A PDMS viscometer for microliter Newtonian fluid

This paper describes a poly( dimethylsiloxane) ( PDMS) microfluidic device for measuring the viscosity of Newtonian fluids. The viscometer utilized the high solubility and permeability of air in PDMS to generate Poiseuille flow in the degassed PDMS microfluidic device. By measuring the distance the fluids traveled and the flow velocity in the PDMS microchannel, the ratio of the viscosity of the sample fluid to the viscosity of a reference fluid was determined, and the viscosity of the sample fluid was then obtained. Only 5 mu L or less volume was consumed for the viscosity measurement. For most of the tested fluids, the results were in good agreement with the results from Ubbelohde viscometers, and the coefficients of variance were 3% or better. The wettability of the fluids on PDMS did not affect the measurement as the capillary forces were cancelled out in the data analysis. The PDMS viscometer was found applicable to a broad range of fluids, including aqueous solutions, non-PDMS-swelling organic solvents, fluorinated oil and blood plasma.