Electronic components that can be elongated or twisted (known as "stretchable" electronics) could soon be used to power electronic gadgets, the onboard systems of vehicles, medical devices, and other products. And a 3-D printing-like approach to manufacturing may help make stretchable electronics more prevalent, say researchers at Missouri University of Science and Technology.

Missouri S&T researchers are assessing the emerging field of stretchable electronics, focusing on a type of conductor that can be built on or set into the surface of an elastomer. These conductors could one day replace the rigid, brittle circuit board that powers many of today's electronic devices. They could be used, for example, as wearable sensors that adhere to the skin to monitor heart rate or brain activity, as sensors in clothing, or as thin solar panels that could be plastered onto curved surfaces.

Key to the future of stretchable electronics is the surface or substrate. Elastomer is a flexible material with high elasticity, which means that it can be bent, stretched, buckled, and twisted repeatedly with little impact on its performance.

One challenge facing this class of stretchable electronics involves "overcoming mismatches" between the flexible elastomer base and more brittle electronic conductors, explain the researchers. Unique designs and stretching mechanics have been proposed to harmonize the mismatches and integrate materials with widely different properties as one unique system.

Additive manufacturing may help resolve this issue. It allows manufacturers to create 3-D objects, layer by layer, much like 3-D printing but with metals, ceramics, or other materials. The researchers suggest that it could be used to "print" very thin layers of highly conductive materials onto an elastomer surface.

"With the development of additive manufacturing, direct writing techniques are showing up as an alternative to the traditional subtractive patterning methods," say the researchers, who are testing an approach called "direct aerosol printing." The process involves spraying a conductive material and integrating with a stretchable substrate to develop sensors that can be placed on skin. "With the increase of complexity and resolution of devices, higher requirements for patterning techniques are expected," they say. "Direct printing, as an additive manufacturing method, would satisfy such requirements and offer low cost and high speed in both prototyping and manufacturing. It might be a solution for cost-effective and scalable fabrication of stretchable electronics."