A 3D-printed, multimaterial, shape-memory mini-gripper, consisting of shape-memory hinges and adaptive touching tips, grasps a cap screw. (Qi Ge)

Engineers are using light to print three-dimensional structures that “remember” their original shapes. The process of 3D printing shape-memory materials can also be thought of as 4D printing, as the structures are designed to change over the fourth dimension — time.

The material can bounce back to its original printed form within a specific temperature range — in this case, between 40 and 180 C. To demonstrate a simple application for the shape-memory structures, the team printed a small, rubbery, claw-like gripper. They attached a thin handle to the base of the gripper, then stretched the gripper’s claws open. When they cranked the temperature of the surrounding air to at least 40 C, the gripper closed around whatever the engineers placed beneath it.