Researchers in the USA have developed a tiny, autonomous robot carrying sensors to perform tasks such as catching gas leaks or tracking warehouse inventory (writes Nick Flaherty).

The researchers at the University of Washington (UW) created the MilliMobile four-wheeled robot to be powered by light or radio waves. At 10 x 10 mm, it is about the size of a penny and weighs 1.1 g.

The robot uses a solar panel-like energy harvester to move about 10 m per hour, even on a cloudy day with light conditions as low as 20 W/m2 and -10 dBm of radio-frequency (RF) power. It moves towards light sources using a sensor.

Able to drive on surfaces such as concrete or packed soil, the robot can carry equipment that is three times its own weight, such as a camera or sensors. Carrying a 1 g payload only reduces its speed by 25%.

Miniaturising the robot to gram scale significantly reduced the energy required to move it. The team developed methods to produce intermittent motion by discharging a small capacitor (47-150 μF) to move a motor in discrete steps, enabling motion from as little as 50 μW of power or less.

“We took inspiration from ‘intermittent computing’, which breaks complex programs into small steps, so a device with very limited power can work incrementally as energy is available,” said UW researcher Kyle Johnson.

Software-defined techniques were used to maximise power harvesting, operating in the optimal part of the charging curve by varying the charging time to achieve speeds up to 5.5 mm/s.

The researchers have added light, temperature and humidity sensors, as well as Bluetooth, enabling the robot to transmit data over 200 m.