A Planar RF Sensor for Single-Cell Measurements

An RF parallel Co-planar waveguide (CPW) Transmission-line (T.L.) for characterization of individual cells is presented. The planar capacitive device designed and microfabricated on a fused-silica substrate measures cell impedance inside a micro-fluidic channel with a narrow region (<50 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu\mathrm{m}$</tex> wide). The narrow region is equipped with micro-pillars to catch cells in the flow and to enable visual inspection of cells. Measured forward transmission coefficient (S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf>) of the device when four cells are trapped in between the proposed CPW parallel microelectrodes over a wide-band leads to 0.5 fF capacitance difference between the case of Phosphate Buffered Saline (PBS) solution and the case of suspended cells in the same PBS solution in the frequency range 1–6 GHz and 13-16GHz.