Carroll, Nick J.4; Jensen, Kaare Hartvig1; Parsa, Shima4; Holbrook, N. Michele4; Weitz, David A.4
1 Department of Physics, Technical University of Denmark2 Biophysics and Fluids, Department of Physics, Technical University of Denmark3 Harvard University4 Harvard University
We present a simple, noninvasive method for simultaneous measurement of flow velocity and inference of liquid viscosity in a microfluidic channel. We track the dynamics of a sharp front of photobleached fluorescent dye using a confocal microscope and measure the intensity at a single point downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer theological properties of the liquid. This technique provides a simple method for simultaneous elucidation of flow velocity and liquid viscosity in microchannels.