'Talking' Robofish to Swim in Puget Sound

June 17, 2008 -- Marine creatures have communicated with each other for millions of years. Now swimming robots can too.

Three robofish, each 20 inches long and weighing just over six pounds, have been equipped with acoustic transmitters to communicate wirelessly with each other while underwater.

The robofish, created by University of Washington researcher Kristi Morgansen, could eventually monitor the migrations of large mammals and the diffusion of environmental pollutants.

"When the robofish are underwater we can't communicate with them." said Morgansen. "They have to be very independent."

Actual fish can communicate (albeit primitively) using an organ known as the lateral line, which runs down each side of the body and detects movement and vibration in the water via waves of physical pressure, or sound waves.

The robofish, which swim like regular fish by using a flapping tail instead of a rotating propeller, communicate by using acoustic modems, pinging sound waves to each other.

More familiar forms of above-water communications, like radio waves, don't work well under water. In freshwater, a radio signal can only travel about 10 feet. In saltwater, radio signals travel even shorter distances.

Trailing a long wire can create radio waves that travel farther, but they are only practical on large submarines.

Besides the acoustic modems, the robofish are also equipped with pressure sensors (to monitor depth) and a 3D compass, all powered by nickel-metal hydride rechargeable batteries.