CAREER: Condensed Phases of Polymorphic Filaments Driven by Active Forces

NON-TECHNICAL ABSTRACT: Our body’s cells and tissues take shape by weaving strong webs from tiny fibers through hierarchical assembly. Outside of the body, biotechnology struggles mimicking this weaving process because it is almost impossible to pick up single fibers one by one to build webs. Instead, fibers are left to move around randomly, bump into each other, and stick to form larger structures. This creates problems: the types of structures are limited, and, for longer rods, the process is sluggish with weak and misshapen structures. The goal of this proposal is to use molecular fuel to push biological fibers faster and in desired directions. That will free fibers to rearrange and form stronger structures with less material. For example, fibers will merge into thick bundles, which will attach to form tough networks. These methods could lead to advances in biotechnology applications by constructing new materials for wound healing and artificial organ growth. Additionally, these ideas will be shared with the broader community through outreach demonstrations and activities with kids of all ages to inspire science-related careers. TECHNICAL ABSTRACT: This project will study disordered systems of long rod-like particles immersed in a liquid, driven by active forces. Rod-like particles, or filaments, make up a broad range of soft materials like fiber suspensions, glasses and gels. The existing selection of filament-based materials is limited by the fixed thermal energy per particle that imposes an inverse relation between size and motion. Long, thermally-driven filaments get trapped easily in weak arrangements and do not readily form more complex, and possibly stronger, structures. This project will lift these limitations by introducing a chemical energy source along with molecular motors that convert this energy to directed force. Microtubules, long protein filaments derived from cells, and kinesin motor proteins, that walk on the microtubules, make a well-studied versatile model system for generating active forces. This active system will be merged with bacterial flagellar filaments as model rod-like particles. Flagella are inert, stiff filaments whose helical shape and length can be precisely controlled. The goal will be to find how active forces disrupt arrangements of flagellar filaments that would be stable to thermal motions. Repulsively interacting flagella form entangled networks called glasses that resist deformation. Active forces may relieve the entanglements and allow the filaments to flow. Attractively interacting filaments form weakly bonded random networks, or gels. Active forces may rearrange the filaments to form bundles which will then build larger more robust structures. Overall, the results of this research will advance biotechnology by revealing how active forces may form lighter and stronger filament-based materials. The research ideas will be shared broadly through a Research Experiences for Teachers component, as well as demonstrations and activities with kids of all ages to inspire science-related careers. 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. NSF Award ID: 2541531 | Program: 01003031DB NSF RESEARCH & RELATED ACTIVIT,01002930DB NSF RESEARCH & RELATED ACTIVIT,01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Itamar Kolvin | Institution: Georgia Tech Research Corporation, ATLANTA, GA | Award Amount: $475,604 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2541531 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2541531.html