3D printed photoresponsive structures offer remotely controlled actuators

The international team’s findings are detailed in Polymers.

“We knew that you could 3D print hydrogels that would contract when heated,” said Joe Tracy, co-corresponding author and Professor of materials science and engineering at North Carolina State University. “And we knew that you could incorporate gold nanorods into hydrogels that would make them photoresponsive, meaning that they would contract in a reversible manner when exposed to light.

“We wanted to find a way to incorporate gold nanorods into hydrogels that would allow us to 3D print photoresponsive structures.”

Hydrogels - polymer networks that contain water – are present in everyday products including contact lenses and the absorbent material in nappies. Key to the team’s success was a printed solution containing gold nanorods and the items needed to create a hydrogel.

“And when this printed solution is exposed to light, the polymers in the solution form a cross-linked molecular structure,” said Julian Thiele, co-corresponding author of the paper and chair of organic chemistry at Otto von Guericke University Magdeburg, Germany. “This turns the solution into a hydrogel, with the trapped gold nanorods distributed throughout the material.”