CN108151949B - Flexible electronic pressure sensing device and preparation method thereof - Google Patents
Flexible electronic pressure sensing device and preparation method thereof Download PDFInfo
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- CN108151949B CN108151949B CN201711384185.0A CN201711384185A CN108151949B CN 108151949 B CN108151949 B CN 108151949B CN 201711384185 A CN201711384185 A CN 201711384185A CN 108151949 B CN108151949 B CN 108151949B
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- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/02—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning
- G01L9/04—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in ohmic resistance, e.g. of potentiometers, electric circuits therefor, e.g. bridges, amplifiers or signal conditioning of resistance-strain gauges
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Abstract
The invention is suitable for the technical field of sensor manufacturing and packaging, and discloses a flexible electronic pressure sensing device and a preparation method thereof. The flexible electronic pressure sensing device comprises a flexible shell, an internal accommodating cavity is formed in the flexible shell and comprises a plurality of array channels and a communicating cavity communicated with the same end face of the array channels, a liquid metal conductor is arranged in the internal accommodating cavity, and the flexible shell is connected with at least two electrodes connected with the liquid metal conductor. The preparation method of the flexible electronic pressure sensing device is used for preparing the flexible electronic pressure sensing device. According to the flexible electronic pressure sensing device and the preparation method thereof, the flexible electronic pressure sensing device can completely fit a three-dimensional complex static/dynamic surface and simultaneously complete the measurement of contact pressure, and has the advantages of high stability, precision, accuracy and reliability, high temperature resistance, wide application range and long service life.
Description
Technical Field
The invention belongs to the technical field of manufacturing and packaging of electronic pressure sensors, and particularly relates to a flexible electronic pressure sensing device and a manufacturing method thereof.
Background
With more and more attention paid to the health condition of people, wearable equipment capable of collecting and analyzing motion states of real-time physiological parameters is gradually enthusiastic. A sensor system, which is one of the core elements of a wearable device, has insufficient flexibility, so that further development of the wearable device is limited, and a high-performance flexible electronic device is urgently needed in applications such as real-time health detection, implantable medical devices, smart homes, skin electronic devices and the like. Most of the current pressure sensors are still made of inorganic materials such as silicon and the like. Once stretching or bending deformation is generated, the hardware structure of the sensor is damaged to fail, and in the signal acquisition process, the sensitivity is low, the sensor is easily interfered by physiological noises such as respiration and muscle contraction, and data cannot be acquired completely and clearly.
And with the popularization of intelligent terminals, the daily activities of people are connected in series in the intelligent life. Wearable electronics represent a huge market prospect, and almost all major consumer electronics companies worldwide have introduced their own wearable products, such as Apple Watch from Apple, Microsoft brand, and hua Huawei Watch, among others. Various wearable devices are emerging continuously for as little as a few years, monitoring chronic disease warnings from step counting, calorie consumption, eating habits, sleep, electronic tattoos, retinal implants, and the like. Greatly enriching our lives. However, wearable sensing technologies are often based on rigid substrates, sensors need to be embedded in rigid packages, mechanical mismatch exists between the sensors and the flexible three-dimensional skin surface of a human body, and user experience and measurement results are affected.
The prior art flexible sensors are mainly prepared in the following way.
1. The high-density touch sensor array is prepared by using the vertically-oriented zinc oxide (ZnO) nanowires, the piezoelectric effect is generated by using the zinc oxide nanowires under the stretching condition, the piezoelectric current is used as a grid electrical signal, and the electronic skin sensor with the detection sensitivity is obtained under the condition that only two terminal electrodes are needed.
2. The film formed by the elastic low-modulus microstructure hollow sphere polypyrrole polymer generated by multiphase reaction detects loads with different sizes along with the change of the contact area between the film and the electrode.
3. Through the structure and shape design, the flexible elastic conductive element with a three-dimensional wave structure can be made of traditional inorganic materials such as metal, silicon base and the like. So that the traditional inorganic conductive material can be stretched and deformed along with the extension of the elastic substrate without being damaged by fracture and the like.
