Liquid measurements at microliter volumes using 1-port coplanar interdigital capacitor

A coplanar waveguide based 1-port interdigital capacitor is presented as 0.1 μL dielectric liquid sensor for frequencies up to 1 GHz. An equivalent circuit circuit of the sensor is given, from which capacitance C and conductance G are used to compute the complex permittivity of the material under test (MUT). 3D FEM simulations show a linear relationship between real and imaginary parts of the complex permittivity of the MUT and the C and G of the equivalent circuit, respectively, which has been validated by measurements on water-isopropanol mixtures. Time-resolved spectral measurements on baker's yeast cells were also conducted and are analysed in this paper.