September 25, 2008: A team of researchers at the U. of Maryland’s A. James Clark School of Engineering, funded by the US Army Research Laboratory and US Army Research Office, has succeeded in manufacturing micromachines — tiny pumps, motors, and turbines to be integrated into a microscale liquid-fuel power generation system to significantly reduce a soldier’s battery load.
The engineers’ advances also hold promise in technologies for health care (micropumps for implantable medical devices) and first responders (bio-chemical sensors).
“For the first time, we have achieved a level of miniaturization for machines like that achieved over the last decades in electronics,” said Reza Ghodssi, associate professor of engineering in the Clark School’s department of electrical and computer engineering and Institute for Systems Research. “Our work shows that it is feasible to manufacture and integrate reliable, robust micromachines that apply tiny pumps, motors, and turbines in ways never before possible.”
The central component of their research is the ball bearing, a technology now used in everything from jet engines to dentists’ drills — devices in which parts move at high speeds in close proximity to each other. Ball bearings are simply spheres made of metal, silicon, or other substances that when placed between two surfaces, such as the components of a motor or generator, allow those components to move with less friction and heat than if they were moving in direct contact with each other. The less friction and heat, the faster the components can spin and the more power they can produce.
Using manufacturing techniques similar to those used in the semiconductor industry to make computer chips, the Clark School researchers have successfully miniaturized ball bearing support mechanisms with microballs as wide as a few human hairs and nearly invisible to the naked eye. Using these components, they have built tiny silicon pumps, motors, and turbines demonstrating rotational speeds of up to 87,000 rpm, comparable to the speed of large-scale machinery.
Schematic of the turbogenerator and viscous pump. (Source: U. of Maryland)
For troops on the battlefield, small-scale combustion generators using such micromachines, and combined with batteries in hybrid technologies, will significantly reduce the soldier’s load. “The Army needs small-scale, liquid-fueled power generators that can provide higher energy, at lighter weight and lower cost, than current fielded power sources,” stated Bruce Geil, acting branch chief for the Power Components Branch of the US Army Research Laboratory. “Dr. Ghodssi’s team is developing key fuel delivery and electrical generator components to meet our requirements.”
Micromachine systems also will help power land or air-based “micro vehicles” that will venture into risk-filled environments ahead of soldiers or first responders and send back information. Microgenerators fabricated completely in silicon and supported on microball bearings could power the vehicles’ electrical systems without weighing them down.