Iltifat Husain MD contributed to this piece

Researchers at North Carolina State University recently published a paper in Nanoscale on their use of silver nanowires to create stretchable, multifunctional sensors that can be used in biomedical, military and athletic applications.

The sensors can measure strain, pressure, human touch and bioelectrical signals.

Shanshan Yao, Ph.D. candidate at NC State and lead author of the paper describes how the sensors work.

“The technology is based on either physical deformation or “fringing” electric field changes. 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.”

This research was built on top of the previous work of Dr. Yong Zhu, associate professor of mechanical and aerospace engineering at NC State and senior author of the paper, in which highly conductive and elastic conductors were made from silver nanowires. The sensors work by measuring the change of capacitance (the ability of the material store charge) in the nanowires. A push, pull or touch of the nanowires causes a change in capacitance.

“These sensors could be used to help develop prosthetics that respond to a user’s movement and provide feedback when in use,” says Zhu.  “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 say that the sensors are low cost and simple to build and have already demonstrated them in several prototype applications. In one such application, the sensors were used to monitor thumb movement which is useful in controlling robotic and prosthetic devices. In another application, knee movement was measured while the subject was running, walking and jumping.

“The deformation involved in these movements is large, and would break a lot of other sensor devices,” Zhu says. “But our sensors can be stretched to 150 percent or more of their original length without losing functionality, so they can handle it.”

The researchers have also developed sensors which map pressure distribution, important for use in robotics and prosthetic applications. The sensors have a quick response time of 40 milliseconds, allowing strain and pressure to be monitored in real time. As body sensors and fitness devices continue to explode in popularity, one of the main issues is how the devices can be uncomfortable. Versatile sensors such as these could pave the way for more mobile and compact sensors that are easier to wear.

Source: North Carolina State University