  Electrowetting of nanodrops is studied for aqueous electrolyte mixtures. We
report a new method for controlling the degree of deformation and minimum
attainable contact angle by varying the difference of solvation strengths
between the two solvents, which determines the ratio of ion concentrations.
This implies that the commonly observed saturation of the contact angle with
the applied electric field can be suppressed by increasing the solvation energy
difference, a finding of practical significance for micro and nanofluidics.
Saturation is traced to be caused by the transfer of ions from the drop to the
surrounding medium. Furthermore, we derive an expression, based on the
electrokinetic equations, for the dependency of the drop's contact angle on the
ion concentration and the strength of the solvation potential in the absence of
external electric fields.
