A new flexible, electricity-conducting material mimics the adaptive strength of cornstarch slurries, offering promising applications in wearable and medical sensor technology.
Accidents happen every day, and if you drop your smartwatch, or it gets hit really hard, the device probably won’t work anymore. But now, researchers report on a soft, flexible material with “adaptive durability,” meaning it gets stronger when hit or stretched. The material also conducts electricity, making it ideal for the next generation of wearables or personalized medical sensors.
The researchers presented their results today at the spring meeting of the American Chemical Society (ACS). ACS Spring 2024 is a hybrid meeting being held virtually and in person March 17-21; it features nearly 12,000 presentations on a range of science topics.
Inspiration From Cooking Ingredients
Inspiration for the new material came from a mixture commonly used in cooking — a cornstarch slurry.
“When I stir cornstarch and water slowly, the spoon moves easily,” explains Yue (Jessica) Wang, a materials scientist and the project’s principal investigator. “But if I lift the spoon out and then stab the mixture, the spoon doesn’t go back in. It’s like stabbing a hard surface.” This slurry, which helps thicken stews and sauces, has adaptive durability, shifting from malleable to strong, depending on the force applied. Wang’s team set out to mimic this property in a solid conductive material.
Postdoctoral researcher Di Wu talks about a polymer material he is helping to develop that is flexible and becomes tougher, depending on how the body moves.
Development of the Material
Many materials, such as metals, that conduct electricity are hard, stiff, or brittle. But researchers have developed ways to make soft and bendable versions using conjugated polymers — long, spaghetti-like molecules that are conductive. Yet, most flexible polymers break apart if they undergo repeated, rapid or large impacts. So, Wang’s team at the University of California, Merced, set out to select the right combination of conjugated polymers to create a durable material that would mimic the adaptive behavior of cornstarch particles in water.
Initially, the researchers made an aqueous solution of four polymers: long, spaghetti-like poly(2-acrylamido-2-methylpropanesulfonic