College of Engineering -- University of Wisconsin-Madison
n short, Professor Nicholas Abbott's microfluidics research is making waves. Through his work, Abbott hopes to create processes that will enable scientists to control the surface properties of liquids as a function of time and position, and create controlled gradients through an externally manipulated variable.
Abbott (right) and graduate student Craig Rosslee (left) are addressing problems associated with scaling integrated chemical processes to submillimeter scales, and their discoveries may impact both the medical and agricultural industries. Rather than using the more inefficient shaking method conducive to mixing macroscale reactants, scientists eventually may be able to use the results of Abbott's research to rapidly transport and mix reagents within millimeter and smaller-scale droplets of liquid supported on surfaces by creating gradients in surface tension. The method will thus provide new processes for molecule screening technologies used in medical drug discovery. "Our interest in this topic is largely derived from the fact that many phenomena involving the motion of liquids on millimeter and smaller scales are dominated by the effects of surfaces," says Abbott.
They are designing and synthesizing water-soluble detergentlike molecules, and by using electrochemical and photophysical methods, they can create a surface gradient in a solution by switching the molecules between surface active and inactive states. They also can vary the molecules' transformation rates, manipulate the location in which the switches occur, and use illumination to control the molecules' size and shape.
In related research, Abbott is revealing principles for creating microscale total analysis systems, which scientists might use to rapidly test agricultural chemicals on the spot--rather than transporting them to a lab--and control their application.
Extractor improves protein purification
Protein purification plays a vital and expensive role in the process of isolating chemicals used to make products ranging from pharmaceuticals to laundry detergents, yet current liquid-liquid protein extraction technology can cause inefficient protein transfer and excessive protein degradation.
Associate Professor Michael Graham and his team hope to solve these problems by developing a new liquid-liquid extractor for bio-separations. Team member Gretchen Baier, who recently earned her PhD, experimented with the two-fluid Taylor-Couette extractor designed by Emeritus Professor Edwin Lightfoot in which two immiscible fluids flow between inner and outer cylinders rotating in parallel directions at different speeds. Using lasers to observe the fluids' interface, she found that when the inner cylinder is rotated at a critical rate above that of the outer cylinder, vortices occurred, allowing proteins to diffuse efficiently across the interface. This centrifugally induced hydrodynamic instability is known as the two-fluid Taylor-Couette flow.
"We have a prototype that shows vortices do dramatically improve mass-transfer rates," says Graham. Once perfected, the extractor may be available commercially.
Researching "chain" reactions
Medical products, paints and coatings, automobile body parts, boats and other recreational gear, household utensils, carpeting, clothing, food containers and other materials are abundant in our daily lives. All can be made from polymers, but their properties differ depending on the characteristics of the products for which they're used. Scientists largely determine those properties during the polymerization step, in which small molecules combine to form a long chain, called a polymer.
Through research supported by gifts from more than 15 polymer producers and by grants from the National Science Foundation and the Department of Energy, Professor W. Harmon Ray and his research group, the University of Wisconsin Polymerization Reaction Engineering Laboratory (UWPREL), are developing a deeper understanding of the polymerization step through careful experiments and detailed computer modeling. And to help them model, design and control polymerization processes, they've developed a commercially available computer-aided-design software package, which researchers use in industry around the world. UWPREL's work also has resulted in methods that increase control of the polymer material structure, offer more efficient and less costly production, and allow safer production-plant operation.
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