The new composite material consists of two substances: an adhesive material (blue) and an elastic LCE (yellow). The LCE is made up of azobenzene molecules that bend – thus bending the whole material – when they are irradiated with UV light. This bending causes the adhesive microstructures to detach from an object. Image: Emre Kizilkan and Jan Strueben.The natural adhesive materials used by geckos and other animals to walk upside down on the ceiling are always strongly adhesive without employing glues or leaving residues. Inspired by these natural adhesive materials, scientists at Kiel University in Germany have now succeeded in developing a synthetic version that can be controlled remotely using ultraviolet (UV) light.
Their light-controlled adhesive material could be used to transport microscale objects and could find applications in the fields of robotics, industry and medical technology. The Kiel-based research team's findings are published in a paper in Science Robotics.
"The advantage of light is that it can be used very precisely. It is reversible, so it can be switched on and off again, and very quickly," says Emre Kizilkan from the Functional Morphology and Biomechanics research group at Kiel University’s Zoological Institute.
This work began with an elastic porous material known as a liquid crystal elastomer (LCE), which is made up of azobenzene molecules that bend when illuminated with UV light. Kizilkan and his colleagues noticed that the more porous the material, the more it bent, and decided to make use of this discovery. "Due to their structures, porous materials can be very easily incorporated with other materials," explains Kizilkan. "So we tested what happens when we combined the elastic material, which reacts well to light, with a bioinspired material that has good adhesive properties."
The result is an intelligent, adhesive composite material, comprising a polymer-based adhesive layer and an LCE, that can be controlled with light. The surface of the adhesive layer is patterned with mushroom-shaped adhesive microstructures, similar to those found on the feet of some species of beetle. These microstructures will naturally stick to the surface of flat or three-dimensional objects such as microscope slides or glass spheres, allowing them to be picked up. To release the objects, the composite material is simply illuminated with UV light, causing it to bend and gently detach itself.
"We were able to show that our new material can be used to transport objects. Moreover, we demonstrated that the transport can be controlled very precisely with light – on a micro-level," explains Kizilkan.
"We use light as a remote control, so to say. Our bioinspired adhesive material doesn't leave any residues on the objects, either," adds Stanislav Gorb, who leads the Functional Morphology and Biomechanics research group.
The research group's discovery could prove particularly useful for building sensitive sensors or computer chips, which need to be manufactured in an environment that is protected from external influences and impurities. "In the long term, we would like to use the new material to develop micro-robots which can be controlled by light to move forwards and climb walls," says Gorb.
This story is adapted from material from Kiel University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.