Micromachines.

Will microscopic subs, minute rovers, And minuscule spy planes soon Invade your life?

Picture a tiny submarine on patrol, making its way through murky territory. Its task? To destroy enemy invaders and keep vital passageways free and clear. Its current location? Your bloodstream! This cell-sized sub performs search-and-destroy maneuvers on viruses and patrols your body for any signs of potential infections. Its mission: to heal wounds and prevent future disease.

Ready for the future of Micromachines? Scientists are scrambling to turn sci-fi dreams into reality with ever-shrinking micromachines--machines built with parts smaller than a micrometer. How small is small? A micrometer is 1/1,000 of a millimeter, which itself is .039 inch. To get an idea of a micromachine part, think of a speck of dust!

What's spurred the scramble to create the tiniest machines possible? Micromachines are easily portable--you can carry them around in the palm of your hand. Machines built from very small complex parts can perform sophisticated tasks unthinkable for simpler, heftier machines. For example, engineers are hatching prototypes, or experimental models, of tiny robotic rovers to scour earthquake rubble for survivors. Researchers are devising machine capsules that inch their way through industrial pipes in search of hairline cracks. And bug-sized spy planes that detect land mines and pinpoint enemy troop positions will soon go through "test flights" (see diagram above). "If you want to be unnoticed, you want a machine to be small and quiet," says aerospace expert Steve Morris.

SMALL SCIENCE

The idea of diminutive machines isn't new. Craftsmen have used tiny parts to make intricate toys and wristwatches for hundreds of years. With the birth of electronics in the 20th century, smaller and smaller parts (like the microchip) have been devised to run TVs, stereos, computers, calculators, and a host of other high-tech gadgets.

In 1988 micromachines took a leap forward when University of California researchers assembled an electric motor 60 microns in diameter (60 millionths of a meter), .002 inch less than the width of a human hair. In 1996 Japanese scientists assembled a replica of a 1936 Toyota sedan the size of a grain of rice (see below). The miniature car, with 24 parts, including drive shaft, axles, and a motor propelling it up to 5 centimeters (2 in.) per second, was developed to show how the technology that made it can be used to develop many other tiny complex structures. Maybe the Toyota could give an ant a ride!

MEET MEMS!

The technology to produce working micromachines is still in early stages, and scientists say it could be a decade before the process is perfected. When researchers first started tinkering with micromachines in the 1970s, they drew heavily on microchip technology (see "Making a Micromachine Part, "p. 16).

Microchips are made from a single crystal of a substance called silicon (the most abundant element on Earth after oxygen). Tiny electronic elements are laid on a sliver of the crystal, no bigger than your little fingernail. But while microchips are fiat or 2-dimensional, micromachines are 3-dimensional--they have length, width, and height. Scientists' ultimate goal is to create 3-D micromachines made of an all-in-one unit: a sensor, microprocessor (the brain), and an actuator, like a pump or motor. Engineers call these ail-in-one machines MEMS--microelectromechanical systems.

For example, engineers at Georgia Tech's microflier program hope to perfect flying bug-sized MEMS called micro air vehicles (MAVS) that might spy on terrorists holed up inside a skyscraper or test air samples after a bomb explosion. "One day you might even use a MAV to fly around your house and make sure the doors are locked," says Georgia Tech's David Parekh.

The challenge in malting such minuscule MEMS work is to create single parts that have double uses: "You might shape a battery so it's also a wing," Parekh says. Antennas could help steer the flying microplane; landing gear might double as a camera. A single MEMS in a microplane might consist of a sensor to detect direction, a microchip to guide wing angle, and a micromotor to flap the wing. Georgia Tech engineers are on the verge of test-flying their insect-like MAV, which they call an entomopter. Guess it won't need a runway!

BUG'S EYEVIEW

Don't expect to see a squadron of microplanes flying anytime soon. Mass-producing micromachines is a mammoth task scientists are tackling one step at a time. An intermediate step is building mesomachines, machines not quite as small as tomorrow's micromachines.

Tom Weber, an electrical engineer at Sandia National Labs in Albuquerque, New Mexico, helped develop a prototype of MARV (miniature autonomous robotic vehicle), a one-inch-square robotic rover that could someday sniff out chemical and nuclear weapons and track land mines (see photo, below). MARV was mostly hand-made of the same small parts you might find in a cellular phone. Building MARV has given Weber and his group an idea of what challenges they'll face when creating even smaller micromachines.

