Silver Nanowire Sensors Hold Promise for Prosthetics

Wearable, multifunctional sensors made from silver nanowires could be used in biomedical, military, or athletic applications.

Developed by researchers at North Carolina State University (NCSU, Raleigh, USA), the highly stretchable multifunctional sensors can simultaneously detect multiple stimuli such as stretch, strain (up to 50%), pressure (up to ~1.2 MPa), temperature, or touch with high sensitivity, fast response time (~40 ms), and good pressure mapping function. The sensors utilize the capacitive sensing mechanism, with silver nanowires used as electrodes and Ecoflex used as a dielectric. The silver nanowire electrodes are screen-printed onto an insulating material between two stretchable capacitance conductors that have the ability to store electric charges.

Pushing, pulling or touching the stretchable conductors changes the capacitance, which is measured by the silver nanowires. The sensors have been tested for several wearable applications, including monitoring thumb movement, sensing knee strain in patellar reflex and other human motions, illustrating the potential utilities of such sensors in robotic systems, prosthetics, for measuring bioelectronic signals such as electrocardiograms (ECGs), and for use in flexible touch panels. The study describing the nanowires was published early online on January 14, 2014, in Nanoscale.

“The technology is based on either physical deformation or “fringing” electric field changes,” said lead author Shanshan Yao, a PhD student at NCSU. “The latter is very similar to the mechanism used in smartphone touch screens, but the sensors we’ve 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,” said senior author Associate Professor Yong Zhu, PhD, of the department of mechanical and aerospace engineering. “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.”

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