Rubbery camouflage skin exhibits smart and stretchy behaviors

Led by Cunjiang Yu, Dorothy Quiggle Career Development Associate Professor of Engineering Science and Mechanics and Biomedical Engineering, the team published its findings on June 1 in the Proceedings of the National Academy of Sciences. 

Cephalopod skin is a soft organ that can endure complex deformations, such as expanding, contracting, bending and twisting. It also possesses cognitive sense-and-respond functions that enable the skin to sense light, react and camouflage its wearer. While artificial skins with either these physical or these cognitive capabilities have existed previously, according to Yu, until now none has simultaneously exhibited both qualities -- the combination needed for advanced, artificially intelligent bioelectronic skin devices.  

"Although several artificial camouflage skin devices have been recently developed, they lack critical noncentralized neuromorphic processing and cognition capabilities, and materials with such capabilities lack robust mechanical properties," Yu said. "Our recently developed soft synaptic devices have achieved brain-inspired computing and artificial nervous systems that are sensitive to touch and light that retain these neuromorphic functions when biaxially stretched."  

To simultaneously achieve both smartness and stretchability, the researchers constructed synaptic transistors entirely from elastomeric materials. These rubbery semiconductors operate in a similar fashion to neural connections, exchanging critical messages for system-wide needs, impervious to physical changes in the system's structure. The key to creating a soft skin device with both cognitive and stretching capabilities, according to Yu, was using elastomeric rubbery materials for every component. This approach resulted in a device that can successfully exhibit and maintain neurological synaptic behaviors, such as image sensing and memorization, even when stretched, twisted and poked 30% beyond a natural resting state.  

"With the recent surge of smart skin devices, implementing neuromorphic functions into these devices opens the door for a future direction toward more powerful biomimetics," Yu said. "This methodology for implementing cognitive functions into smart skin devices could be extrapolated into many other areas, including neuromorphic computing wearables, artificial organs, soft neurorobotics and skin prosthetics for next-generation intelligent systems."

The Office of Naval Research Young Investigator Program and the National Science Foundation supported this work.

Co-authors include Hyunseok Shim, Seonmin Jang and Shubham Patel, Penn State Department of Engineering Science and Mechanics; Anish Thukral and Bin Kan, University of Houston Department of Mechanical Engineering; Seongsik Jeong, Hyeson Jo and Hai-Jin Kim, Gyeongsang National University School of Mechanical and Aerospace Engineering; Guodan Wei, Tsinghua-Berkeley Shenzhen Institute; and Wei Lan, Lanzhou University School of Physical Science and Technology.