With a wide range of healthcare, energy, and military applications, stretchable electronics are valued 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. This sheds light on why Smooth-On Ecoflex, a substance most commercially used to create molds, movie masks, and prosthetics, is the most prominent silicone elastomer found in research.

While handling a sample of the material, Professor Matt Pharr and graduate student Seunghyun Lee, recently discovered a new type of fracture they call sideways cracking. This phenomenon is when a fracture branches from a crack tip and extends perpendicular to the original tear.

“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. This conceptualization is critical to innovation and advancement in stretchable electronics.

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