the current side.
The size of the concave units is the same or different, and the distance between the adjacent concave units is the same or different.
The strain sensor body is prepared by the following method:
firstly, carrying out laser cutting on a flexible porous material to obtain a flexible substrate, dissolving a nano conductive material in a dispersing agent and uniformly stirring to obtain a nano conductive material mixed solution, then placing the flexible substrate in the nano conductive material mixed solution for fully soaking and drying until the dispersing agent is completely volatilized, so that a conductive layer is formed on the outer surface of the flexible substrate, and the conductive flexible substrate is obtained; and finally, placing the conductive flexible substrate in a mold, pouring an external packaging material into the mold, heating, curing and molding to form a main body packaging layer, and obtaining the strain sensor main body.
The strain signal reading interface mainly comprises a copper needle and a signal transmission lead connected with the copper needle, the copper needle is arranged in the strain sensor main body, and the copper needle is electrically connected with the strain sensor main body.
The axial direction of the copper needle is parallel to or perpendicular to the stretching direction of the stretching strain sensor.
The working principle of the invention is as follows:
the flexible strain sensor is internally deformed when being subjected to external tensile force, so that the number of microscopic filamentous conductive paths inside the strain sensor is changed, the resistance value is changed, and the magnitude of the electrical parameter resistance value of the strain sensor can be used for detecting external force and deformation.
The flexible substrate has a skeleton structure, and a plurality of micro cracks can be generated during stretching to cause irregular breakage of the substrate, so that the main reasons of uneven breakage are as follows: errors exist in the forming process of the flexible substrate, so that the geometric shape of the outer part of the flexible substrate is not completely symmetrical; errors exist in the forming process of the porous structure of the flexible substrate, so that the size and the distribution of gaps of the porous structure in the flexible substrate are not uniform; the inner pores of the silica gel filled sponge are not uniform; the position precision of the flexible substrate is low and the flexible substrate is not positioned in the positive center of the packaging material; the outer packaging material has defects such as bubbles, which cause tensile stress concentration.
In order to solve the problem of irregular fracture of the flexible substrate, the invention designs a plurality of fracture-controllable external packaging material structures, realizes fracture controllability of the flexible substrate in the sensor, and improves the linearity and the fitting accuracy of signals.
The technical scheme for realizing controllable fracture is as follows: constructing regular convex structures or concave structures on the left side surface, the right side surface or the front side surface and the rear side surface of the strain sensor main body, wherein the shapes of the convex structures or the concave structures are semi-ellipses and are connected with the surface of the strain sensor main body through fillets; the stress concentration phenomenon of the strain sensor main body corresponding to the structure in the stretching process can be reduced through the convex structure, the breakage of the flexible substrate and the conductive sensitive material attached to the surface of the substrate is inhibited, and the stability of an electric signal is ensured; the stress concentration position of the strain sensor main body in the stretching process can be controlled by designing the position and the size of the concave structure, so that the fracture crack position of the conductive flexible substrate is controllable, and the regulation and control of the sensing performance are realized according to actual requirements.
The invention improves the sensitivity of the flexible sensor and is embodied in that: the thin flexible porous material is adopted as the substrate material, the substrate material has a skeleton structure, a plurality of microcracks can be generated during stretching to increase the resistance, the electric signal change is obvious when unit deformation occurs, and the conductive sensitivity of the substrate material is improved. In addition, the strong adsorbability of the porous material also provides a proper carrier for the conductive sensitive material, and the porous material has a skeleton structure which enables the conductive sensitive material to generate larger deformation, so that the stretchability is improved.
The invention improves the tensile property of the flexible tensile strain sensor by the following steps: a layer of material is packaged outside the flexible substrate and covers the surface of the traditional flexible strain sensor substrate, so that the flexible substrate and the conductive material are both embedded in the external packaging material, and when external tensile stress acts on the upper end and the lower end of the strain sensor body, the external packaging material has stretchability, namely, a larger elastic deformation range. The silica gel has higher stretchability, can be used as an external packaging material, and simultaneously isolates the substrate material from directly contacting the outside with the conductive layer to prevent the substrate material from rubbing to cause the conductive sensitive material to fall off; the flexible porous material is prevented from absorbing substances such as water vapor in the air, so that the property is changed, and the stability of the sensor is improved.
The invention improves the repeatable performance of the flexible tensile strain sensor manufacturing: the special structural treatment is carried out on the packaging structure, so that the stress dispersion and the fracture distribution are more uniform, the cracks are controllable, the larger deformation can be borne, the stretchability of the sensor is improved, and the consistency of the cracks is also improved. The corresponding mould is designed to enable the packaging structure formed each time to be the same, and the flexible substrate can be arranged at the center of the packaging material and distributed in a centrosymmetric mode through the fixing of the mould, so that the sensor can be manufactured repeatedly.
