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.

Magnetic control: A setup of electromagnetic coils controlled by a computer allows careful control of the microbots. Carnegie Mellon University

Microscopic machines might one day deliver drugs directly to a sickly cell or a tumor, or allow researchers to fabricate electronics components more easily. But first, scientists need to figure out how to power and control such tiny devices. Methods currently being explored range from piggybacking on bacteria to harnessing magnetic fields.

Magnetic control has shown only limited success, partly because it's hard to control microscopic objects individually. Metin Sitti, an associate professor of mechanical engineering at Carnegie Mellon University (who has previously developed tape that mimics geckos' sticking power and a robot that can stick to a stomach without damaging it), has now come up with such a control technique.

Previously, Sitti showed that a permanent magnet about 200 microns wide can be maneuvered using alternating magnetic fields, allowing it to crawl forward across a surface. Now, by adding electrostatic "traps" to the surface, Sitti can stop or move an individual micro magnet within a group on command.

The microbots move across a glass surface covered with a grid of metal electrodes. When a high voltage is applied to an electrode, it generates a field. In a recent issue of Applied Physics Letters, Sitti, together with Chytra Pawashe and Steven Floyd, shows how these electrodes can be used to anchor one or more microbots while allowing others to continue to move freely around the surface.

The movie below shows several microbots moving across a four-by-four array of electrodes.

Credit: CERN

Physicists and science enthusiasts were excited last month when the Large Hadron Collider, the most ambitious particle accelerator ever built, went online. Nine days later, the accelerator was shut down because of a helium leak. (The superconducting magnets that steer particles on their 27-kilometer collision course are cooled with large volumes of liquid helium.)

Yesterday, CERN, the European Organization for Nuclear Research, released a report detailing what went wrong. Steven Nahn, an MIT physics professor currently working from CERN, says that the analysis took some time because the area had to be warmed up from near absolute zero before it could be accessed for investigation. The problem, the report concludes, arose because of a faulty electrical connection between two magnets, which led to mechanical problems.

"The fact that this happened surprised no one in this business," says Nahn. "You're just starting up a machine that's taken you 20 years to build, you're gonna run into some problems--you can't possibly foresee everything." Over the next several years, Nahn and his thousands of collaborators hope to use the accelerator to solve long-standing physics problems, such as why fundamental particles have mass.

The collider is slated to go online again in early 2009.