Collaborative Research: Theoretical and Experimental Investigation of Synthetic Micro/Nano-Swimmers in Shear-thinning Fluids

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Synthetic swimmers are engineered microscopic or nanoscopic objects that mimic how natural microorganisms swim through their environment. Synthetic swimmers that can move through biological fluids show great promise in biomedical applications such as drug delivery and microsurgery. Successful applications of these swimmers to biomedical tasks rely on their ability to move through biological fluids, such as blood, with complex and varying properties that respond to their surroundings. While there have been recent studies on the subject of locomotion in these fluids, much remains to be learned about the influence of directional applied forces or other motions such shaking and agitation, on swimming. This research project aims to quantify and elucidate the impacts of complex (non-Newtonian) fluid properties on the locomotion of synthetic micro-swimmers. The outcomes will enable the development of micro-robots with robust swimming capabilities for next generation healthcare applications. The project will integrate research and education through senior design projects and undergraduate research participation. By leveraging existing university programs with new activities derived from the research project, the researchers will provide outreach to approximately 120 high-school students annually. The project will also support an exhibition entitled "Swallowing a Surgeon" at the California Science Center (Los Angeles, CA) in order to expose the general public to the challenges and progress made towards designing biomedical micro-robots.In this collaborative research project between Santa Clara University and the California Institute of Technology, computations and experiments will be used to understand locomotion in shear-thinning fluids and to identify effective strategies to account for this non-Newtonian fluid behavior in the design of synthetic swimmers. Existing propulsion mechanisms can be broadly categorized into chemically-powered swimmers that harvest energy from local chemical reactions, and swimmers that require external fields for actuation. In this research project, representative model systems from each category will be studied to evaluate the impacts of shear-thinning rheology on major types of synthetic swimmers at small scales. Theory and experiments will use catalytic motors and flexible magnetic nanowire propellers to provide a comprehensive understanding of how distinct types of non-Newtonian fluid behaviors and their interactions affect locomotion at small scales. The completion of this project will lead to new fundamental knowledge on fluid-structure interactions and phoretic motion in complex fluids. This improved understanding will in turn guide the design of next-generation synthetic swimmers that can move through biological fluids effectively.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.