Glass Microwave Microfluidic Devices for Broadband Characterization of Diverse Fluids

We demonstrate a glass microwave microfluidic device for determining the permittivity of a wide range of liquid chemicals from 100 MHz to 30 GHz with associated uncertainties. Conventional microwave microfluidic devices use polymer-based microfluidic layers for fluid delivery, but these polymers swell in organic solvents and are not suitable for many applications. Our device incorporates glass microfluidic channels with platinum coplanar waveguides (CPWs) to provide a solvent-resistant architecture for broadband dielectric spectroscopy. We utilize broadband scattering parameter measurements with a vector network analyzer (VNA) on a wafer probing station and multiline thru-reflect–line (mTRL) calibrations to extract the distributed circuit parameters of transmission lines and solve for fluid permittivity. In this work, we demonstrate the utility of the device by measuring the permittivity of four organic solvents difficult to measure otherwise: hexane, heptane, decane, and toluene.