CN107478148B - Flexible wearable electronic strain sensor and preparation method thereof - Google Patents
Flexible wearable electronic strain sensor and preparation method thereof Download PDFInfo
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- CN107478148B CN107478148B CN201710570331.2A CN201710570331A CN107478148B CN 107478148 B CN107478148 B CN 107478148B CN 201710570331 A CN201710570331 A CN 201710570331A CN 107478148 B CN107478148 B CN 107478148B
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- 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
Abstract
The invention is suitable for the technical field of sensor manufacturing and packaging, and discloses a flexible wearable electronic strain sensor and a manufacturing method thereof. The utility model provides a flexible wearable electronic strain sensor includes flexible base member, has flexible microchannel in the flexible base member, is provided with liquid conductor or semi-liquid conductor in the microchannel, and the both ends of microchannel are provided with the electrode. The wearable device is provided with the flexible wearable electronic strain sensor. The preparation method comprises the following steps: preparing a flexible substrate with microchannels; injecting liquid conductor or semi-liquid conductor into the micro-channel, and inserting electrodes at two ends of the micro-channel. The flexible wearable electronic strain sensor and the preparation method thereof provided by the invention have the geometrical characteristics of high flexibility, stretchability and thinness, can be directly integrated with any flexible actuating mechanism, have high sensitivity and strong anti-interference capability, and can still normally work when the strain reaches 300%.
Description
Technical Field
The invention belongs to the technical field of sensor manufacturing and packaging, and particularly relates to a flexible wearable electronic strain sensor and a manufacturing method thereof.
Background
With the increasing application demand of the information age, the expected values and the ideal requirements for various performance parameters such as the range, the precision and the stability of the measured information are gradually increased. Sensor systems applied to wearable devices gradually show limitations in some applications, including that the current sensors are not flexible enough and cannot be stretched really, and once the strain or bending angle is too large, the structure of the whole sensor is damaged and fails; the sensitivity is low, and the interference of human physiological signal noise is easy to cause the fuzzy and incomplete signal acquisition.
Since the 2012 google company held a great conference on developers, the push for "google glasses" has greatly stimulated market interest in wearable devices. The emergence of various wearable devices in as short as a few years brings various conveniences to our lives. For example, the intelligent watch has functions of body temperature and pulse detection and step counting, high-sensitivity electronic skin transmits skin touch information to the brain, and a three-dimensional microelectrode is utilized to realize the control of a cerebral cortex artificial limb and the like. The sensor, as one of the core components, will affect the functional design and future development of the wearable device. In the actual use process of the wearable device, the sensor is required to be transparent, flexible, extensible, freely bendable or even foldable, high in sensitivity and the like in many times, and particularly, the working environment is directly on various complex and irregular skin surfaces of a human body with large deformation, such as the deformation detection of joints and the like.
The prior art flexible sensors are mainly prepared in the following way.
1. A field effect transistor is manufactured by attaching a semiconductor nanowire to a flexible material by using a contact printing method, a source electrode of the field effect transistor is grounded through a pressure-sensitive rubber, and the conductivity of a piezoresistor is changed due to external pressure, so that the property of the transistor is changed, and a corresponding load is obtained by detecting the change of an output signal.
2. The carbon nano tubes are sprayed on the PDMS sheet to form the rectangular conductive array, so that the capacitive sensor array with good transparency is manufactured, and the curled carbon nano tubes and the net structure formed by the curled carbon nano tubes enable macroscopic wires to stretch along with the stretching of the elastic material and ensure the conductivity.
3. The conductive textile is manufactured into a flexible electrode to be embedded into PDMS, the upper layer single electrode and the bottom layer four electrodes respectively generate capacitance, and the detection of multidimensional force can be realized by measuring the relative change of the four capacitance values.
4. The external load is measured by taking porous nylon with skin-like mechanical properties as a matrix and electrochemically depositing polypyrrole as a conductive dopant in the matrix, and when the load is loaded, the conductivity of the sensor is increased.
5. The flexible spiral electrode with high elasticity and durability is adopted, and PDMS is used as a main structural material. A highly distorted tactile sensor array is fabricated. Complex working surfaces can be accommodated without destroying the sensor structure and the sensing array on the metal interconnects.
