Gallium, take the wheel. A small metal droplet can propel a wheeled robot forward with a simple electric current. The technique paves the way for larger robots that can trundle like tumbleweeds through unfriendly terrain.
Shi-Yang Tang at the University of Wollongong in Australia and his colleagues started with a plastic wheel about five centimetres across with walls along its edges, shaped like a car tyre. Inside the wheel they placed a drop of liquid metal made mostly of gallium. A pair of electrodes sit in front of and behind the drop on a small platform that slides along the walls as the wheel turns.
When the electrodes are turned on, powered by either a tiny onboard battery or an external power source, they create a voltage across the metal droplet that pushes it along towards one of the electrodes. Like a hamster running in a wheel, the metal drop keeps moving forward as the tiny tyre turns. As the drop changes the robot鈥檚 centre of gravity, it continues to roll.
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The system takes less than 0.4 seconds to accelerate to a maximum steady speed of 5.5 centimetres per second. This rolling motion takes less power and can reach higher speeds than other ways that robots can move around, says Tang.
Eventually the researchers hope that this liquid-metal-driven wheel will be used in a larger robot that can change its shape and roll to hard-to-reach areas, possibly for use in search and rescue missions after natural disasters.
鈥淲e envisage such a soft robot could adapt to sophisticated environment by reconfiguring its shape, and the self-healable property of the liquid metal can reduced the chance of malfunction, as well as the need of regular maintenance,鈥� says Tang.
Advanced Materials
