News in Science

Electronic whiskers could help navigation

Tiny sensors Pressure-sensitive 'whiskers' containing silver nanoparticles could help robots navigate and improve the sensitivity of artificial skin, say researchers.

Dr Kuniharu Takei, of Osaka Prefecture University in Japan, and colleagues, report their findings today in the Proceedings of the National Academy of Sciences

"We can use this kind of device in many kinds of applications," says Takei.

Whiskers are essential tactile sensors on animals. For example, whiskers on a cat's face help it to navigate around objects and hairs on our skin detect more subtle things, such as the breeze.

Scientists have been trying to develop electronic whiskers that could be used, for example, to help robots get around.

"Even if a robot can't see an object it can detect spatial distribution by using this device on the side of its arm or foot," says Takei.

He says such whiskers could also be incorporated into the development of artificial e-skin to help make it more sensitive.

"The applications are mainly for robotic skin, prosthetic skin, and some other human interface devices," says Takei.

Pressure sensors

Electronic whiskers are pressure sensors that can detect the direction and force with which the whisker is bent, when it comes in contact with something.

Takei and colleagues have developed pressure sensors that are ten times more sensitive than any previously developed whiskers.

"It's the most sensitive pressure sensor yet developed," says Takei.

The whiskers consist of silver nanoparticles and carbon nanotubes printed onto elastic fibres.

As the whisker bends, the distance between the nanoparticles changes and this in turn changes the electrical resistance of the whisker.

The carbon nanotubes help maintain electrical flow when the silver nanoparticles are very far apart and can increase the range of pressure the whisker can sense, says Takei.

"If we have carbon nanotubes, we can increase the dynamic range of the sensing."

The amount of pressure, and the direction it is coming from, can be detected, using a processor connected to the whisker.

Sensitivity

In their lab tests the researchers found the whiskers were able to pick up the direction and force of flow of a wind that was blown past the whiskers - with a pressure as low as 1 Pa with high sensitivity.

This suggests these new whiskers could be useful for enhancing the sensitivity of artificial skin.

"Usually our skin can detect very low pressures. Hair on the skin can help to detect wind flow," says Takei. "Current artificial skin can't detect very low pressures like wind."

For use in robot navigation, the electronic whiskers would need to be "tuned" so they are less sensitive and don't pick up the vibrations caused simply by the movement of the robot.

"If the sensors are too sensitive they will pick up the robot's vibrations and that will not be good," says Takei.

"By changing the ratio of the carbon nanotubes and silver nanoparticles we can change the sensitivity and resistivity of the sensors," says Takei.