WO2021243647A1

WO2021243647A1 - Conductive hydrogel injection-based flexible sensor and manufacturing method therefor

Info

Publication number: WO2021243647A1
Application number: PCT/CN2020/094373
Authority: WO
Inventors: 叶丰明; 鲁艺; 李梦; 曹燚; 孙重阳; 王璐璐; 潘苏婉
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2020-06-04
Filing date: 2020-06-04
Publication date: 2021-12-09

Abstract

Disclosed in the present invention are a conductive hydrogel injection-based flexible sensor and a manufacturing method therefor. The flexible sensor has skin-like flexible deformation, and comprises a packaging layer, a flexible strain component formed in the packaging layer, and a metal electrode connected to the flexible strain component; and the flexible strain component is formed by injecting conductive hydrogel. The flexible sensor provided by the present invention is simple in manufacturing process technology and high in detection sensitivity, and can be widely applied to the fields of real-time health monitoring, flexible robots, clinical diagnosis, flexible electronic skins and the like.

Description

Flexible sensor based on conductive hydrogel injection and preparation method thereof

Technical field

The present invention relates to the technical field of sensors, and more specifically, to a flexible sensor based on conductive hydrogel injection and a preparation method thereof.

Background technique

Human skin is a soft, stretchable, large and highly integrated multifunctional sensor system, which is the carrier of human touch. Scientists hope to use flexible electronic technology to imitate skin from mechanical properties and sensing capabilities to make electronic devices that are as soft and stretchable as skin to obtain physical signals such as external pressure and temperature, the so-called "electronic skin."

The hydrogel is formed by a hydrophilic polymer network that wraps water in the pores of the network, and exhibits the properties of solid and fluid at the same time. Compared with other traditional materials, the Young's modulus can be adjusted in a wide range by changing the components of the hydrogel. The span range is usually matched with the Young's modulus of biological tissues and organs including skin, so it can The formation of a seamless interface between biological tissues and electronic devices has made it widely used in the field of electronic skin in recent years. In recent years, through the means of material engineering, charge carriers have been added to the hydrogel to make the originally insulating hydrogel possess the ability to conduct electricity. Flexible sensors based on these conductive hydrogels provide sensitive and reliable electrical responses to human movements, such as the bending of fingers, elbows or knees.

However, most of the current flexible sensors based on conductive hydrogels can only detect a relatively large range of human motion signals, and it is difficult to detect weak physiological indicators that reflect human vital signs (respiration, heart rate, blood pressure, etc.). In addition, the use of conductive hydrogel to prepare sensors requires some simple and widely applicable methods to realize the leap from simple material level to integrated system.

Summary of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a flexible sensor based on conductive hydrogel and a preparation method thereof. The conductive hydrogel material is made into a skin-like flexible sensor through material injection technology, so as to realize the detection of animals. And the detection of weak physiological signals of the human body.

According to a first aspect of the present invention, a flexible sensor based on conductive hydrogel injection is provided. The flexible sensor has a skin-like flexible deformation, and includes an encapsulation layer, a flexible strain member formed in the encapsulation layer, and a connection point. The metal electrode of the flexible strain member, wherein the flexible strain member is formed by injecting conductive hydrogel.

In one embodiment, the conductive hydrogel is carbon nanotube-poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate-polyvinyl alcohol-polyacrylamide hydrogel, Young’s model The amount is 1kPa.

In one embodiment, the flexible sensor is a flexible miniature stretch sensor, a flexible miniature pressure sensor or a flexible miniature physiological signal sensor.

According to the second aspect of the present invention, a method for preparing a flexible sensor based on conductive hydrogel injection is provided, which includes the following steps:

Preparation of conductive hydrogel;

Injecting the conductive hydrogel via a syringe into the encapsulation layer to form a flexible strained component or on the surface of a flexible film to form a flexible strained component;

The metal electrode for collecting strain signals is connected with the flexible strain component to make the flexible sensor.

In one embodiment, the flexible sensor is a flexible miniature stretch sensor prepared by the following steps:

Put the conductive hydrogel into a syringe, and squeeze the conductive hydrogel into the silicone rubber tube via the syringe;

Inserting metal wires at both ends of the silicone rubber tube to contact the conductive hydrogel, and encapsulating the openings at both ends of the silicone rubber tube to obtain the flexible miniature tensile sensor.

In one embodiment, the inner diameter of the needle of the syringe is 250 μm.

In one embodiment, the inner diameter of the silicone rubber tube is 300 μm and the length is 3 cm.

In one embodiment, cyanoacrylic glue is used to encapsulate the openings at both ends of the silicone tube.

