The Effect of AC Frequency on the Electrowetting Behavior of Ionic Liquids

Abstract

This paper presents a study of electrowetting of ionic liquids (ILs) under AC voltages, where nine different ILs (including mono-, di-, and tricationic varieties) with three different AC frequencies (60 Hz, 1 kHz, 10 kHz) were experimentally investigated. The main foci of this study are (i) an investigation of AC frequency dependence on the electrowetting of ILs; (ii) obtaining theoretical relationships between the relevant factors that explain the experimentally achieved frequency dependence; and (iii) a systematic comparison of electrowetting of ILs using AC vs DC voltage fields. The frequency of the AC voltage was found to be directly related to the apparent contact angle change (Deltatheta) of the ILs. This relationship was further analyzed and explained theoretically. The electrowetting properties of ILs under AC voltages were compared to that under DC voltages. All tested ILs showed greater apparent contact angle changes with AC voltage conditions than with DC voltage conditions. The effect of structure and charge density also was examined. Electrowetting reversibility under AC voltage conditions was studied for few ILs. Finally, the physical properties and AC electrowetting properties of ILs were measured and tabulated.

Dissipative Particle Dynamics Simulation of Droplet Oscillations in AC Electrowetting

“…A large number of studies have been conducted to investigate the drop behaviors in AC electrowetting [8][9][10][11][12][13][14]. It was found that the AC electrowetting of water and simple electrolytes behaves quite differently from that with the DC voltages [1,[8][9][10].…”

Continuous On-Chip Cell Separation Based on Conductivity-Induced Dielectrophoresis with 3D Self-Assembled Ionic Liquid Electrodes

“…The ionic liquid, [BMIM][PF 6 ], has a conductivity of 140 mS/m and viscosity of 450 cP (0.45 Pa s) at 25 °C. 23,24 Its relative permittivity is ~12 at low frequencies (~50–100 kHz). 25 …”

A Tunable Ionic Liquid Based RC Filter Using Electrowetting: A New Concept

“…Use of [bmim][NTf 2 ] has several practical advantages: (i) having negligible or no vapor pressure so that evaporation is not a concern and no special sealing or packaging is needed for the filter (11), (ii) resistance to vibrations and satellite drop formation, particularly compared to water or aqueous electrolytes (3), (iii) a lower viscosity than most ILs so that response times are faster than other ILs (11) (3,11), and (vi) negligible effect of water when compare to other ionic liquids (3,11).…”

“…Also, the ∆θ is different for different ILs, i.e., some ILs exhibit higher ∆θ at a given voltage, whereas other ILs show lower ∆θ at the same voltage (3,11,12). Therefore, if one needs a wide tunability range of f c , it is desirable to use the first type of ILs, and for fine-tunability the latter types of ILs are desirable.…”