4. The piezoresistive interlocking small arched structure array formed by PDMS and carbon nano-tube (CNT) develops an electronic skin capable of sensing pressure, and the sensor has high sensitivity and can even sense the direction and the intensity of air flow.
5. A pressure sensor array based on a piezoresistive principle is manufactured by utilizing piezoresistive rubber, dispersed circular sensing units are arranged on a flexible PET sheet, and electrodes made of silver for manufacturing the sensor realize the flexibility of the sensor array due to the flexibility of manufacturing materials.
Although the strain sensor has a certain flexibility, it still cannot realize special forms such as random stretching, bending and twisting. Lack of skin-like flexibility and inability to fully conform to three-dimensional complex static/dynamic surfaces while simultaneously performing contact pressure measurements. Even if integrated into a wearable device, the user experience is poor due to the mechanical mismatch with the human skin surface. In addition, due to the limitations of structural design and packaging technology, the accuracy and sensitivity of measurement cannot be considered at the same time. Is easily interfered by the physiological signals of the human body. The problems of immature preparation technology, no high temperature resistance, wide application range, long service life and the like of the existing materials such as carbon nanotubes, graphene and the like for the flexible sensor exist.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a flexible electronic pressure sensing device and a preparation method thereof.
The technical scheme of the invention is as follows: the flexible electronic pressure sensing device comprises a flexible shell, wherein an internal accommodating cavity is formed in the flexible shell and comprises a plurality of array channels and a communicating cavity communicated with the same end face of the array channels, a liquid metal conductor is arranged in the internal accommodating cavity, and the flexible shell is connected with at least two electrodes connected with the liquid metal conductor.
Optionally, the flexible casing is made of a degradable polyester material or a silicon rubber material.
Optionally, a liquid conductor eutectic gallium indium is arranged in the inner accommodating cavity.
Optionally, the flexible housing includes a first flexible substrate and a second flexible substrate that are connected to form the internal cavity, and a convex structure or/and a concave structure for forming the array channel is disposed on an inner wall of the first flexible substrate; the communicating cavity is arranged on the second flexible base body.
The invention also provides wearable equipment which is provided with the flexible electronic pressure sensing device.
The invention also provides a preparation method of the flexible electronic pressure sensing device, which comprises the following steps:
preparing a flexible shell with an internal cavity, wherein the internal cavity comprises a plurality of array channels and a communication cavity communicated with the array channels; and injecting a liquid metal conductor into the inner cavity, and inserting at least two electrodes into the flexible shell to enable the electrodes to be in contact with the liquid metal conductor.
Optionally, preparing the flexible enclosure comprises the steps of:
preparing a first mold, a second mold and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the mixed and bubble-removed flexible material solution into the first mold to form a first flexible substrate with a plurality of array channels;
adding the mixed flexible material solution with bubbles removed into the second mold, and enabling the flexible material solution to form a second flexible substrate with a communication cavity;
and pressing the first flexible substrate on the second flexible substrate which is not completely cured, so that the first flexible substrate and the second flexible substrate are integrally connected to form a flexible shell, and meanwhile, the plurality of array channels and the communication cavity are communicated to form a closed internal containing cavity.
Optionally, injecting a liquid metal conductor into the inner cavity includes the following steps:
two injectors are inserted into two ends of the inner cavity, wherein one injector is internally provided with a liquid metal conductor; and the other injector pumps the air in the inner cavity, the injector with the liquid metal conductor injects the liquid metal conductor into the inner cavity, so that the inner cavity is filled with the liquid metal conductor, and the injector is pulled out.
Optionally, inserting electrodes at both ends of the inner cavity comprises the steps of:
and respectively inserting two electrodes into two ends of the internal cavity, and sealing the internal cavity by using the same semi-solidified flexible material.
