Human skin inspires flexible fracture control method

Engineers at Binghamton University in New York state have created a way to control fracturing in flexible materials, based on the topography of human skin.

human skin
Guy German is an associate professor of biomedical engineering at Binghamton University (Binghamton University)

Described in Scientific Reports, the research could help extend the life of some biomedical devices by directing cracks away from crucial components. The team engineered a series of single and dual-layer membranes from silicone-based polydimethylsiloxane (PDMS), an inert, nontoxic material widely used in biomedical research. The layers were embedded with tiny channels meant to guide any cracks that form. If the membranes were part of a biomedical device, they could control how any cracks developed, potentially avoiding damage to critical areas of flexible electronics, for example, and extending the device’s functional lifespan.

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"Even though this membrane looks and feels exactly like a normal, boring membrane, you stretch it and you can get cracks to deviate at 45-degree angles away from where it ordinarily would have cracked,” said research lead Guy German, Associate Professor of Biomedical Engineering at Binghamton.

"In this relatively new field of hyperelastic materials - materials that can really stretch - there's been a lot of work, but not in the area of fracture control. Fracture control has only been explored in more brittle materials."

From his research on human skin, German realised that the outermost layer - known as the stratum corneum - exhibits a network of v-shaped topographical microchannels that appear to be capable of guiding fractures to the skin. This latest study sought to recreate this effect in nonbiological materials. According to the researchers, previous attempts to direct microcracks have used more solid means, such as copper films around the most sensitive parts of flexible electronics components. Silicon-based PDMS is more flexible, and has the advantage of being commonly used in biomedical applications.

"We do it without using any exotic material," said Binghamton PhD student Christopher Maiorana, who led the work with German. "We're not inventing some new metal or ceramic. We're using rubber or modifying normal glass to do these things. We've taken this really basic idea and made it functional."