Accueil > Séminaires > Précédents séminaires > Microscale mechanics of rigid-rod biopolymer networks

Microscale mechanics of rigid-rod biopolymer networks

Megan T. Valentine Department of Mechanical Engineering University of California, Santa Barbara

We explore the microscale mechanical properties of networks of biologically-derived polymers called microtubules. Our study takes advantage of the unique features of protein-based polymers, including crosslinker lability, extreme single-filament stiffness, and the ability to incorporate fluorescent markers to visualize network deformation. Using a suite of custom-designed magnetic tweezers devices, we probe the microscopic mechanical properties of microtubule networks subjected to localized loads. We find that the mechanical properties of chemically crosslinked networks depend sensitively on the single-molecule properties of the crosslinking molecules they contain. In particular, for the most rigid networks, a small number of crosslinkers bear stress, and their force-induced detachment determines the time-dependent network rearrangements. The network retains its elastic modulus even under conditions of significant plastic flow, suggesting that crosslinker breakage is balanced by the formation of new bonds. This leads to a remarkable resilience under repeated loading, as long as a sufficient number of the original crosslinkers are preserved per loading cycle. Our results are important to understanding how network architecture and crosslinker properties influence network mechanics, and provide new insight into the creation of materials with enhanced toughness and resiliency. Such materials have a wide range of applications : as smart structural materials that can heal after failure, as tissue replacements for damaged joints, and as scaffolds for the large-scale manufacture of stem cell cultures. Our results are also important to understanding the role of stress-transmitting structures in biological contexts, for example, in the mitotic spindle, a microtubule-based machine that controls cell division.