The world's smallest battery has been designed to power a computer the size of a grain of dust, that could be used as discrete sensors, or for medical implants. A team led by Chemnitz University of Technology in Germany say these microscopic batteries are needed to power the ongoing miniaturisation of electronics. Smart dust devices, including biocompatible sensor systems in the body, require computers to handle data at sizes smaller than a grain of dust, but while the devices are getting smaller, powering them has proved to be problematic. The current generation of microbatteries involve stacking films on a chip, but there is a limit to how small they can become before energy storage levels are too low. To solve this problem, the German team created a system that involved winding up strips of the same films used in current microbatteries, that can be released and re-coiled to generate and release enough tension to power a tiny computer.