Electrohydrodynamic patterning of micro/nano-structures on thin polymer films

Electrohydrodynamic (EHD) patterning provides an alternative to fabricate the controllable polymeric micro/nanostructures, which have wide applications in industry. Both steady state and dynamic development of EHD patterning structures are discussed in this paper. For the steady state modeling, a discontinuous boundary element coupled with finite element method is applied. Numerical results reveal that a critical voltage exists, below which a small amplitude structure is obtained and above which polymer evolves into patterns with a large height/width ratio. The transient process of EHD patterning is represented by the numerical solution of the phase field equation coupled with the electric field and Navier-Stokes equation. The computer model is capable of describing the dynamic development of the electrically-induced transport and surface deformation phenomena during EHD patterning. The coupled multi-field equations are discretized in finite difference with an enhancement by parallel computing. For structured templates, the application of an electric field creates the conformal structures in the polymer film with the periodicity and aspect ratios of the polymer structures controlled by template patterns and applied electric fields. Analysis indicates that the interaction between the applied field and the fluids leads to an occurrence of complex flow structures and free surface deformation and plays an important role in determining the dynamics of an EHD patterning process.