This paper reports on the performance of a sub-THz liquid sensor tool coupled to a microfluidic system. Non-invasive, non-destructive and on line measurements are demonstrated for the determination of methanol, ethanol and biomolecule concentrations and for controlling microfluidic devices. Techniques to characterize liquids are of fundamental importance for chemistry and life sciences [1][2]. The frequency 10\textasciicircum{}10 to 10\textasciicircum{}13 Hz range allows sensors for such interrogation in a label-free manner through electromagnetic measurements of small permittivity changes. We have developed a chemical sensing methodology that integrates subterahertz sensor technology into microfluidic devices fabricated on silicon, glass and polydimethylsiloxane.