The invention prepares the sponge dielectric layer with excellent strain-resistance curve by dissolving nano conductive materials (such as carbon nano materials, nano metal particles, nano metal wires, nano metal sheets and the like) in a dispersing agent (such as normal hexane and the like), solidifying the nano conductive materials on the surface of a flexible substrate (such as polyurethane sponge and the like), placing the flexible substrate in a designed mould, assisting silica gel as a packaging material, and removing residual air in the external packaging material by using a vacuum defoaming machine, thereby completing the preparation of the flexible strain sensor by a simpler method.
The invention has the beneficial effects that:
the unique external packaging structure of the flexible sensor is easy to deform such as stretching, has the advantages of larger deformation amount than that of an unpackaged structure and larger measurement range under the condition of the same external force action, can still recover under the condition of large deformation amount and keep the sensing function, can effectively buffer the contact of an object (such as a human body) and a sensing device, reduces the interference of the external environment to the sensor, improves the stability of the sensor during working, is applied to various working scenes and prolongs the fatigue life. Through the high strength of optimal design strain sensor main part, tensile structure, showing the tensile properties that has improved the flexible strain sensor who uses porous material as the base, effectively overcome the flexible strain sensor mechanical properties of traditional nothing packaging structure poor, easy fracture, measuring range is little and the lower problem of sensitivity. Through the design of the special structure of the external packaging material, the fracture position of the flexible substrate is controllable, and the stability and the linearity of electric signal transmission are improved.
On the other hand, the invention can change the characteristics of the sensor by changing the structural design, allows a user to freely adjust and obtain flexible sensors with different sensitivities and measurement ranges according to different use conditions to adapt to different requirements, and has a wider use range. The arrangement surface, arrangement mode and size of the convex structure or the concave structure can be customized, adjusted and optimized according to the actual use condition, for example: when the strain sensor is attached to the surface of a human body and used as a bending strain sensor, the surface, which is used as a bending tensile strain sensor and is attached to the surface of the human body, needs to be flat and has no special structure, so that the comfort is ensured, and the special structure on the other surface plays a role in performance regulation. The stress on different positions is not uniform, for example, when the sensor is attached to the outer surface of an elbow joint, the stress on the salient point of the elbow joint is the largest, so that the convex units or the concave units are densely arranged in the middle and sparse at two ends, and the uniform stress on sensitive materials in the sensor can be ensured; the size of the convex unit or the concave unit in the middle of the strain sensor main body is required to be enlarged, the size of the convex unit or the concave unit at the two ends of the strain sensor main body is required to be reduced, the stress action can be enhanced in the middle to initiate fracture, or the stress is reduced to inhibit fracture, and then the sensing performance is improved in the aspects of linearity, tensile strain degree and the like.
Drawings
FIG. 1 is a schematic diagram of the basic structure of a high tensile flexibility strain sensor based on porous flexibility material; wherein the copper pins are arranged longitudinally in the strain sensor;
FIG. 2 is a front view and a half sectional view of a high tensile flexibility strain sensor based on porous flexible material according to the present invention;
FIG. 3 is a schematic diagram of a structure in which copper pins are transversely arranged in a strain sensor;
FIG. 4 is a schematic view of two positions of a raised structure on a strain sensor frame;
FIG. 5 is a schematic view of two positions of a dimple arrangement on a strain sensor frame;
FIG. 6 is a flow chart of manufacturing a sensor body, taking a basic structure as an example;
FIG. 7 is a schematic diagram of a mold in a manufacturing process of a sensor body with a bump structure;
FIG. 8 is a schematic diagram of a mold in a manufacturing process of a sensor body with a recessed structure;
in the figure: the strain sensor comprises a strain sensor body 1, a strain signal reading interface 2, a flexible substrate 3, a conductive layer 4, a body packaging layer 5, copper pins 6, signal transmission leads 7, left and right side surfaces 8, upper and lower side surfaces 9, a convex unit 10 and a concave unit 11.
Detailed Description
The invention is further described below with reference to the following examples:
as shown in fig. 1 and 2 (a) and 2 (b), the flexible tensile strain sensor of the present invention is symmetrically arranged, and comprises a strain sensor body 1 and a strain signal reading interface 2;
the two ends of the strain sensor main body 1 are respectively provided with a strain signal reading interface, and the strain signal reading interfaces at the two ends of the strain sensor main body 1 are respectively and electrically connected with the two ends of the strain sensor main body;
the strain sensor main body 1 is composed of a strain sensor substrate 3, a conducting layer 4 and a main body packaging layer 5, the conducting layer 4 is attached to the outer surface of the strain sensor substrate 3, the strain sensor substrate 3 attached with the conducting layer 4 is embedded in the main body packaging layer 5, the main body packaging layer 5 completely wraps the strain sensor substrate 3 attached with the conducting layer 4, and strain signal reading interfaces at two ends of the strain sensor substrate 3 penetrate through corresponding ends of the main body packaging layer 5 respectively and then are arranged at two ends of the strain sensor substrate 3.
