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.