Although the strain sensor has certain flexibility, the strain sensor cannot be really stretched, lacks of flexibility similar to skin elasticity, and cannot completely realize measurement of external loads under the condition of covering three-dimensional complex static/dynamic surfaces. At higher strain or bend angles, the entire system will fail. Meanwhile, the surface of the skin of a human body still shows certain rigidity, so that the human body can generate uncomfortable feeling, integration is difficult, and the stability, precision and accuracy of measurement are greatly limited. In addition, human physiological signals are easily interfered by external factors, such as sweat stain and muscle contraction, and the user cannot eliminate the influence factors, so that data acquisition ambiguity and incompleteness are caused, and the reliability is poor.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a flexible wearable electronic strain sensor and a preparation method thereof, wherein the flexible wearable electronic strain sensor has good stability, precision, accuracy and reliability.
The technical scheme of the invention is as follows: the flexible wearable electronic strain sensor comprises a flexible substrate, wherein a flexible micro-channel is arranged in the flexible substrate, a liquid conductor or a semi-liquid conductor is arranged in the micro-channel, and electrodes are arranged at two ends of the micro-channel.
Optionally, the flexible substrate is made of a degradable polyester material or a silicon rubber material.
Optionally, a liquid conductor eutectic gallium indium is disposed in the microchannel.
Optionally, the microchannel is in the shape of a strip, a dog-leg, a serpentine, a circle, or an arc; or/and the micro-channel is provided with one or at least two.
The invention also provides a wearable device which is provided with the flexible wearable electronic strain sensor.
The invention also provides a preparation method of the flexible wearable electronic strain sensor, which comprises the following steps:
preparing a flexible substrate with microchannels; and injecting a liquid conductor or a semi-liquid conductor into the micro-channel, and inserting electrodes at two ends of the micro-channel.
Optionally, preparing the flexible substrate comprises the steps of:
preparing a micro-channel mold and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the flexible material solution into the micro-channel mould, and mixing and removing bubbles to form a flexible matrix main body;
dripping the mixed and bubble-removed flexible material solution on the substrate, and enabling the flexible material solution to form a layer of flexible material film;
and pressing the flexible substrate body on the flexible material film which is not completely cured, so that the flexible substrate body and the flexible material film form a flexible substrate with a micro-channel.
Optionally, injecting a liquid conductor or a semi-liquid conductor into the microchannel includes the following steps:
two injectors can be used to insert into both ends of the microchannel, wherein one injector has a liquid conductor inside; and pumping air in the microchannel by using the other injector, injecting a liquid conductor into the microchannel by using the injector with the liquid conductor to fill the microchannel with the liquid conductor, and pulling out the injector.
Optionally, inserting electrodes at both ends of the microchannel comprises the steps of:
and respectively inserting two electrodes into two ends of the microchannel, and sealing the microchannel by using a flexible material solution.
Optionally, mixing and de-bubbling the solution of the flexible material comprises the steps of:
the Ecoflex series silicone rubber solution can be placed into a container of a centrifugal mixer, the rotating speed of the centrifugal mixer is 300-400rpm, the holding time is 10-15s, the rotating speed of the centrifugal mixer is increased to 1400-1600rpm, and the holding time is 25-30s, so that the mixed silicone rubber solution is obtained;
putting the mixed silicon rubber solution into a vacuum filtration device, and starting a vacuum pump of the vacuum filtration device to obtain the silicon rubber solution with bubbles removed;
forming the flexible substrate body comprises the steps of:
spraying at least one layer of release agent film on the surface of the microchannel mold, and then filling the silicon rubber solution with bubbles removed into the microchannel mold by using a liquid moving machine;
moving the micro-channel mould into an oven, baking for 45-60min at 80 ℃, and demoulding to obtain a flexible matrix main body;
dripping the silicon rubber solution without bubbles on the substrate, and putting the substrate into a spin coater to rotate to form a layer of silicon rubber film, wherein the rotation speed of the spin coater is set to be 350-400rpm, and the spin time is 25-30 seconds;
and pressing the demolded flexible substrate body on the silicone rubber film when the silicone rubber film is in a semi-solidified state, and standing at room temperature for 45-60min when the flexible substrate body is well bonded and sealed with the silicone rubber film to obtain the flexible substrate with the micro-channel.