At least one of the four outer side surfaces of the strain sensor body 1 is provided with a protruding structure, the protruding structure is composed of a plurality of protruding units 10 which are arranged in parallel and at intervals along the stretching direction of the strain sensor, each protruding unit 10 is arranged on the current side surface, and two side surfaces of each protruding unit 10 are flush with two adjacent side surfaces of the current side surface. As shown in fig. 4, (a) and (b) of fig. 4 are schematic views in which the left and right side surfaces 8, and the upper and lower side surfaces 9 of the strain sensor frame are provided with the convex structures, respectively. It is effective in suppressing breakage at a position where breakage is likely, but tensile properties are inferior to those of the basic structure because the internal conductive sponge is not broken. In addition to the transverse rupture of the sponge caused by the width shrinkage during stretching, the sponge is also ruptured in the longitudinal direction due to the reduction of the thickness. The breaking position is controllable, so that the conductivity of the sponge substrate is uniform, but the resistance of the breaking position is suddenly changed.
The sizes of the protruding units 10 are the same or different, and the distances between the adjacent protruding units 10 are the same or different, and are specifically set according to actual situations.
At least one side of four lateral surfaces of the strain sensor body 1 is provided with a sunken structure, the sunken structure is composed of a plurality of sunken units 11 which are arranged in parallel and at intervals along the stretching direction of the strain sensor, each sunken unit 11 is arranged on the current side, and two side notches of each sunken unit 11 are flush with two adjacent sides of the current side. As shown in fig. 5, in which (a) and (b) of fig. 5 are respectively schematic views of the left and right side surfaces 8, and the upper and lower side surfaces 9 of the strain sensor frame provided with the concave structure, the longitudinal breakage of the conductive sponge can be controlled.
The sizes of the concave units 11 are the same or different, the distances between the adjacent concave units 11 are the same or different, and the concave units are specifically arranged according to actual conditions, in the embodiment, the convex units 10 and the concave units 11 are both semi-elliptical and are excessively connected with the surface of the strain sensor body 1 through round corners; the stress concentration phenomenon of the strain sensor body 1 corresponding to the structure in the stretching process can be reduced through the convex structure, and the fracture of the flexible substrate 3 and the conductive layer 4 attached to the surface of the substrate is inhibited; the stress concentration position of the strain sensor main body 1 in the stretching process can be controlled by designing the position and the size of the concave structure, so that the fracture crack position of the conductive flexible substrate 3 is controllable, and the sensing performance is further regulated and controlled.
The arrangement surface of the convex structure or the concave structure can be customized, adjusted and optimized according to the actual use condition, for example: when the strain sensor is required to be attached to the surface of a human body, the surface, which is used as a bending and stretching strain sensor and is attached to the surface of the human body, is required to be flat and has no special structure, so that the comfort is ensured, and the special structure on the other surface plays a role in performance regulation. Therefore, the arrangement surface of the convex structure or the concave structure can be adjusted according to the actual use requirement, and the front surface 9 and the rear surface 10 are not necessarily both provided with structures;
the arrangement mode of the convex structures or the concave structures can be customized, adjusted and optimized according to the actual use condition, for example: when the strain sensor is attached to the surface of a human body and used as a bending strain sensor, the stress borne by different positions is not uniform, for example, when the strain sensor is attached to the outer surface of an elbow joint, the stress at the salient point of the elbow joint is the largest, so that the structure arrangement of the convex unit or the concave unit is dense in the middle and sparse at two ends, the stress uniformity of sensitive materials in the sensor can be ensured, and the sensing performance is improved in the aspects of linearity degree, tensile strain degree and the like; therefore, the arrangement mode of the convex structures or the concave structures can be adjusted according to the actual use requirement and is not necessarily evenly arranged at equal intervals.
The size of the convex structure or the concave structure can be customized, adjusted and optimized according to the actual use condition, for example: when the strain sensor is attached to the surface of a human body and used as a bending strain sensor, the stress applied to different positions is not uniform, for example, when the strain sensor is attached to the outer surface of an elbow joint, the stress at a convex point of the elbow joint is maximum, so that the size of the convex unit 10 or the concave unit 11 in the middle of the strain sensor main body 1 is expanded, the size of the convex unit 10 or the concave unit 11 at two ends of the strain sensor main body 1 is reduced, the stress action can be enhanced in the middle to cause fracture, or the stress is reduced to inhibit fracture, and further the sensing performance is improved in the aspects of linearity, tensile strain degree and the like; in addition, the shape of the convex unit 10 or the concave unit 11 can be changed, such as a triangle, which can improve the stress concentration effect; therefore, the size and shape of the convex structure or the concave structure can be adjusted according to the actual use requirement, and are not necessarily fixed.