In one embodiment, the flexible sensor is a flexible miniature pressure sensor prepared by adopting the following steps:

Depositing conductive polymer ink on the surface of the plasma-treated polyimide film by inkjet printing to form interconnection lines, the interconnection lines having distributed discontinuities;

Injecting the conductive hydrogel through a syringe into the discontinuity of the interconnection line and filling it;

A layer of silicone rubber is coated on the surface of the polyimide film as an encapsulation layer to prepare the flexible miniature pressure sensor.

In one embodiment, the conductive polymer ink is poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid.

Compared with the prior art, the advantage of the present invention is that the flexible sensor manufactured based on the conductive hydrogel injection technology has a smaller device size and can realize the accurate detection of weak physiological signals such as respiration and pulse.

Through the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, other features and advantages of the present invention will become clear.

Description of the drawings

The drawings incorporated in the specification and constituting a part of the specification illustrate the embodiments of the present invention, and together with the description are used to explain the principle of the present invention.

Fig. 1 is a schematic diagram of a process of preparing a flexible micro-tensile sensor according to an embodiment of the present invention;

Fig. 2 is a physical schematic diagram of a flexible micro stretch sensor according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a process of preparing a flexible miniature pressure sensor according to an embodiment of the present invention;

4 is a schematic diagram of a stretch detection curve of a flexible micro stretch sensor according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of detecting finger bending by a flexible micro stretch sensor according to an embodiment of the present invention;

Fig. 6 is a schematic diagram of detecting mice in different states by a flexible miniature tensile sensor according to an embodiment of the present invention;

Fig. 7 is a schematic diagram of the detection of human radial artery pulse and carotid artery pulse by a flexible miniature pressure sensor according to an embodiment of the present invention.

In the figure, Time-Time; Anaesthetic-anesthesia; Pinch-pin; Alcohol-alcohol stimulation; Free-moving-free movement; Strain sensor-stretch sensor; Stain-stretch; Mean-average; Fitting line-fitting line ; PI substrate-PI substrate, PDMS-polydimethylsiloxane; PI-polyimide.

detailed description

Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless specifically stated otherwise, the relative arrangement, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present invention.

The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present invention and its application or use.

The techniques, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the techniques, methods, and equipment should be regarded as part of the specification.

In all examples shown and discussed herein, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiment may have different values.

It should be noted that similar reference numerals and letters indicate similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further discussed in the subsequent drawings.

In the embodiment of the present invention, flexible sensors are prepared based on conductive hydrogel injection technology, including flexible micro stretch sensors, flexible micro pressure sensors, and micro physiological signal sensors. The prepared sensors can achieve skin-like flexible deformation and can It can accurately detect weak physiological signals and can be widely used in real-time health monitoring, flexible robots, clinical diagnosis, flexible electronic skin and smart homes.

The flexible sensor provided by the embodiment of the present invention includes an encapsulation layer, a flexible strain component formed in the encapsulation layer, and a metal electrode connected to the flexible strain component. The flexible strain component is formed by injecting conductive hydrogel. It is the main functional part of the sensor, used to produce deformation in response to pressure, stretching, etc. In the following, specific flexible micro-tensile sensors and flexible pressure sensors will be used as examples to introduce the preparation methods.

As shown in Figure 1, in this embodiment, a material injection technology is used to combine conductive hydrogel with packaging materials and interconnected conductive materials to fabricate a flexible micro-tensile sensor. Conductive hydrogels are usually composed of conductive polymers and hydrophilic functional molecules, which have adjustable physical and chemical properties and good biocompatibility. In the present invention, various types of conductive hydrogels, such as poly Electrolyte conductive hydrogel, acid doped conductive hydrogel, inorganic added conductive hydrogel, etc.

In one embodiment, the conductive hydrogel is carbon nanotube-poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate-polyvinyl alcohol-polyacrylamide hydrogel, Young’s model The amount is only 1kPa. The inventor has verified through experiments that this conductive hydrogel has excellent electrical conductivity, mechanical properties, and flexible mechanical properties, which enhances the performance and application range of the flexible sensor prepared.

Specifically, as shown in FIG. 1 and FIG. 2, in one embodiment, the steps of preparing a flexible micro stretch sensor include:

In step S210, the conductive hydrogel is loaded into the syringe, and then the conductive hydrogel is extruded through the syringe, and then into the silicone rubber tube.

The size of the syringe matches the size of the silicone tube and can be selected according to needs. For example, the diameter of the syringe needle is 250 μm, and the inner diameter of the silicone tube is only 300 μm and the length is 3 cm. In addition, in addition to silicone tube, other packaging materials can also be used.

