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Cover of the Fall 2010 Annual Report issue


FALL 2010


Mechanical Engineering

Probing the mysteries of nanoscale wear

Kevin Turner, David Grierson and Jingjing Liu. Photo by David Nevala.

From left: Assistant Professor Kevin Turner with graduate students David Grierson and Jingjing Liu. Photo by David Nevala. view larger image

Assistant Professor Kevin Turner is working with Illinois-based Advanced Diamond Technologies (ADT) and collaborators at the University of Pennsylvania to design and fabricate high-performance, wear-resistant diamond probes for atomic-force microscopy, or AFM. AFM is a widely used research technique for measuring the nanoscale topography of surfaces. A sharp probe with a point that has a radius of 10 to 50 nanometers is attached to a cantilever beam and scanned across a surface. The probe follows the topography of the surface like a phonograph needle on a record, and a laser is reflected off the cantilever to create an image of the surface with nanoscale resolution.

Probe durability is crucial as AFM expands to industrial and manufacturing settings. ADT, which spun out of Argonne National Lab to commercialize a new type of ultrananocrystalline diamond material, developed a proposal with Turner and then-Engineering Physics Associate Professor Rob Carpick, now at the University of Pennsylvania. With a 2007 Small Business Technology Transfer grant from the National Science Foundation, the team created a new AFM diamond probe that performs better than almost any other type of probe and is by far more durable and wear-resistant than traditional probes made from silicon-based materials. ADT now sells a commercial version of the probe, for which the team received a 2009 R&D 100 Award.

“This project has been great as it not only led to a commercial AFM probe, but also required fundamental research into wear at the nanoscale,” says Turner. “The small-scale contact between AFM probes and samples is a unique platform to investigate the more fundamental mechanisms of wear.”

The original project examined probe performance in the contact mode of AFM, where the tip maintains constant contact with the surface during a scan. Turner’s team now is studying wear during the tapping mode of AFM, where a tip “taps” the surface billions of times to create an image. The researchers are also working to study better approaches to fabricate probes with sharper tips for imaging small-scale features.

Plastics techniques, for people

Bionates image

Six years ago, Professor Lih-Sheng (Tom) Turng and then-PhD student Adam Kramschuster brainstormed how to use their expertise in polymer processing to make a larger difference for society. Out of their discussions came the idea to transfer polymer fabrication techniques to the field of tissue engineering — and the pair are now part of a major interdisciplinary project expected to yield a new process for mass-producing tissue scaffolds within three to five years.

The project, called Bio-Nanocomposite Tissue Engineering Scaffolds, or Bionates, is one of five proposals included in the new Wisconsin Institute for Discovery, a public institution at UW-Madison focused on enhancing human health and welfare through interdisciplinary research.

The Bionates team will develop and study tissue engineering scaffolds, which are biological substrates used for constructing human tissue outside of the body. The scaffolds are used in conjunction with specially designed micro-environments, which help guide how stem cells differentiate into various cell types and then grow into tissues on scaffolds. The ultimate goal is to use these tissues for a wide variety of medical treatments, such as skin patches for burn victims or insulin-generating cell implants, to name only a couple.

While researchers have successfully fabricated tissue scaffolds, they can only do so one at a time. Bionates researchers will blend their expertise to develop a manufacturing process to mass-produce scaffolds with consistent quality and properties. Several manufacturing processes used to produce various plastics have potential for use in mass-producing tissue scaffolds. A patent-pending injection molding process developed in the Polymer Engineering Center — which Turng co-directs — is particularly promising.

Led by Turng, the Bionates team includes Engineering Physics Professor Wendy Crone; Biomedical Engineering Associate Professors Shaoqin (Sarah) Gong, Kristyn Masters and Bill Murphy , and Assistant Professor Wan-Ju Li; Physiology Professor Tim Kamp; and Medical History and Bioethics Associate Professor Linda Hogle. Kramschuster, now an assistant professor of engineering and technology at UW-Stout, rounds out the current team, which will expand to include more faculty members in the coming years.

Solar researchers freeze out cancer


Cryoprobe view larger image

One method for treating cancer involves injecting a patient with a metal probe in close proximity of a tumor. The probe is then rapidly cooled to the point of freezing and killing the surrounding tissue. Called a cryoprobe, the technique is gaining traction in medicine, but the procedure isn’t as simple or fast as many doctors would like.

The solution for optimizing cryoprobes may not come from a medical lab, but rather, from the UW-Madison Solar Energy Laboratory (SEL).

SEL includes researchers who study refrigeration cycles at a variety of temperatures. Elmer R. and Janet Ambach Kaiser Chair and Associate Professor Gregory Nellis is most directly involved with the cryoprobe project, along with Ouweneel-Bascom Professor and SEL Director Sanford Klein and Professor John Pfotenhauer.

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provided initial funding in 2004 for SEL researchers to develop a model to design more powerful, yet small, cryoprobe systems. Ideally, probe systems would involve one probe, rather than the three or four currently used in treatment sessions, that would freeze cancer tissue so quickly the whole procedure could take around an hour and the entire system, including compressors, refrigerant fluid lines and the probe itself, would be small enough to fit in a doctor’s office.

With another ASHRAE grant, the researchers now are building an experiment to rigorously test their model and measure the performance of various cryoprobes. American Medical Systems in Minnetonka, Minnesota, provided the lab with a cryoprobe system, and PhD student Harrison Skye has worked on designing and fabricating a method to test cryoprobe efficacy. For example, changing the composition of the fluid used to cool the probe can alter its performance, and the SEL team is particularly interested in finding the optimal fluid mixture. “This is an extremely sophisticated experiment, and I’m excited to see how the data compares to the model,” says Klein.

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