We present a simple method for fabricating high aspect-ratio polymer nanostructures on a solid substrate by sequential application of molding and drawing of a thin polymer film. In this method, a thin polymer film is prepared by spin coating on a solid substrate and the temperature is raised above the polymer's glass transition while in conformal contact with a poly(urethane acrylate) (PUA) mold having nano-cavities. Consequently, capillary force induces deformation of the polymer melt into the void spaces of the mold and the filled nanostructure was further elongated upon removal of the mold due to tailored adhesive force at the mold/polymer interface. The optimum value of the work of adhesion at the mold/polymer interface ranged from 0.9 to 1.1 times that at the substrate/polymer interface. Below or above this range, a simple molding or detachment occurred, corresponding to earlier findings.
A simple method for fabricating micro/nanoscale hierarchical structures is presented using a two-step temperature-directed capillary molding technique. This lithographic method involves a sequential application of molding process in which a uniform polymer-coated surface is molded with a patterned mold by means of capillary force above the glass transition temperature of the polymer. Various microstructures and nanostructures were fabricated with minimum
resolution down to ~ 50 nm with good reproducibility. Also contact angle measurements of water indicated that two wetting states coexist on a multiscale hierarchical structure where heterogeneous wetting is dominant for microstructure and homogeneous wetting for nanostructure. A simple theoretical model combining these two wetting states was presented, which was in good agreement with the experimental data. Using this approach, multiscale hierarchical
structures for biomimetic functional surfaces can be fabricated with precise control over geometrical parameters and the wettability of a solid surface can be tailored in a controllable manner.