ABSTRACT
An optofluidic birefringent lens is demonstrated using hydrodynamic liquid-liquid (L(2)) interfaces in a microchannel. The L(2) lens comprises a nematic liquid crystal (NLC) phase and an optically isotropic phase for the main stream and the surrounding sub-stream, respectively. When the optofluidic device is subjected to a sufficiently strong electric field perpendicular to the flow direction, NLCs are allowed to orient along the external field rather than the flow direction overcoming fluidic viscous stress. The characteristics of the optofluidic birefringence lens are investigated by experimental and numerical analyses. The difference between the refractive indices of the main stream and the sub-stream changes according to the polarization direction of incident light, which determines the optical behaviour of the lens. The incidence of s-polarized light leads to a short focal point, while p-polarized light has a relatively long focal distance from the same L(2) interface. The curvatures and focal lengths of the lens are successfully evaluated by a hydrodynamic theory of NLCs and a simple ray-tracing model.
ABSTRACT
A new method was investigated to produce nanopatterns on polymeric surfaces with high resolution, good productivity, and low cost. It has certain advantages when compared with such conventional techniques as nanoimprint lithography (NIL), hot embossing, and injection molding. Polyvinyl alcohol (PVA) was utilized for preparation of the stamp with nanopatterns on its surface. The nanoimprinted PVA film was inserted into the cavity and the polymer melt was injected into the mold. Nanopatterns with pillars smaller than 100 nm were produced on the polymeric surface. The water soluble PVA film was used as the inserted template to overcome the difficulties of releasing the nanopatterned film from the substrate.
