Skin-Like Pressure Sensor
October 25, 2011 1 Comment
Researchers at Stanford University have developed a thin, elastic pressure-sensing device that could have applications for restoring touch-sensitive skin to burn victims or amputees, or for giving a subtle sense of touch to machines. They have a pretty decent video explaining and demonstrating it:
That enviable elasticity is one of several new features built into a new transparent skin-like pressure sensor that is the latest sensor developed by Stanford’s Zhenan Bao, associate professor of chemical engineering, in her quest to create an artificial “super skin.” The sensor uses a transparent film of single-walled carbon nanotubes that act as tiny springs, enabling the sensor to accurately measure the force on it, whether it’s being pulled like taffy or squeezed like a sponge.
“This sensor can register pressure ranging from a firm pinch between your thumb and forefinger to twice the pressure exerted by an elephant standing on one foot,” said Darren Lipomi, a postdoctoral researcher in Bao’s lab, who is part of the research team.
“None of it causes any permanent deformation,” he said…
The sensors could be used in making touch-sensitive prosthetic limbs or robots, for various medical applications such as pressure-sensitive bandages or in touch screens on computers.
The key element of the new sensor is the transparent film of carbon “nano-springs,” which is created by spraying nanotubes in a liquid suspension onto a thin layer of silicone, which is then stretched.
When the nanotubes are airbrushed onto the silicone, they tend to land in randomly oriented little clumps. When the silicone is stretched, some of the “nano-bundles” get pulled into alignment in the direction of the stretching.
When the silicone is released, it rebounds back to its original dimensions, but the nanotubes buckle and form little nanostructures that look like springs.
“After we have done this kind of pre-stretching to the nanotubes, they behave like springs and can be stretched again and again, without any permanent change in shape,” Bao said.
Basically, pressure is detected because the silicone in the middle layer of the sensor stores varying amounts of electric charge depending on how far the two carbon nanotube-covered outer silicone layers are from each other, i.e. how compressed the sensor is.
Earlier, I discussed prosthetic limbs that have a rudimentary sense of touch; I hope more advanced sensors like this one can eventually be applied to prosthetic limbs to more legitimately restore feeling for amputees. That being said, I should note that sensing pressure is only one part of our idea of “touch”; there are separate mechanisms in our nervous system for sensing pain, temperature, and body positioning.