Robot fish could monitor water quality

Posted by Emma Woollacott

An engineer and an ecologist at Michigan State University are developing robots that swim like fish to monitor water quality.  

"Fish are very efficient," explained Xiaobo Tan, an assistant professor of electrical and computer engineering. "They can perform very efficient locomotion and maneuvering in the water."

Robotic fish could operate autonomously for months, giving precise data on aquatic conditions.

They will carry sensors recording such things as temperature, dissolved oxygen, pollutants and harmful algae. Tan also is developing electronics to allow the devices to navigate and communicate  sampling lakes, monitoring aquafarms and safeguarding water reservoirs.

"The robotic fish will be providing a consistent level of data that hasn't been possible before," Elena Litchman, an assistant professor of zoology, explained. "With these patrolling fish we will be able to obtain information at an unprecedentedly high spatial and temporal resolution."    
 
To mimic how fish swim and maneuver, Tan builds 'fins' for robotic fish with electro-active polymers that use electricity to change shape. Similar to real muscle tissue, ion movements twist and bend the polymer when voltage is applied. The effect works in reverse, too – slender 'feelers' could signal maneuvering circuits in a sort of electro-active central nervous system. Infrared sensors also could be used for 'eyes'.

The robots will communicate wirelessly with a docking station after surfacing at programmed intervals and could similarly be linked to other robotic fish for coordinated maneuvers or signal relay. Global positioning system technology and inertial measurement units will allow precise navigation.

A nine-inch prototype now swimming in Tan's laboratory tank is modeled on the yellow perch. The device isn't strong enough to resist stiff currents, so for now must be confined to relatively still waters. Future versions will incorporate the ability to change buoyancy to assist locomotion and maneuver.