CN112129814A

CN112129814A - Liquid conductor and preparation method thereof, and sensor and preparation method thereof

Info

Publication number: CN112129814A
Application number: CN202011000477.1A
Authority: CN
Inventors: 邢孟秋; 周小金; 吕国忠; 陈洁; 叶海雁; 刘抗; 郭瀛军
Original assignee: Zhejiang Depp Medical Polytron Technologies Inc
Current assignee: Zhejiang Depp Medical Polytron Technologies Inc
Priority date: 2020-09-22
Filing date: 2020-09-22
Publication date: 2020-12-25

Abstract

The invention relates to a liquid conductor, a preparation method thereof, a sensor and a preparation method thereof, wherein the liquid conductor is obtained by self-liquefying egg white hydrogel. The liquid conductor provided by the embodiment of the invention has the advantages of good transparency, high conductivity, small hysteresis, higher ductility, abundant sources, lower manufacturing cost and easiness in industrial production, in addition, the sensor comprising the liquid conductor has higher sensitivity, lower hysteresis, quicker response and recovery time and better stability and durability, and the liquid conductor can also be used for wearable equipment, a gesture console and a triboelectric nano-generator and is favorable for promoting the development of the field.

Description

Liquid conductor and preparation method thereof, and sensor and preparation method thereof

Technical Field

The invention relates to the technical field of conductor materials, in particular to a liquid conductor and a preparation method thereof, a sensor and a preparation method thereof, wearable equipment, a gesture console and a triboelectric nano engine.

Background

The new generation of wearable electronic devices for health monitoring, internet of things systems, "invisible interfaces", green energy harvesting devices and the like have great demands for conductive materials with good transparency, small hysteresis, industrial production and high ductility.

However, the existing conductive materials have the disadvantages of insufficient transparency, poor ductility, high manufacturing cost or potential toxicity, and thus cannot meet the requirements.

Therefore, the development of a novel conductive material having good transparency and ductility, low hysteresis, and low manufacturing cost has become a problem to be solved.

Disclosure of Invention

In order to solve the above technical problems, an object of the present invention is to provide a liquid conductor which has good transparency, high conductivity, low hysteresis, high ductility, abundant sources, low manufacturing cost, and easy industrial production.

Another object of the present invention is to provide a method for preparing the liquid conductor.

It is a further object of the present invention to provide a sensor comprising the above-mentioned liquid conductor.

It is a further object of the present invention to provide a method for preparing the above sensor.

It is a further object of the present invention to provide a wearable device containing the above sensor.

It is still another object of the present invention to provide a gesture console containing the above liquid conductor.

It is still another object of the present invention to provide a triboelectric nanogenerator comprising the above-described liquid conductor.

In order to achieve the purpose, the invention adopts the following technical scheme:

according to an embodiment of the first aspect of the invention, the liquid conductor is obtained by self-liquefaction of an egg white hydrogel.

Preferably, the liquid conductor has a light transmittance of greater than 85% for light having a wavelength of 555 nm.

Preferably, the liquid conductor has an electrical conductivity of 19 to 21S m at 25 ℃^-1。

According to a second aspect of the invention, a method of making a liquid conductor includes:

step S1, mixing the egg white solution and alkali to prepare egg white hydrogel;

and step S2, carrying out self-liquefaction treatment on the egg white hydrogel to obtain the liquid conductor.

Preferably, in the step S1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20.

preferably, the base is sodium hydroxide, potassium hydroxide or lithium hydroxide.

Preferably, in the step S2, the egg white hydrogel is subjected to self-liquefaction treatment at 25-150 ℃.

A sensor according to an embodiment of the third aspect of the present invention comprises a first substrate and a second substrate arranged oppositely, and a liquid conductor as in any of the embodiments above enclosed between the first substrate and the second substrate.

Preferably, the first substrate and the second substrate are Ecoflex00-50 products.

Preferably, the sensor is a tension sensor or a compression sensor.

A method of manufacturing a sensor according to an embodiment of the fourth aspect of the invention includes:

step m1, mixing the egg white solution with alkali to prepare egg white hydrogel;

step m2, providing a cured first substrate;

step m3, 3D printing an egg white hydrogel layer on the surface of the solidified first substrate;

step m4, pouring a second matrix forming solution on the first matrix printed with the egg white hydrogel to encapsulate the printed egg white hydrogel;

and m5, solidifying the second matrix forming solution to form a second matrix and carrying out self-liquefaction on the egg white hydrogel into a liquid conductor to obtain the sensor.

Preferably, in the step m1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20.

Preferably, in the step m5, the second matrix forming solution is solidified at 20-30 ℃ to form a second matrix and the albumen hydrogel is self-liquefied into a liquid conductor.

Preferably, the extrusion pressure for 3D printing is 70-80psi and the nozzle diameter is 0.25-0.45 mm.

A wearable device according to an embodiment of the fifth aspect of the invention comprises the sensor of any of the above embodiments.

According to the gesture console of the sixth aspect of the present invention, the gesture console is used for controlling an electronic device, and the liquid conductor of any one of the above embodiments is packaged in the gesture console.

According to a seventh aspect of the present invention, a triboelectric nanogenerator is provided, wherein the liquid conductor of any one of the above embodiments is packaged in the triboelectric nanogenerator.

The invention has the beneficial effects that:

carry out from the liquefaction through albumen aquogel and obtain the liquid conductor, this liquid conductor transparency is good, the conductivity is high, the hysteresis quality is little, higher ductility has, and the source is abundant, low in manufacturing cost, easily industrial production, in addition, including the sensor of this liquid conductor, higher sensitivity has, lower hysteresis quality, response and recovery time are very fast, and have better stability and durability, this liquid conductor still can be used to wearable equipment, gesture control cabinet and triboelectric nanogenerator and do benefit to the development that promotes this field.

The foregoing is a summary of the present invention, and in order to provide a clear understanding of the technical means of the present invention and to be implemented in accordance with the present specification, the following is a detailed description of the preferred embodiments of the present invention.

Drawings

FIG. 1 is a schematic illustration of SDS-PAGE analysis of egg white solutions and liquid conductors obtained from 24 hours and 48 hours of self-liquefaction;

FIG. 2 is a schematic diagram of a phase transition of an egg white hydrogel during self-liquefaction;

FIG. 3 is a schematic view of an oscillation time scan of an egg white solution, an egg white hydrogel, and a liquid conductor;

FIG. 4 is a schematic representation of the EWL resulting from the self-liquefaction process at 60 ℃ and 150 ℃, respectively, by the EWH;

FIG. 5 is a graph showing the time for the EWH to self-liquefy at different temperatures to obtain EWL;

FIG. 6 is a schematic graph of the oscillation time scanning of egg white hydrogels prepared with different bases;

FIG. 7 is a schematic diagram of the oscillation time scanning of egg white solutions and egg white hydrogels prepared from the egg white solutions and liquid conductors at different storage times;

FIG. 8 is a schematic representation of rheological measurements of an egg white solution and base prepared at different weight ratios to give an EWH;

figure 9 is a graph of light transmittance of EW and the resulting EWH during self-liquefaction at a visible wavelength of λ 555 nm;

FIG. 10 is an impedance profile of EWH measured at different times from liquefaction;

FIG. 11 is a schematic diagram of a closed circuit repaired with an EWL demonstrating that the EWL is a conductor;

FIG. 12 is a graphical representation of the conductivity of the EWH measured at different times of self-liquefaction;

FIG. 13 is a graphical representation of the viscosity of EWH as a function of shear rate;

FIG. 14 is a cross-sectional view of a hydrogel strand encapsulated in an elastomeric matrix at various travel speeds and the elastomeric matrix;

FIG. 15 is a schematic representation of the change in resistance with tensile deformation for sensors of different EWL widths;

FIG. 16 is a schematic representation of the change in resistance of the sensor with tensile deformation at different tensile rates (30mm/min, 300mm/min, 600mm/min, 900mm/min, 1800 mm/min);

FIG. 17 is 300mm min^-1A hysteresis curve diagram of the sensor for different EWL widths at the draw rate of (a);

FIG. 18 is a schematic of the response and recovery time of the sensor under dynamic pressure;

FIG. 19 is a schematic view of a compressive strain curve of the sensor;

FIG. 20 is a graphical representation of the cyclic compressive strain curve of the sensor at 80% strain;

FIG. 21 is a schematic diagram of the variation of the resistance of the sensor with different finger bend angles;

FIG. 22 is a schematic diagram of the variation of the resistance of the sensor with the movement of the wrist;

FIG. 23 is a schematic diagram of the resistance of the sensor as a function of the inflation and deflation of the balloon;

FIG. 24 is a graphical representation of the resistance of a vascular-shaped sensor as a function of the magnitude of expansion;

FIG. 25 is a schematic diagram of a sensor transmitting long and short electronic signals of Morse code in response to a touch;

FIG. 26 is a graph showing the variation of the resistance of the sensor with the pulse;

FIG. 27 is a schematic diagram of the variation of the resistance of the sensor with the fine contraction of the frontal lobe;

FIG. 28 is a schematic of the change in resistance of the sensor with shock;

FIG. 29 is a schematic representation of the variation in resistance of the sensor as the brush slides across its surface;

FIG. 30 is a schematic illustration of the change in resistance of a material with a sensor slid across a surface of different roughness;

FIG. 31 is a schematic diagram of an integrated circuit diagram integrating an EWL as a conductor for a microcontroller switch;

FIG. 32 is a schematic view of a tilt recognition device utilizing angle of tilt and gesture change control;

FIG. 33 is a schematic diagram of a presentation of a gesture console encapsulating an EWL, wherein (a): the gesture console encapsulated with the EWL is connected to the schematic diagrams of the plurality of microcontrollers; (b) the method comprises the following steps A schematic of the flow path of the EWL and the corresponding current when the gesture changes; (c) the method comprises the following steps A schematic diagram in which a plurality of programs are opened in sequence as the gesture changes;

FIG. 34 is a schematic of a casting process of a bulk TENG;

FIG. 35 is a graph of open circuit voltages generated by TENG at different frequencies from 0.5 to 3 Hz;

FIG. 36 is a graph of the voltage generated by TENG at a constant frequency as a function of pressure;

FIG. 37 is a schematic view of a TENG array with V-shaped plates repeatedly approaching and separating;

FIG. 38 is a schematic of the voltages generated by the TENG array of FIG. 37 as the V-plates repeatedly approach and separate.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention, but are not intended to limit the scope of the invention.

According to the liquid conductor provided by the embodiment of the invention, the liquid conductor is obtained by self-liquefying egg white hydrogel.

Preferably, the liquid conductor has a light transmittance of greater than 85% for light having a wavelength of 555 nm. The excellent light transmittance of the liquid conductor facilitates the realization of a highly optically transparent interface for sensors comprising the liquid conductor, and thus wearable devices and the like comprising the sensor.

Preferably, the liquid conductor has an electrical conductivity of 19 to 21S m at 25 ℃^-1. Therefore, the liquid conductor becomes a potential ion conductor due to the excellent conductivity of the liquid conductor, and is convenient to popularize and apply in multiple fields.

The preparation method of the liquid conductor of the embodiment of the invention comprises the following steps:

The preparation method of the liquid conductor is simple and convenient, the raw material source is rich, the manufacturing cost is low, the industrial production is easy to realize, the prepared liquid conductor is good in transparency, high in conductivity, small in hysteresis and high in ductility, in addition, the sensor comprising the liquid conductor is high in sensitivity and low in hysteresis, quick in response and recovery time and high in stability and durability, and the liquid conductor can be further used for wearable equipment, a gesture control console and a triboelectric nano-generator and is beneficial to promoting the development in the field.

Preferably, in step S1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20. not only is beneficial to ensuring the strength of the obtained egg white hydrogel, but also is convenient to ensure the excellent performance of the obtained liquid conductor.

Preferably, the base is sodium hydroxide, potassium hydroxide or lithium hydroxide. So as to obtain a better liquid conductor with lower cost.

Preferably, in step S2, the egg white hydrogel is subjected to self-liquefaction treatment at 25-150 ℃. Thus, the self-liquefaction processing time can be ensured, and the liquid conductor with excellent performance can be obtained through the self-liquefaction processing.

The sensor comprises a first base body, a second base body and a liquid conductor, wherein the first base body and the second base body are oppositely arranged, and the liquid conductor is packaged between the first base body and the second base body.

The sensor comprises a first base body and a second base body which are oppositely arranged and a liquid conductor which is packaged between the first base body and the second base body, has better transparency, has higher sensitivity in a wider deformation range, can bear extremely fast stretching, has lower hysteresis, has quicker response and recovery time, has better stability and durability, has lower cost and is beneficial to obtaining wide application.

Preferably, the first substrate and the second substrate are Ecoflex00-50 parts. Therefore, the sensor is convenient to manufacture in the actual production process, and the sensor is ensured to have better stretchability, biosafety and lower cost.

Preferably, the sensor is a tension sensor or a compression sensor. The sensor can be used as a tension sensor or a compression sensor, and has high sensitivity, stability and durability.

The preparation method of the sensor of the embodiment of the invention comprises the following steps:

step m2, providing a cured first substrate;

The preparation method of the sensor is simple and convenient, is convenient for batch production, and can be convenient for ensuring that the prepared sensor has excellent performance.

Preferably, in step m1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20. the strength of the obtained egg white hydrogel is ensured, the 3D printing is facilitated, the excellent performance of the obtained liquid conductor is ensured, and the excellent performance of the prepared sensor is ensured.

Preferably, the base is sodium hydroxide, potassium hydroxide or lithium hydroxide. So as to obtain a better sensor with lower cost.

Preferably, in step m5, the second matrix-forming solution is solidified at 20-30 ℃ to form a second matrix and the egg white hydrogel undergoes self-liquefaction into a liquid conductor. This ensures that the performance of the resulting sensor is optimal.

Preferably, in step m3, the extrusion pressure for 3D printing is 70-80psi and the nozzle diameter is 0.25-0.45 mm. So as to ensure the structural continuity of the egg white hydrogel layer printed on the surface of the first substrate in a 3D manner, and further ensure that the manufactured sensor has excellent performance.

A wearable device according to an embodiment of the invention comprises the sensor of the above-described embodiment of the invention. Therefore, the wearable device can identify nuances of health conditions, can sense dynamic stimulation, is suitable for non-planar surfaces, and has high sensitivity and precision.

According to the gesture control console provided by the embodiment of the invention, the gesture control console is used for controlling the electronic equipment, and the liquid conductor provided by the embodiment of the invention is packaged in the gesture control console. Therefore, the gesture control console can simply realize control over the electronic equipment, and a simplified and reliable bridge can be erected between the man-machine and the Internet of things.

According to the triboelectric nano-generator provided by the embodiment of the invention, the liquid conductor provided by the embodiment of the invention is packaged in the triboelectric nano-generator. Thus, the triboelectric nanogenerator comprising the liquid conductor is convenient and green to manufacture, and additionally has a stable and rapid response to external motion.

The invention is described below by means of specific examples.

Example 1

Preparation of liquid conductor

Removing yolk and thin yolk bands from fresh eggs purchased from a supermarket, separating out a crude egg white solution, uniformly mixing the dense part and the thin part for 2min to obtain a yellowish uniform solution, removing a supernatant after several minutes to obtain an egg white solution (EW), mixing the egg white solution and sodium hydroxide solid for 1min according to a weight ratio of 50:10, gelling for about 300s to obtain an Egg White Hydrogel (EWH), and standing the egg white hydrogel at 25 ℃ for self-liquefaction to obtain a liquid conductor (EWL).

The hydrolysis process was revealed by SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and the molecular weight of the final hydrolysate was revealed. As shown in FIG. 1, the molecular weight of the original egg white solution is firstly proved, and the major protein bands such as ovalbumin (44.5kDa), ovotransferrin (77.7kDa), ovomucin (28.0kDa), lysozyme (14.3kDa) and avidin (68.3kDa) can be clearly distinguished by electrophoresis; in contrast, no significant band above 17kDa was found in the liquid conductor obtained after 24 hours of alkaline hydrolysis, i.e.self-liquefaction treatment; in addition, the pattern of the bands after 48 hours of self-liquefaction treatment was similar to that after 24 hours of self-liquefaction treatment, thus demonstrating the rapid self-liquefaction process of egg white hydrogels and the hydrolysate stability after complete hydrolysis. Experiments show that the formation of an egg white hydrogel from an egg white solution can lead to the rebalancing of electrostatic repulsion and the rearrangement of protein chains, such a hydrogel system can maintain stability through secondary cross-linking between multivalent cations and carboxyl groups, and the denaturation of proteins due to an alkaline environment changes the secondary, tertiary or quaternary structure without affecting the primary structure. Considering the effect of this denaturing behavior on the natural integrity, it is speculated that without further intervention (i.e. cationic secondary cross-linking) the egg white hydrogel would undergo simultaneous hydrolysis after primary gelation, leaving only a small amount of amino acid salts behind after the hydrolysis process, most protein structures being cleaved at high pH (i.e. pH > 12).

Two cylindrical EWH blocks, each stained with a green and red fluorescent dye, were vertically stacked and sealed in a room, and the phase change process was macroscopically observed. The result is shown in fig. 2, where the stacked egg white hydrogels first each maintain a stable shape and the two pieces fuse together over time under the force of gravity. In general, the sol-gel transition from an egg white solution to EWH is accompanied by a transient and stable network formation, the hydrogel prepared maintains shape stability to gravity until the time of disturbance, i.e. under strong alkaline hydrolysis, the interweaving between the protein chains is gradually disentangled under strong alkaline hydrolysis with the passage of time, and during the phase transition the bulk is transformed from a solid hydrogel into a spontaneously flowing EWL in which smaller peptide or amino acid fragments are dispersed instead of intact protein chains, a phenomenon known as self-liquefaction.

Oscillation time sweep measurements were performed to quantitatively assess the change in mechanical properties of EWH liquefaction to EWL over time. As shown in FIG. 3, the gelled EWH has a storage modulus of about two orders of magnitude (G' at 770Pa), whereas the original EW has a storage modulus of 3Pa, and after complete liquefaction, the EWL has a storage modulus that drops to 1.1 Pa. This significant drop is not only significantly lower than EWH, but also lower than the original EW, suggesting that the change in physical state of the self-liquefaction process is due to the hydrogel network and the collapse of a large number of protein chains.

Furthermore, temperature is an important parameter in the kinetics of alkaline hydrolysis. Several EWHs were placed in a series of constant temperature ovens, respectively, and the time from liquefaction was recorded to assess the effect of temperature on phase change. Complete liquefaction of the EWH takes about 4 hours at room temperature (25 ℃), and it is notable that the EWH, even when subjected to self-liquefaction at 150 ℃, results in EWL, rather than a milky white solid, as shown in fig. 4. As shown in fig. 5, the self-liquefaction time was reduced to around 568s at 60 c, the EWL sample was still transparent, while the egg white solution was heat-denatured from a translucent texture to opaque at this temperature, and the self-liquefaction time averaged 227s at 80 c. The self-liquefaction time continued to decrease with increasing self-liquefaction temperature and reached a plateau at 140s after 130 ℃. Theoretically, EW solutions thermally denature above 60 ℃, the intact long protein chains are interwoven into a firm network, and the phenomenon of EWH and EWL, which appears counterintuitive, also demonstrates that alkaline denaturation completely destroys the high-order conformation of the protein.

In addition, the effect of the storage time of an EW on its gelation and self-liquefaction was also investigated. Results as shown in figure 7, aged EW also demonstrated the formation of EWH and subsequent self-liquefaction, which exhibited a significantly higher storage modulus than the original aged EW solution even after 2 months of refrigeration at 4 ℃, and resulted in a thin liquid from self-liquefaction (G' of 0.5 Pa). In particular, EW stored for 1 and 2 months prior to gelation exhibited similar storage modulus (G 'at about 1 Pa), but less than the storage modulus of the fresh EW sample prior to gelation (G' at about 3 Pa). The hydrogel phase revealed a decay in storage modulus of EWHs obtained for EW stored for 2 months relative to that obtained for 1 month (630Pa and 310Pa for samples of 1 and 2 months of age) due to time-dependent kinetic behavior.

OTHER EMBODIMENTS

Mixing an egg white solution and an alkali sodium hydroxide solid in a weight ratio of 50:5 and 50:20 to obtain the egg white hydrogel, and then carrying out self-liquefaction treatment on the prepared egg white hydrogel at 150 ℃ to obtain the liquid conductor. Concentration ratio-related changes in mechanical properties were evaluated by viscoelastic modulus and as a result, as shown in figure 8, all EWHs prepared from egg white solution and alkali sodium hydroxide at different weight ratios exhibited similar linear viscoelastic strains from 0.1% to 2%, with storage modulus (G') about an order of magnitude greater than loss modulus (G "), indicating classical gel behavior, but higher or lower component ratios affected hydrogel strength by disruption of the electrostatic equilibrium in the hydrogel network.

Mixing the egg white solution with potassium hydroxide or lithium hydroxide to prepare egg white hydrogel, and then carrying out self-liquefaction treatment on the egg white hydrogel at 100 ℃ to obtain a liquid conductor, wherein the egg white solution is respectively mixed with the potassium hydroxide and the lithium hydroxide according to the weight ratio of 50:10 to obtain the egg white hydrogel. The rheological evaluation of the obtained different egg white hydrogels was performed, and the results are shown in fig. 6, the egg white hydrogels prepared by different types of alkali were stable, and the storage modulus and loss modulus of the different egg white hydrogels were almost unchanged.

Based on the performance evaluation of the liquid conductor obtained by performing self-liquefaction treatment on the egg white hydrogel prepared by mixing the egg white solution and the sodium hydroxide according to the weight ratio of 50:10 in the example 1, the specific performance test is as follows:

test 1

The EW solution exhibited a translucent yellow color while the prepared egg white hydrogel was more transparent, the EWH sample was sealed in a transparent cell, and the transmittance at the main visible wavelength (500-.

Experimental results show that, compared with the original EW solution, the optical performance of the freshly prepared EWH is significantly improved, and the light transmittance is further improved in the self-liquefaction process.

As shown in fig. 9, EW solutions can be obtained, as well as the transmittance of the prepared EWH at a visible wavelength λ 555nm during self-liquefaction, which increases significantly from 45.71 ± 2.06% to 88.38 ± 1.51% after gelation, and reaches a peak of 96.61 ± 3.16% 24h after self-liquefaction, which is attributed to smaller and shorter peptide chain residues after hydrolysis, thus greatly reducing insoluble aggregates in the final liquid. And it has been experimentally shown that EWL is sufficiently transparent that white light can pass through and be dispersed into the rainbow spectrum in a triangular glass prism.

Test 2

In order to eliminate capacitive interference in the direct current evaluation method, the conductivity of the prepared EWH and EWL is obtained by using an electrochemical impedance spectrum under the action of alternating current. As shown in fig. 10, Cole-Cole curves are depicted for the impedances of EWH and EWL, all of which contain intersecting linear portions of a distorted semicircle of the high frequency region, representing ionic resistance dominating in charge transfer at high frequencies, and a low frequency region, representing due to the ion diffusion process at low frequencies. As can be seen from fig. 10, the semicircular region at high frequency gradually decreases with the lapse of time, indicating that the EWH self-liquefaction process has a great influence on the electrical characteristics.

As shown in fig. 11, in a circuit that is open at a certain position with a Light Emitting Diode (LED) as an on/off indicator, dropping a few drops of EWL at the position where the circuit is open can effectively restore the circuit connection.

Further, the conductivity σ of the samples of the prepared EWH and EWL was determined by σ RbA/l, where l is the length of EWH and EWL, and a is the contact area between the samples and the parallel electrodes. The prepared EWH sample was tested at 25 ℃ and the initial conductivity of the EWH was 16.9S m as shown in FIG. 12^-1The conductivity increased significantly with increasing self-liquefaction time of the EWH, and after 5 hours, the conductivity increased to 20.4S m when the EWH was fully liquefied to EWL^-1And reached an equilibrium state after 24h of standing. The majority charge carriers and transport in EWH are due to Na⁺And OH^-The migration of positive and negative ions in the network structure gives the egg white hydrogel a lower conductivity, and the increase in conductivity of EWL is believed to be an increase in the total ion concentration by the residues of hydrolyzed peptides or free amino acids, as well as an unconstrained migration path from the collapse of the porous structure during self-liquefaction.

Other test examples

Two EWL samples are taken to be tested at 25 ℃, and the conductivity of the liquid conductor is measured to be 19S m respectively^-1And 21S m^-1。

Some applications of the liquid conductor of the embodiments of the present invention are described in detail below, specifically as follows:

application 1 sensor

Three-dimensional printing (3D printing) is a technology that can efficiently realize a three-dimensional structure of high fidelity and wide-sized patterns from microscopic to macroscopic without using a template and a mask, and is a reliable high-throughput technology in a plurality of fields such as integrated electronic devices. However, unsatisfactory viscoelasticity limits the range of alternative inks for manufacturing flexible sensors by 3D printing. The EWH of the embodiments of the present invention, as a shear-thinning ink, can be directly 3D printed at room temperature without UV curing, addition of rheology modifiers, or oxygen substitution required for free radical polymerization.

Based on the EWH prepared in example 1, the rheology of the EWH was characterized by viscoelastic evaluation. Results As shown in FIG. 13, the EWH as a direct printing ink exhibited typical shear thinning behavior, showing when the shear rate was from 10^-1s^-1Is raised to 10²s^-1In this case, the viscosity of EWH is reduced from 3200Pa · s to 9Pa · s, that is, smoothness of printing can be achieved by the correct nozzle. It is also clear that viscosity and modulus enable EWH to maintain geometry after extrusion and also to adhere on various substrates and do not require the subsequent UV curing treatment currently required for most printing inks.

The printing parameters of 3D printing, such as extrusion pressure, needle diameter and travel speed, affect not only the continuity of the printed structure, but also the consistency between theoretical design and experimental results. The present embodiment characterizes the printing line geometry in terms of height and width under exactly the same printing path, at constant extrusion pressure (75psi) and nozzle diameter (0.337mm) and varying speed of travel, demonstrating that the extrusion pressure ensures continuous extrusion of the EWH. As shown in fig. 14, an experiment was conducted with EWH made in example 1, and after extrusion and encapsulation with an elastomeric matrix, the printed hydrogel threads embedded in Ecoflex elastomeric matrix showed regular semi-elliptical shapes in cross-sectional view.

Silicone rubber is widely used as a flexible substrate for stretchable electronic devices due to advantages of bio-safety, cost saving, and excellent mechanical properties (ductility and strength), and three silicone rubber products of Sylgard 184 and Ecoflex series (00-35 and 00-50) were selected as flexible substrates for encapsulating EWL for experiments. Contact angle evaluation showed that the three silicone rubbers are inherently hydrophobic to EW or EWL (contact angles >100 °), and Ecoflex00-50 has the highest repellency to both EW and EWL (contact angles 109.3 ± 2.9 ° and 109.5 ± 2.7 °, respectively), better than Sylgard 184 and Ecoflex 00-35, indicating that EWH and EWL would be repelled rather than diffused or penetrated into the silicone rubber. Because the EWL is kept in a liquid state, the stretching property of the EWL is good, another consideration of the soft matrix is how to exert infinite deformation capacity to the maximum extent, and the Ecoflex has better stretching property and more skin-like texture and is more suitable for advanced soft electronic products and detection of large deformation. And in soft device manufacturing, another key criteria for substrate selection is proper cure time, which should be synchronous or shorter than EWH liquefaction time, the cure time of Ecoflex00-50 is about 3 hours at 23 ℃, and is prolonged at lower temperature, which coincides with EWH self-liquefaction time, the extremely short cure time of Ecoflex 00-35 limits the practical operation in the current manufacturing process, while the cure time of Sylgard 184 far exceeding EWH self-liquefaction time leads to impaired cure capability and EWL exposure.

The increased travel speed resulted in a reduction of the hydrogel deposited on the substrate per unit time, which greatly reduced the resolution of the lines, the average height of the printed lines from the baseline speed (1000mm min)^-1) 0.47mm of (2) is reduced to 1700mm min^-10.35mm, the average width decreases from 1.19mm to 0.65mm, at a relatively high speed (1700mm min)^-1) The line width is still larger than the nozzle diameter.

Based on the above, the sensor was prepared by the method of 3D printing.

Example 1

In this example, the method of manufacturing the sensor includes the steps of: step m1, mixing the egg white solution and sodium hydroxide according to the weight ratio of 50:10 to prepare egg white hydrogel; step m2, providing a cured first substrate, wherein the first substrate is an Ecoflex00-50 product; step m3, 3D printing an egg white hydrogel layer on the surface of the cured first substrate, wherein the extrusion pressure of the 3D printing is 75psi, and the diameter of a nozzle is 0.337 mm; step m4, pouring a second matrix forming solution on the first matrix printed with the egg white hydrogel to encapsulate the printed egg white hydrogel; and m5, solidifying the second matrix forming solution at 25 ℃ to form a second matrix and carrying out self-liquefaction on the egg white hydrogel into a liquid conductor to obtain the sensor, wherein the second matrix is an Ecoflex00-50 product. The sensor thus produced comprises a first substrate and a second substrate which are oppositely arranged and a liquid conductor which is encapsulated between the first substrate and the second substrate.

Example 2

The method of manufacturing the sensor in this example was substantially the same as the method of manufacturing the sensor in example 1, except that: m1, mixing the egg white solution and potassium hydroxide in a weight ratio of 50:5 to prepare an egg white hydrogel; the extrusion pressure for 3D printing in step m3 was 70psi, with a nozzle diameter of 0.25 mm; the second matrix-forming solution is cured at 20 ℃ in step m5 to form a second matrix and the egg white hydrogel is allowed to self-liquefy.

Example 3

The method of manufacturing the sensor in this example was substantially the same as the method of manufacturing the sensor in example 1, except that: m1, mixing the egg white solution and lithium hydroxide in a weight ratio of 50:20 to prepare egg white hydrogel; the extrusion pressure for 3D printing in step m3 was 80psi, with a nozzle diameter of 0.45 mm; the second matrix-forming solution is solidified at 30 ℃ in step m5 to form a second matrix and the egg white hydrogel is allowed to self-liquefy.

Hereinafter, the sensor prepared in the above example 1 was tested for its performance.

Since the storage modulus of the EWL is significantly lower than that of the silicone rubber matrix, as in the present study Ecoflex (storage modulus around 100MPa), this means that in EWL-based sensors there is no mechanical mismatch or "delamination" with cracks even at large deformations (the main drawback of solid or hydrogel sensors). The influence of the channel morphology of the liquid conductor on the sensitivity of the EWL-Eco tensile sensor is verified through experiments, and the resistance change Delta R% of the sensor is defined as (R1-R0)/R0 multiplied by 100%, wherein R0 and R1 are resistance values before and after deformation. Δ R% increases with increasing tensile deformation and the sensor exhibits a reliable and repeatable response when stretched from 0% to 200%, while the magnitude of the resistance change value is closely related to the size of the channel of the liquid conductor, with the average value of the resistance change value of the tensile sensor increasing gradually at EWL widths of 3mm, 2mm and 1mm, respectively. As a main parameter of the tensile sensor, sensitivity is defined by GF ═ Δ R/, as shown in fig. 15, the sensitivity varies with the width of the EWL liquid conductor, the smaller width shows the larger GF at any specific deformation, and further, the sensitivity of the EWL-Eco sensor is 0.86 in deformations below 80% and 0.21 at strains 80-200%, and the sensor also shows a linear response at a slight strain (less than 5%), which indicates that the EWL-Eco sensor has a high sensitivity in a wide deformation range.

Generally, sensors that encapsulate solid conductors (e.g., hydrogels) suffer delamination and signal attenuation due to high-speed deformation due to mechanical property mismatch and poor interfacial bonding between the conductors and the elastic matrix, so the stretching speed is always limited to a few tens of micrometers per minute, and furthermore, most hydrogel conductors have poor electrical properties when moving at high speeds because the conductors cannot recover their original shape and resistance after being deformed after high-speed stretching. It is worth noting that the EWL-Eco sensor prepared in example 1 has "speed insulation" properties, as shown in FIG. 16, which can withstand extremely fast stretching (1800mm min)^-1) And maintain reliable sensitivity.

Another advantage of liquid conductors is the lower degree of hysteresis, most polymer hydrogel based conductors exhibit significant hysteresis due to viscoelastic effects and relative sliding between the conductor and the substrate. The experiment tests that the concentration is 300mm min^-1The hysteresis (DH) of the EWL-Eco sensor at a resistance change within 100% of the stretch is calculated by DH ═ astrech-aremax/Astretch × 100%, where Astretch and aremax represent the area of the resistance curve during stretch and release, respectively, as shown in fig. 17, the hysteresis of the EWL-Eco sensor decreases with increasing EWL width, and the DH values are about 12.13%, 4.21% and 0.77% for 1mm, 2mm and 3mm EWL widths, respectively.

To further demonstrate the performance of the prepared sensors, the response and recovery time of the sensors were recorded as dynamic pressure movements (about 1 Hz). As a result, as shown in FIG. 18, the response time of the EWL-Eco sensor was 10ms, and the recovery time was 12.5ms, which was faster than the skin (recovery time was about 40 ms). In addition, the durability and the service life of the EWL-Eco sensor are verified through experiments, and the stability performance of the EWL-Eco sensor after continuous heavy load in short time and long-term storage is further verified, wherein the EWL-Eco sensor has the stability performance of 300mmmin^-1After 10000 cycles of stretch relaxation to 100% strain at a stretch rate of (c), it was confirmed that a highly reproducible and stable resistance recording was obtained without significant peak loss, hysteresis, or fatigue.

In addition, further testing with the EWL samples after long-term storage (completely from 7, 14 and 30 days after liquefaction) showed great stability and repeatability of the resistance response of the sensor, with the resistance changes of the sensor for the 7, 14 and 30 days after liquefaction being 67.1%, 66.7% and 67.9%, respectively, at 100% strain, which is close to that of the fresh EWL samples.

The electronic response of the sandwich-type EWL-Eco composite as a compression sensor to external pressure was also experimentally characterized, and as a result, as shown in fig. 19, the compression sensor showed excellent compression compliance up to 90% due to the fluidity of EWL and the high elasticity of Ecoflex matrix.

Furthermore, as shown in fig. 20, the deviation of the observed pressure-strain curve is negligible at different loading cycles.

In addition, the resistance curves of the compression sensor at different load pressures were also tested, and the resistance change ratios were 9.15%, 12.54%, and 13.5% for load pressures of 3kPa, 6kPa, and 9kPa, respectively. The experimental results show that the sensitivity of the EWL-based compression sensor is 0.03kPa when the pressure is below 3.74kPa^-1And, when the pressure is in the range of 3.74 to 12kPa, the pressure is lowered to 0.003kPa^-1Moreover, the stability and durability of the compression sensor was demonstrated over 300 cycles with pressures up to 12 kPa.

Application 2 wearable device

The following is a detailed description of the application of the sensor prepared according to the method for preparing the sensor in example 1.

As shown in FIG. 21, the sensor attached to the index finger can repeatedly respond to the bending motion of the index finger, whereby the EWL-Eco sensor can more easily recognize the motion of a larger amplitude. As shown in fig. 22, when two fibrous EWL-Eco sensors are vertically mounted on the wrist, they convert the movement of the wrist into an electric signal to show the bending movement of the wrist, the resistance of the sensor coaxial with the bending direction is increased by 3 times (1.5% to 0.5%) than the sensor perpendicular to the bending direction, thereby showing that the sensors are also capable of detecting delicate motions, which is highly desirable in future wearable textiles.

In addition to the planar connection, the EWL-Eco sensor also has form adaptability on a non-planar surface, both ends of the sensor are attached to the surface of the balloon to avoid relative sliding during inflation, as shown in FIG. 23, and the sensor output resistance signal clearly shows the rapid response of the sensor and the synchronous change of resistance with the continuous inflation and deflation of the balloon.

By applying Ecoflex solution to a cylindrical template and curing to form a vascular rubber tube with an inner diameter of 5mm, printing EWH on the surface of the rubber tube, then covering the rubber tube surface printed with EWH with another layer of Ecoflex and completely liquefying EWH, when the rubber tube is inflated by injecting different volumes of water to simulate the expansion of blood vessels, as shown in fig. 24, the increased lateral pressure compresses EWL and causes a change in resistance, and the change in the amount of injected water can be repeatedly and accurately detected by the sensor, further indicating the potential use of the sensor on non-planar surfaces.

The application of the EWL-Eco sensor as a man-machine interaction interface for Morse code recognition is also proved, the sensor can transmit long and short electronic signals of Morse codes according to touch, and the term "EGG WHITE" can be expressed by alternately clicking or long pressing the surface of the sensor as shown in FIG. 25.

Furthermore, the advanced sensitivity and potential for full-range monitoring of the EWL-Eco sensor is further demonstrated by various subtle body motion and kinetic stimuli. The EWL-Eco device is attached to the wrist surface of the radial artery to monitor the pulse in sedentary and post-exercise conditions. As shown in FIG. 26, the average heart beats in the first 1 minute and the last 1 minute of mild exercise were 81 min^-1And 112 min^-1At the same time, the resistance change amplitude increased from 5.7% in the sedentary state to 6.2% after exercise.

In addition to distinguishing states by weak amplitude and frequency, there are more methods, generally, the wrist pulse curve is composed of a distinguishable rising peak (P1) reflecting the contraction of the left ventricle and the peaks P2 and P3, not only the heart activity but also the vascular function can be shown by quantifying the wrist pulse recording since the wrist pulse originates from the heart contraction and the vascular transportation, two main parameters, i.e., radial artery augmentation index (AIr ═ P2/P1) and Pulse Transit Time (PTT) between P1 and P2, are extracted from the recording measured by the EWL-Eco device and used to evaluate the health condition, the corresponding amplitudes and positions of P2 and P3 change after a short exercise, P2 tends to disappear, the average values of AIr after a long sitting and exercise are 83.2% and 64.7%, respectively, and PTT decreases from 97 to 82 msec. As shown in fig. 27, when the strip sensor is vertically installed on the forehead wrinkles, the fine contraction of the frontal lobe can be clearly detected.

Sound detection in a non-contact mode is also important in daily life, and as shown in fig. 28, when a metal cube (weighing 10 g) falls freely from a height of 10 cm or 5cm, the EWL packaged in the sensor, which is 1cm from the vibration center, can absorb shock and cause a change in resistance, thereby generating a distinct signal with good reproducibility.

In addition to pressure sensing, where the perception of friction and texture is a bright spot on human skin, the change in resistance clearly reveals the motion pattern, the first contact of the brush applying a slight pressure on the surface results in a slight but significant gap in resistance reduction, then the friction force as it slides across the sensor surface results in an increase in resistance, the gradual lifting of the brush from the sensor results in a falling tail, with each fluctuation corresponding to a different pressure and sliding intensity, respectively, as shown in fig. 29, which demonstrates the ability of the sensor to sense such dynamic stimuli through real verification.

The texture discrimination ability of the sensor was verified using three materials with surfaces of different roughness (glass, paper and 120 grit sandpaper), and as a result, as shown in fig. 30, a smoother curve was obtained when the sensor was slid over the glass, a more fluctuating curve was observed when slid over the paper, and the most jagged curve represented the roughest surface slid over the sandpaper.

The above experimental results confirm that the EWL-Eco sensor can be used to identify nuances of health conditions, can sense dynamic stimuli, and is suitable for non-planar surfaces, which represents its potential as a wearable sensor with high sensitivity and precision for real-time monitoring, and thus can be used to prepare wearable devices.

Application 3 gesture console

The application of the liquid conductor prepared in the above embodiment 1 in a gesture console will be described in detail below.

Gestures originating from body movements or states, the electronic device can be controlled by means of front-end dynamics devices and back-end algorithms without physical contact, which undoubtedly frees both hands on keyboard, mouse and screen, so due to the flowability and shape-suitability of the conductive EWL a novel simplified gesture console with switches for controlling the electronic device is further proposed. As shown in fig. 31, a conductive EWL is integrated into a hierarchical circuit as a flow contact to alternately turn on/off signals, the EWL is poured into a designed cavity to connect the current branches and implement the corresponding electronic function according to a gesture change, and the EWL may enter another cavity to make the previous branch off and the new branch connected according to the gesture change. As shown in fig. 32, the tilt recognition device is manufactured by sealing the EWL in a 3D printing plastic mold with an LED as an indicator, flowing the EWL into a corresponding cavity by lifting one end of the device, connecting the current branches, and lighting the lamp. A gesture console as shown in fig. 33, a four-point star shaped polylactic acid (PLA) mold is manufactured by a commercial 3D printer and coated with a thin layer of Ecoflex00-50 on the inner surface of the mold to increase hydrophobicity, as shown in fig. 33-a, each microcontroller (denoted Cn) is arranged in parallel and connected to an EWL gesture console, and an EWL liquid flows into a corresponding designed cavity to contact with a copper wire when the gesture is changed, thereby forming an electrical connection, the flow path and the corresponding current are as shown in fig. 33-b, and when the EWL gesture console activates a branch, the corresponding microcontroller is opened and the corresponding designed program is opened, as shown in fig. 33-c, and as the hand is rotated in a clockwise direction, the document, the calculator, the multimedia and the desktop are successively opened. A great deal of research has been done to facilitate the computer-based solution of human gesture language through image or video-based gesture capture, but this requires sophisticated capture devices and more sophisticated algorithms of deep learning platforms that could, in the foreseeable future, build a simplified and reliable bridge between man-machines and the internet of things.

Application of 4 triboelectric nano-generator

The application of the liquid conductor prepared in the above example 1 in a triboelectric nanogenerator will be described in detail.

Triboelectric nano-generators (TENG) have received a great deal of attention since their inception and are a potential green energy source to mitigate energy crisis. As shown in fig. 34, bulk TENG can be made by a simple casting process that achieves self-liquefaction by sandwiching EWH between two layers of Ecoflex. The produced TENG followed the general law of triboelectrification and as shown in fig. 35, the performance of EWL-based TENG was evaluated by open circuit voltage at different frequencies, about 20V for pig skin of the same size as TENG (5 × 5cm) mounted on a linear motor to simulate human body movement contact, and independent of frequency (0.5 to 3Hz), demonstrating the stable and rapid response of the produced TENG to external movement. The TENG output performance versus pressure was evaluated experimentally, the TENG was connected to a 10M Ω resistor, and the entire device was tested by recording the voltage change under varying pressure at a constant frequency (0.5Hz), as shown in fig. 36, the limitation of pressure detection was about 1kPa when the voltage reached 0.05V, and the voltage increased to about 0.52V when the external pressure was increased to 80.6kPa, while the voltage profile maintained similar amplitude and shape under the same pressure cycle. The pressure sensitive function of this soft TENG stimulated the fabrication of an alternative electronic skin array, as shown in fig. 37, EWH printed in a 3 x 3 patch pattern (1 cm side) on an Ecoflex substrate and encapsulated with another elastomeric substrate (5 x 5cm), a V-shaped plate (polyacrylic) mounted on a stepper motor directly pressed against the patch array, each patch sensing the pressure above and independently generating a voltage, while the voltage curve for each patch correctly reflects the effective contact area, as shown in fig. 38.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The liquid conductor is characterized by being obtained by self-liquefying egg white hydrogel.

2. The liquid conductor of claim 1, wherein the liquid conductor has a light transmittance of greater than 85% for light having a wavelength of 555 nm.

3. The liquid conductor of claim 1, wherein the liquid conductor has an electrical conductivity of 19-21S m at 25 ℃^-1。

4. A method of producing a liquid conductor according to any one of claims 1 to 3, comprising:

5. The method for preparing a liquid conductor according to claim 4, wherein in the step S1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20.

6. the method of claim 4, wherein the base is sodium hydroxide, potassium hydroxide, or lithium hydroxide.

7. The method for preparing a liquid conductor according to claim 4, wherein in step S2, the egg white hydrogel is subjected to self-liquefaction treatment at 25-150 ℃.

8. A sensor comprising first and second oppositely disposed substrates and a fluid conductor according to any one of claims 1 to 3 encapsulated between the first and second substrates.

9. The sensor of claim 8, wherein the first and second substrates are Ecoflex00-50 parts.

10. The sensor of claim 9, wherein the sensor is a tension sensor or a compression sensor.

11. A method of making a sensor according to any one of claims 8 to 10, comprising:

step m2, providing a cured first substrate;

12. The method for preparing the sensor, according to claim 11, wherein in the step m1, the weight ratio of the egg white solution to the alkali is 50: 5-50: 20.

13. the method of manufacturing a sensor according to claim 11, wherein the base is sodium hydroxide, potassium hydroxide, or lithium hydroxide.

14. The method of claim 11, wherein in step m5, the second matrix-forming solution is solidified at 20-30 ℃ to form a second matrix and the albumen hydrogel is self-liquefied into a liquid conductor.

15. The method of manufacturing a sensor according to claim 11, wherein the 3D printing has an extrusion pressure of 70-80psi and a nozzle diameter of 0.25-0.45 mm.

16. A wearable device, characterized in that it comprises a sensor according to any of claims 8-10.

17. A gesture console for controlling an electronic device, characterized in that a liquid conductor according to any of claims 1-3 is enclosed in the gesture console.

18. A triboelectric nanogenerator, wherein the liquid conductor according to any one of claims 1 to 3 is encapsulated in the triboelectric nanogenerator.