Servo - March 2014

bots

IN BRIEF

SERVO 03.2014 23

WHISKERS ARE CAT’S MEOW

Robots have been relying on whiskers of sorts for a long time. In a general sense, a whisker is simply a switch attached to some sort of sticky-outy thing, such that when the sticky-outy thing encounters an obstacle, it transmits that encounter to the switch, warning the robot that it's about to run into said obstacle. These sorts of primitive whiskers are like infrared or sonar obstacle detectors, except cheaper, simpler, and (depending on the application) more robust.

The current generation of robotic whiskers are much more directly inspired by biology. Specifically, they're intended to provide a reliable method of sensing in very dark, very cluttered environments. If you recall from a few years ago, there was a robot from the Bristol Robotics Lab that featured a mobile whisker array modeled on the Etruscan pygmy shrew. It was able to not only detect objects, but was also able to analyze their shape and texture through touch alone. This is an impressive capability, although it requires an equally impressive amount of hardware to get it to work. The downside of this is that implementing intelligent whiskers like these turns into a project that defines the robots, as opposed to just another sensing system that can be added to increase the robot's adaptability and versatility.

So, what about the next generation, then? Recently, researchers from Lawrence Berkeley National Laboratory and UC Berkeley went nanoscale, with a design for electronic whiskers that are far smaller (and about 10 times more sensitive) than ever before. The researchers say the sensor could "enable a wide range of applications in advanced robotics and human/machine interfacing."

To illustrate the potential cuteness factor of robotic whiskers, they created the image you see at the top, showing their device next to its natural counterpart (i.e., real cat whiskers).

The first thing you'll notice about these e-whiskers is that they're tiny. Part of the reason they're tiny is that the mechanical infrastructure required to support them is minimal. This is because the whiskers themselves are made of tunable composite films of carbon nanotubes and silver nanoparticles patterned onto elastic fibers that form their own strain sensors, allowing deformation to be measured by changes in voltage. The e-whiskers can sense changes in pressure down to about one single Pascal, which is about the equivalent of the pressure that a dollar bill puts on a surface it's resting on.

Such high sensitivity (along with high dynamic range) means that the e-whiskers can be used for much more than just obstacle detection. The graphic shows the e-whiskers sensing three-dimensional gas flow, which means they'd be just fine at sensing wind speed and direction outside. The key here really is that these things are small, lightweight, tunable, and easy and cheap to manufacture.