Permittivity measurements using adjustable microscale electrode gaps between millimeter-sized spherical electrodes

This paper presents a technique for measuring the electrical permittivity of liquids and gases using millimeter-sized spherical electrodes with adjustable microscale separation. This technique eliminates the need for wet calibration by using the precise adjustment of electrode separation to remove the inherent errors of parasitic capacitance and electrode polarization. The spherical electrode geometry also eliminates the need for precise parallel adjustment of electrode separation, and enables small-volume, small-electrode-gap measurements where the applied electric field is constrained in a region of well-defined geometry. By further leveraging the fact that spherical electrodes can be obtained with extremely high diametrical accuracy, absolute permittivity measurement accuracies within 1% of the established values has been demonstrated. Finally, the apparatus also enables the creation of nanometer electrode gaps between macroscopic electrodes with precisely controlled separation, which can be used to study the electrical properties of liquids in highly confined states. The electrode gaps created in this manner can be adjusted from 20 nm to 50 μm, in increments of 0.25 nm