"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."
"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."
I have to see this seems pretty cool, but I think there is a long way to go before we can control bacteria with any finesse.