The structure of the strain sensor main body 1 is a thin structure with a large length-width ratio, and the left side surface 8, the right side surface 8, the upper side surface 9 and the lower side surface 9 of the strain sensor main body can be provided with regular convex structures or concave structures; the stress concentration phenomenon of the strain sensor main body 1 corresponding to the structure in the stretching process can be reduced through the convex structure, and the fracture of the conductive sensitive materials of the flexible substrate 3 and the conductive layer 4 attached to the surface of the substrate is inhibited; the stress concentration position of the strain sensor main body 1 in the stretching process can be controlled by designing the position and the size of the concave structure, so that the fracture crack position of the flexible substrate 3 attached with the conductive layer 4 is controllable, and the sensing performance is further regulated and controlled; because of the stability and the sealing property of the silica gel, the silica gel can be used as an external packaging material 5 to ensure the stable work of the sensor, and can be used for various working conditions of humidity and underwater.
The strain sensor body 1 is prepared by the following method:
firstly, a flexible substrate 3 is obtained after a flexible porous material (such as polyurethane sponge and melamine sponge) is subjected to laser cutting, the flexible substrate 3 is in a long and narrow film structure and has a high length-width ratio, and the flexible substrate is ensured to be easily packaged and easily applied to the fields of wearable health monitoring equipment, human-computer interaction interfaces and soft robot skin; the internal microscopic porous structure of the conductive sensitive material can be used as a carrier of the conductive sensitive material, so that the continuous transmission of electric signals is ensured, and the electrical property of the conductive sensitive material is changed by changing the deformation degree of the internal microscopic structure; dissolving nano conductive materials (such as carbon nano materials, nano metal particles, nano metal wires and nano metal sheets) in a dispersing agent (deionized water, ethanol, isopropanol and n-hexane) according to the mass concentration of 30g/L, uniformly stirring to obtain a nano conductive material mixed solution, then placing the flexible substrate 3 in the nano conductive material mixed solution, fully soaking, and drying until the dispersing agent is fully volatilized, so that a conductive layer 4 is attached to the flexible substrate 3, namely the nano conductive materials are fully covered on the porous flexible substrate to obtain the flexible substrate, and the nano conductive materials form a conductive path on the surface of the flexible porous substrate to obtain the conductive flexible substrate; and finally, placing the conductive flexible substrate in a mold, pouring an external packaging material (namely, a silicone-like soft material with a liquid precursor, such as polydimethylsiloxane) into the mold, and heating, curing and molding by a mold method to form a main body packaging layer 5, thereby obtaining the strain sensor main body 1.
The flexible porous material has the characteristics of easy deformation, low density and strong adsorbability, and a conductive path can be constructed on the framework of the flexible porous material by adsorbing the conductive sensitive material to transmit an electric signal; by utilizing the characteristic of the flexible porous material, the sensing principle of the flexible tensile strain sensor is as follows: after the conductive sensitive material is attached to the surface of the flexible porous material, external tensile stress acts on the upper end and the lower end of the strain sensor main body 1, so that the strain sensor main body 1 generates tensile strain, the number of microscopic wire-shaped conductive paths in the conductive layer 4 attached to the flexible substrate 3 is changed, the resistance value of the sensor main body is changed, and the tensile stress and the tensile strain applied to the strain sensor main body 1 from the outside are reflected by the resistance value change;
when no external packaging material is added, external tensile stress acts on the upper end and the lower end of the conductive layer 4 attached to the flexible substrate 3, so that the conductive layer 4 is cracked, the microscopic filiform conductive paths are cracked, the number of the conductive paths is reduced, and when the flexible substrate 3 is completely cracked, the conduction cannot be realized, the open circuit is realized, and the recovery cannot be realized;
after an external packaging material is added to form a main body packaging layer 5, the flexible substrate 3 and the conducting layer 4 containing the nano conducting material are both embedded in the main body packaging layer 5, when external tensile stress acts on the upper end and the lower end of the strain sensor main body 1, because the external packaging material has stretchability, namely, a larger elastic deformation range, when the external tensile stress acts on the flexible substrate 3, the microscopic filamentous conducting paths of the nano conducting material are reduced, but because the flexible substrate 3 and the conducting layer 4 containing the nano conducting material are both embedded in the main body packaging layer 5, the microscopic filamentous conducting paths cannot be completely broken, and the microscopic filamentous conducting paths recover to the original state when the external tensile stress acts on the flexible substrate 3, the conducting layer 4 and the main body packaging layer 5, and the shapes and the electrical properties of the flexible substrate 3, the conducting layer 4 and the main body packaging layer 5 recover to the unstretched state;
therefore, the use of the external packaging material plays a role in improving the sensing performance of the sensor based on the flexible porous material, the measuring range (stretchability) can be expanded, the mechanical property of the sensor can be improved, the fatigue life can be prolonged, and the signal stability can be improved.
