Electric field and dewetting induced hierarchical structure formation in polymer/polymer/air trilayers

Abstract

Electrohydrodynamics were studied in a trilayer thin film system consisting of two different polymeric layers and air. A polymer with a higher dielectric constant, poly(methyl methacrylate), was sandwiched between air and a lower dielectric constant polymer, polystyrene. An electric field was applied normal to the interfaces. Along with electrostatic forces, dewetting forces were significant at two of the interfaces, namely, the polystyrene/silicon wafer and the polystyrene/poly(methyl methacrylate) interfaces. These two combined forces produce novel closed-cell structures that are difficult to produce by other existing techniques.

Electric field induced surface diffusion and micro/nano-scale island growth

“…Note the distinction between the recent work in the literature on processes such as LISA (Lithographically Induced Self Assembly) (Chou and Zhuang, 1999a;Chou et al, 1999b;Suo and Liang, 2001) and other similar techniques (Leach et al, 2005;Xiang et al, 2004;Schaeffer et al, 2000;Kim and Lu, 2006a,b;Lu and Kim, 2006), in which a polymer dielectric layer above its glass transition temperature is subjected to an electric field, which then undergoes a surface instability and develops islands. Such a technique deals with dielectric polymers or liquids in which the mechanism of shape change is bulk flow of the dielectric (governed by the NavierStokes equation); whereas the phenomenon under discussion in this paper pertains to conducting materials such as metals and doped semiconductors and the mechanism of shape evolution is surface diffusion.…”

Multiscale Pattern Generation in Viscoelastic Polymer Films by Spatiotemporal Modulation of Electric Field and Control of Rheology

“…The wavelength of the electric fi eld induced patterns depends on the applied fi eld which in turn depends on the fi lm thickness, applied voltage and the gap distance between the two electrodes. [ 47 , 48 , 52 , 56 , 65 , 66 ] Large-area ordering becomes possible for columnar, doubly periodic, [ 53 ] and phase inverted [ 63 ] microstructures by imposing a spatial variation in the fi eld [ 65 , 66 , 68 , 73 , 77 , 78 , 80 ] via patterned electrodes. Electric fi eld lithography (EFL) using a spatially varying fi eld is thus emerging to be an effective method for generating ordered meso structures in soft polymers, both in liquid and solid viscoelastic fi lms.…”

Electric field induced instabilities in thin confined bilayers

“…The typical parameter values used in this work are listed in Table 1. These parameter values are motivated by the typical experimental situations [20,24] and by a rich variety of behavior that can be already captured by these values. Set I consists of the thinner and less viscous films [20], whereas the set II comprises of thicker and higher viscosity films [24].…”

“…from a single (liquid-liquid [22]) and multiple (liquid-liquid and liquid-air [23]) deformable interface(s) under the influence of electric fields. The multiple deformable interfaces can also lead to phase inverted columnar structures when subjected to an electric field, as shown in a recent experimental work [24].…”

“…Detailed linear [42] and nonlinear analyses [43] of unstable viscoelastic bilayers have also been pursued. The electric field induced morphologies at the coupled liquid-air and liquid-liquid interfaces of viscous bilayers are of interest in view of their potential in meso-patterning applications and in understanding of a rich variety of behavior uncovered in recent experiments [20,23,24].…”