This CAREER award supports theoretical and computational research integrated with education on active matter, an area of soft matter inspired by biology that focuses on understanding soft matter made from fundamental building blocks that are maintained far from the steady state of equilibrium by injecting energy at microscopic scales. It takes a trip to the local aquarium for one to admire schools of small fish forming spectacular patterns as they swim and swirl in a coherent synchronous manner. The tiniest jolt from an intruder, a big fish perhaps, sends the school into a momentary frenzy, where the little creatures explode in all directions, only to reform the swarm seconds later. Squint a little and the school of fish appears like one object, one continuous "living" material with a life and intelligence of its own; grander than the sum of its parts, smarter than the individual organisms. The dynamic properties of such "living materials" contrast sharply with the static characteristics of traditional materials. The former consists of "active" components such as bacteria, self-propelled nanorods, or molecular motors, that locally consume energy to move, exert forces or perform chemical reactions, and so, are inherently out of equilibrium, while the latter have fundamental building blocks that are "passive", such as molecules at equilibrium. The PI envisions designing a new and distinct class of materials by putting together active components to create active materials. In the same way that schools of fish respond to predators, swarms of bacteria swim towards nutrients, or skin heals itself when wounded, an artificial active material of self-propelled colloids or insect drones can respond to stimuli, restore coherence of the flock or "self-heal", adapt, store energy and information, assemble and disassemble at will. The PI aims to formulate a framework for understanding active matter based on statistical physics which focuses on systems composed of a large number of particles that will contribute to the foundations for developing design rules for making living materials with functionality beyond ordinary materials.
Applications with broad societal impact range from novel active materials that are responsive, adaptive and self-healing, to aquatic swarming robots, for example for ocean exploration, under-water maintenance, remediation of oil, detection and collection of plastics in the ocean, to novel drug delivery platforms. The research and education plans are tightly integrated to one another, and both are designed to incorporate diversity. The PI will collaborate with programs that promote and advise on diversity, as well as evaluate success, and will include minorities and underrepresented groups both in her group and through outreach. Undergraduate and graduate students and postdoctoral fellows will receive training in a highly interdisciplinary field that combines computational, and analytical skills and draws knowledge from materials, physics, chemistry, biology, mathematics and engineering. Broader outreach with the public will be achieved through three exciting avenues: (i) podcast interviews; (ii) online material and a blog for students and postdocs with children; (iii) soft matter video project and (iv) local community outreach at science fairs.
This CAREER award supports theoretical and computational research integrated with education on active matter under conditions of intermediate Reynolds number flow. The complexity of emergent active-matter behavior has been demonstrated at many length-scales in both biological and artificial systems. Most studies so far have either developed minimal models without hydrodynamic interactions or focused on microscopic scales, where the Reynolds number approaches zero, Stokes flow. Both approaches are vibrant fields of research showing novel emergent behavior and providing insight for nonequilibrium theories of active matter. However, a whole region of parameter space. active matter of inertial particles at intermediate Reynolds numbers, remains largely unexplored. The intermediate regime covers at least three orders of magnitude in the Reynolds number and opens numerous possibilities for materials science, and describing millions of different organisms that one can study as model systems. The overarching goal of this project is to study active particles in fluids where viscous and inertial forces coexist with the aim to build a framework for describing mesoscale active matter suspensions. The two main thrusts that build upon each other towards that goal are to: (1) study and classify single model swimmers, at the point they transition from low to intermediate Reynolds numbers, and then for increasing Reynolds numbers; (2) examine the pairwise interactions for different model swimmers and establish an understanding of their collective behavior, emergent swarming and many-body interactions. In this way, the research will contribute to formulating a statistical mechanics based framework of active inertial suspensions.
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.
