Silver nanowires used to create wearable sensors

The sensors can measure strain, pressure, human touch and bioelectronic signals such as electrocardiograms. They are expected to find use in applications ranging from biomedical, military and athletics, to prothetics, robotics and flexible touch displays. "The technology is based on either physical deformation or fringing electric field changes," explained Shanshan Yao, a Ph.D. student at NC State University. "The latter is very similar to the mechanism used in smartphone touchscreens, but the sensors we've developed are stretchable and can be mounted on a variety of curvilinear surfaces such as human skin." The research builds on earlier work carried out by Dr Yong Zhu in 2012, in which highly conductive and elastic conductors were created from silver nanowires. By sandwiching an insulating material between two of the silver nanowire-based conductors, the researchers have now been able to create a device with capacitance, or the ability to store an electrical charge. Pushing, pulling or touching the stretchable conductors changes the capacitance, and this is what equips the device with its sensing capabilities. "These sensors could be used to help develop prosthetics that respond to a user's movement and provide feedback when in use," Dr Zhu commented. "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." Zhu says the method to create the sensors is simple and low cost. So far, the researchers have used them to the knee movements of a test subject while running, jumping and walking. "The deformation involved in these movements is large, and would break a lot of other sensor devices," noted Zhu. "But our sensors can be stretched to 150% or more of their original length without losing functionality, so they can handle it."