Researchers at the University of California, Berkeley have made highly sensitive, lightweight "electronic whiskers" that can detect the lightest of touches or a gentle breeze. Made from a mixture of carbon nanotubes and silver nanoparticles, the whiskers could be used to create "skin" for robots and in interfaces between humans and machines, says the team.

Animals use their whiskers to gauge the wind and to navigate around obstacles. The new electronic whiskers, or e-whiskers, made by Ali Javey's team could be the next best thing to their natural counterparts in terms of size and weight. The researchers made the whiskers by painting composite films of carbon nanotubes and silver nanoparticles onto thin elastic fibres made of the polymer PDMA. The carbon-nanotube "paste" forms a conductive matrix that can be bent and unbent at will without suffering any damage. The silver nanoparticles further increase the conductivity of the composite and also make it highly sensitive to strain.

"The strain sensitivity and electrical resistivity of our composite film is readily tuned by changing the composition ratio of the carbon nanotubes and the silver nanoparticles," explains Javey.

When the e-whiskers experience a light touch or a gentle breeze, they bend and their resistance changes dramatically. The structures are sensitive to changes in pressure of just 8% – the highest value reported to date for such tactile sensors.

Better-balanced robots

If mounted into arrays, the whiskers could be placed on robotic e-skin so that the machines are better able to navigate. They could also be used in human–machine interfaces, says team member Zhibin Yu. "They might even be ideal for some medical applications, for example in devices that monitor heartbeat and blood pressure," he says.

The Berkeley team says that it is now looking to make the devices using different printing processes and produce them on a larger scale.

Structures such as these whiskers that mimic biological systems could help in the development of so-called smart and user-interactive electronics, explains Yu. Researchers have already made rudimentary e-skin and electronic eyes on thin, flexible substrates. Such devices are capable of "feeling" and "seeing" their local environment. "Electronic whiskers are another important class of sensor, capable of monitoring surrounding air flow and touch," he says. "They can also spatially map nearby objects (just like naturally occurring whiskers) – a property that might help improve balance in robots of the future."

Javey and colleagues describe their research in PNAS.