According to the flexible wearable electronic strain sensor and the preparation method thereof, provided by the invention, the strain sensor takes the highly flexible Ecoflex series material as a basic material. Pouring into a micro-mold prepared by photolithography to form micro-channels or micro-channel array, and spin coating a film of the same material to seal the micro-channels. Injecting liquid conductor eutectic gallium indium to fill the whole channel. And finally, inserting electrodes at two ends of the micro-channel and sealing again to finish the preparation. When the sensor works, the length and the cross section of the micro-channel are changed due to the action of external load, so that the resistance is changed. A constant current source is added at two ends of the electrode. The resistance signal is changed into a voltage signal convenient to measure, and a corresponding strain value is obtained through analysis of the voltage signal. The flexible sensor can still work normally when the strain reaches 300%, and can work with any complex three-dimensional surface in an integrated mode.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic plan view of a flexible wearable electronic strain sensor provided by an embodiment of the present invention;
fig. 2 is a schematic plan view of a flexible wearable electronic strain sensor according to an embodiment of the present invention, in which the micro channel has a serpentine shape;
fig. 3 is a schematic plan view of a silicone rubber solution prepared in a method for preparing a flexible wearable electronic strain sensor according to an embodiment of the present invention;
fig. 4 is a schematic plan view of a flexible wearable electronic strain sensor according to an embodiment of the present invention after mixing a silicone rubber solution;
fig. 5 is a schematic plan view of a flexible wearable electronic strain sensor according to an embodiment of the present invention after bubbles are removed from a silicone rubber solution;
fig. 6 is a schematic plan view illustrating a process of filling a silicone rubber solution on a microchannel mold in a method for manufacturing a flexible wearable electronic strain sensor according to an embodiment of the present invention;
fig. 7 is a schematic plan view of a flexible wearable electronic strain sensor manufactured according to a method of manufacturing a flexible wearable electronic strain sensor according to an embodiment of the present invention after baking after filling a silicon rubber solution on a microchannel mold;
fig. 8 is a schematic plan view of a flexible wearable electronic strain sensor according to a manufacturing method of the present invention after a silicone rubber solution is dropped on a substrate;
fig. 9 is a schematic plan view of a flexible substrate body and a film being pressed together in a manufacturing method of a flexible wearable electronic strain sensor according to an embodiment of the present invention;
fig. 10 is a schematic plan view of a flexible wearable electronic strain sensor obtained in a manufacturing method of a flexible wearable electronic strain sensor according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present.
It should be noted that the terms of orientation such as left, right, up and down in the embodiments of the present invention are only relative to each other or are referred to the normal use state of the product, and should not be considered as limiting.
As shown in fig. 1, a flexible wearable electronic strain sensor provided by an embodiment of the present invention includes a flexible substrate 1, where the flexible substrate 1 may be made of a silicone rubber material (e.g., Ecoflex series). The flexible substrate 1 is internally provided with a flexible micro-channel, the length and the cross section of the flexible micro-channel can be changed under the action of external force, the micro-channel 10 is a closed cavity, a semi-liquid conductor or a liquid conductor 3 is arranged in the micro-channel 10, and the micro-channel 10 can be filled with the semi-liquid conductor or the liquid conductor 3. The electrodes 2 are arranged at two ends of the micro-channel 10, the end of the electric plate is contacted with the semi-liquid conductor or liquid conductor 3 in the micro-channel 10, when the sensor works, the length and the cross section of the micro-channel 10 are changed due to the action of external load, and therefore the resistance of the semi-liquid conductor or liquid conductor 3 is changed. A constant current power supply is applied to the electrodes 2 at both ends. The sensor mainly collects resistance change signals of a liquid conductor or a semi-liquid conductor in a sealed micro-channel 10 during working, has the geometrical characteristics of high flexibility, stretchability and thinness, can be directly integrated with any flexible actuating mechanism, has high sensitivity and strong anti-interference capability, can still normally work when the strain reaches 300%, is particularly suitable for the field of wearable equipment, especially large deformation conditions and the like, and has high stability, precision, accuracy and reliability.
