A controllable material was developed that can transform into complex, pre-programmed shapes via light and temperature stimuli, allowing it to morph into a different shape before fully reverting to its original form. The ability to form materials that can repeatedly oscillate back and forth between two independent shapes by exposing them to light could enable applications in additive manufacturing, robotics, and biomaterials.
Previous efforts used a variety of physical mechanisms to alter an object's size, shape, or texture with programmable stimuli; however, such materials have historically been limited in size or extent and the object state changes have proven difficult to fully reverse.
The new material achieves readily programmable two-way transformations on a macroscopic level by using liquid crystal elastomers (LCEs), the same technology underlying modern television displays. The unique molecular arrangement of LCEs makes them susceptible to dynamic change via heat and light.
A light-activated trigger was installed on LCE networks that can set a desired molecular alignment in advance by exposing the object to particular wavelengths of light. The trigger then remains inactive until exposed to the corresponding heat stimuli; for example, a hand-folded origami swan programmed in this fashion will remain folded at room temperature. When heated to 200 °F, however, the swan relaxes into a flat sheet. Later, as it cools back to room temperature, it will gradually regain its pre-programmed swan shape.
The ability to change and then change back gives this new material a wide range of possible applications, especially for future biomedical devices that could become more flexible and adaptable than ever before.