Rapid measurement of fluid viscosity using co-flowing in a co-axial microfluidic device

This article presents a simple microfluidic method to measure the Newtonian fluid viscosity. This method is carried out in a co-axial microfluidic device. A stable liquid/liquid annular co-laminar flow in the co-axial microfluidic device has been realized, which can be described by Navier-Stokes equations. The viscosity of either fluid can be measured based on the equations when the viscosities of another fluid is known. Proper conditions to form stable annular co-laminar flow for the viscosity measurement were investigated. Several fluids were tested with viscosity ranging from 0.6 to 40 mPa s. The measured results fit very well with those measured by a commercial spinning digital viscometer. The novel method is highly controllable and reliable, and has the advantage of less time and material consumption, as well as easy fabrication of the device.