ABSTRACT

NONTECHNICAL SUMMARY

This CAREER award supports theoretical and computational research to describe and understand the behavior of biologically inspired active solids. The models developed in this research are motivated by mechanical force-driven shape changes in living matter occurring in the cell cytoskeleton and multicellular tissues. Living matter utilizes chemically patterned mechanical forces to change shape in programmed and robust ways during crucial biological processes such as tissue development and cell migration. They are thus excellent examples of active matter which comprise microscopic components that consume energy to generate mechanical forces and motion. Unlike active fluids where constituent components move freely, biological materials typically contain connected networks of polymers that respond to mechanical force by deforming like elastic springs. Further, unlike ordinary solids that deform under externally applied forces to reach a well-defined minimal energy state, the force-generating units of active solids are embedded within the material itself and can be redistributed by the deformations that they themselves generate. These unique features enable active solids to autonomously generate patterns and shapes not found in ordinary solids under thermodynamic equilibrium. The PI and his research team will create theoretical and computational models of shape-changing active solids by combining mechanical and chemical factors. The general aim is to theoretically and computationally investigate the unique shape changes and self-organization phenomena that are possible in active solids. The results will be compared with experimental data on cytoskeletal materials and blood clots obtained from the PI?s collaborators. Our research will provide fundamental understanding of self-organization in cell biology and tissue morphogenesis. It may influence strategies in tissue engineering as well as the design of synthetic soft materials capable of autonomous shape change.

Education and outreach activities are integrated with this research. These center on creating unique interdisciplinary learning opportunities involving computation for students at multiple levels. The PI will (1) deliver summer computational workshops to high school students; (2) develop computational modules for the introductory physics classes for life science majors as well as core physics classes; and (3) train beginning graduate students in scientific computing basics through a summer bridge module. These educational and outreach efforts will help recruit and train the future STEM workforce in the underserved San Joaquin Valley of California and beyond.

TECHNICAL SUMMARY

This CAREER award supports the development of a physical theory of spontaneous shape change and self-organization in elastic active matter through biologically inspired mechano-chemical feedback. It also supports the PI?s educational initiative to train students at multiple levels in scientific computation through interdisciplinary biophysical models. Active matter refers to collections of entities that consume chemical energy and generate mechanical forces and motion. In contrast to active fluids that contain self-propelling particles, active solids comprise constituents connected via elastic spring-like constraints that exhibit deformations instead of large-scale flows in response to mechanical force. In living matter, these mechanical forces are generated by molecular motors whose activity is patterned by chemical signals. The research will be inspired by the inherently mechano-chemical nature of living matter occurring both in the cell cytoskeleton and in multicellular tissue. The PI and his research team will develop a class of models combining active mechanical forces, elastic deformation, orientational order and chemical gradients, and their mutual interactions, leading to spontaneous shape change and pattern formation. The team of the PI will focus on two nonlinear mechanical systems that respond sensitively to mechanical forces: thin elastic shells that undergo 3D shape changes by buckling because of their inherent geometric nonlinearity, and disordered fiber networks that exhibit complex nonlinear deformation modes. Complementary modeling strategies will be used, including continuum models amenable to theoretical analysis, as well as discrete network models for numeric computation. The research will reveal how elastic deformations of living matter contribute to 1) the regulation of chemical concentration by geometry and strain; 2) mutual elastic interactions between active units driving their self-organization dynamics into ordered states; 3) long-range orientational order and associated topological defects through deformation-induced alignment, and 4) complex 3D shapes arising through various buckling instabilities.

The PI proposes an integrated educational plan involving computational training at multiple levels, from K-12 to undergraduate and graduate students. This will be delivered through 1) summer computational workshops and demonstrations designed for K-12 school students; 2) computational modules for the introductory physics classes for life science majors as well as core physics classes; and 3) training beginning graduate students through a summer bridge program on computational skills. These educational and outreach activities will contribute to the recruitment, retention, and training of students in STEM fields in the underserved San Joaquin Valley region of California. The research will provide training for a graduate student and a postdoc, and impact several fields including active matter physics, cell biology and tissue engineering, as well as bio-inspired soft materials design.

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.

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