Gears about 10 micrometres wide made from etched silicon, viewed with an electron microscopeGan Wang / Myfab Chalmers
Minuscule gears that are thinner than a human hair and powered by light could be used to study human cells or power tiny, complex robots.
Gear systems often struggle to work at a size below a tenth of a millimetre, about the thickness of an average piece of paper, because it is difficult to miniaturise the power systems that drive them. Some simple systems, such as rotors built from DNA, can be built at nanoscales, but these are bespoke and…