CAREER: Topological dynamics of three-dimensional active fluids

Brandeis University, Waltham MA

Investigators

Abstract

Non-Technical Abstract Spontaneous collective motion can be witnessed at different scales in nature: flocks of birds, migrating ants, and even cells within our own body moving collectively to close a wound. The goal of this research project is to better understand how these collective motions appear by employing simple three-dimensional biomimetic materials. These active materials are composed of proteins that can self-propel by harvesting energy from their environment. Two types of 3D liquid crystals will be investigated where the propulsion is driven by either molecular motors or by biofilaments that grow from one end and shrink from the other, recapitulating two fundamental mechanisms employed by living cells to migrate. This research project will address how to relate the forces generated at the microscopic scale to the emergent collective properties in 3D, a critical step towards the predictive design of novel active materials for robotic or bioengineering applications. On the educational side, this project will improve diversity and retainment of underrepresented minorities at each academic level, from Kindergarten through postsecondary education. The principal investigator will leverage the tangible nature of active matter to i) create a bilingual science children’s book, ii) monthly Science/Pizza talks and iii) interactive demonstrations in local schools, and iv) an annual active matter bootcamp for REU students. Technical abstract Simple biomimetic materials composed of biopolymers have become a paradigm for studying active fluids that spontaneously flow. At the macroscale, these flows often drive the nucleation of motile singularities such as topological defects. Investigating such topological dynamics in 3D presents novel conceptual and experimental challenges. In addition, connecting these system-sized topological features to the microscopic driving forces is required to rigorously test hydrodynamic theories of active fluids. This CAREER award aims to elucidate how the magnitude and the symmetry of mesoscopic active stresses drive the emergent topological dynamics of 3D active fluids with orientational order, with a particular focus on 3D active nematics and 3D polar fluids. Together, these two complementary research projects provide a comprehensive description of the out-of-equilibrium hydrodynamics of motile topological defects in 3D. They will set the foundations for building advanced biomimetic materials endowed with life-like properties. 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.