Bionic smart film comes with "tireless" sports characteristics

【Chinese Packaging Network News】 Petal-shaped double-layer film absorbs acetone molecules, the petals dance, like a radish shake in the wind. “This is a biomimetic deformation of a polyvinylidene fluoride/polyvinyl alcohol double-layer film.” Du Xuemin, a research associate at the Institute of Advanced Technology of Shenzhen, Chinese Academy of Sciences, told the journal “China Science Journal”.

Recently, Zhang Lidong, a doctoral tutor of the East China Normal University’s School of Chemistry, teamed up with Du Xuemin’s research group to study polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) polymer materials and simulate the derivation of biological structures. A new type of smart flexible double polymer film material.

Biomimetic Deformation of PVDF/PVA Bilayer Films The film can last a long time. If you use permanent motion to generate electricity, you 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.

An accidental encounter

In the first half of 2016, Zhang Lidong’s identity was still a postdoctoral scholar at New York University’s Abu Da School of Scores. He and Du Xuemin both participated in an international conference held in Singapore. They both made academic presentations at the conference and were serious. Listened to their respective reports.

“We are small peers, and the exchanges at the meeting were particularly smooth. We are also very interested in the research of each other.” After learning that Zhang Lidong is ready to return to China, Du Xuemin will be able to invite him to come to the Shenzhen Advanced Institute for guidance and exchange in the second half of 2016. Also officially opened around the polymer film material.

With the deepening of human understanding and understanding of the natural world's biological structure, bionic nature technology has also matured through the design of materials and structures, which has stimulated the development of stimuli-responsive biomimetic materials. Zhang Lidong pointed out: "In recent years, devices based on stimulus response biomimetic materials have been well applied in industrial, medical, electronics, and military fields."

Du Xuemin said: "In the future, the value of bionic soft materials will be even greater, especially in the flexible electronics industry, bionic sensors, software robots, etc." However, there are still simulations on the bionic structure of stimulus-responsive materials. Many technical problems.

Zhang Lidong revealed that the existing theoretical analysis believes that in order to achieve efficient and controllable bionic performance, in addition to the precise design of the material's bionic structure, the material must not only have very good tensile wear resistance, but also have a The ability to maintain optimal mechanical properties must also have reversible stimuli-responsive behaviors. These are the basic elements of stimuli-responsive biomimetic materials to achieve biomimetic performance, as well as basic conditions for expanding their applications.

Du Xuemin said: "Only by designing a reasonable bionic structure, understanding the mechanism of bionics, and optimizing the mechanical properties of materials can we control the dynamic bionic process and promote the application of materials."

The research on the bionic performance mechanism of the flexible intelligent double-layer film carried out by Zhang Lidong's research group coincides with the study of bionic intelligent materials carried out by the Du Minxue group.

"Indefatigable" movement

The scientific research team of both sides takes low-cost and readily available polymer materials as the research object. Zhang Lidong's research team proposed the concept of double-layer film design. By simply modifying the material, a polymer double-layer film with self-driven performance was prepared and designed. A variety of flexible devices; Du Xuemin's research group based on photolithography technology, prepared a silicon template with a micro-channel structure.

The research team used the template technology to copy the micro-channel biomimetic structure to the PVDF membrane surface, making the PVDF/PVA bilayer membranes have a periodic mechanical tensor in the structure, achieving the biomimetic performance of the bilayer membrane, and through external stimuli. The manipulation of the bionic behavior of the double-layer membrane was realized.

Zhang Lidong said that the two-layer membrane is extremely sensitive to the acetone molecule stimuli, and through the rapid absorption and release of acetone molecules, it is possible to achieve long-term continuous directional deformation of the bilayer membrane. Let inert polymers move "tirelessly," comparable to the complex movements of nature.

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

So there is a wonderful phenomenon in this article: The petal-shaped double film produces a deformation movement like a radish flower.

Du Xuemin told reporters: “When the acetone concentration in the environment is too high, the sensor spontaneously turns on the circuit and the light is on. When the acetone concentration gradually decreases, the sensor returns to its original shape and disconnects the circuit. The light is off. Using the change of the light, you can tell The level of acetone vapor in the environment."

Therefore, thin-film sensors designed with this biomimetic motion can continuously monitor the concentration of acetone in the environment for a long time, which greatly expands 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 a few hours, which lays a solid foundation for the expansion of stimulus response materials in the fields of energy, flexible sensors, artificial muscles, and soft body robots.

Small film use large

Ordinary polymeric films tend to have fast-response, “tireless” motion characteristics that require sacrificing the mechanical properties of the material, such as the Young's modulus of the sacrificial material (the physical quantity that describes the ability of the solid material to resist deformation), abrasion resistance, and corrosion resistance Other mechanical properties. This kind of ordinary polymer film can now be widely used in medical, electronic and daily life.

When the bionic smart film developed by Zhang Lidong and Du Xuemin's team is stimulated, once the stimulus is removed, the film can quickly restore its original mechanical properties, thus achieving “tireless” sports characteristics. In addition, the use of this "tireless" film design to become a flexible sensor, can be used repeatedly for many long-term, greatly saving the material cost.

Du Xuemin revealed to reporters: "In the future, we can design this film as a sensor that is sensitive to acetone molecules only, and it can be used in chemical companies to monitor the concentration of acetone in the environment in real time and prevent acetone from harming people. We can tailor this kind of film to practical needs in areas such as energy harvesting, artificial muscles, soft body robots, etc., and personalize design for specific products in different fields.”

He cited energy harvesting as an example. The film can last a long time. If the permanent motion characteristics are used to generate electricity, it can greatly expand the application of related technologies in self-generating wearable and implantable electronic devices, while wearable and implantable. The industry has a market size of over 100 billion yuan.