The strain signal reading interface 2 mainly comprises a copper needle 6 and a signal transmission lead 7 connected with the copper needle 6, wherein the copper needle 6 is arranged in the strain sensor body 1, and the copper needle 6 is electrically connected with the strain sensor body 1. The copper needle is used as an electrode, is a common copper needle electrode, has the size of more than 500 micrometers, even millimeter level, is slightly larger than the aperture of the strain sensor main body 1, when the electrode is inserted into the strain sensor main body 1, the electrode can be stably contacted with the surface of the strain sensor main body to form a stable circuit for transmitting electric signals, and is suitable for being used as an electric signal reading interface of a porous material, one end of the exposed copper needle is welded with a signal transmission lead 7, and the electric signals are transmitted to external sensing signal detection equipment.
As shown in fig. 3, the axial direction of the copper needle 6 is parallel or perpendicular to the stretching direction of the tensile strain sensor. Namely, the copper needle 6 has two insertion modes: longitudinal insertion and transverse insertion. The copper needle 6 is longitudinally inserted to be longer in exposed length and easy to connect with a signal transmission lead 7, but the copper needle 6 is made of a metal material and has no ductility, and the flexible substrate 3 is made of a flexible porous material and has ductility, so that the copper needle 6 and the flexible substrate 3 can generate relative displacement in the stretching process of the sensor; the mode of transversely inserting the copper needle 6 is beneficial to reducing relative displacement, the stability is higher, but the length of the copper needle extending out of the flexible substrate 3 is limited, the signal transmission lead 7 is inconvenient to connect, and the symmetrical copper needle 6 needs to symmetrically penetrate through the whole flexible substrate 3 in order to meet the requirement;
after the copper needle 6 is inserted, the main body packaging layer 5 plays a role in fixing and packaging the copper needle 6, so that the copper needle 6 can be tightly attached to the flexible substrate 3 and the conductive layer 4, and the stability of the copper needle 6 and the stability of signal reading are ensured.
The preparation process of the flexible tensile strain sensor is as follows:
completely immersing a cut and formed flexible substrate 3 (such as polyurethane sponge and melamine sponge) into a solution prepared by a conductive sensitive material (such as carbon nano material, nano metal particles, nano metal wires and nano metal sheets) which is obtained by dissolving a nano conductive material (such as deionized water, ethanol, isopropanol and n-hexane) in a dispersing agent (such as deionized water, ethanol, isopropanol and n-hexane) according to a certain proportion and uniformly stirring, putting the flexible substrate 3 which is repeatedly extruded and soaked into an oven for drying until the dispersing agent is completely volatilized, taking out the dried flexible substrate 3, cleaning the flexible substrate 3 with the dispersing agent and drying again, and fully covering the nano conductive material on the surface of porous material fibers to form a plurality of conductive paths so as to obtain the flexible substrate 3 attached with the conductive layer 4.
Placing the dried flexible substrate 3 attached with the conductive layer 4 in a mold with a corresponding convex structure or concave structure, injecting an external packaging material 5 such as polydimethylsiloxane into the mold, uniformly covering, extracting residual air in the external packaging material 5 by using a vacuum defoaming machine, and then placing in an oven to quickly cure the external packaging material 5; the external packaging material 5 has good fluidity before curing, and can fully fill the pores of the porous material; the cured porous material has good stretchability, the irregular tensile fracture of the porous material is effectively inhibited, and the measurement range of the sensor is improved.
Taking out the external packaging material 5 and the flexible substrate 3 from the mold, inserting copper needles 6 into two sides of the conductive flexible substrate, and welding signal transmission leads 7; and then placing the flexible tensile strain sensor in a mould without a groove, slowly injecting an external packaging material 5 into the mould until the mould is filled, placing the mould in a vacuum defoaming machine to extract residual air, and then placing the mould in an oven until the external packaging material 5 is cured to obtain the flexible tensile strain sensor.
For the above steps, because the residual air in the external packaging material 5 is extracted by using the vacuum defoaming machine so that the external packaging material 5 is completely immersed into the porous structure of the flexible substrate 3, the initial resistance of the sensor is large, the relative change percentage of the resistance is small when the deformation degree is constant, and the sensitivity is low; however, the external packaging material 5 is completely filled in the porous structure, so that the tensile strain strength of the prepared flexible tensile strain sensor can be improved.
