Sub-THz Non-contact Probing System for On-Chip Microfluidic Applications

We present a novel sub-THz probe station enabling contact-free characterization of liquids within integrated microfluidic channels on quartz substrates. The chip substrate and the 3D printed flow-cell are optically transparent, enabling microscopic visual alignment and compatibility with the optical inspection system. In the F band (90–140 GHz), we demonstrate measurements of a coplanar waveguide combined with the microfluidic system, using ethanol and bovine serum albumin protein concentration gradients. The data are stable and repeatable: traces for different concentrations remain clearly separated, and their standard-deviation envelopes never overlap (S₁₁-S₂₁ mean SD across all measurements: EtOH 3.46-0.21 %, BSA 3.89-0.18 %). This demonstrates the method’s high reliability, particularly for the transmission coefficient S₂₁. Designed for flexibility and rapid prototyping, the platform supports operation up to 1 THz and provides a versatile tool for high-frequency dielectric spectroscopy in fluidic environments and system-level lab-on-chip applications.