Optionally, mixing and de-bubbling the solution of the flexible material comprises the steps of:
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 first flexible substrate includes the steps of:
spraying at least one layer of release agent on the surface of the first mold, and then filling the silicone rubber solution with bubbles removed into the cavity of the first mold by using a liquid moving machine;
moving the first mold into an oven, baking for 45-60min at 80 ℃, and demolding to obtain a first flexible substrate with a plurality of array channels;
spraying at least one layer of release agent on the surface of the second mold, filling the cavity of the second mold with the silicone rubber solution with bubbles removed by using a liquid transfer device, and closing the mold;
and opening the mold when the silicon rubber solution in the cavity of the second mold is semi-solidified to form a second flexible substrate, and then pressing the first flexible substrate on the second flexible substrate to ensure that the first flexible substrate and the second flexible substrate are connected in a butt joint manner to form a communicating cavity and a communicating cavity communicated with the same end face of the plurality of array channels.
According to the flexible electronic pressure sensing device and the preparation method thereof, the flexible electronic pressure sensing device has the characteristics of high flexibility, good stretchability, simple geometric structure and thin size, so that the sensor is free from the constraint of physical accessories and can be attached to the skin in a fitting manner, and therefore the measurement of any position is realized, even if the position of each joint with extremely large deformation is positioned. And, this sensor is at work, mainly gather the liquid conductor resistance change signal that is aroused by sealed microarray channel deformation, and sensitivity is high, and the interference killing feature is strong, can stretch at will, crooked and twist reverse, and especially be applicable to wearable equipment field especially the big deformation condition etc. can accomplish the measurement of contact pressure when laminating three-dimensional complicated quiet/dynamic surface completely, and stability, precision, degree of accuracy and reliability are high, are difficult to receive human self physiological signal's interference, and the inside appearance chamber is closed structure, and its is high temperature resistant, application scope is wide, long service life.
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 cross-sectional view of a flexible electronic pressure sensing device provided by an embodiment of the present invention;
FIG. 2 is a schematic cross-sectional view of a flexible housing of a flexible electronic pressure sensing device according to an embodiment of the present invention;
FIG. 3 is a schematic plan view of a flexible electronic pressure sensing device having a circular flexible housing according to an embodiment of the present invention;
FIG. 4 is a schematic plan view of a flexible electronic pressure sensing device having a rectangular flexible housing provided by embodiments of the present invention;
FIG. 5 is a schematic plan view of a silicone rubber solution prepared in a method for preparing a flexible electronic pressure sensing device according to an embodiment of the present invention;
FIG. 6 is a schematic plan view of a silicone rubber solution after mixing in a method for manufacturing a flexible electronic pressure sensing device according to an embodiment of the present invention;
FIG. 7 is a schematic plan view of a flexible electronic pressure sensor device according to an embodiment of the present invention after bubbles are removed from a silicone rubber solution;
fig. 8 is a schematic plan view illustrating a first mold filled with a silicone rubber solution in a manufacturing method of a flexible electronic pressure sensing device according to an embodiment of the present invention;
fig. 9 is a schematic plan view of a first mold filled with a silicone rubber solution and baked in a manufacturing method of a flexible electronic pressure sensing device according to an embodiment of the present invention;
FIG. 10 is a schematic plan view of a flexible electronic pressure sensing device according to an embodiment of the present invention after a silicone rubber solution is added to a second mold and the molds are closed;
FIG. 11 is a schematic plan view of a first flexible substrate and a second flexible substrate in a method of manufacturing a flexible electronic pressure sensing device according to an embodiment of the present invention;
