Microassembler for building micromachines

3 April 2007

University of Illinois engineers have created a micro device that uses agile, human-like fingers that can assemble micromachines made of micron-sized parts. The device has potential to be refined to manipulate parts and components for machines at the nano scale.

Future microscopic-sized machines assembled with micrometer or nanometer-scale parts will need to be made with devices that use tiny, agile "fingers" that can grip, lift and do the assembly work in a controlled, coordinated way.

Engineers at the University of Illinois at Chicago have developed and demonstrated a one-square centimetre device they call the "micromanipulator station" that accomplishes this goal.

"We think this will be useful in the microfactories of the future," said Laxman Saggere, assistant professor of mechanical and industrial engineering.

He and graduate student Sandeep Krishnan describe their device in the March issue of the Journal of Micromechanics and Microengineering.

Within their tiny chip-like station, four micro "fingers" can grasp and move micron-sized particles as commanded. Micro tweezer-like devices now commercially available can only grip and hold small particles in place, but to manipulate them requires accessory devices that make the process cumbersome. The UIC engineers got around this problem.

"We thought of mimicking the functionality of human fingers," said Saggere. "The device has multiple, coordinated fingers that grip a particle and take it from one given position to another within a small area."

Saggere and Krishnan have proved this works, using a laboratory device they built. The prototype is proof of the concept, but refinements are planned.

"We can increase the number of fingers, increase the area in which manipulation can occur, or enable more dexterous positioning of even smaller particles by improving the fingertip design," he said. "We can also add a little more flexibility and reduce the footprint size of the device in an improved design."

Making the fingers flexible and dexterous enough to do precise work at the micro-scale level has yet to be accomplished. Saggere and Krishnan developed systematic algorithms to design the configuration of the flexible fingers in the micromanipulator to coordinate with each other like human fingers at the micro- or even nanometer scale.

"We've verified our design algorithms. We've grabbed tiny microspheres — diameters of 15 microns — using these fingertips to push it from one location to another, but exact positioning is not yet possible," Saggere said. "It's the first time that use of coordinated fingers has been demonstrated, but there's a lot more to accomplish."

A micron is a millionth of a meter, or 39 millionths (.000039) of an inch. A grain of table salt measures about 60 microns on a side. A nanometer is 1,000 times smaller than a micron.

The engineers said future designs will likely employ piezoelectric actuators to refine the sophistication of finger movement. They are also looking into methods of overcoming certain adhesion forces that are predominant at the micro scale and cause problems in releasing these ultra-small particles from the fingers after manipulation.

While it may be years before micromanipulator stations go to work on a commercial basis, Saggere and Krishnan's prototype holds promise for creation of micro-scale machines that are only concepts today.

"Currently, a major limiting factor in development of micro-scale machines is the assembly process," Saggere said. "Manual assembly is prohibitively expensive, and the required precision, operator stress and eye strain associated with assembling such minute parts under a microscope make it impractical. If we want to make a micro-motor, we need to assemble it with micro-gears, shafts and other components at micro scale. We can't do that today."

The future generation micromanipulator station may also prove useful in mechanically manipulating and patterning biological cells to better understand how they communicate, which could help in understanding diseases and lead to better drug development.

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