Optionally, the thickness of the flexible wearable electronic strain sensor may be less than 1mm, that is, the thickness of the flexible substrate 1 may be less than 1mm, and the flexible wearable electronic strain sensor may be well applicable to smart wearable devices.
Alternatively, the flexible substrate 1 may be made of a degradable polyester material or a silicone rubber material, in this embodiment, the flexible substrate 1 is made of an Ecoflex series silicone rubber material as a base material, and in a specific application, an aliphatic aromatic random copolyester (Ecoflex) manufactured by BASF corporation of germany may be used, and the monomers may be: adipic acid, terephthalic acid and 1, 4-butanediol. The degradable material is generally considered to be plastic which can be decomposed into low molecular substances by solar radiation, microorganisms in soil and the like, and has the properties of easy processing and meeting the use requirements besides degradability. The completely biodegradable plastic is easy to degrade when produced by using aliphatic polyester, polyvinyl alcohol (PVA) and polyethylene glycol in a chemical method. The biodegradable plastics are researched and developed by utilizing the characteristic that the high polymers are easy to biodegrade, and the excellent research on the aliphatic polyester is highlighted. Among aliphatic polyesters, Polycaprolactone (PCL) is widely used, and is a thermoplastic crystalline polyester which can be hydrolyzed by lipase into small molecules and then further assimilated by microorganisms, and can be used for products such as surgical products, adhesive films, release agents, and the like. Aliphatic polyesters and nylons undergo an amine-ester exchange reaction to synthesize a polyamide ester Copolymer (CPAE), and when they are synthesized from natural polymers of animals and plants, cellulose, starch, etc. of plants, chitosan, gelatin, algae of marine organisms, etc. of animals can produce valuable biodegradable materials. Biodegradable polyester is a novel polymeric material that can be synthesized by fermentation, chemical methods, and enzymatic catalysis.
The degradable plastics can also be synthesized by a chemical method and a natural polymer blending technology, and the main varieties comprise PHB/PCL, gelatinized starch/PCL and other products. The main characteristics of the biodegradable plastic are that the biodegradable plastic can be completely degraded, and simultaneously the heat resistance and the water resistance of the biodegradable plastic are improved and the cost is reduced by blending, so that the biodegradable plastic becomes a universal degradable plastic.
Optionally, a liquid conductor eutectic gallium indium is arranged in the microchannel 10 as a liquid conductor, and of course, other liquid metal conductors may also be arranged. The electrodes 2 can be inserted from both ends of the flexible substrate 1 in the length direction or both ends of the microchannel 10 to the front end to contact with the semi-liquid conductor or the liquid conductor 3 provided in the microchannel 10. The electrodes 2 and the flexible substrate 1 may be sealed with a sealing material therebetween to further improve the reliability thereof. The sealing material may be a silicone rubber solution material (Ecoflex).
In a specific application, the micro channel 10 may be in a shape of a strip, a zigzag, or a snake, as shown in fig. 2, the snake-shaped micro channel 10 in the flexible wearable electronic strain sensor 100 is in a reciprocating bending shape, which is more deformable, and can be used on a skin surface of a human body with a relatively large area, so that the sensing accuracy and stability can be further improved. Of course, the micro-channel 10 may have other structural shapes, such as a circle, an arc, an involute shape, or a special shape, and the like, all falling within the scope of the present invention.
Optionally, the microchannel may be provided with one or at least two, the number of microchannels may be one or multiple, at least two microchannels may form a microchannel array, and the microchannels in the microchannel array may be in a rectangular array or a circular array, etc.
In the tensile test of the flexible wearable electronic strain sensor, the sensitivity is high, the acquired signals show good linearity and repeatability, and the stability, the precision, the accuracy and the reliability are high. The strain reaches 300%, the artificial limb still can work normally, can be well attached to complex three-dimensional dynamic and static curved surfaces, such as large-deformation human joints (elbow joints and knee joints), has good skin affinity, and hardly influences normal work and study of people. Is an ideal flexible sensor of wearable equipment.
