Non-linearity and dynamics of low-voltage electrowetting and dewetting.

As an electrically controllable wetting effect, electrowetting on dielectrics (EWOD) is applied in diverse fields including optics, display technology and lab-on-a-chip systems. For the further development of EWOD applications, the reduction of the operation voltage is an essential issue. Recently, a low-voltage EWOD system with a threshold of 2 V was developed. In its sessile drop configuration, an aqueous electrolyte droplet with microliter scaled volume is actuated on an EWOD electrode in oil. The integration of this low-voltage EWOD system into a multiparameter measurement system enables the non-linearity and dynamics of the EWOD system to be online investigated during electrowetting and dewetting. The non-linearity was characterized by the hysteresis in the droplet deformation and that in the thickness variation of an oil layer, which is entrapped between the droplet and the electrode, in the nm range. The dynamics was evaluated with the characteristic time for the droplet deformation upon voltage jumps. This study of electrowetting and dewetting focuses on the conversion efficiency of the electrical energy in the deformation processes.