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2005-2006 HIGHLIGHTS








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Adam Kramschuster, Sarah Gong, Alex Chandra and Tom Turng

Mechanical Engineering

Making more functional biopolymers

As a result of decades of well-funded research, petroleum-based plastics for packaging have such desirable properties as superior strength, toughness, rigidity and temperature resistance. However, nearly half the packaging produced in a given year ends up in landfills, where it could take a long time—if ever—to degrade.

In response to skyrocketing oil prices and increased environmental concerns, engineers are working to perfect plastic packaging that holds up well in use, yet breaks down quickly in a landfill.

Bio-based polymers

Made from renewable resources like corn or soybeans, these bio-based polymers for plastics are commonly used in products ranging from composting bags and mulch film to baby diapers. They’re products, says Professor Lih-Sheng Turng, that emphasize biodegradability and not function.

Function is an area in which bio-based polymers fall short, says Turng (above right). Collaborating with University of Wisconsin-Milwaukee Assistant Professor of Mechanical Engineering Sarah Gong (seated) and graduate students Adam Kramschuster (left) and Alex Chandra (second from right), Turng is hoping to enhance the material properties of bio-based plastics.

With National Science Foundation grants and UW-Madison Graduate School Industrial and Economic Development Research funding, the group is incorporating additives like nano clay, carbon nanotubes and natural fibers into bio-based polymers to improve key properties such as strength and temperature resistance. In addition, the researchers are studying ways that they can exploit special molding processes to alter bio-based polymer properties and microstructure for a variety of biomedical applications. Already, they are working with industry to incorporate their findings.

Good sports: Hamstring study may help injured athletes stay healthy

Athletes who strain a hamstring could avoid re-injuring the muscle by participating in targeted physical therapies and improving their running mechanics, says Associate Professor Darryl Thelen.

Hamstring strains occur when muscle fibers tear at the junction of muscle and tendon. Such injuries often occur as athletes sprint during sports like track, soccer, football and baseball.

Combining magnetic resonance imaging, studies of sprinting biomechanics, and computer simulations, Thelen and graduate students Liz Chumanov and Amy Silder are learning more about how hamstring strains heal and why injuries may recur. “We are particularly interested in how the muscle remodels following injury,” says Thelen.

So far, the researchers have learned that athletes are most likely to injure a hamstring during the late-swing phase of sprinting, during which both feet are off the ground and the leg is extended. “That’s when the hamstring is loaded and stretched and seems to be most susceptible to injury,” says Thelen.

In addition, they also discovered that strengthening the core muscles—the abs and lower back—is related to fewer re-injuries. The group currently is studying whether mobilizing the muscle in a controlled way shortly after injury will help the muscle remodel in a way that reduces re-injury risk.

Funded by the NFL Charities and the Aircast Foundation, the group’s studies of how muscles heal after injury also are relevant to other muscles susceptible to injury, as well as tissues cut during surgical procedures, says Thelen.

Metal-embedding method makes tiny sensors work in extreme environments

UW-Madison mechanical engineers have developed a method for fabricating “packages” of tiny sensors that measure temperature more accurately than bulk thermo-couples. Inserted unobtrusively in critical locations, these metal-embedded micro-thin film thermocouples could more effectively monitor conditions and diagnose problems during processes such as injection-molding or die-casting.

Recent technological advances have made micro thin film thermocouples, with thicknesses of about 100 nanometers, a more responsive alternative to bulk sensors, which are destructively inserted into critical locations or placed too far from the product to gather accurate data, says Associate Professor Xiaochun Li.

Currently, micro thin film thermocouples are fabricated onto substrates. Once in the manufacturing setting, however, the sensors are directly exposed to extreme conditions that can cause them to fail prematurely.

With graduate students Xugang Zhang and Hongseok Choi, and postdoctoral researcher Arindom Datta, Li developed a method to embed such micro sensors in nickel—an innovative process that protects them from oxidation, chemical corrosion, wear and contamination, yet enables their placement at key manufacturing locations.

The resulting metal-embedded sensors could be applied as a unit or laser-cut out of a metal wafer for individual use. Because of their small size, they can be embedded without impairing the structural integrity of tooling, says Li. In addition, he says, researchers also could use the embedding method to package any micro or nano devices for application in harsh environments.

The group patented the method through the Wisconsin Alumni Research Foundation.

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