EWOD using nonaqueous liquids

Abstract

Electrowetting on Dielectric (EWOD) has been studied for more than a decade and used for different applications but still there are few works on non-aqueous liquids such as mixtures of polyols. We have found that significant contact angle change can be achieved at voltages of 10V and bellow and that the recovery, when the voltage is withdrawn, exceeds 92% in all the cases. The dynamic change of contact angle has been measured applying 2Hz and 5Hz square 10V amplitude signal. The operation is stable but has a cut-off frequency in the range of frequency explored. Those results have been achieved using a glass substrate covered by an ITO electrode followed by a thin alumina layer and by a Teflon layer. We have also observed that the use of an HMDS layer followed by an ALD alumina layer prior to Teflon deposition provides better initial contact angle value, and that it can be achieved a significant contact angle change at lower voltages. Up to 1000 switch cycles have been performed and the contact angle change when using DI water rapidly becomes insignificant whereas with the polyol mixtures, although we have observed contact angle change degradation, it gets to a stable value thereafter.