In step S220, metal wires are inserted into the two ends of the silicone rubber tube to contact the conductive hydrogel, and the openings at both ends are sealed with cyanoacrylic glue to produce a miniature tensile sensor.

The metal wire can be copper, aluminum, silver, etc. Preferably, the copper wire is selected after comprehensive consideration of conductivity, loss and cost factors. In addition, other adhesives can also be used to encapsulate the opening of the silicone rubber tube.

In the embodiment of the present invention, the flexible stretch sensor made by injecting conductive hydrogel can achieve high stretchability, ensure linearity, high sensitivity, and be small in size, and can be used to monitor human body motion signals, such as pulse. And joint movement, for example, the bending angle of the wrist and the bending degree of the finger joints can be clearly recognized.

In another embodiment, a bottom-up device manufacturing method is adopted, combining injection technology and inkjet printing technology to fabricate a flexible pressure sensor.

As shown in Figure 3, the steps of preparing a flexible pressure sensor include:

In step S310, the conductive polymer ink is deposited on the surface of the plasma-treated polyimide film by inkjet printing to form a thin-layer interconnection line, wherein predetermined discontinuities are distributed on the interconnection line.

Plasma treatment can increase the surface roughness of the material and increase the hydrophilicity. The size of the polyimide film can be selected according to needs, for example, the length and width of the polyimide film are 2cm×4cm.

The conductive polymer ink can use PEDOT/PSS (poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid).

In step S320, the material injection technology is used to inject the conductive hydrogel into the discontinuity of the interconnection line and fill it up as the functional part (ie the strain component) of the pressure sensor.

In step S330, a layer of silicon rubber is coated on the surface of the device as a packaging material to fabricate a flexible miniature pressure sensor.

It should be understood that the preparation of the flexible miniature pressure sensor also includes connecting the metal electrode for collecting the strain signal with the strain component, and the process of connecting the electrode may be before or after the packaging, which is not limited by the present invention.

In the embodiment of the present invention, the inkjet printing technology and the material injection technology are combined, and the flexible sensor can be designed and manufactured with a bottom-up concept. The shape and size of the material can be defined by itself, and the inner diameter of the syringe needle can be selected. The size can realize micron-level line width processing, which makes the flexible pressure sensor more compact and can detect finer strain.

It should be noted that the conductive hydrogel injection technology of the present invention can be combined with other mechanical accessories to upgrade to conductive hydrogel 3D printing technology, and can also be used to manufacture other types of sensors, such as miniature physiological signal sensors.

In order to further verify the effect of the present invention, the tensile sensing ability of the prepared tensile sensor was tested, and the electrochemical workstation (CH Instruments CHI 660D) was used to record the tensile sensor at 20%, 40%, 60%, respectively. _{The current change rate ΔI/I 0} under tensile strain of %, 80% and 100% is shown in Fig. 4. It can be seen that ΔI/I ₀ has a linear response to the deformation, indicating that it is suitable for tensile testing to a certain extent.

As shown in Figure 5, in the experiment, the miniature flexible stretch sensor is fixed on the volunteer's index finger, it can be seamlessly attached to the surface of the finger, and its signal strength increases linearly with the bending angle. Experiments have proved that the micro stretch sensor can quantitatively detect the degree of body movement. For example, when the bending angle is 30 degrees, 60 degrees and 90 degrees, the current change rate also linearly increases, and the degree of finger bending can be determined by measuring the current change rate.

Further, the flexible stretch sensor is surrounded and fixed on the chest cavity of the anesthetized mouse to monitor the respiratory condition of the anesthetized mouse. When the mouse inhales, the stretch sensor is pulled, and when it exhales, it returns to its original state. This process causes the stretch sensor to have a repetitive and stable current signal response to breathing, as shown in Figure 6, where Figure 6(a) is for anesthesia Mice, Figure 6(b) is for anesthetized mice that are experiencing pain stimulation, Figure 6(c) is for anesthetized mice that are experiencing alcohol stimulation, and Figure 6(d) is for freely moving mice, where the mice are anesthetized The breathing rate of 162 times per minute (bpm), in the experiment, the mice were also given painful stimulation (such as tail pinching) and let the mice smell alcohol. The results recorded by the stretch sensor showed that the breathing amplitude and frequency of mice experiencing painful stimulation under anesthesia were twice and 1.22 times that of non-stimulated mice under anesthesia, and the breathing amplitude and frequency of mice experiencing painful stimulation under anesthesia. They are more than 2 times and 0.86 times that of unstimulated mice under anesthesia, respectively, as shown in Figure 6(b) and Figure 6(c). In addition, the stretch sensor can also detect the breathing conditions of freely moving mice. As shown in Figure 6(d), when the mouse stops running and starts to smell, the signal pattern of the sensor changes, which indicates a micro stretch Sensors are conducive to quantifying the physiological responses of animals under different conditions and improving the understanding of certain behavioral phenomena in animals on the basis of biology.