The invention also provides a wearable device which is provided with the flexible wearable electronic strain sensor. Wearable equipment can be for intelligent wrist-watch, intelligent bracelet, intelligent glasses, intelligent clothing, virtual reality helmet etc.. Through the application of the flexible wearable electronic strain sensor, the flexible wearable electronic strain sensor has the performance thickness of less than 1mm, and very good flexibility, can still normally work when the tensile strain reaches 300 percent, is comparable to the skin of a human body, can adopt biocompatible Ecoflex material as a basic material, and hardly causes discomfort to people when being integrated into a wearable device. In addition, the sensor collects the resistance signals of the sealed micro-channel 10, so that the interference of external noise to the signals is eliminated, and the collected data is accurate. The micro-channels 10, which are patterned by a photolithographic process, greatly improve the sensitivity of the sensor. Of course, the flexible wearable electronic strain sensor provided in the embodiment of the present invention may also be applied to other devices, and also fall within the protection scope of the present invention.
An embodiment of the present invention further provides a method for manufacturing a flexible wearable electronic strain sensor, as shown in fig. 3 to 10, including the following steps:
preparing a flexible substrate 1 having sealed microchannels 10; injecting a semi-liquid conductor or a liquid conductor 3 into the micro-channel 10, and inserting electrodes 2 at two ends of the micro-channel 10. The semi-liquid conductor or liquid conductor 3 may fill the micro-channel 10 with the end of the electrode 2 in contact with the semi-liquid conductor or liquid conductor 3.
Alternatively, the preparation of the flexible substrate 1 comprises the following steps:
preparing a micro-channel mold 41 and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the flexible material solution into the micro-channel mold 41 after mixing and removing bubbles to form a flexible matrix main body 11;
dropping the flexible material solution mixed and bubble-removed on the substrate 42, and forming a layer of flexible material film (silicone rubber film 12) from the flexible material solution;
pressing the flexible substrate body 11 on the incompletely cured flexible material film (silicone rubber film 12) to form the flexible substrate 1 with the microchannels 10 by the flexible substrate body 11 and the flexible material film (silicone rubber film 12);
optionally, injecting a semi-liquid conductor or a liquid conductor 3 into the microchannel 10 comprises the following steps:
two syringes may be used to insert into both ends of the microchannel 10, wherein one syringe has a liquid conductor 3 therein; and the other injector pumps air in the micro-channel 10, the injector with the liquid conductor 3 injects the liquid conductor 3 into the micro-channel 10, so that the micro-channel 10 is filled with the liquid conductor 3, and the injector is pulled out.
Optionally, inserting the electrodes 2 at both ends of the microchannel 10 comprises the following steps:
two electrodes 2 are respectively inserted into both ends of the microchannel 10, and the microchannel 10 is sealed with a flexible material solution.
Optionally, mixing and de-bubbling the solution of the flexible material comprises the steps of:
the Ecoflex series silicone rubber solution can be placed into a container of a centrifugal mixer, the rotating speed of the centrifugal mixer is 300-400rpm, the holding time is 10-15s, the rotating speed of the centrifugal mixer is increased to 1400-1600rpm, and the holding time is 25-30s, so that the mixed silicone rubber solution is obtained;
putting the mixed silicon rubber solution into a vacuum filtration device, and starting a vacuum pump of the vacuum filtration device to obtain the silicon rubber solution with bubbles removed; it is to be understood that the flexible material solution is not limited to a silicone rubber solution.
Forming the flexible substrate body 11 comprises the steps of:
spraying at least one layer of release agent film on the surface of the microchannel mold 41, and then filling the microchannel mold 41 with the silicone rubber solution with bubbles removed by using a liquid transfer machine;
moving the micro-channel mold 41 into an oven, baking for 45-60min at 80 ℃, and demolding to obtain a flexible matrix main body 11;
the silicon rubber solution with bubbles removed is dripped on the substrate 42 and put into a spin coater to rotate to form a layer of silicon rubber film 12, the rotation speed of the spin coater is set to 350-400rpm, and the spin time is 25-30 seconds;
and pressing the demolded flexible substrate main body 11 on the silicone rubber film 12 when the silicone rubber film 12 is in a semi-solidified state, and standing at room temperature for 45-60min when the flexible substrate main body 11 and the silicone rubber film 12 are bonded and sealed completely to obtain the flexible substrate 1 with the microchannel 10.
