  We report a novel technique capable of measuring the kinematic shear
viscosity of Newtonian liquids with steady streaming in microfluidic devices.
This probe-free microrheological method utilizes sub-kilohertz liquid
oscillation frequencies around a cylindrical obstacle, ensuring that the inner
streaming layer is comparable in size to the cylinder radius. To calibrate the
viscometer, the evolution of the inner streaming layer as a function of
oscillation frequency for a liquid of known viscosity is characterized using
standard particle tracking techniques. Once calibrated, we show how the steady
streaming viscometer can be used to measure low-viscosity liquids and volatile
liquids.