In the experiment for the miniature flexible pressure sensor, it was placed on the volunteer's wrist and neck, and the same electrochemical workstation was used to collect sensor signals at the same time. Experiments show that the flexible pressure sensor can successfully detect the pulse signal on the volunteer's radial artery and carotid artery, which are 78bpm and 66bpm, respectively. See Figure 7, where Figure 7(a) is the radial artery pulse, Figure 7( b) is the carotid pulse. Experiments have proved that the miniature pressure sensor can even clearly identify more refined physiological activities, such as emitted waves (P ₁ ), reflected waves (P ₂ ), and double _{wave waves (P 3} ). The radial artery magnification factor (AIr=P ₂ /P ₁ ) and the time difference between the two peaks (ΔT _DVP ) are usually used to diagnose arteriosclerosis. The AIr and ΔT _{DVP of the} tested volunteers are 0.58 and 180 ms, respectively, reflecting the good volunteers Physical condition.

In summary, the skin-like flexible sensor prepared by the injection technology of the present invention has an excellent ability to detect human body surface signals, and the use of micro-manufacturing technology can further reduce the size of the flexible sensor, which is beneficial for detecting weaker physiological signals. In addition, the hydrogel-based flexible sensor provided by the present invention can be used for the detection of stretching, pressure, etc., and can realize the detection of tiny physiological signals and violent human movement. The preparation process of the flexible sensor designed by the present invention is simple and saves time and effort. , Excellent performance, can be widely used in health monitoring, flexible robots, clinical diagnosis, flexible electronic skin and other fields.

The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Without departing from the scope and spirit of the described embodiments, many modifications and changes are obvious to those of ordinary skill in the art. The choice of terms used herein is intended to best explain the principles, practical applications, or technical improvements of the various embodiments in the market, or to enable other ordinary skilled in the art to understand the various embodiments disclosed herein. The scope of the invention is defined by the appended claims.

Claims

A flexible sensor based on conductive hydrogel injection. The flexible sensor has a skin-like flexible deformation and includes an encapsulation layer, a flexible strain component formed in the encapsulation layer, and a metal electrode connected to the flexible strain component, wherein , The flexible strain member is formed by injecting conductive hydrogel.
The flexible sensor based on conductive hydrogel injection according to claim 1, wherein the conductive hydrogel is carbon nanotube-poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate-poly Vinyl alcohol-polyacrylamide hydrogel, Young's modulus is 1kPa.
The flexible sensor based on conductive hydrogel injection according to claim 1, wherein the flexible sensor is a flexible miniature stretch sensor, a flexible miniature pressure sensor, or a flexible miniature physiological signal sensor.
A method for preparing a flexible sensor based on conductive hydrogel injection includes the following steps:

Obtain conductive hydrogel;

Injecting the conductive hydrogel via a syringe into the encapsulation layer to form a flexible strained component or on the surface of a flexible film to form a flexible strained component;

The metal electrode for collecting strain signals is connected with the flexible strain component to make the flexible sensor.
The method according to claim 4, wherein the flexible sensor is a flexible miniature tensile sensor prepared by the following steps:

Put the conductive hydrogel into a syringe, and squeeze the conductive hydrogel into the silicone rubber tube via the syringe;

Inserting metal wires at both ends of the silicone rubber tube to contact the conductive hydrogel, and encapsulating the openings at both ends of the silicone rubber tube to obtain the flexible miniature tensile sensor.
The method according to claim 5, wherein the inner diameter of the needle of the syringe is 250 μm.
The method according to claim 6, wherein the inner diameter of the silicone rubber tube is 300 μm and the length is 3 cm.
The method according to claim 5, wherein cyanoacrylic glue is used to encapsulate the openings at both ends of the silicone rubber tube.
The method according to claim 4, wherein the flexible sensor is a flexible miniature pressure sensor prepared by the following steps:

The conductive polymer ink is deposited by inkjet printing on the surface of the plasma-treated polyimide film to form interconnection lines, the interconnection lines having distributed discontinuities;

Injecting the conductive hydrogel through a syringe into the discontinuity of the interconnection line and filling it;

A layer of silicone rubber is coated on the surface of the polyimide film as an encapsulation layer to prepare the flexible miniature pressure sensor.
The method of claim 9, wherein the conductive polymer ink is poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid.