CN110136891B

CN110136891B - Method for preparing flexible and elastic electrode through selective laser patterning

Info

Publication number: CN110136891B
Application number: CN201910454291.4A
Authority: CN
Inventors: 王靖; 孔德圣; 周赟磊
Original assignee: Nanjing University
Current assignee: Nanjing University
Priority date: 2019-05-24
Filing date: 2019-05-24
Publication date: 2021-01-12
Anticipated expiration: 2039-05-24
Also published as: CN110136891A

Abstract

The invention relates to a method for preparing a flexible elastic electrode by selective laser patterning, which is characterized in that the flexible elastic electrode is processed by infrared laser so as to prepare the flexible elastic electrode with high electrical property and stability. The medicine provided by the invention can be used in the field of wearable electronic devices, and has the characteristics of simple process, high precision, stable electrical performance and the like.

Description

Method for preparing flexible and elastic electrode through selective laser patterning

Technical Field

The invention belongs to the field of wearable devices, and particularly relates to a method for preparing a flexible elastic electrode through selective laser patterning.

Background

The rapid development of stretchable electrodes has driven the emerging field of skin electronics, from new soft electronic materials to prototype human-friendly electronic devices, including biocompatible electronics and soft robotics. In the future, our senses will be greatly extended by electronic products built into our clothing and accessories, attached to our skin, and even implanted into our body. Such biocompatible electronics, including wearable devices, epidermal devices, and implantable electronics, play an increasingly important role in human health monitoring and biomedical applications, which will greatly change future healthcare and our relationship to electronics. Meanwhile, biologically inspired soft robots have made tremendous progress due to advances in soft materials and flexible electronics technology. Bionic soft robots with skin-like sensors and soft drives are expected to interact with humans and the surrounding environment with significant enhanced safety, high sensitivity and adaptive response, complete human robot circulation, seamless and tight interaction. Organs such as the heart, arteries and alveoli experience periodic regional strains of up to tens of percent. Conventional wire-like or membrane-like electrodes cannot be mounted on the surface of these organs or tissues because they cannot detect useful physiological signals or perform medical treatment in vivo. Therefore, highly stretchable and conformable electrodes become indispensable for skin-like electronics, which provides promise for next-generation healthcare and biomedical applications.

Over the past few decades, one-dimensional metallic nanostructures have received much attention due to their different electrical, optical, magnetic and thermal properties. In addition, these one-dimensional metallic nanostructures have found possible applications in a variety of devices. The silver nanowire is a novel nano material, and due to high conductivity, the silver nanowire can be simply prepared on a large scale, the synthesis method of the polyol with low price receives great attention and research, and the electrode prepared from the silver nanowire has excellent conductivity and tensile property, which is one of the popular directions of the research at present. The hard electrodes on the market are limited in development due to the characteristics of being incapable of being bent and folded, and the like, and the electrodes based on the silver nanowires are considered as the main materials which are most hopeful to replace the traditional hard electrodes in the next generation. The electrode based on the silver nanowires is mainly manufactured by methods such as spin coating, drop coating, blade coating, spray coating, screen printing, transfer and the like. The invention mainly realizes the transfer of the silver nanowires to the flexible elastic substrate to form the flexible elastic device by a high-temperature transfer method.

The working principle of the infrared laser is mainly to vaporize substances on the surface of the material through the thermal effect, so that the aim of removing part of the material is achieved. This is commonly referred to as hot working. The wavelength of the laser is 1064 nm. Its main advantages are very small light spot, high energy density, high machining speed, easy automation, low cost and small occupied area. This makes infrared laser the most popular laser source in the market and the most popular laser source in material processing.

Among the different deformation modes of a flexibly elastic electronic device, stretchability is the most demanding and challenging. Conductive electrodes based on silver nanowires have emerged from a wide variety of stretchable electrodes due to their excellent conductive and mechanical properties. The laser, as one of the modern novel processing technologies, has the characteristics of high speed, high processing precision, good stability and the like. The invention mainly provides a method for patterning a silver nanowire electrode by using a laser technology, which can enable a conductive electrode to have a special two-dimensional pattern hollow structure, so that the conductive electrode has electrical stability, and overcomes the change of the electrode on electrical properties due to stretching, namely the electrode keeps extremely small resistance value change in the stretching process. The method expands the application prospect of the conductive electrode in the aspects of medical treatment, robots, heaters, radio frequency antennas and the like, and has stronger significance and value.

Disclosure of Invention

According to the invention, a film formed by depositing the silver nanowires prepared by the polyol method is embedded on the carbon black-doped thermoplastic polyurethane elastic rubber by using a high-temperature hot-pressing transfer method, and the film is processed by using infrared laser, so that the film has a two-dimensional pattern hollow structure, and the electrical stability of the flexible elastic electrode during stretching is improved.

The technical scheme adopted by the invention is as follows:

a method for preparing a flexible elastic electrode by selective laser patterning comprises the following steps:

(1) dissolving thermoplastic polyurethane elastic rubber and carbon black in tetrahydrofuran, heating and stirring uniformly to prepare a tetrahydrofuran solution with the thermoplastic polyurethane elastic rubber concentration of 10 wt% and the carbon black concentration of 0.5%; putting the tetrahydrofuran solution on glass upside down, and drying at normal temperature to form a black elastic rubber substrate; preparing 10 wt% thermoplastic polyurethane elastic rubber tetrahydrofuran solution in the same way;

(2) uniformly dispersing silver nanowires prepared by adopting a polyol method in an aqueous solution to obtain a silver nanowire aqueous solution, depositing the silver nanowire aqueous solution on a steel sheet to form a silver nanowire film, and spin-coating a layer of thermoplastic polyurethane elastic rubber on the silver nanowire film;

(3) adhering a black elastic rubber substrate and the silver nanowire film coated with the thermoplastic polyurethane elastic rubber in a spinning mode together by utilizing hot pressing, and peeling off the steel sheet to form the thermoplastic polyurethane elastic rubber covered with the silver nanowires;

(4) and processing the silver nanowire electrode by using infrared laser processing, and clearing out useless parts to obtain the patterned two-dimensional hollow silver nanowire electrode. Further, the silver nanowire prepared by the polyol method comprises the following steps: and sequentially dissolving polyvinylpyrrolidone, silver nitrate and ferric chloride in ethylene glycol, transferring to 130 ℃, standing for reaction for 12 hours, cooling to room temperature, and centrifuging to obtain the silver nanowire.

Further, the weight average molecular weight of polyvinylpyrrolidone was 360000.

Further, the wavelength of the infrared laser is 1064 nm.

The thickness of the thermoplastic polyurethane elastic rubber of the electrode prepared by the method for preparing the flexible elastic electrode by utilizing the selective laser patterning is 0.5-1.5 mm, the silver nanowires are completely embedded into the thermoplastic polyurethane elastic rubber, the diameter of the silver nanowires is 50-150 nm, the length of the silver nanowires is 60-120 mu m, and the resistance change rate of the silver nanowires is only 1% relative to that of a linear flexible elastic electrode along with the change of the tensile rate.

The method for preparing the flexible elastic electrode through selective laser patterning is applied to the field of wearable devices.

Compared with the prior art, the invention has the following advantages:

1. according to the invention, the silver nanowires are completely embedded into the surface of the thermoplastic polyurethane elastic rubber, and the prepared flexible elastic electronic device has the advantages of friction resistance, easiness in long-term storage, bending resistance and the like;

2. the flexible elastic electrode prepared by the invention can be used for preparing high electrical property stability by patterning laser treatment, and the resistance change rate of the flexible elastic electrode is only 1% of that of a common linear conductive electrode under the condition of high stretching.

Drawings

The invention will be further described with reference to the following examples with reference to the accompanying drawings.

FIG. 1 Scanning Electron Microscope (SEM) images of silver nanowires;

FIG. 2 is a Scanning Electron Microscope (SEM) image of the surface of a flexible electrode; wherein a is before stretching, and b is after stretching;

FIG. 3 is a two-dimensional structure silver nanowire electrode prepared based on selective laser processing;

FIG. 4 shows the relationship between the tensile strength and resistance value variation of a common silver nanowire electrode and a laser-processed structural electrode;

Detailed Description

The present invention will be further described with reference to the following examples. It is to be understood that the following examples are intended to illustrate, but not to limit the scope of the present invention, and that various changes and/or modifications in form may be made without departing from the scope of the present invention.

Example 1: synthesis of silver nano-wire by polyol method

1) After 0.2g of polyvinylpyrrolidone was dissolved in 25ml of Ethylene Glycol (EG) using a brown reagent bottle at room temperature, it was stirred using a magnetic stirring heating stage until completely dissolved to form a uniform and stable solution. After the solution was cooled to room temperature, 0.25g of silver nitrate powder was added, and stirred at room temperature until completely dissolved, and finally 3.5g of 600. mu.M ethylene glycol solution of ferric chloride was added and stirred on a hot stage for 1 to 2 minutes to obtain a solution before reaction.

2) After the three-necked flask was placed in an oil bath and preheated at a certain temperature, the solution was transferred to the three-necked flask and reacted at 130 ℃ for 12 hours. The reaction is kept in a dark condition during the reaction. And taking out the solution after the solution completely reacts and cooling the solution to room temperature.

3) Dissolving the mixed solution in a three-neck flask with ethanol at a ratio of 1: 5, shaking uniformly, transferring to a centrifuge tube, and centrifuging with a table centrifuge at 1000rpm for 10 min; after centrifugation, the supernatant was removed leaving a bottom sediment, ethanol was added in an additional 5 volumes, and after complete shaking, centrifugation was carried out under the same conditions. And finally, pouring out the supernatant after centrifugation, adding a certain volume of water, and shaking uniformly to obtain a clean aqueous solution of the silver nanowires.

Example 2: preparation of silver nanowire flexible elastic electrode

1) The silver nanowires were diluted to a 1mg/ml silver nanowire solution and 304 steel discs were additionally attached to the bottom of a 12 x 12cm square container. And adding 172ml of silver nanowire solution into the container, horizontally standing for 3h, transferring the silver nanowire solution into a blast drying oven in a horizontal state, and drying until the silver nanowire solution is completely dried to obtain the silver nanowire film with uniform distribution.

2) Thermoplastic polyurethane elastic rubber and carbon black are dissolved in tetrahydrofuran, heated to 80 ℃ and stirred uniformly to prepare a tetrahydrofuran solution with the thermoplastic polyurethane elastic rubber concentration of 10 wt% and the carbon black concentration of 0.5%. 30ml of this solution was poured onto a 10cm diameter glass and dried at ambient temperature to form a black elastic rubber substrate. And preparing 10 wt% thermoplastic polyurethane elastic rubber tetrahydrofuran solution in the same way.

3) And (3) spinning the tetrahydrofuran solution prepared in the step (2) on the silver nanowire film at the rotating speed of 1000rpm/s for 60s to form a layer of thermoplastic polyurethane elastic rubber covered on the silver nanowire film. And (3) carrying out hot pressing on the silver nanowire film and the black elastic rubber substrate in a hot press, wherein the specific parameters are 180 ℃, 2000Pa and 10min, so that the silver nanowires can be completely transferred onto the black elastic rubber.

4) The black elastic rubber is placed on a laser engraving machine for processing, and the specific parameters are as follows: the sample was laser treated at a cutting speed of 1000mm/s, 10% power, 100Hz frequency, and a finish delay of 30000ms, resulting in a highly electrically stable electrode.

The silver nanowires prepared by the method for synthesizing the polyhydric alcohol are shown in figure 1.

The conductive electrode after the hot-pressing transfer is utilized, as shown in fig. 2, the silver nanowires are completely coated on the thermoplastic polyurethane elastic rubber, are not easy to fall off, and the thermoplastic polyurethane elastic rubber is partially cracked after being stretched, but the structure of the thermoplastic polyurethane elastic rubber is maintained.

The picture of the flexible and elastic stretchable electrode after laser processing and patterning is shown in fig. 3, and it can be seen that the processing precision of the laser processing is high, and the material keeps a complete structure after the laser processing.

The flexible and elastic stretchable electrode of the invention improves the electrical stability after laser processing patterning, as shown in fig. 4, the resistance value of the patterned electrode in the stretching process is kept at a lower value, only about 1% of the resistance value of the linear conductive electrode is changed, and the stability of the electrical property is excellent.

Claims

1. A method for preparing a flexible and elastic electrode by selective laser patterning is characterized by comprising the following steps:

(4) and processing the silver nanowire electrode by using infrared laser processing, and removing useless parts to obtain the patterned two-dimensional hollow silver nanowire electrode.

2. A method of selective laser patterning a flexible electrode according to claim 1, wherein: the method for preparing the silver nanowires by adopting the polyol method comprises the following steps: under the condition of shade, polyvinylpyrrolidone, silver nitrate and ferric chloride are sequentially dissolved in ethylene glycol, the mixture is transferred to 130 ℃ to be kept stand for reaction for 12 hours, then the mixture is cooled to room temperature, and the mixture is centrifugally cleaned for a plurality of times by alcohol to obtain the silver nanowires.

3. A method of selective laser patterning a flexible electrode according to claim 2, wherein: the weight average molecular weight of the polyvinylpyrrolidone is 360000.

4. A method of selective laser patterning a flexible electrode according to claim 1, wherein: the wavelength of the infrared laser is 1064 nm.

5. An electrode prepared by the method for preparing the flexible elastic electrode by selective laser patterning according to any one of claims 1 to 4, wherein: the thickness of the thermoplastic polyurethane elastic rubber is 0.5-1.5 mm, the silver nanowires are completely embedded into the thermoplastic polyurethane elastic rubber, the diameter of the silver nanowires is 50-150 nm, the length of the silver nanowires is 60-120 mu m, and the resistance change rate of the silver nanowires is only 1% relative to that of the linear flexible elastic electrode along with the change of the tensile rate.

6. Use of a method of selective laser patterning of a flexible and elastic electrode according to any of claims 1 to 4 in the field of wearable devices.