If the vacuumizing link is omitted and other manufacturing links are unchanged, the interior of the flexible substrate 3 is still in a porous structure, the initial resistance is small, the relative change percentage of the resistance is large when the deformation degree is fixed, and the sensitivity is high; and because the interior of the porous structure is not filled with the external packaging material 5, the tensile strain strength of the prepared flexible tensile strain sensor is low.
The molds are mainly classified into grooved molds and non-grooved molds, and are manufactured by 3D printing, the grooved molds being provided as shown in fig. 7 (a) and (c), fig. 8 (a) and (c), and the non-grooved molds being shown as fig. 7 (b) and (D), fig. 8 (b) and (D). The groove die is mainly used for fixing the flexible substrate, and the symmetry of the structure and the position accuracy of the substrate are guaranteed. Placing the flexible substrate in the groove, shielding the lower half part of the flexible substrate by the mold, and injecting silica gel into the mold to package the upper half part of the silica gel; the groove die is not arranged for supplementing the silica gel, the packaged part of the flexible substrate which is partially packaged and connected with the strain signal reading interface is downwards arranged in the die, the upper half part of the flexible substrate is not covered due to the fact that the upper half part of the flexible substrate is shielded by the groove die, and the silica gel is injected into the die to package the upper half part of the flexible substrate, so that the whole flexible substrate is packaged. For a particular configuration, the use of a mold configuration as shown in fig. 7 and 8 can be used to make four configurations of sensor bodies.
In order to improve the tensile property, a high length-width ratio is required, and meanwhile, in consideration of the aspects of strength, use scene and the like, a basic structure shown in fig. 1 is designed, wherein the inner part is rectangular thin sponge, and the outer part is rectangular colloidal silica.
The preparation conditions of the high-tensile flexible strain sensor based on the porous flexible material are shown in table 1.
TABLE 1
| Nano conductive material (carbon nano tube) | 3.000g |
| Dispersant (n-hexane) | 100ml |
Taking the basic structure as an example, as shown in fig. 6, the flexible sensor is obtained by the following steps:
i. adding a certain mass of carbon nano tubes into a clean and dry beaker, and adding n-hexane according to the proportion shown in the table 1 to obtain a mixed solution required for soaking. Adding a magnetic stirrer into the mixed solution, and stirring the mixture to be uniform by using a magnetic stirrer. And completely soaking the cut sponge into the mixed solution for about 5 minutes, and continuously extruding the sponge by using a glass rod in the process. And putting the sponge which is repeatedly extruded and soaked into an oven for drying until the dispersing agent is completely volatilized, taking out the dried sponge, washing the sponge by using normal hexane, drying the sponge again, and fully covering the surface of the porous material fiber by using the nano conductive material to form a plurality of conductive paths so as to obtain the porous sponge attached with the nano conductive material.
And ii, putting the dried porous sponge attached with the nano conductive material into a groove of a specified groove mould.
iii, according to 1: 1, slowly injecting the liquid silica gel into the mold until the mold is filled.
And iv, putting the mould filled with the sponge and the silica gel into a vacuum defoaming machine to extract residual air.
v. putting the silicon gel into a constant temperature box, and heating the silicon gel for about 20 minutes at about 60 ℃ until the silicon gel is solidified.
And vi, taking out the silica gel and the sponge, inserting the copper needles 6 into two sides of the porous sponge attached with the nano conductive material, and welding the lead.
And vii, placing the sponge welded with the lead in a non-groove mold, and slowly injecting liquid silica gel into the mold until the sponge is filled.
Repeating steps iv and v to produce a flexible sensor.
Step iv can cause the silica gel to be completely immersed into the porous structure of the sponge, so that the initial resistance of the sensor is large, the relative change percentage of the resistance is small when the deformation degree is constant, and the sensitivity is low. If the step iv is omitted, other manufacturing links are unchanged, the interior of the flexible substrate is still in a porous structure, the initial resistance is small, the relative change percentage of the resistance is large when the deformation degree is fixed, and the sensitivity is high; the tensile strain strength of the prepared flexible tensile strain sensor is low due to the fact that silica gel is not filled in the porous structure.
Claims (8)
1. A flexible tensile strain sensor based on a packaging material structure is characterized in that the flexible tensile strain sensor is symmetrically arranged and comprises a strain sensor main body (1) and a strain signal reading interface (2);
strain signal reading interfaces are respectively arranged at two ends of the strain sensor main body (1), and the strain signal reading interfaces at the two ends of the strain sensor main body (1) are respectively and electrically connected with the two ends of the strain sensor main body;
the strain sensor comprises a strain sensor body (1), a conductive layer (4) and a body packaging layer (5), wherein the conductive layer (4) is attached to the outer surface of the strain sensor substrate (3), the strain sensor substrate (3) attached with the conductive layer (4) is embedded in the body packaging layer (5), and strain signal reading interfaces at two ends of the strain sensor body respectively penetrate through the corresponding ends of the body packaging layer (5) and then are arranged at two ends of the strain sensor substrate (3).
