Fishy sensors

Taking their cue from fish, scientists in the US have built a navigational aid that will help robots and remote sensors find their way around the world’s oceans.

The team describes its research today in the Institute of Physics publication Journal of Micromechanics and Microengineering.

Fish and many amphibian animals find their way through even the murkiest of waters, navigate raging torrents and spot obstacles, predators and prey using a sensory organ known as the lateral line system.

Sometimes known as the fish’s sixth sense, the lateral line is a system of thousands of tiny hair cells that run the length of the fish’s body. The lateral line responds to fluid flow around the fish and allows it to detect obstacles and sense the movement of water even in complete darkness.

Now, electrical engineer Chang Liu, entomologist Fred Delcomyn and their colleagues at the University of Illinois at Urbana-Champaign, USA have developed an artificial lateral line that could give underwater vehicles and robots a sixth sense. Robots equipped with the lateral line system will be able to navigate and feel in water.

The artificial lateral line was built by micromachining a sliver of silicon so that three-dimensional hairlike structures are formed on its surface. The hair cells in a fish’s lateral line are each connected to a nerve cell and, by analogy, Liu and Delcomyn have connected each of their silicon hairs via a micro-hinge to an electronic sensor.

When the artificial lateral line comes into contact with moving water, the silicon hairs are bent slightly depending on the rate of flow and the sensors detect the degree and direction of bending. A computer then interprets this movement to build up a picture of the flowing water, much as does the fish’s brain.

The artificial lateral line the researchers are developing has 100 silicon hairs per square millimetre.

‘This arrayed sensor will provide a unique fluid mechanics measurement tool,’ says Liu. ‘We are collaborating with marine researchers at Massachusetts Institute of Technology to apply the sensors to autonomous underwater vehicles,’ He adds that, ‘the lateral line sensor might also help marine biologists to understand better the functions of biological lateral line sensors.’