If you ever wanted to stick a square peg in a round hole, it may soon be easier than you think. Researchers at the University of Colorado (CU) Boulder are working on a new material that responds to light and heat by shifting between complex, pre-programmed shapes. Not only will it allow you to cheat at peg board tests, but it also holds promise in many applications, including manufacturing, robotics, biomedical devices, and prosthetic muscles.

Developed by a team led by Christopher Bowman, a Distinguished Professor in CU Boulder's Department of Chemical and Biological Engineering (CHBE), the new material is designed to overcome the limitation of other shape-shifting materials that change their form or texture. These have had a certain degree of success, but CU says they have been limited in terms of size or the extent that they could change or regain their original shape.

The new material overcomes this by using liquid crystal elastomers (LCEs), which are slightly cross-linked liquid crystalline polymer networks that posses both the elasticity of an elastomer and the self-organization of the liquid crystal. They are also sensitive to heat and light, allowing the CU team to program the material at the macroscopic level.

This is achieved by incorporating a light-activated trigger into LCE networks. This trigger responds to specific wavelengths of light, causing the molecular structure to rearrange itself, Once the object changes shape, the trigger locks. When reactivated by a corresponding heat stimulus, the object reverts to its original form.

One simple example provided by the team is an origami swan that turns into a flat sheet when heated to 200° F (93° C). As it cools, it returns to its swan shape.

"The ability to form materials that can repeatedly oscillate back and forth between two independent shapes by exposing them to light will open up a wide range of new applications and approaches to areas such as additive manufacturing, robotics and biomaterials," says Bowman.

The findings were published in Science Advances, and the video below shows various versions of the new material shape-shifting.