2. An encapsulated material structure based flexible tensile strain sensor according to claim 1, wherein at least one of the four sides of the body encapsulation layer (5) of the strain sensor body (1) is provided with a bump structure, the bump structure is composed of a plurality of bump units (10) arranged in parallel and at intervals along the stretching direction of the strain sensor, and each bump unit (10) is provided on the current side.
3. A flexible tension strain sensor based on a packaging material structure according to claim 2, characterized in that the protruding units (10) have the same or different sizes and the distance between adjacent protruding units (10) is the same or different.
4. An encapsulated material structure based flexible tensile strain sensor according to claim 1, wherein a recessed structure is provided on at least one of the four sides of the body encapsulation layer (5) of the strain sensor body (1), the recessed structure is composed of a plurality of recessed units (11) arranged in parallel and at intervals along the stretching direction of the strain sensor, and each recessed unit (11) is opened on the current side.
5. A flexible tension strain sensor based on a packaging material structure according to claim 4, characterized in that the size of the concave units (11) is the same or different, and the distance between adjacent concave units (11) is the same or different.
6. A flexible tensile strain sensor based on an encapsulating material structure according to claim 1, characterized in that the strain sensor body (1) is prepared by the following method:
firstly, carrying out laser cutting on a flexible porous material to obtain a flexible substrate (3), dissolving a nano conductive material in a dispersing agent and uniformly stirring to obtain a nano conductive material mixed solution, then placing the flexible substrate (3) in the nano conductive material mixed solution to be fully soaked and dried until the dispersing agent is completely volatilized, so that a conductive layer (4) is formed on the outer surface of the flexible substrate (3), and thus the conductive flexible substrate is obtained; and finally, placing the conductive flexible substrate in a mold, pouring an external packaging material into the mold, heating, curing and molding to form a main body packaging layer (5), and obtaining the strain sensor main body (1).
7. The flexible tension strain sensor based on the packaging material structure is characterized in that the strain signal reading interface (2) mainly comprises a copper needle (6) and a signal transmission lead (7) connected with the copper needle (6), the copper needle (6) is arranged in the strain sensor body (1), and the copper needle (6) is electrically connected with the strain sensor body (1).
8. A flexible tensile strain sensor based on an encapsulating material structure according to claim 7, characterized in that the axial direction of the copper needle (6) is parallel or perpendicular to the tensile direction of the tensile strain sensor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210093766.3A CN114440759B (en) | 2022-01-26 | 2022-01-26 | Flexible tensile strain sensor based on packaging material structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210093766.3A CN114440759B (en) | 2022-01-26 | 2022-01-26 | Flexible tensile strain sensor based on packaging material structure |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114440759A true CN114440759A (en) | 2022-05-06 |
| CN114440759B CN114440759B (en) | 2023-01-10 |
Family
ID=81369464
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210093766.3A Active CN114440759B (en) | 2022-01-26 | 2022-01-26 | Flexible tensile strain sensor based on packaging material structure |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114440759B (en) |
Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014023275A1 (en) * | 2012-08-09 | 2014-02-13 | Imo Holding Gmbh | Method and apparatus for detecting and monitoring states |
| CN108553102A (en) * | 2018-03-14 | 2018-09-21 | 浙江大学 | A kind of flexible extensible multichannel convex surface myoelectricity pole and preparation method thereof |
| CN109612383A (en) * | 2018-12-25 | 2019-04-12 | 国家纳米科学中心 | A kind of strain transducer and preparation method thereof |
| CN109855526A (en) * | 2019-02-28 | 2019-06-07 | 吉林大学 | A kind of resistance-type flexibility strain transducer and preparation method thereof based on dry mediation self assembly |
| CN110132461A (en) * | 2019-04-19 | 2019-08-16 | 浙江大学 | A kind of changeable type flexible sensing device based on porous structure |
| CN110375636A (en) * | 2019-07-09 | 2019-10-25 | 浙江大学 | A kind of flexible strain transducer of high stretching based on porous flexible material |
| WO2019222969A1 (en) * | 2018-05-24 | 2019-11-28 | 深圳先进技术研究院 | Flexible pressure sensor based on hemispheric microstructure and fabrication method therefor |
| CN111551294A (en) * | 2020-05-21 | 2020-08-18 | 浙江大学 | Flexible pressure sensor based on liquid metal photocuring printing technology |
