Improved broadband electrical detection of individual biological cells

Based on a homemade probe station on top of an inverted microscope for simultaneous microwave measurement and visual validation, broadband detection of live Jurkat cells was successfully extended from 2–3.5 GHz to 0.5–20 GHz with comparable sensitivity and reproducibility. With a carefully optimized coplanar waveguide, closely spaced microwave probes, and frequent calibrations, reference planes were established next to the microfluidic channel, which resulted in smooth and well-behaved scattering parameters without spurious resonances. From the measured scattering parameters, the extracted cytoplasm resistance of 190 kΩ was consistent with the previously reported value but validated over a much wider bandwidth.