What is a micro machine?
One of the most important steps in computing technology in the coming years is likely to be a return to mechanical methods. Using the same sort of process used to create chips it is possible to fabricate mechanical parts - levers, gear wheels and small motors. The basic idea is that you start with a slab of polycrystalline silicon and using photographic techniques you etch away parts that are not required and deposit new layers of silicon to build up axles and to free cogs to rotate.
The best known example of a micro machine was created by the Sandia Laboratories in New Mexico. It is a complete motor developing 50uW of power in one square millimeter - still a bit big for some of the micromachines planned for the future! The motor consists of two interlocking sets of silicon fingers which can attract or repel each other as a voltage is applied. In this case the motive power is electrostatic but the same sort of principles could be applied to produce motion from heat or chemical action. The movement of two sets of combs is timed to move a small cog against a larger cog - so converting reciprocal motion to rotation.
The first micro motor may not be very exciting but remember these are early days yet and, like electronic chips, mechanical chips benefit from automatic mass production. When you print on a wafer of silicon you make not one machine but lots, all identical. The next step is to add the electronic control circuits next to the motor - but of course if we had developed mechanical computing this hybridisation would be unnecessary!
A close up of the output gear of Sandia’s micro engine
The micro engine
What are micromachines going to be used for? At the moment the answers are often restrained for fear of seeming to make ridiculous claims. Obvious applications, the ones that most workers are concentrating on, are sensors, gyros and drug delivery. The idea is that a micromachine could have a strain sensor or a gyroscopic attitude sensor and electronics built into a single chip sized package. The idea of using a micromachine to deliver drugs is getting a bit closer to the more sci fi applications. Why not swallow a micromachine and let it decide when you need a dose of something - delivered of course with a motorised micro pipette. Only a tiny step further on is the idea of building insect sized robots that could do difficult jobs in very small places. Swallowing an ant sized machine to cure whatever ails you or popping one inside some failed machinery seems like a really good idea!
A micro machine - the large white lumps are grains of rice - the car has an electric motor which runs!