  Field-induced self-organized patterning in ultrathin (< 100 nm) polymer films
produces resolutions of the order of 10 {\mu}m or more because of the high
energy penalty for the surface deformations on small scales. We propose here a
very simple but versatile method to fabricate sub-micron (~100 nm) ordered and
tunable polymeric structures by self-organized room temperature dewetting of
ultrathin polystyrene films by minimizing the surface tension limitation. We
illustrate this technique by fabricating sub-micron lens arrays of tunable
curvature. This is achieved by switching to controlled room temperature
dewetting under an optimal mix of water, acetone and methyl-ethyl ketone (MEK).
Organic solvents used decrease the glass transition temperature, greatly
decrease the interfacial tension, intensify the field and increase the contact
angle/aspect ratio of the resulting tunable nano-structures, without a
concurrent solubilization of PS owing to water being the majority phase in the
outside mixture.
