We show that the electric field driven surface instability of visco-elasticfilms has two distinct regimes: (1) The visco-elastic films behaving like aliquid display long wavelengths governed by applied voltage and surfacetension, independent of its elastic storage and viscous loss moduli, and (2)the films behaving like a solid require a threshold voltage for the instabilitywhose wavelength always scales as ~ 4 x film thickness, independent of itssurface tension, applied voltage, loss and storage moduli. Wavelength in anarrow transition zone between these regimes depends on the storage modulus.
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