Electrorheological Effects Depending On The Wettability Of Particles

Electrorheological(ER) Fluid is a smart material in industry and its phase can be changed between solid and liquid phase within milli-seconds.It is composed of nano-size or micro-size dielectric particles and oils.The rheological properties of colloidal ER fluids are controllable by the application of an electric field.In this paper,our focus is the relation among electrorheological(ER) effects of ER fluids,zero-field dispersity of colloidal particles and particle wettability. We find that well dispersed particles resulting from particle wettability have much stronger attraction than those aggregated into different clusters.We reveal that,to achieve ER effects,besides improving dielectric properties of ER particles,it is also helpful to reduce the surface tension of liquids,which leads to higher wettability of suspended particles and thus better zero-field dispersity of the particles due to lyophilic repulsive forces between them.To value the particle wettability in the liquid,new equations are deduced by spontaneously capillary rise method with the hydrostatic effect,in order to describe the relation between the liquid front height and time,which enables us to experimentally measure contact angles of capillary tube surfaces directly.