Collaborative Research: Chiral Objects in Microfluidic Shear Flows: Chiral Separation and Microbial Locomotion

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The PIs investigate the dynamics of chiral particles and chiral organisms in shear flows, using a combination of microfluidic experiments and mathematical modeling. Chiral particles are particles with shapes that cannot be superimposed upon their mirror images, and are of broad interest for both basic science and technology. Chiral particles are ubiquitous in biology: for example, amino acids are chiral molecules. Since the intermolecular reactions involved in life processes depend on the geometry of participating molecules, different enantiomers of chiral drugs, pheromones, pesticides, and odorants have different biological effects. As a consequence, there is much interest in devising ways to separate pure enantiomeric samples out of a mixture of both enantiomers. Furthermore, in biology chirality occurs not only at the molecular scale, but also at the cellular scale. Many swimming microorganisms have chiral helical structures, such as the propulsion-generating flagella of most bacteria. At the same time, the watery environments of microbes are constantly subject to fluid flow, and hence shear, such as in the oceans, groundwater, industrial pipe flow, and catheters. This project has two specific aims: (i) exploiting the chirality-dependent motion of particles in shear flows to separate a mixture of enantiomers by handedness in a microfluidic channel, and (ii) understanding how chiral morphologies of microbes affect their swimming and foraging. These aims are unified by the ultimate goal of better understanding the behavior of chiral particles in shear flows, and hence amenable to the same experimental and theoretical research tools. The proposed research has the potential to (i) transform our technological capability to separate a racemic mixture into component enantiomers, by developing a simpler and less expensive separation strategy than those currently available, and (ii) improve our understanding of microbial motility, with applications ranging from the recycling of limiting elements in natural systems to the spreading of disease and biofilm formation.