Robot swims without an engine

The mini-submarine is 7.5 centimetres long and equipped with plastic paddles that act like “muscles”. The paddles use temperature fluctuations in the water for propulsion by expanding in warm water, which causes the bistable element to quickly snap, triggering a paddle stroke. The directional motion, force and timing of the paddle strokes are precisely defined by the robot’s design.  

At present, the mini-submarines can execute a single paddle stroke and must then be reprogrammed manually, explains the Federal Institute of Technical (ETH) in Zurich in a statement. However, it could be possible to change this. The scientists have already made a mini-submarine that can paddle forward with one stroke, release its cargo (in this case, a coin) and then navigate back to the starting point with a second paddle stroke in the opposite direction.

In the future, the underwater robots could react to other environmental factors other than water temperature, such as the acidity or salinity of the water.

“The main takeaway from our work is that we have developed a new and promising means of propulsion that is fully 3D printed, tuneable and works without an external power source,” said ETH Professor Kristina Shea. This could be developed further to create a low-power vessel for exploring ocean depths.

The ETH researchers developed the underwater robot together with colleagues at the California Institute of Technology (Caltech).