In specific applications, the following process can be referred to:
a microchannel mold 41 (made of SU-8 photoresist) fabricated by photolithography; the eutectic gallium indium (EGaIn) of the liquid metal conductor, the Ecoflex series material with high flexibility, the ease release 200 mold release agent concretely comprises the following steps:
the first step is as follows: as shown in fig. 3 and 4, Ecoflex 1A and Ecoflex 1B with equal mass can be respectively taken and put into a container of a centrifugal mixer, in order to ensure that the two silicone rubbers are fully and uniformly mixed. The rotation speed of the centrifugal mixer is 300-400rpm, the holding time is 10-15s, and then the rotation speed is increased to 1400-1600rpm, and the holding time is 25-30 s.
The second step is that: as shown in fig. 4 and 5, the silicone rubber solution in the first step can be put into a vacuum filtration device, and the vacuum pump is turned on until all air bubbles in the solution are removed.
The third step: as shown in fig. 6, a mold release agent film 12 may be sprayed on the surface of the microchannel mold 41, and then the mold may be filled with the silicone rubber solution obtained in the second step using a pipette, as shown in fig. 6.
The fourth step: the filled microchannel mold 41 may be moved to an oven and baked at 80 degrees celsius for 45-60min, as shown in fig. 7, to obtain the flexible substrate body 11.
The fifth step: an appropriate amount of the silicone rubber solution obtained in the second step can be dropped on the substrate 42, and the substrate is placed into a spin coater to be rotated to form a layer of thin film 12, wherein the rotation speed of the spin coater is set to 350-400rpm, and the spin coating time is 25-30s, as shown in FIG. 8.
And a sixth step: when the film 12 formed in the fifth step is in a semi-solidified state, the demolded microchannel silicone rubber (flexible substrate body 11) may be lightly pressed against the film 12, and left to stand at room temperature for 45 to 60min when the bonding and sealing are intact, as shown in fig. 9.
The seventh step: two micro-syringes may be inserted into both ends of the micro-channel 10, one syringe for pumping air inside the micro-channel 10 and draining the liquid conductor-EGaIn, and one syringe for continuously injecting the liquid conductor (EGaIn) into the micro-channel 10. When the liquid conductor (EGaIn) fills the entire microchannel 10, the electrode 2 is inserted and a small amount of silicone rubber solution (obtained in the second step) is taken to seal the port, so that a flexible stretchable electronic strain sensor can be obtained, as shown in fig. 10. The method is simple to prepare, can realize batch production at one time, and improves time and cost benefits. The wearable device is particularly suitable for the field of wearable devices, especially for the large deformation condition and the like.
According to the flexible wearable electronic strain sensor and the preparation method thereof provided by the embodiment of the invention, the strain sensor takes the highly flexible Ecoflex series material as the basic material. The inner microchannel 10 or array of microchannels 10 may be back-molded by pouring into a micromold previously prepared by a photolithographic process, followed by spin-coating a thin film 12 of the same material to seal the entire microchannel 10. Injecting liquid conductor eutectic gallium indium to fill the whole channel. Finally, inserting electrodes 2 at two ends of the micro-channel 10 and sealing again to finish the preparation. During operation of the sensor, the length and cross-section of the microchannel 10 change due to the external load, thereby changing the resistance. A constant current source is applied across the electrodes 2. The resistance signal is changed into a voltage signal convenient to measure, and a corresponding strain value is obtained through analysis of the voltage signal. The flexible sensor can still work normally when the strain reaches 300%, and can work with any complex three-dimensional surface in an integrated mode.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents or improvements made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. The flexible wearable electronic strain sensor is characterized by comprising a flexible substrate, wherein a flexible micro-channel is arranged in the flexible substrate, a liquid conductor or a semi-liquid conductor filled with the micro-channel is arranged in the micro-channel, and electrodes are arranged at two ends of the micro-channel;
the length and the cross section of the flexible micro-channel can be changed under the action of external force, the micro-channel is a closed cavity, the end part of the electrode is in contact with a semi-liquid conductor or a liquid conductor in the micro-channel, the electrode and the flexible substrate are sealed through a sealing material, and the length and the cross section of the micro-channel are changed under the action of external load, so that the resistance of the semi-liquid conductor or the liquid conductor is changed; wherein the content of the first and second substances,
the flexible substrate is made of degradable polyester material or silicon rubber material.
