"It's the equivalent of what civil engineers use to test a steel beam under 100,000 pounds of pressure, shrunk to the micro level," said co-author Roberto Ballarini, a professor of civil engineering formerly at Case Western Reserve and now chairman of civil engineering at the University of Minnesota. Ballarini is one of the inventors of the device to test the fibrils' strength.
In the first tests of their kind, the scientists glued one end of fibrils taken from a sea cucumber to a stationary base and the other end to a movable pad. When pulled apart, the fibrils stretched up to 100 percent of their resting length before breaking. A tendon stretches only 10 to 20 percent before breaking.
The new technology, developed by Zhilei Shen during her Ph.D. dissertation work, allowed her to keep the fibrils hydrated in saline to mimic their condition in the body. Earlier testing on dehydrated fibrils and tendons gave her different results.
The investigators believe water actually toughens fibrils and tendons as a whole. Since the proteoglycans in the cement largely control the degree of hydration around the fibrils, the team suspects they may be useful targets when designing drugs to control tendon strength.
In collaborations with nanoscientists at Yeshiva University and multi-scale modeling experts at MIT, the researchers took the lead in applying for funding to continue their work.
Their next steps include more detailed testing of bundles of fibrils and whole tendons as well as computer modeling that connects behavior of individual atoms and their bonds to molecular behavior and finally to mechanics of simulated fibrils and tendons. The models will
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Case Western Reserve University