Researchers in Canada have created a solar-powered micro-machine that is no bigger than the period at the end of this sentence. The tiny machine can carry out basic sensing tasks and can indirectly control the movement of a swarm of bacteria in the same Petri dish.

Sylvain Martel, Director of the NanoRobotics Laboratory at the École Polytechnique de Montréal, previously showed a way to control bacteria attached to microbeads using an MRI machine. His new micro-machine, which measure 300x300 microns and carry tiny solar panels, will be presented this week at ICRA '09 in Japan.

On such a small device there is little room for batteries, sensors or transmitters. So the solar cell on top delivers power, sending an electric current to both a sensor and a communication circuit. The communication component sends tiny electromagnetic pulses that are detected by an external computer.

The sensor meanwhile detects surrounding pH levels--the higher the pH concentration, the faster the electromagnetic pulses emitted by the micro-machine. The external computer uses these signals to direct a swarm of about 3,000 magnetically-sensitive bacteria, which push the micro-machine around as it pulses. The bacteria push the micro-machine closer to the higher pH concentrations and change its direction if it pulses too slowly. This is more practical than trying to attach the bacteria onto the micro-machines, says Martel, since the bacteria only have a lifespan of a few hours. "It's like having a propulsion engine on demand," he says.

Martel suggests that micro-machines could one day be used for medical purposes although there's still a long way to go.

The video below shows 3,000 bacteria maneuvering a V-shaped robot around via computer control.