Physics (Internal)

Microscale propulsion in biological and engineered systems

This event is part of the Physics Department Colloquia Series.

Abstract: In this talk, I begin by describing some of the nonintuitive features of the hydrodynamics of microscale objects and organisms. Then I provide two examples showing how this type of hydrodynamics affects biological locomotion and engineered propulsion. In the first example, we examine swimming microorganisms such as sperm, algae, or bacteria. In biological scenarios, these organisms may navigate environments such as mucus, which have microstructural lengthscales similar to the organisms' size. Thus, they may be viewed as swimming through a heterogeneous "obstacle course" rather than a simple continuum fluid. I will describe a fundamental difference that arises from swimming through such a heterogeneous medium as compared to a continuum fluid: the heterogeneity leads to fluctuations in swimming speeds which reflects the microstructure. In the second example, we examine engineered magnetic artificial microswimmers which can be propelled by rotating them using a rotating magnetic field. Such microswimmers have been investigated for possible biomedical applications. I will describe our recent work which elucidates the minimal geometries that are required to achieve propulsion for such swimmers. Notably, we find that contrary to common biomimetically-inspired expectations, even achiral rigid geometries can be propelled by rotating magnetic fields.