fig. 12 is a schematic cross-sectional view of a flexible electronic pressure sensing device obtained by a method for manufacturing a flexible electronic pressure sensing device 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 and fig. 2, the flexible electronic pressure sensing device provided by the embodiment of the present invention includes a flexible housing 1, and the flexible housing 1 may be made of silicone rubber material (e.g., Ecoflex series) or the like. The flexible shell 1 is internally provided with an internal cavity with length and cross section capable of deforming under the action of external force, the internal cavity 10 can be a closed cavity, the internal cavity 10 is internally provided with a liquid metal conductor 3, and the internal cavity 10 can be filled with the liquid metal conductor 3. The internal cavity 10 includes a plurality of array channels (micro-array channels) 101 and communicating cavities 102 communicating with the same end surfaces of the plurality of array channels 101, the array channels 101 may be uniformly distributed at intervals transversely or longitudinally, or may adopt a criss-cross communicating arrangement form (i.e., local arrangement in a shape of a Chinese character 'jing'), and of course, the array channels 101 may also be formed by cylindrical cavities or hemispherical cavities arranged in a matrix, etc. Two ends of the flexible shell 1 are provided with at least two electrodes 2 connected with the liquid metal conductor, the end parts of the electrodes 2 are in contact with the liquid metal conductor 3 in the inner containing cavity 10, and when the sensor works, the shape (length and cross section) of the inner containing cavity 10 is changed due to the action of external load, so that the resistance of the liquid metal conductor 3 is changed. The electrodes 2 at two ends can be connected with an amplifying module and a constant current power supply module, and the electrodes 2 at two ends are added with a constant current power supply. The sensor mainly collects resistance change signals of the liquid metal conductor 3 in the sealed inner cavity 10 during working, has the geometric 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%, can be randomly stretched, bent and twisted, is particularly suitable for the field of wearable equipment, particularly for large deformation and the like, can completely fit three-dimensional complex static/dynamic surfaces and simultaneously complete the measurement of contact pressure, has high stability, precision, accuracy and reliability, is not easily interfered by self physiological signals of a human body, and has a closed structure of the inner cavity 10, it is high temperature resistant, and application scope is wide, long service life.
Optionally, one or at least two internal cavities 10 may be disposed in the same flexible housing 1, and each internal cavity 10 may be correspondingly disposed with two or at least two electrodes 2.
Alternatively, the height of the array channel 101 and the height of the communication chamber 102 may both be less than 1 mm.
Alternatively, the overall height of the inner volume 10 may be less than 1 mm.
Optionally, the thickness of the flexible electronic pressure sensing device may be less than 1mm, that is, the thickness of the flexible housing 1 may be less than 1mm, and the flexible electronic pressure sensing device may be well applicable to smart wearable devices. The flexible cover 1 may be flat. As shown in fig. 3 and 4, the outer shape of the flexible casing 1 may be polygonal (e.g., rectangular, etc.), circular, irregular, etc.
Alternatively, the flexible outer shell 1 is made of a degradable polyester material or a silicone rubber material, in this embodiment, the flexible outer shell 1 is made of an Ecoflex series silicone rubber material as a base material, and in a specific application, aliphatic aromatic random copolyester (Ecoflex) manufactured by BASF corporation of germany may be used, and the monomer of the aliphatic aromatic random copolyester may be: adipic acid, terephthalic acid and 1, 4-butanediol.
Optionally, a liquid conductor eutectic gallium indium is disposed in the inner cavity 10 as a liquid metal conductor, and of course, other liquid metal conductors may also be disposed. The electrodes 2 can be inserted from the two ends of the flexible housing 1 in the length direction or the two ends of the internal cavity 10 to the front ends to be in contact with the liquid metal conductor 3 arranged in the internal cavity 10. The electrodes 2 and the flexible housing 1 may be sealed by a sealing material to further improve the reliability thereof. The sealing material may be a silicone rubber solution material (Ecoflex).
