Electrical characterizations of electrodes microfluidics system for microbio object analysis

We have designed and fabricated electrodes microfluidics system for microbio object analysis. Two parallel plate electrodes were fabricated using soft lithography technique integrated with PDMS microfluidics channel. Gold (Au) material was decomposed to fabricate the electrodes. Voltage response through charging and discharging of the electrodes were observed using oscilloscope. For a constant dc voltage of 5 V we have obtained the time constant of the electrodes as 3.6 ms. On the other hand, it requires 850 ms to discharge completely without an external load. We have measured the capacitance of the electrodes as 0.37 pF in air (room environment) medium, on the other hand in distilled water medium electrodes capacitance is 0.77 pF. This is because of the high dielectric constant of distilled water (80.1). We have also measured electrodes capacitance by changing the medium to microbio objects such as; yeast cells (5 pF) and live bacteria cells (30 pF). Results showed that, bacteria have a higher electrical capacitance rather than yeast.