A poly(dimethylsiloxane) viscometer for microliter power law fluids

Abstract

This paper describes a poly(dimethylsiloxane) (PDMS) microfluidic device for measuring the viscosity of power law fluids. The viscometer utilized the high solubility and permeability of air in PDMS to generate vacuum and drive the Poiseuille flow in the degassed PDMS microchannels. Wide ranges of shear rates in PDMS microchannels were generated by controlling the chamber sizes of the PDMS viscometer. By measuring the distance the fluids traveled and the flow velocity in the PDMS microchannel, the flow behavior index n was determined and the viscosity profile of the sample fluid under a range of shear rates was obtained. Only 5 µL or less volume was consumed for the viscosity measurement. Viscosities of poly(ethylene oxide) solutions and blood control standard were successfully measured under shear rates varying from 10 to 500 s−1, and the results were consistent with those from conventional cone–plate rheometers. The PDMS viscometer was applicable to a broad range of power law fluids, such as diluted polymeric solutions and colloidal suspensions.