Optionally, the flexible housing 1 includes a first flexible substrate 11 and a second flexible substrate 12 that are connected to form the internal cavity, and a convex structure or/and a concave structure for forming the array channel 101 is/are disposed on an inner wall of the first flexible substrate 11; the second flexible substrate 12 is provided with a communication cavity 102, and the communication cavity 102 is arranged at the upper end of the second flexible substrate 12. The first flexible substrate 11 and the second flexible substrate 12 are abutted (sealed and bonded), and the array channel 101 can be communicated with the communication cavity 102 to form the sealed inner cavity 10. First flexible substrate 11 and second flexible substrate 12 may be bonded to form flexible enclosure 1 having interior volume 10
Alternatively, a plurality of columnar protrusions arranged in a matrix may be integrally formed in the first flexible substrate 11, and gaps between the columnar protrusions may form the array channel 101. Alternatively, a plurality of cavities arranged in a matrix may be integrally formed in the first flexible substrate 11, and the cavities may communicate with each other to form the array channel 101. It is to be understood that the formation of the array channel 101 may be unlimited.
In the tensile test of the flexible electronic pressure sensing device, 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 wearable equipment which is provided with the flexible electronic pressure sensing device. Wearable equipment can be for intelligent wrist-watch, intelligent bracelet, intelligent glasses, intelligent clothing, virtual reality helmet etc.. Through the application of the flexible electronic pressure sensing device, the flexible electronic pressure sensing device has the performance thickness of less than 1mm, and has very good flexibility, the stretching strain can still work normally even reaching 300 percent and is comparable to the skin of a human body, and in addition, the biocompatible Ecoflex material is adopted as a basic material, so that people hardly have uncomfortable feeling when being integrated into a wearable device. In addition, the sensor collects resistance signals of the sealed inner cavity 10, interference of external noise to the signals is eliminated, and data collection is accurate. The internal volume 10, which is characterized by a photolithographic process, greatly improves the sensitivity of the sensor. Of course, the flexible electronic pressure sensing device provided by the embodiment of the present invention may also be applied to other apparatuses, and also falls within the protection scope of the present invention.
The embodiment of the invention also provides a preparation method of the flexible electronic pressure sensing device, which comprises the following steps as shown in fig. 5 to 12:
preparing a flexible shell 1 with a sealed inner cavity 10, wherein the inner cavity 10 comprises a plurality of array channels 101 and a communication cavity 102 communicated with the same end face of the plurality of array channels 101; a liquid metal conductor 3 is injected into the inner cavity 10, and electrodes 2 are inserted into two ends of the flexible shell 1. The liquid metal conductor 3 may fill the inner volume 10 with the end of the electrode 2 in contact with the liquid metal conductor 3.
Specifically, the preparation of the flexible cover 1 comprises the following steps:
preparing a first mold 41, a second mold 42 and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the flexible material solution after mixing and removing bubbles into the first mold 41 to form a first flexible substrate 11 with a plurality of array channels 101;
adding the mixed and bubble-removed flexible material solution on the second mold 42, and enabling the flexible material solution to form a semi-solidified second flexible substrate 12 with a communication cavity 102;
pressing the first flexible substrate 11 on a second flexible substrate (second flexible substrate 12) made of the incompletely cured flexible material, so that the first flexible substrate 11 and the second flexible substrate 12 are integrally connected to form a flexible shell 1, and meanwhile, the plurality of array channels 101 and the communication cavity 102 are communicated to form a closed internal containing cavity 10;
specifically, the step of injecting the liquid metal conductor 3 into the inner cavity 10 includes the following steps:
two injectors are inserted into two ends of the inner cavity 10, wherein one injector is internally provided with a liquid metal conductor 3; and the other injector pumps the air in the inner cavity 10, the injector with the liquid metal conductor 3 synchronously injects the liquid metal conductor 3 into the inner cavity 10, so that the inner cavity 10 is filled with the liquid metal conductor 3, and the injector is pulled out.
Specifically, inserting the electrodes 2 into the two ends of the flexible housing 1 (the inner cavity 10) includes the following steps:
two electrodes 2 are respectively inserted into two opposite ends of the internal cavity 10, and the same semi-solidified flexible material is sealed between the electrodes 2 and the flexible casing 1.
Specifically, mixing and de-bubbling the flexible material solution comprises the following steps:
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; it is to be understood that the flexible material solution is not limited to a silicone rubber solution.
