What is the use of bionic smart film?

Biomimetic deformation of PVDF/PVA bilayer membrane

This kind of film can last for a long time. If it uses long-lasting motion characteristics to generate electricity, it can greatly expand the application of related technologies in self-generating wearable and implantable electronic devices. The wearable and implantable industries have a market of over 100 billion yuan. scale.

After the double-layered film of the petal shape absorbs the acetone molecules, the petals dance like a radish flower shaken in the wind. “This is a biomimetic deformation of a polyvinylidene fluoride/polyvinyl alcohol double-layer film.” Du Xuemin, an associate researcher at the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, told the Journal of the Chinese Academy of Sciences.

Recently, Zhang Lidong, a doctoral supervisor of the School of Chemistry of East China Normal University, cooperated with Du Xuemin's research group to study the biodegradation of bio-structures by using polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) polymer materials. New intelligent flexible double-layer polymer film material.

An accidental encounter

In the first half of 2016, Zhang Lidong’s identity was still a postdoctoral fellow at New York University’s Abu Dhabi campus. It was a coincidence that he and Du Xuemin both attended an international conference in Singapore. Both of them gave academic reports at the meeting and were serious. I listened to their reports.

"We are small peers, and the exchanges are particularly smooth. We are also very interested in each other's research." Du Xuemin was invited to come to Shenzhen Advanced Institute to guide exchanges in the second half of 2016 after learning that Zhang Lidong was preparing to return to China. It is also officially opened around polymer film materials.

As human understanding and understanding of the biological structure of nature deepens, the bionic nature technology through material and structure design is also becoming more mature, which promotes the development of stimulating response bionic materials. Zhang Lidong pointed out: "In recent years, devices based on the development of stimulating response bionic materials have been well applied in the fields of industry, medical, electronics, military and so on."

Du Xuemin said: "In the future, the application value of bionic soft materials will be even greater, especially in the flexible electronics industry, biomimetic sensors, software robots and other aspects will have broad prospects." However, there is still a simulation of the biomimetic structure of the stimulus response material. Many technical problems.

Zhang Lidong revealed that the existing theoretical analysis believes that in order to achieve high-efficiency and controllable bionic performance, in addition to the precise design of the material bionic structure, the material must not only have very good tensile and wear resistance, but also after long-term stimulation to the outside world. To maintain the desired mechanical properties, it must also have reversible stimulating response behavior. These are the basic elements for stimulating responsive biomimetic materials to achieve biomimetic performance, and are also the basic conditions for expanding their application.

Du Xuemin said: "Only a well-designed bionic structure, a deep understanding of the bionic mechanism, and optimization of the mechanical properties of the material can control the dynamic bionic process and promote the application of materials."

The research on the biomimetic performance mechanism of the flexible intelligent double-layer membrane developed by Zhang Lidong's research group coincides with the research on the biomimetic intelligent materials conducted by Du Minxue's research group.

"Untired" movement

The research team of both sides took the cheap and easy-to-obtain polymer materials as the research object. Zhang Lidong's research group proposed a two-layer membrane design concept. By simply modifying the material, a polymer double-layer membrane with self-driving properties was prepared and designed. Various flexible devices; Du Xuemin's research group based on photolithography technology, prepared a silicon template with microporous structure.

The research team used template technology to replicate the microporous biomimetic structure onto the surface of the PVDF membrane, so that the prepared PVDF/PVA bilayer film has a cyclically varying mechanical tensor in the structure, realizing the biomimetic performance of the bilayer membrane, and through external stimulation. The manipulation of the bionic behavior of the two-layer membrane is realized.

Zhang Lidong said that the bilayer membrane is extremely sensitive to the stimulation of acetone molecules, and long-term continuous orientation deformation of the bilayer membrane can be achieved by rapid absorption and release of acetone molecules. Let the inert polymer move "indifferently", which is comparable to the complex movements in nature.

The experimental process is quite interesting: when the microchannel arrangement on the surface of the PVDF membrane and the long axis of the film are maintained at 30° or 60°, the film is stimulated by acetone molecules to produce a right chiral entanglement motion. Conversely, when the microchannel alignment and the long axis of the film are maintained at -30 or -60, the film exhibits a left-handed winding deformation. When this angle is maintained at 90°, the bilayer membrane absorbs acetone molecules to produce a directional bending deformation toward the PVA layer.

So there is a wonderful phenomenon at the beginning of this article: the double-layered membrane in the shape of a petal produces a deformation movement like a radish flower.

Du Xuemin told the reporter: "When the acetone concentration in the environment is too high, the sensor spontaneously transforms into the circuit, and the electric light is on; when the acetone concentration is gradually reduced, the sensor returns to the original shape and the circuit is turned off, and the electric light is off. The change of the electric lamp can be used to inform The concentration of acetone vapor in the environment."

Therefore, the thin film sensor designed by using this bionic motion can continuously monitor the concentration of acetone in the environment for a long time, thereby greatly expanding the application potential of the material. At the same time, the double-layer membrane can maintain a continuous and reversible response to the external acetone vapor stimulation for several hours, which lays a solid foundation for expanding the application of the stimuli-responsive material in the fields of energy, flexible sensors, artificial muscles, and soft body robots.

Small film use

Ordinary polymeric films often want to have fast-responding, "indefatigable" motion characteristics, and need to sacrifice the mechanical properties of the material, such as the Young's modulus of the sacrificial material (the physical quantity that describes the resistance of the solid material to deformation), wear resistance, corrosion resistance And other mechanical properties. These common polymer films are now widely used in medical, electronic and everyday life.

After the biomimetic smart film developed by Zhang Lidong and Du Xuemin's team is stimulated, once the stimulus source is removed, the film can quickly restore its original mechanical properties, thus achieving "indefatigable" sports characteristics. In addition, the thin film design using this "indefatigable" characteristic becomes a flexible sensor, which can be recycled many times for a long time, which greatly saves material cost.

Du Xuemin told reporters: "In the future, we can design this film as a sensor sensitive only to the stimulation of acetone molecules, for real-time monitoring of acetone concentration in the chemical industry, and to prevent acetone damage to humans. We can combine this film with the actual needs of energy harvesting, artificial muscles, flexible robots, etc., and personalize the design for specific products in different fields."

He uses energy harvesting as an example. This film can last for a long time. If you use long-lasting motion characteristics to generate electricity, you can greatly expand the application of related technologies in self-generating wearable and implantable electronic devices. Wearable and implantable. The industry has a market scale of over 100 billion yuan.