Speaker: Amy Q. Shen, Ph.D., Micro/Bio/Nanofluidics Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
Topic: Viscoelastic instabilities in microfluidic flows
Microfluidics has been used as a versatile platform of manipulating fluids at small length-scales, and in particular, offers a large range of deformation rates and direct visualization of resulting flow fields, providing unique opportunities for capturing the flow instabilities of viscoelastic fluids in real time. By using the subtractive three-dimensional (3D)-printing technique of selective laser-induced etching (SLE), glass microfluidic devices can sustain very high flow rates, provide access to little-explored flow regimes, and enable flow visualization from multiple planes of observation, allowing the quantitative study of 3D flows.
In this talk, I will highlight microfluidic platforms involving microfluidic cylinders to investigate the intricate viscoelastic instabilities of complex fluids. To model synchronized or coupled motions of motile objects (e.g., cilia) translating in biological fluids, we present the first example of viscoelastic fluid-structure interaction in a glass microfluidic device containing free-standing microfluidic circular cylinders. Our studies demonstrate that slender bodies in viscoelastic flow can exhibit highly correlated dynamics, which sheds insight on the analogous processes in biological systems. To expand this system, we further study the coupling between the viscoelastic fluid and the micropillar arrays, and discover the spontaneous emergence of metachronal waves in the system. We suggest that the waves originate from pulses of localized high elastic stresses propagating through the elastic wakes that form around the pillars. The occurrence of the wave is chaotic and shows characteristic fingerprints of elastic turbulence.