Steady streaming rheology for Newtonian fluids

Steady streaming in microfluidic devices has received considerable attention over the past decade due to its applications in particle manipulation, cell trapping, and microscale mixing. In this work, we discuss experimental results on the use of steady streaming for rheology, with a focus on characterizing the kinematic viscosity of Newtonian liquids. An oscillatory flow field is setup in a microfluidic channel using an electroacoustic transducer over a range of frequencies . The resulting steady streaming flow around a cylindrical post is observed using stroboscopic and high-speed imaging of passive tracer particles on an inverted microscope. The velocity fields are acquired through particle tracking velocimetry methods. Features of the radial stream function profile, which serve as a measure of the dynamic response, are used to characterize the liquid as a function of excitation frequency and non-dimensional oscillation amplitude.