Asymmetry in charging or fringing-field strength for opposite lithium-niobate polarities

Determine why the electrostatic force acting on RM734 ferroelectric-nematic droplets is stronger near lithium-niobate crystals with negative polar axis than near crystals with positive polar axis, specifically whether the asymmetry arises from different fringing-field magnitudes or from polarity-dependent droplet electrification.

Background

The experiments show that RM734 ferroelectric-nematic droplets move more rapidly, and therefore experience a stronger inferred force, when the lithium-niobate crystal has a negative polar axis. Because crystals with opposite polar axes generate fringing fields of opposite sign, the authors suggest that the sign of the bound charge produced in splayed regions may affect electron transfer from the droplet to the PTFE substrate. They tentatively propose that negatively charged splayed regions may release electrons more readily than positively charged regions, but do not establish whether this mechanism explains the observed asymmetry or whether the fringing fields themselves differ in magnitude.