Optimization and characterization of inkjet printed interdigitated electrode geometries for impedance measurements

There is an increasing demand for continuous monitoring of biochemical parameters. Such applications require label-free sensing techniques which can be implemented on a variety of substrates. An impedance spectroscopy-based technique, using interdigitated electrodes is described. The electrodes with different geometrical parameters are fabricated by inkjet printing of silver nanoparticles on a flexible polyethylene substrate. The electrodes geometries differ in their metallization ratios. Impedance measurements are performed with DI water to determine the influence of metallization ratio on the electrode capacitance. From these results, the electrode that offers the highest capacitance is further characterized by measurements with ethanol-water mixtures. The results show that there is a decrease in capacitance of 0.1 pF per % increase of ethanol concentration. This is due to the decrease in permittivity as the ethanol concentration increases. The sensor is sensitive to the changing permittivity values. Therefore, an impedance-based, label-free, sensor concept on flexible substrate has been implemented.