All fingers, no thumbs

Device that mimics the functionality of human fingers could be used to move and manipulate components in micro-factories of the future. Siobhan Wagner reports.

Mass production of micro-electromechanical and nano-electromechanical systems could be much easier in the future, with a device that uses tiny, agile fingers that can grip, lift and assemble components in a controlled, co-ordinated way.

Engineers at the University of Illinois at Chicago have developed the ‘micromanipulator station’ — just one centimetre square — which can be used in potential micro-factories.

Within the device’s tiny chip-like station, four micro fingers can grasp and move micron-sized particles on command. Traditional micro tweezer-like devices can only grip and hold small particles in place but to manipulate them requires accessories, and this makes the process cumbersome.

To solve this, the researchers developed a device that mimics the functionality of human fingers. It has multiple, co-ordinated fingers that grip a particle and take it from one position to another within a small area.

At present a major limiting factor in the development of micro-scale machines is the assembly process. Manual assembly is prohibitively expensive and the required precision, as well as the operator stress and eye strain associated with assembling such minute parts under a microscope, makes it impractical.

If manufacturers wanted to assemble a micro-motor, for example, they would need to put together micro-gears, shafts and other components at micro scale. With current technology, this is a difficult task.

The Illinois researchers admit a few kinks need to be smoothed out to prepare their device for commercial use. For instance, they say that its fingers are not flexible and dexterous enough to do precise work at the micro-scale level.

They developed systematic algorithms to design the configuration of the flexible fingers in the micromanipulator to co-ordinate with each other like human fingers at the micron or even nanometre scale. They verified the design algorithms by using their device’s fingertips to grab tiny micro-spheres with diameters of 15 microns and push the spheres from one location to another.

With an improved fingertip design, the researchers might enable the devices to be more dexterous in positioning even smaller particles. The designs will probably use piezoelectric actuators to refine the sophistication of finger movement.

The researchers are also investigating methods of overcoming adhesion forces that are predominant at the micro scale and which hinder the release of these ultra-small particles from the fingers after manipulation.

Other possible improvements include increasing the number of fingers and the area in which manipulation can occur. An improved design might also add more flexibility and reduce the footprint of the device.

The smaller the device gets, the more efficient it will be for manufacturers. Now, problems with mass and thermal growth mean making small, super-precise parts with large, conventional machines is usually impossible. A typical machine tool running small parts has a machine-to-workpiece-volume ratio of about 1,000,000 to 1. But with miniature machines, it is closer to 10,000 to 1. The smaller and more dedicated the machine tools are, the less likely it is that thermal-growth will be a problem.

While this tiny device offers hope to the future of micro-manufacturing, there are also many other applications in which it could be used. A future generation micromanipulator station may be 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.