Forming the first flexible substrate 11 comprises the steps of:
spraying at least one layer of release agent (ease release 200 release agent) on the surface of the first mold 41, and then filling the cavity of the first mold 41 with the silicone rubber solution with bubbles removed by using a pipette;
moving the first mold 41 with the cavity filled with the silicone rubber solution with bubbles removed into an oven, baking for 45-60min (for example, 46-59 min) at 80 ℃, and demolding to obtain a first flexible substrate 11;
forming the second flexible substrate 12 includes the steps of:
the second mold 42 comprises an upper mold 421 and a lower mold 422, at least one layer of release agent is sprayed on the surface of the cavity of the lower mold 422 of the second mold 42, then a liquid transfer device is used for filling the cavity of the lower mold 422 of the second mold 42 with the silicone rubber solution with bubbles removed, and then the upper mold 421 is clamped on the lower mold 422;
and when the silicon rubber solution in the cavity of the second mold 42 is semi-solidified to form the second flexible substrate 12, opening the mold (removing the upper mold 421), then buckling and pressing the first flexible substrate 11 on the second flexible substrate 12, and standing at room temperature for 45-60min when the first flexible substrate 11 and the second flexible substrate 12 are bonded and sealed completely, so that the first flexible substrate 11 and the second flexible substrate 12 are connected with the flexible shell 1 in a matching manner and form the inner cavity 10.
In specific applications, the following process can be referred to:
a first 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. 5 and 6, Ecoflex 1A and Ecoflex 1B with equal mass are respectively taken and put into a container of a centrifugal mixer, so as 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 (12-14s), 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 FIGS. 6 and 7, the silicone rubber solution in the first step was placed in a vacuum filtration apparatus, and the vacuum pump was turned on until all air bubbles in the solution were removed.
The third step: as shown in fig. 8, a release agent is sprayed on the surface of the first mold 41, and then the cavity of the mold is filled with the silicone rubber solution obtained in the second step using a pipette.
The fourth step: in the third step, the first mold 41 filled with the silicone rubber solution is moved to an oven and baked at 80 ℃ for 45-60min, as shown in fig. 9, to obtain the first flexible substrate 11.
The fifth step: a release agent is sprayed on the cavity surface of the second mold 42, the cavity of the lower mold 422 is filled using a pipette, and the upper mold 421 is fitted to the lower mold 422, as shown in fig. 10.
And a sixth step: and when the second flexible substrate 12 formed in the fifth step is in a semi-solidified state, slightly pressing the demolded first flexible substrate 11 on the second flexible substrate 12, and standing at room temperature for 45-60min when the bonding and sealing are complete to obtain the flexible shell 1, as shown in fig. 11. The flexible cover 1 is then removed from the lower mold 422.
The seventh step: two micro syringes are respectively inserted into two opposite side walls of the flexible shell 1 and extend into two ends of the internal cavity 10, one syringe is used for pumping air in the internal cavity 10 and guiding a liquid conductor (EGaIn), and the other syringe is used for synchronously and continuously injecting the liquid conductor (EGaIn) into the internal cavity 10. Of course, it is also possible to first evacuate the inner volume 10 and then inject the liquid conductor into the inner volume 10. When the liquid conductor (EGaIn) fills the entire inner volume 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 (gap between the electrode 2 and the side wall of the flexible housing 1), so that a flexible, stretchable electronic strain sensor is obtained, as shown in fig. 12. 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 electronic pressure sensing device 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 flexible electronic pressure sensing device has the geometrical characteristics of being extremely thin, the thickness of the flexible electronic pressure sensing device can be less than 1mm, the flexible electronic pressure sensing device shows very good flexibility, the flexible electronic pressure sensing device can still normally work when the tensile strain reaches 300%, and can be integrated with any complex three-dimensional surface to work almost, in addition, the size (the height and the width of the cross section of the micro array channel can be less than 1mm) of the micro array channel 101 is small, the micro array can be deformed by very small pressure to cause resistance change, meanwhile, the acquired resistance change signal is originated from a liquid conductor sealed in the micro array, and the pressure sensor has high sensitivity and noise interference resistance. The