S-parameters of Parylene C microwave microfluidic devices

Broadband S-parameter measurements of Parylene C microwave microfluidic devices from 100 MHz - 110 GHz. The Parylene C devices consisted of 400 nm platinum coplanar waveguides (CPW) (50 um center conductor, 5 um gaps, 200 um ground planes) deposited on fused silica with 6.5 um of Parylene C on top, capped with a PDMS microfluidic layer aligned over the CPWs. The dimensions of the PDMS microfluidic channels were approximately 210 um wide by 100 um deep. The total CPW line length was 10.000 mm and the channel length was 4.160 mm, where the channel was aligned over the center of the CPW. We measured the S-parameters of Parylene C devices filled with three different fluid conditions at different intervals over a 2 month period: H2O at 20 degrees Celsius, 1xPBS (phosphate-buffered saline) at 20 degrees Celsius, and 1xPBS at 37 degrees Celsius. We obtained measurements of both the fluid-filled and empty channel at each measurement day. We measured broadband S-parameters with a vector network analyzer and extender heads at a source power of -17 dBm on a temperature-controlled probe station. The S-parameters were calibrated to the probe tips with measurements of a gold reference chip in combination with multiline TRL in the NIST Microwave Uncertainty Framework. The differences in S-parameters from day 0 were plotted over time to observe changes in the dielectric properties of the Parylene C device during soaking.