Microfluidic Diffusion Viscometer for Rapid Analysis of Complex Solutions.

The viscosity of complex solutions is a physical property of central relevance for a large number of applications in material, biological, and biotechnological sciences. Here we demonstrate a microfluidic technology to measure the viscosity of solutions by following the advection and diffusion of tracer particles under steady-state flow. We validate our method with standard water-glycerol mixtures, and then we apply this microfluidic diffusion viscometer to measure the viscosity of protein solutions at high concentrations as well as of a crude cell lysate. Our approach exhibits a series of attractive features, including analysis time on the order of seconds and the consumption of a few μL of sample, as well as the possibility to readily integrate the microfluidic viscometer in other instrument platforms or modular microfluidic devices. These characteristics make microfluidic diffusion viscometry an attractive approach in automated processes in biotechnology and health-care sciences where fast measurements with limited amount of sample consumption are required.