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New scientific findings have the potential to lead to greater stretchability and tear-resistance in stretchable electronics materials replacing rigid circuit boards. This field of research is designed for building electronic circuits by depositing stretchable electronic devices and circuits onto stretchable substrates or embed them completely in a stretchable material.

With a wide range of healthcare, energy and military applications, stretchable electronics are revered for their ability to be compressed, twisted and conformed to uneven surfaces without losing functionality. By using the elasticity of polymers such as silicone, these emerging technologies are made to move in ways that mimic skin.

In the military sphere, flexible electronics are used in advanced electronics applications, such as WiFi portable devices and military antennas for communication and surveillance, or in wearable devices. Stretchable electronic devices can be used on prosthetic limbs. Electronics could be woven right into fabric (just like elastic is today) to make smart garments for athletic teams, military uniforms, etc. Smart patches can supply athletes or soldiers with more precise physical conditioning, training and injury prevention.

Smooth-On Ecoflex, a substance most commercially used to create molds and movie masks and prosthetics, is the most prominent silicone elastomer (a rubber-like substance) found in research. While handling a sample of the material, Dr. Matt Pharr, assistant professor in the J. Mike Walker ’66 Department of Mechanical Engineering at Texas A&M University, and graduate student Seunghyun Lee, recently discovered a new type of fracture.

The research deals with sideways cracking, when a fracture branches from a crack tip and extends perpendicular to the original tear.

The team’s findings not only provide a fresh, new perspective on the formation of fractures and how to increase stretchability in elastomers, but also lay the foundation for more tear- and fracture-resistant materials.

“Initially this material is isotopic, meaning it has the same properties in all directions. But once you start to stretch it, you cause some microstructural changes in the material that makes it anisotropic—different properties in all different directions,” said Pharr. “Usually, when people think about fracture of a given material, they’re not thinking about fracture resistance being different based on direction.”

By investigating how to reverse engineer microstructures that lead to sideways cracking, researchers can harness the benefits associated with it and develop application methods to materials that do not normally exhibit such fractures. This would lead to better fracture resistance in the very thin layers of elastomers used in stretchable electronics, as well as greater stretchability—both of which are key to the advancement and future usability of such technologies, according to