2. The flexible wearable electronic strain sensor of claim 1 wherein a liquid conductor eutectic gallium indium is disposed within the microchannel.
3. The flexible wearable electronic strain sensor of any of claims 1-2 wherein the micro-channel is in the shape of a strip, a dogleg, a serpentine, a circle, or an arc; or/and the micro-channel is provided with one or at least two.
4. A wearable device having a flexible wearable electronic strain sensor of any of claims 1-3.
5. A preparation method of a flexible wearable electronic strain sensor is characterized by comprising the following steps:
preparing a flexible substrate with microchannels; injecting a liquid conductor or a semi-liquid conductor filled with the micro-channel into the micro-channel, and inserting electrodes at two ends of the micro-channel; the electrode and the flexible substrate are sealed through a sealing material;
forming the flexible substrate body comprises the steps of:
and pressing the demolded flexible matrix main body on the silicone rubber film when the silicone rubber film is in a semi-solidified state.
6. The method of claim 5, wherein the step of preparing the flexible substrate comprises the steps of:
preparing a micro-channel mold and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the flexible material solution into the micro-channel mould, and mixing and removing bubbles to form a flexible matrix main body;
dripping the mixed and bubble-removed flexible material solution on the substrate, and enabling the flexible material solution to form a layer of flexible material film;
and pressing the flexible substrate body on the flexible material film which is not completely cured, so that the flexible substrate body and the flexible material film form a flexible substrate with a micro-channel.
7. The method of claim 6, wherein the step of injecting the liquid conductor or semi-liquid conductor into the micro-channel comprises the steps of:
inserting two injectors into two ends of the microchannel, wherein one injector is internally provided with a liquid conductor; and pumping air in the microchannel by using the other injector, injecting a liquid conductor into the microchannel by using the injector with the liquid conductor to fill the microchannel with the liquid conductor, and pulling out the injector.
8. The method of claim 5, wherein inserting electrodes into two ends of the microchannel comprises:
and respectively inserting two electrodes into two ends of the microchannel, and sealing the microchannel by using a flexible material solution.
9. The method of claim 6, wherein mixing and de-bubbling the solution of flexible material comprises:
placing Ecoflex series silicon rubber solution into a container of a centrifugal mixer, wherein the rotating speed of the centrifugal mixer is 300-400rpm, the holding time is 10-15s, the rotating speed of the centrifugal mixer is increased to 1400-1600rpm, and the holding time is 25-30s, so as to obtain the mixed silicon rubber solution;
putting the mixed silicon rubber solution into a vacuum filtration device, and starting a vacuum pump of the vacuum filtration device to obtain the silicon rubber solution with bubbles removed;
forming the flexible substrate body comprises the steps of:
spraying at least one layer of release agent film on the surface of the microchannel mold, and then filling the silicon rubber solution with bubbles removed into the microchannel mold by using a liquid moving machine;
moving the micro-channel mould into an oven, baking for 45-60min at 80 ℃, and demoulding to obtain a flexible matrix main body;
dripping the silicon rubber solution without bubbles on the substrate, and putting the substrate into a spin coater to rotate to form a layer of silicon rubber film, wherein the rotation speed of the spin coater is set to be 350-400rpm, and the spin time is 25-30 seconds;
and pressing the demolded flexible substrate body on the silicone rubber film when the silicone rubber film is in a semi-solidified state, and standing at room temperature for 45-60min when the flexible substrate body is well bonded and sealed with the silicone rubber film to obtain the flexible substrate with the micro-channel.
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