A team of scientists at North Carolina State University, Raleigh, used silver nanowires to develop wearable, multifunctional sensors that, they say, could be used in biomedical applications, including new prosthetics or robotic systems. The sensors can measure strain, pressure, human touch, and bioelectronic signals such as electrocardiograms.

A sensor based on silver nanowires is mounted onto a thumb joint to monitor the skin strain associated with thumb flexing. The sensor shows good wearability and large-strain sensing capability. (Credit: Shanshan Yao)

They explained that the technology is similar to the mechanism used in smartphone touch screens, but the sensors they have developed are stretchable and can be mounted on a variety of curvilinear surfaces such as human skin.

“These sensors could be used to help develop prosthetics that respond to a user’s movement and provide feedback when in use,” says Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State. “They could also be used to create robotics that can ‘feel’ their environment, or the sensors could be incorporated into clothing to track motion or monitor an individual’s physical health.”

The researchers sandwiched an insulating material between two layers of stretchable conductors. Pushing, pulling or touching the stretchable conductors changes the capacitance, or the ability to store electric charges. The sensors work by measuring that change in capacitance.

For example, the researchers employed these sensors to monitor thumb movement, which can be useful in controlling robotic or prosthetic devices. The researchers also demonstrated an application to monitor knee movements while a test subject is running, walking, and jumping.

They also developed an array of sensors that can map pressure distribution, which is important for use in robotics and prosthetics applications.