Collaborative Research: Multiscale engineering of active stress in biomaterials

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Nontechnical Abstract:Biological systems exhibit remarkable behaviors, including the ability to heal, reproduce, and be self-motile. Conventional synthetic materials do not display such properties because they are composed of inanimate molecules. In contrast, biological systems consist of active, energy transducing molecules which continuously push and pull on each other, producing active stresses. These active stresses make biological systems examples of active matter, and are ultimately are responsible for many of their unusual behaviors. Creating artificial active matter opens up a new route towards constructing materials with lifelike functionalities. However, a significant obstacle to realizing this possibility is an absence of understanding of how active stresses are produced: given specific elemental building blocks, there are not currently tools to either measure or theoretically predict the magnitude, type, or even the sign of the active stresses. The project will elucidate the foundational principles of active stress generation using a synergistic combination of experiments, simulations, and theory. The work will result in the creation of new experimental tools for measuring active stresses, new synthesis procedures for creating active materials, and new multi-scale modeling techniques for studying active matter. An integrated outreach program will bring the excitement of active matter to K-12 education, undergraduates, and graduates by combining interactive demonstrations, advanced interdisciplinary training, and intensive summer courses.Technical Abstract:The research focuses on studying assemblages of microtubules and kinesin-14 molecular motors. The work addresses three fundamental challenges in understanding active stresses generated by such active materials. First is the development of tools to measure active stresses at different length scales using optical tweezers, fluid flow measurements, microfluidics, and 3D printing, in combination with theory and simulations. Second, a novel system will be created in which active stress generation will be modulated by directly affixing kinesin-14 to microtubules in predetermined patterns. Theory and simulations will be used to guide which patterns to create, and conversely, measuring the resulting active stress generation in these designed materials will provide a stringent test of theory and simulations. Third, a multi-scale modeling framework will be developed and tested. These will be subsequently related to each other through a combination of analytical calculations and simulations. The resulting models will be made with continual feedback from experiments. Taken together, this work will establish new paradigms to study, understand, and engineer active stresses in active materials.This DMR grant supports research to understand the assemblages of microtubules and kinesin-14 molecular motors with funding from the Condensed Matter Physics (CMP) and Biomaterials (BMAT) Programs in the Division of Materials Research of the Mathematical and Physical Sciences Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.