Colloquium- January 23, 2015

Friday, January 23, 2015 (3:00 p.m. in Yost 306)

Title: Microscale propulsion in engineering and biology

Speaker: Henry Fu (Ralph E. Hoeper Assistant Professor of Engineering- University of Nevada at Reno)

Abstract: At the microscale, hydrodynamic constraints lead to nonintuitive features of propulsion for engineered as well as living systems.  I begin by describing the characteristics of microscale (low Reynolds number) flow, the challenges they present to propulsion and life, and some ways microorganisms have found ways to thrive despite those challenges.  Then, I discuss recent work in which we show that biomimetic strategies for engineered magnetic microswimmers, which have been investigated for biomedical applications, have neglected a large design space for such microrobots.  In particular, even achiral rigid geometries can be propelled by rotating magnetic fields.  We discuss the implications for both previously studied magnetic microswimmers and future possibilities enabled by our work.  Next, I discuss how swimming microorganisms such as sperm, algae or bacteria navigate biological environments which are more complex than simple Newtonian fluids. In the case of environments like mucus, which have microstructural lengthscales similar to the organisms’ size, microorganisms swim through an “obstacle course” rather than a continuum medium.  I will discuss how the heterogeneity leads to fluctuations in swimming speeds that reflect the microstructure, and how forces on the microstructure contain information about their influence on swimming.  Finally, I describe ongoing experiments to visualize such forces in locomotion through complex media.

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