Lumped-Element Circuit Modelling of Microfluidic Channels in Microstrip Transmission Lines

A lumped-element equivalent circuit model (ECM) for a short length of microstrip transmission line incorporating a microfluidic channel filled with dielectric fluid is proposed. With this model, advanced microstrip circuits containing microfluidic channels can be designed in a fast and accurate manner. For verification, an ECM is extracted for a 1-mm length of 50 Omega transmission line on a 1.5-mm thick substrate with f, = 3.55 that has a 0.5-mm long x 0.5-mm tall x 6.9-mm wide microfluidic channel underneath it filled with a dielectric fluid of epsilon(r) = 81. The model parameter values are extracted using the structure's two-port S-parameter response obtained through full-wave 3D electromagnetic simulation. The extracted ECM is then used to design a fluidic phase shifter.