Nanoliter Liquid-Mixture Characterization Using Millimeter-Wave Lab-on-a-Waveguide Sensor

This paper presents the nanofluidic-integrated millimeter-wave sensor design, which is based on a near-field transmission-line technique implemented by a single loop slot antenna operating at 91 GHz and fabricated into the lid of a photolaser-based subtractive manufactured WR-10 rectangular waveguide. The nanofluidic subsystem, which is mounted on the top of the antenna aperture, is fabricated by using multiple PTFE layers to encapsulate and isolate the liquid sample during measurement. The novel sensor can measure a liquid volume of as low as 210 nanoliters, while still achieving a discrimination accuracy of better than 2% of ethanol in the ethanol/deionized-water liquid mixture.