Electrically induced concentration banding in particulate sols and emulsions

Anomalous Particle Rotation and Resulting Microstructure of Colloids in AC Electric Fields

“…These structures include tumbling clouds and toroidal rings in DC fields 18 and the formation of dense bands and vortices of colloidal particles in AC fields. [19][20][21][22][23][24][25][26] Bands and vortices of colloidal particles in AC electric fields were reported by Stauff 19 and were also discussed by Gamayunov and co-workers in their work in thinly spaced optical slides. 20 Isherwood et al 21 showed in their experiments that band formation is a time dependent phenomenon and occurs only in AC fields.…”

“…[19][20][21][22][23][24][25][26] Bands and vortices of colloidal particles in AC electric fields were reported by Stauff 19 and were also discussed by Gamayunov and co-workers in their work in thinly spaced optical slides. 20 Isherwood et al 21 showed in their experiments that band formation is a time dependent phenomenon and occurs only in AC fields. This observation was confirmed by Jennings et al, 22 who theorized that the bands are a direct result of developing instabilities in the presence of AC electric fields.…”

“…Electric fields also lead to the formation of structures and flows in colloidal suspensions which disrupt or complicate the aim of creating ordered 2D and 3D arrays of colloidal particles. These structures include tumbling clouds and toroidal rings in DC fields and the formation of dense bands and vortices of colloidal particles in AC fields. − …”

Electrokinetic Vortices and Traveling Waves in Nondilute Colloidal Dispersions

“…AC fields of 40 Hz and E 0 values of 20 V cm −1 and between 100 and 700 V cm −1 in 100 V cm −1 intervals were used. The field required to form chains and bands depends on frequency, , but a fixed low frequency of 40 Hz was chosen because it reduced the number of experimental parameters and resulted in the rapid formation on bands. All experiments were conducted for 15 min, when the observed phenomena had approached steady state.…”

“…Gamayunov and Murtosovkin first demonstrated that rotating bands are highly dependent on the electric field intensity and frequency . Isherwood et al showed that rotating bands can occur in aqueous dispersions of quartz particles and emulsions of kerosene in water . They briefly reported that their systems displayed an optimal frequency and electric field intensity for rapid band formation.…”