Curiosity inspires light-controlled materials

AUTUM C. PYLANT, NEWS EDITOR autum.pylant@photonics.com

Finnish researchers at Tampere University of Technology (TUT) have achieved a breakthrough in reconfiguring light-controlled materials, while also gaining a greater degree of control over their movements. The researchers changed the shape, length, and/or thickness of the materials, using light as the stimulus.

While potential applications range from microrobotics to tunable optical materials, associate professor Arri Priimägi, who leads the Smart Photonic Materials (SPM) group at TUT, told Photonics Media that the research — published in Nature Communications (https://rdcu.be/8LfK) — is not technology driven per se.

TUT researchers employ UV light to program the shape the material adopts, and then elicit the different types of movements by shining red light on it. Courtesy of the Smart Photonic Materials group, Tampere University of Technology.

“We are inspired rather by scientific curiosity of what light-controllable materials are capable of. Using the words of Einstein: Curiosity has its own reason for existing,” Priimägi said. “This being said, we do believe that our materials have many prospects also in applied research.”

Obvious uses of such a technology include optics and photonics applications, but Priimägi thinks light-responsive and light-actuable materials have a lot to offer in biomaterials science as well.

“While continuing with extending our understanding on what our materials can do and making them autonomous, programmable, and reconfigurable, we will keep our eyes open on spotting the niche applications where they can be the game changers,” he said.

Light-controlled materials typically exhibit only one predetermined state of deformation under a specific stimulus. The material may bend or twist, but a single sample does not do both. The TUT method enables the employment of UV light to program the shape the material adopts and then elicit the different types of movements by shining red light onto the material.

“Our concept for developing this material is actually quite simple. It is based on a combination of two well-known light-induced control mechanisms. No one has ever tried this before, despite, or maybe because of, the simplicity of the underlying idea,” Priimägi said. “Our results are a good example of how novel results can be achieved by combining something known in a new way.”

Light-controlled polymers are a new approach to the field of soft robotics. Light as a controlled stimulus can be applied in a noncontact manner to change properties of a material. It is noninvasive, and its wavelength, intensity, and polarization can all be controlled. This light can also be applied to the target with very high spatial-temporal resolution, allowing for precise, controlled, and reversible manipulation of materials.

“The material properties that can be changed with light are [multitudinous]; for instance, color, refractive index, surface topography, toughness, and — as used in our present work — shape,” Priimägi said.

Because many properties can be controlled with light, there are numerous potential photonics and optics applications for light-responsive materials, such as controlling color and refractive index changes and topography control in diffractive optics. For biomaterials science applications, changes in topography, Young’s modulus, and light-induced creation of strains onto cell culture substrates can be implemented and studied. And light-induced stresses and shape changes can have a huge impact on the field of robotics. For soft robotics, the TUT researchers’ main goal is to develop photoactuators that are smart, autonomous, self-regulating, and multiresponsive.

While the SPM group may credit scientific curiosity for their findings, there’s no doubt that light-controlled materials could very well shape future technology in a variety of fields.