As scientists shrink machines, they have to consider the world from a bug's eye view. Freezing rain can have the impact of bombs on tiny microplanes; a drop of lubricating oil can become a glop of glue in a microscopic motor; and static electricity can act like a clamp on a tiny gear.

Weber's chief concern at the moment is how to fuel a tiny machine. "The biggest and heaviest part in MARV is the battery," says Weber. "It only has enough power to last 20 minutes." So Weber's lab is now experimenting with higher powered fuels like butane to create more "juice" for MARV. But the most daunting obstacle is trying to move MARV around. "With such little wheels, the rover can't climb over a pencil," says Weber. He now has to rethink how MARV will make its moves. So, for example, Weber questions whether small rovers like MARV might move more effectively if they hopped like grasshoppers rather than rolled on wheels.

Scientists themselves don't know where the future of micromachines will lead, but they do know the possibilities are endless. Already simple MEMS parts are in use. A tiny silicon flap like a diving board senses when to activate airbags in many cars. You can also find tiny MEMS sensors that monitor blood pressure in hospital IV (intravenous) tubes. The next generation of MEMS will inspire more amazing uses. We'll keep you posted about them--if we can see them,] that is!

[ILLUSTRATION OMITTED]

RELATED ARTICLE:

Engineers from AeroVironment used a see-through design to create this 15-cm-wide model:

1. Lithium batteries fuel a little electric motor, which powers a tiny propeller.

2. The plane's flight path is directed by Global Positioning System (GPS) satellites.

3. An electronic sensor helps keeps the plane level.

4. In a final model, the disc would be hinged, and actuators, or electronic arms, would cause the outer disc parts to rotate like flaps, or little wings.

5. The video camera would snap spy pictures.

6. Radio antennas would transmit data by remote control back to a soldier. The final mode might fly 56km/h (35 mph) for one hour, send back vital information, then self-destruct--no round trip for this tiny spy plane.

RELATED ARTICLE: Making a micromachine part

Building a micromachine part is very similar to making a microchip. Here's how:

1. Scientists start with a silicon base (yellow) and a layer of glass (green) on top. Then they coat the glass with a photoresist, a compound that is sensitive to light (orange).

2. Designers draw a picture of the micromachine part on a light mask (like a transparency), which acts like a photographic negative. Usually, several masks are needed to create one part.

3. Technicians shine light through the first mask and onto the photoresist. The part exposed to the light (the hole) softens. Then chemicals can wash it off.

4. Additional chemicals etch away the glass underneath that is not protected by the photoresist. Then a different chemical strips off the photoresist. Glass with a hole in the center is left behind.

5. A layer of polysilicon (blue) is deposited over the glass, and another layer of photoresist coats the polysilicon. The polysilicon partially fills in the hole in the glass.

6. Step 3 is repeated again, this time using a second mask (with drawing of the micromachine part). Chemicals etch away the polysilicon underneath that is not protected by the photoresist. The photoresist is stripped off again.

7. Finally, a strong acid dissolves the underlying glass layer, leaving behind a raised micromachine part.

RELATED ARTICLE: THE FUTURE:

As small as it gets

Keep shrinking the size of a micromachine, and you finally reach the very molecules and atoms, or basic chemical elements, a machine is made of. Can scientists really produce a cell sub not much bigger than a molecule that zaps through your bloodstream?

They can if they perfect nanotechnology (a nanometer is one-billionth of a meter), the technique of building micromachines from individual atoms and molecules. Still, figuring out how to piece together enough atoms to create molecular micromachines could take decades of research and development.

To actually see single atoms, scientists had to invent an entirely new microscope. The first instrument was built in 1981, and it's called a scanning tunneling microscope. The superpowerful microscope can peer through electron clouds that surround atoms and pinpoint individual atoms.

The microscope's most vital part is its needle or probe, which scientists have perfected to actually pick up single atoms on the needle tip! Now researchers can move single atoms or molecules around one at a time. Using this technique, they may one day be able to build atom-by-atom, custom-designed molecules that fight disease. But as you can imagine, moving one atom at a time is very tedious.

So chemists are experimenting with chemical solutions and reactions to make molecules replicate themselves. Creating instant quantities of particular molecules instead of assembling them atom-by-atom may be the key to mass-producing nano-products. "Human diseases are caused by damage on the molecular level," says research scientist Ralph Merkle. "One day we're going to be able to build molecular-scale surgical tools and instruments guided by molecular computers."

Those cell-sized subs will be injected into your bloodstream, while shatterproof rockets made of materials developed from nanotechnology will propel you through space. When it comes to micromachines, a single cell and the entire universe become fair game for science to conquer.