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Researchers at CU Boulder have developed a new technique that can study friction between soft materials like those inside the body, paving the way for improvements to medical devices used by millions each year.

Devices such as catheters and balloons are used to diagnose and treat a number of issues, including clogged arteries, carpal tunnel syndrome and blocked tear ducts. Although the treatments are commonplace, better understanding how the tissues are behaving during those treatments could lead to lower risk and greater effectiveness for patients.

Mechanical Engineering Associate Professor Mark Rentschler and Assistant Professor Rong Long led the work creating the Micro-Indentation and Visualization system, The new system can be used to study soft material contact under normal and shear forces. When combined with a laser scanning confocal microscope, the system allows researchers to see how soft materials are stretching and deforming in 3D during the experiments.

“Catheters and balloons are engaged to temporarily anchor in the body or to deploy other medical device implants such as stents. Lots of the balloons are smooth and need high pressure to get good engagement because their friction is so low,” Rentschler said. “If we tune the geometric design of these materials better through this approach, we could reduce the amount of pressure needed and ultimately improve device performance in the body.”

Rentschler said that soft material contact is not as well studied as hard material contact, so this system and work should help fill that gap. Although the medical uses are interesting and numerous, the work could have applications “anywhere there is contact,” from the hulls of ships covered in barnacles to airplane wings covered in ice, he said.

PhD students Karl Johannes, Kristin Calahan and Yuan Qi in the mechanical engineering department are also authors on the paper. Johannes led the mechanical design, fabrication and building of the system in the first year. Calahan took over after and has been working on operations, tuning and collecting the data.

Calahan said it was awesome to have the work written up and available to share.

"I love working in this field of research and hope to continue focusing on this type of research in the future," said Calahan, a fourth-year PhD student studying contact mechanics.

Johannes is also starting his fourth year as a PhD student, studying adhesion of micro-textured surfaces for medical devices. He had similar feelings about the paper.

"It feels great to have this work written up. It took longer than planned, but it feels great that we were able to do it," he said.

Rentschler said the team will continue to work on the topic through a grant from the National Science Foundation that is set to end in 2020.

“We are trying to stay at the front of the curve, and we are sure other people will mimic this technique now that we have shown we successfully measure such contact performance,” he said.