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Collagen is the fundamental building block of muscles, tissues, tendons, and ligaments in mammals. It is also widely used in reconstructive and cosmetic surgery. Although scientists have a good understanding about how it behaves at the tissue-level, some key mechanical properties of collagen at the nanoscale still remain elusive. A recent experimental study conducted by researchers at the University of Illinois at Urbana-Champaign, Washington University, and Columbia University on nanoscale collagen fibrils reported on, previously unforeseen, reasons why collagen is such a resilient material.
Because one collagen fibril is about one millionth in size of the cross-section of a human hair, studying it requires equally small equipment. The group in the Department of Aerospace Engineering at U of I designed tiny devices—Micro-Electro-Mechanical Systems—smaller than one millimeter in size, to test the collagen fibrils.
Devices - Collagen - Magnification - Microscope - Fibrils
"Using MEMS-type devices to grip the collagen fibrils under a high magnification optical microscope, we stretched individual fibrils to learn how they deform and the point at which they break," said Debashish Das, a postdoctoral scholar at Illinois who worked on the project. "We also repeatedly stretched and released the fibrils to measure their elastic and inelastic properties and how they respond to repeated loading."
Das explained, "Unlike a rubber band, if you stretch human or animal tissue and then release it, the tissue doesn't spring back to its original shape immediately. Some of the energy expended in pulling it is dissipated and lost. Our tissues are good at dissipating energy-when pulled and pushed, they dissipate a lot of energy without failing. This behavior has been known and understood at the tissue-level and attributed to either nanofibrillar sliding or to the gel-like hydrophilic substance between collagen fibrils. The individual collagen fibrils were not considered as major contributors to the overall viscoelastic behavior. But now...
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