The world’s tiniest batteries could power robots the size of cells

A zinc–air microbattery, with a volume of just two picolitres (10^-12L), can store an average of 7.7 microjoules of energy and deliver up to 2.7 nanowatts of power to electrical components, such as memristors, clock circuits and actuators. These high energy density batteries are simple to produce, which the researchers say they could be made on a massive scale to power colloidal robots – microrobots that can move through liquids, such as blood, by themselves.

Over the past decade, interest in the miniaturisation of sensors, robots and computers has surged, from wireless microelectronic systems to picolitre robots capable of walking using advanced actuators as legs. ‘Unlocking applications that are inaccessible to larger devices is a major driving force behind this trend, which could enable drug delivery to cells through the blood,’ says first author Ge Zhang from Stanford University. But ambitions to miniaturise them even further have been hindered by conventional batteries produced using wet chemistry methods, like slurry casting, which are incompatible with microelectronic manufacturing and restrict most microbatteries to the millimetre-scale.