Electrical recognition of solvent liquids and particles in suspension with needle-plane electrodes

Abstract

Abstract We report a measurement methodology to identify solvent liquids and the presence of suspended nanoparticles with needle-plane capacitive electrodes. Preliminary results were obtained with a low noise measurement system detecting differential electric signals of two needle-plane devices, sensing and compensating respectively. A solvent drop of 3 μl volume is placed between electrodes of the sensing device where electric field perturbations are due to the liquid evaporation process and registered as temporal electric signals. Low noise differential measurement system reduces parasitic capacitances present in the sensing device to a minimun value in order to obtain just the temporal capacitance of the liquid evaporation process, presenting a base noise around 0.15 [fF / √Hz]. The results show that different liquid samples can be recognized electrically with just 3 μl volume drop, analysing its temporal signal shape, amplitude and evaporation time.