Technology advances from UW-Madison engineers

Scientists at UW–Madison are frequently developing new technologies that may have fruitful applications in areas such as health, manufacturing, computing and other sectors of the economy. Beginning with this tipsheet, UW–Madison research communicators will periodically bring you story ideas on interesting and promising technology in development.

This tipsheet includes items on automobile radar systems, fabrication of ultra-thin materials and a new device that improves mobility for stroke sufferers.

Among the latest car safety features are radar-guided systems that can detect an impending crash and then warn the driver or apply the right brake pressure to avoid collision. But the semiconductor materials used to manufacture radar are expensive, limiting these systems so far to pricey luxury cars.

A team led by UW–Madison electrical and computer engineering professor Zhenqiang (Jack) Ma has now devised a way to make auto radar based on the common semiconductor silicon. Because silicon devices are less expensive, more robust and easier to fabricate than those in today’s radar systems, a switch to silicon promises to reduce the cost of auto radar manufacturing.

Transistors are the workhorses of electronics, and those used in radar must operate both at high frequency and high power. Ma’s team has invented a certain arrangement of advanced transistors that achieves these aims without causing the problems, such as hot spots, that currently bar silicon’s use.

Thin is in: Wngineering tool targets plastics, other slender parts

The world abounds with objects that are thin and lightweight, yet strong, including cell phone cases, car body panels, and aircraft hulls, just to name a few. But engineering these parts isn’t as easy as their commonness might suggest; in fact, objects that are thin relative to their overall size tend to confound established engineering methods.

The situation has led former industry researcher and UW–Madison mechanical engineering professor Krishnan Suresh to create his own technique and software for analyzing the structural, thermal and fluid properties of thin parts.

The technique might one day help engineers much more quickly and accurately design molds for injection-molded plastic parts-an industrial sector with an annual U.S. market value of $180 billion. Poorly designed molds can cause problems like warped and weak plastic, or incomplete filling of the mold cavity. And injection-molded parts are usually very thin and complex in shape-making them a perfect match for Suresh’s technique.

For stroke therapy, a device that walks the walk

Watch someone who has had a stroke walk and you likely will see a teetering, asymetric gait that includes a sideways leg swing, a locked knee and uneven steps. Those characteristics, which often develop after the stroke, appear to cause patients walking difficulties.

Current physical therapy techniques attempt to eliminate those characteristics; however, the characteristics may be compensations for an underlying motor-control deficit, says Kreg Gruben, an associate professor of biomedical engineering, mechanical engineering and kinesiology.

A more effective therapeutic approach is to correct the motor-control deficit that’s causing the characteristics, he says. To do that, he and graduate student Matthew Schmidt developed a system that looks somewhat like an exercise bike, but uses feedback to guide users to push a pedal in ways that retrain their natural muscle coordination patterns.

The invention is based on Gruben’s research, which suggests that the underlying cause of stroke patients’ walking difficulties is not just muscle weakness, but rather a control mix-up in the ratio of torque at the hip to torque at the knee as the patient attempts to walk. “After stroke, the hip provides more of the effort than the knee,” says Gruben. “The net effect is it tips you over backwards, and the unusual walking behaviors are likely to be compensations that enable patients to ‘walk,’ in spite of the control abnormality.”

The device could help patients regain a “normal” distribution of effort between the hip and knee. While the system may provide therapy to people who have lost muscle coordination due to stroke, traumatic brain injury, cerebral palsy or Parkinson’s disease, it also could provide training or rehabilitation to athletes who want to strengthen-or avoid re-injuring-specific muscle groups.