| CN213714205U (en) * | 2020-12-03 | 2021-07-16 | 合肥艾创微电子科技有限公司 | High-tensile flexible strain sensor, sensing system and flexible electronic skin |
| CN113237420A (en) * | 2021-05-14 | 2021-08-10 | 东南大学 | High-sensitivity flexible resistance type strain sensor and preparation method thereof |
| CN113263512A (en) * | 2021-05-17 | 2021-08-17 | 浙江大学 | Bionic luminous interactive flexible robot skin |
-
2022
- 2022-01-26 CN CN202210093766.3A patent/CN114440759B/en active Active
Patent Citations (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2014023275A1 (en) * | 2012-08-09 | 2014-02-13 | Imo Holding Gmbh | Method and apparatus for detecting and monitoring states |
| CN108553102A (en) * | 2018-03-14 | 2018-09-21 | 浙江大学 | A kind of flexible extensible multichannel convex surface myoelectricity pole and preparation method thereof |
| WO2019222969A1 (en) * | 2018-05-24 | 2019-11-28 | 深圳先进技术研究院 | Flexible pressure sensor based on hemispheric microstructure and fabrication method therefor |
| CN109612383A (en) * | 2018-12-25 | 2019-04-12 | 国家纳米科学中心 | A kind of strain transducer and preparation method thereof |
| CN109855526A (en) * | 2019-02-28 | 2019-06-07 | 吉林大学 | A kind of resistance-type flexibility strain transducer and preparation method thereof based on dry mediation self assembly |
| CN110132461A (en) * | 2019-04-19 | 2019-08-16 | 浙江大学 | A kind of changeable type flexible sensing device based on porous structure |
| CN110375636A (en) * | 2019-07-09 | 2019-10-25 | 浙江大学 | A kind of flexible strain transducer of high stretching based on porous flexible material |
| CN111551294A (en) * | 2020-05-21 | 2020-08-18 | 浙江大学 | Flexible pressure sensor based on liquid metal photocuring printing technology |
| CN213714205U (en) * | 2020-12-03 | 2021-07-16 | 合肥艾创微电子科技有限公司 | High-tensile flexible strain sensor, sensing system and flexible electronic skin |
| CN113237420A (en) * | 2021-05-14 | 2021-08-10 | 东南大学 | High-sensitivity flexible resistance type strain sensor and preparation method thereof |
| CN113263512A (en) * | 2021-05-17 | 2021-08-17 | 浙江大学 | Bionic luminous interactive flexible robot skin |
Non-Patent Citations (1)
| Title |
|---|
| ZHIQIU YE ET AL.: ""Design and Implementation of Robot Skin using Highly Sensitive Sponge Sensor"", 《IEEE》 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114440759B (en) | 2023-01-10 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN111505065B (en) | Interdigital counter electrode type flexible touch sensor based on super-capacitor sensing principle and preparation method thereof | |
| CN110763378B (en) | Wearable flexible touch force sensor | |
| CN109099832B (en) | Strain sensor and method for manufacturing the same | |
| CN110726364B (en) | Flexible strain sensor with strain isolation effect | |
| CN113074843B (en) | Multifunctional planar capacitive flexible sensor and preparation method thereof | |
| CN113249961B (en) | Flexible device structure based on conductive fiber network and preparation method and application thereof | |
| CN105671654A (en) | Ionic induction type artificial skin array structure and preparation method thereof | |
| CN111504495A (en) | Flexible temperature sensor based on composite temperature-sensitive hydrogel and preparation method thereof | |
| CN113970394A (en) | Flexible piezoresistive sensor based on porous microstructure and preparation method thereof | |
| JP2010214107A (en) | Integrated sensor assembly and methods for forming the same | |
| CN114440759B (en) | Flexible tensile strain sensor based on packaging material structure | |
| CN114440760B (en) | Flexible tensile strain sensor | |
| CN113237420A (en) | High-sensitivity flexible resistance type strain sensor and preparation method thereof | |
| CN113733697A (en) | High-sensitivity wide-sensing-range flexible composite film and application thereof | |
| CN114354032A (en) | Multilayer bionic touch sensor based on skin touch perception architecture and preparation method | |
| CN114489340B (en) | Wearable human body posture data feedback equipment based on flexible tensile strain sensor | |
| Lei et al. | Highly Sensitive, ultrawide range, and multimodal flexible pressure sensor with hierarchical microstructure prepared by a one‐step laser printing process | |
| Xu et al. | Performance characterization of ionic-hydrogel based strain sensors | |
| CN114459333B (en) | Tensile strain sensor based on porous flexible material | |
| CN113340481B (en) | Pressure sensor and preparation method thereof | |
| CN210154720U (en) | High-sensitivity electronic skin | |
| CN113340483A (en) | Flexible mechanical sensor of bionic microstructure and preparation method thereof | |
| KR102059546B1 (en) | Strain sensor comprising insulation structure and method of manufacturing the same | |
| CN113405448B (en) | Composite flexible sensor and preparation method thereof | |
| CN114199424A (en) | Piezoresistive sensor and preparation process thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |