Molecular machinery

HAYDEN WALLES

Grease, steam, noise and pounding metal were the hallmarks of the earliest machines of the Industrial Revolution.

Those machines still exist, but the machines we are most familiar with in the 21st century, and the ones that we are most proud of, are generally small, smooth, clean and quiet. Few machines epitomise this trend more than MEMS, or micro electromechanical systems.

These are machines so small that you can't make them out with the naked eye, from practical devices like orientation sensors to toy cars built to show off the prowess of the micro-engineers.

MEMS have been around, in a crude form at least, for several decades. Soon after the development of the silicon microchip for electronics in the 1950s, some of the interesting properties of silicon were put to good use by building tiny chips that sensed pressure or force directly.

True MEMS appeared in the 1970s, when the techniques used to etch electronic circuits on silicon were adapted to etch mechanical devices instead, such as tiny motors and valves with actual moving parts.

MEMS have found their way into many parts of our lives. Early applications were the nozzles in ink-jet printers and sensors which feed reliable information to a car's onboard computer.

More recently MEMS have provided some of near-magical abilities of consumer electronics, such as the tiny gyroscopes and compasses that tell a smart phone which way it is facing, and the accelerometers that tell it when it is moving and in which direction.

These abilities are finding more applications. The race is on right now to provide a so-called interior positioning system for navigating inside buildings where satellite signals cannot reach, and MEMS orientation and motion sensing is a key component of navigating such places.

That MEMS came about should hardly surprise us, since miniaturisation is an obvious trend in technological development. It's easy to miss just how far miniaturisation has come, though, especially when the machines are too small to see.

Yet MEMS are not the end of the road. Cars the size of grains of rice that actually move are all very well, but even these seem huge and lumbering next to experimental mechanical systems being developed at the nano scale, thousands, or even millions of times smaller again.

Tufts University chemist Charles Sykes recently demonstrated an electric motor made from one molecule, one-billionth of a metre in size.

Ben Feringa, of the University of Groningen in the Netherlands, showed off a molecular remote-controlled "car".

The full scope of MEMS has not been explored and new micro-machines are appearing all the time in areas such as optics, chemical and physical sensing and biomedical automation.

Nanotechnology promises complete machines too tiny to see without the aid of an electron microscope. Tiny they may be, but the effects of these machines on our lives are huge.

- © Fairfax NZ News