In liquid electrophotograpy inks are colloidal solutions of toner particles suspended in a dielectric liquid together with typically micellar toner charging components. Toner particles and charging agents are in physicochemical equilibrium with toner acquiring charge that may be temperature dependent. Viscous dissipative forces are primarily governed by carrier liquid viscosity which is also temperature dependent. Measurements of time dependent currents at high fields indicate that viscosity effects dominate temperature behaviour of Indigo electroinks.
Henryk Birecki, "Temperature Effects on Liquid Electrophoretic Inks" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP28), 2012, pp 213 - 214, https://doi.org/10.2352/ISSN.2169-4451.2012.28.1.art00062_1