The sensor, which can be worn on the skin or implanted inside the body, can measure both physical movement and electrical signals. It is made from soft, stretchable materials that mimic human skin and is designed to work for long periods of time without losing performance.

“Usually, when you try to combine different materials to get the best of both worlds, you have to make a tradeoff,” said Huanyu “Larry” Cheng, James L. Henderson, Jr. Memorial Associate Professor of Engineering Science and Mechanics at Penn State and lead co-author of the study in Advanced Functional Materials. “With this design, we were able to avoid that. We achieved low contact resistance with the skin, high sensitivity, stretchability and long-term stability, all in one device.”

Most sensors rely only on electrical conduction, which moves electrons through metal or carbon materials. This dual-modal sensor combines two different types of conductivity: electrical and ionic conduction, which moves charged atoms through a liquid. That mix helps it interface more naturally with the body, especially for internal use where the environment is wet and ion-rich, according to Cheng.