Contact electrification induced microgap breakdown between separating electrodes*

Contact electrification, a process of generating static charge through contact and subsequent separation of two objects, may trigger gas breakdown as the gap distance increases. Although the electrode separation induced discharges have been studied with a long history, the mechanisms and characteristics of charge relaxation remain inexplicit or even controversial. In particular, the effects of electrode separation velocity on microgap breakdown have not yet been accurately quantified by either experiments or numerical simulations. In this work, we investigate gas discharge properties between two separating metal electrodes based on a fluid model incorporating the field electron emission, secondary electron emission, and bulk plasma chemistry processes. The potential difference between metal electrodes during their separation is determined, and the relationship between the potential difference and modified Paschen's curve is examined for the microscale electrode gap. Spatiotemporal distributions of discharge parameters, such as electron density and electric field, are obtained at different electrode separating velocities. The results indicate that the time duration and the intensity of charge relaxation can be tuned by the electrode separating velocity. The findings from this study offer an explicit understanding of the contact electrification induced microgap discharges between moving electrodes.