A new method of 3D printing with liquid elastomer could bring flexible electronics a step closer to reality.

Researchers and electronics companies have been working on developments in this field for years in an attempt to develop bendable cell phones and screens that can be rolled up. Thin-film advancements have led to a handful of pliant items, such as bendable transistors and stretchable circuits that make building flexible electronics easier. However, without an entire array of pliable components, a completely flexible device cannot be produced.

The elastomer-based lattice structure has great stretchability. Image credit: Qiming Wang. Traditional 3D printing is typically associated with rigid plastic structures made of polylactic acid or acrylonitrile butadiene styrene, created one thin layer at a time. While a small selection of rubber-like materials has been developed for 3D printers, they do not provide adequate pliability to build flexible electronics.

Qiming Wang, assistant professor at the University of Southern California's Viterbi School of Engineering, has addressed this by using a new fabrication method. He begins by printing a 3D scaffold of plastic material but, instead of solid beams, he creates hollow channels that are then filled with liquid elastomer. Over a period of several hours, sitting at room temperature, the liquid solidifies. Finally, the plastic, which is water dissolvable, is removed, leaving a freestanding, 3D-printed rubber.

According to Wang, the elastomer can stretch almost twice as much as other 3D-printed materials. In addition to flexible electronics, he says this property could be useful in fields such as robotics that are turning to 3D printing for low-cost part manufacturing.

“In robotics, you have lots of joints, so you need a lot of flexibility to rotate or bend,” Wang says. “We imagine our soft-material 3D printing can do that here. We can bridge rigid structures and do large-angle rotation, large-angle bending and stretching.”

The material also has considerable shock-absorption qualities, outperforming conventional elastomer foams used in cushioning during impact-loading tests, Wang says.