Recently, we've seen a bunch of new "smart" materials being developed that can heal themselves, spring back into their original shape when deformed, or change transparency when stretched. But while most of these have only one such function, researchers at Washington State University have created a material that can both change shape when exposed to heat or light, and assemble and disassemble itself.
As seen with previous projects, smart materials have a wide variety of potential applications. Self healing substances can repair cracks or breaks automatically without weakening over time, and mechanochromic materials could lead to windows that switch between transparent and opaque when a mild mechanical force is applied. But according to the WSU researchers, such materials haven't yet entered mainstream use because they're difficult to make, often only perform one smart function, and their abilities aren't easily repeatable.
The team's goal was to design a material with properties that overcome those three hurdles. They began with liquid crystalline networks (LCNs), which are thermally responsive and can change their shape back and forth, according to the temperature applied. The LCNs were then imbued with azobenzene, which responds to light by bending or reorienting itself, depending on the wavelength. And finally, adding dynamic chemical bonds increased the material's reprocessability.
"We knew these different technologies worked independently and tried to combine them in a way that would be compatible,'' said Michael Kessler, the professor leading the team.
The researchers are able to program the material at a molecular level, to determine the responses it has to different stimuli. As demonstrated in the video below, the material will bend when exposed to blue light, unfold when hit with UV light, and reassemble itself when heated up.
The research results appeared in ACS Applied Materials and Interfaces.