Silk "artificial muscles" make smart fabrics more comfortable

Silk is widely used and has excellent wearing comfort. The artificial muscle production process of silk is in line with current industrial procedures, without chemical modification and additional additives, which opens up more possibilities in industrial applications.

It is changing seasons. When you are running, wearing short sleeves is too cold, wearing long sleeves is too hot. If there is a kind of clothing, it can automatically adjust the length according to body temperature and humidity. When the body sweats, the long sleeves become short sleeves. After sweating and then returning to the original, how amazing it would be. Today, this cool smart fabric is expected to become a reality.

Recently, the State Key Laboratory of Medicinal Chemistry, Biology, Nankai University, Professor Liu Feng compliance research team led won a green pure silk "artificial muscles" that can not only perceive the humidity surface of the skin, it can also be free to expand. In addition to being used in smart fabrics, this new "artificial muscle" will have much to offer in the development of soft robots.

Related research papers were published in the international authoritative journal “Advanced Functional Materials” in the field of materials.

Perceived humidity, automatic expansion and contraction

At present, people have made good progress in the development of smart textiles. The manufactured textiles have many new functions such as energy storage, self-cleaning, color change, temperature and humidity adjustment. However, related research on smart fabrics is not satisfactory.

“If textiles are responsive to humidity, water and heat management can be achieved by adjusting macroscopic shape or porosity, which will provide more comfort for people.” Textiles that sense humidity have caused great interest in Liu Zunfeng, in his opinion, Such textiles not only provide more comfort for people, but also have great market value.

In this study, Liu Zunfeng team used natural silk to make a new type of "artificial muscle" fiber. The researchers did not use any chemical modification and additives. According to the principle of huge volume expansion caused by silk water absorption, through degumming, twisting, and jointing. , industrialization and other common processes such as heat setting.

Liu Zunfeng introduced to the Journal of Chinese Academy of Sciences that silk artificial muscles can sense the stimulus from the environment and respond to these stimuli by integrating functions in the fabric structure. It is possible to change the porosity or macroscopic shape by adapting to sweat, rain, humidity and temperature, resulting in rapid torsion, stretching and contraction movements to achieve moisture and heat management.

In order to achieve reversible driving without external fixation, the Liu Zunfeng team developed a torque-balanced fiber structure that achieved self-balancing by twisting and plying the twisted fibers. Liu Zunfeng also used degummed silk fiber to demonstrate the high-performance silk-twist muscle and silk-stretching muscle driven by water mist and humidity, and studied its mechanism in detail by molecular dynamics simulation.

According to reports, when exposed to water mist, the manufactured silk twisted "artificial muscle" fiber achieved a fully reversible torsional stroke of 547o mm-1, very close to the humidity-driven torsion graphene fiber (588.6o mm-1). When the relative humidity is changed from 20% to 80%, the contraction rate of the wound silk retracting muscle is 70%, which is larger than the organic solvent-driven wound CNT yarn muscle (60%), and the maximum functional force is reached. 73 J/kg.

"This excellent actuability is due to the loss of intracellular hydrogen bonds induced by silk fibers and the associated structural transformation, and is confirmed by molecular dynamics simulation, X-ray diffraction and macroscopic characterization." Liu Zunfeng said. Through molecular dynamics simulation, it was found that water absorption leads to the loss of hydrogen bonds in silk protein, which leads to the change of silk protein structure and provides the basic mechanism of silk muscle drive.

Application opens up more possibilities

Combining traditional textile technology with fiber-based artificial muscles is one of the ways to achieve intelligent textile functions. Although fiber materials such as carbon nanotubes, graphene, polyethylene, and nylon have been reported for the preparation of artificial muscle fibers, these materials are difficult to use as smart textiles for regulating humidity and body temperature, mainly because these materials are expensive to manufacture and manufacturing processes. Disadvantages such as complexity and poor comfort are difficult to commercialize.

As a kind of natural textile fiber, silk is a combination of soft skin-friendly, moisture-absorbing and breathable, and has been favored by people and favored by the textile industry. "Silk has been used as clothing for thousands of years. It is comfortable to wear and is an important textile material." According to research, according to research, it has not been made of natural fibers to make artificial muscles and used in the field of smart fabrics. Report.

Due to the wide range of silk applications and excellent wear comfort, the silk artificial muscle production process is in line with current industrial processes, without chemical modification and additional additives, it will open up more possibilities in industrial applications, such as smart textiles and Flexible robot.

In this regard, the researchers showed a moisture-sensitive smart fabric woven from the same-arm silk stretch muscle. The warp direction of the fabric sleeve is the same-arm silk stretch muscle, and the weft direction is untwisted. Silk fiber. When the humidity increases due to sweat or moisture, the sleeve of the smart fabric shrinks (45%) in the warp (vertical) direction and then returns to its original length when the humidity drops. For example, in the process of exercise, the body is automatically shortened into short-sleeved shorts in the case of sweating, which is convenient for excretion of heat and perspiration; when the body is dry, the clothes become long to achieve warmth.

“Because silk fiber raw materials are very rich, biocompatible, and cost-effective, silk artificial muscles will open up more possibilities for applications such as smart textiles and software robots,” said Liu Zunfeng.

Related paper information: DOI: 10.1002/adfm.201808241