use of biocompatibility as a basic material makes it particularly suitable for wearable electronics integrated on the surface of human skin. The method is simple to prepare, can realize batch production at one time, and improves time and cost benefits. The flexible electronic pressure sensing device provided by the embodiment of the invention has higher sensitivity in pressure test, and the acquired signals show good repeatability on images and are more accurate in measurement. The pressure sensor can be easily attached to the three-dimensional skin surface of a human body without discomfort, and the pressure can be normally sensed and measured even at the knee joint with extremely large deformation. Has good affinity with skin and almost has no influence on normal work and study of people. Is an ideal flexible sensor of wearable equipment
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 (3)
1. A preparation method of a flexible electronic pressure sensing device is characterized by comprising the following steps:
preparing a flexible shell with an internal cavity, wherein the internal cavity comprises a plurality of array channels and a communication cavity communicated with the array channels; injecting a liquid metal conductor into the inner cavity, and inserting at least two electrodes into the flexible shell to enable the electrodes to be in contact with the liquid metal conductor;
the flexible shell comprises a first flexible substrate and a second flexible substrate which are connected in an involutory manner to form the internal cavity, and the inner wall of the first flexible substrate is provided with a convex structure or/and a concave structure for forming the array channel; the communication cavity is arranged on the second flexible substrate; the preparation of the flexible housing comprises the following steps:
preparing a first mold, a second mold and a flexible material solution, and mixing the flexible material solution to remove bubbles;
adding the mixed and bubble-removed flexible material solution into the first mold to form a first flexible substrate with a plurality of array channels;
adding the mixed flexible material solution with bubbles removed into the second mold, and enabling the flexible material solution to form a second flexible substrate with a communication cavity;
pressing the first flexible substrate on the second flexible substrate which is not completely cured, integrally connecting the first flexible substrate and the second flexible substrate to form a flexible shell, and simultaneously communicating the plurality of array channels and the communication cavity to form a closed internal cavity;
mixing and de-bubbling the solution of flexible material includes the steps of:
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 first flexible substrate includes the steps of:
spraying at least one layer of release agent on the surface of the first mold, and then filling the silicone rubber solution with bubbles removed into the cavity of the first mold by using a liquid moving machine;
moving the first mold into an oven, baking for 45-60min at 80 ℃, and demolding to obtain a first flexible substrate with a plurality of array channels;
filling the silicon rubber solution with bubbles removed into the cavity of the second mold by using a liquid transfer device, and then closing the mold; specifically, the second mold comprises an upper mold and a lower mold, at least one layer of release agent is sprayed on the surface of a cavity of the lower mold of the second mold, then a liquid transfer device is used for filling the silicon rubber solution with bubbles removed into the cavity of the lower mold of the second mold, and then the upper mold is closed on the lower mold;
and opening the mold when the silicon rubber solution in the cavity of the second mold is semi-solidified to form a second flexible substrate, and then pressing the first flexible substrate on the second flexible substrate to ensure that the first flexible substrate and the second flexible substrate are connected in a butt joint manner to form a communicating cavity and a communicating cavity communicated with the same end face of the plurality of array channels.
2. The method of claim 1, wherein injecting a liquid metal conductor into the interior cavity comprises:
two injectors are inserted into two ends of the inner cavity, wherein one injector is internally provided with a liquid metal conductor; and the other injector pumps the air in the inner cavity, the injector with the liquid metal conductor injects the liquid metal conductor into the inner cavity, so that the inner cavity is filled with the liquid metal conductor, and the injector is pulled out.
3. The method of claim 1, wherein inserting electrodes into both ends of the interior volume comprises the steps of:
and respectively inserting two electrodes into two ends of the internal cavity, and sealing the electrodes and the flexible shell by using the same semi-solidified flexible material.
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