Janus micro‐thread to micro‐nanodroplets using dynamic contact line lithography

Abstract

Dynamic contact line lithography (DCLL) is generally used for the templateless but well-ordered deposition of polymer micro/nanostructures from the solution of homopolymer. DCLL from the blend of several polymers in a common suitable solvent can generate rich morphologies including nanostructured Janus micro threads on a surface which might be challenging to fabricate using any other method. A blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in toluene with different compositions and concentrations are used for DCLL at a constant contact line speed of 10 μm/s. Variations of compositions and the overall concentration of polymer, engender Janus micro threads to undulated threads and multi-layered micro/nanodroplets of PS/PMMA. Interestingly, the more soluble PS phase separates first compared to less soluble PMMA near the contact line due to the enhanced local concentration of PS during the convective flow of the solvent toward the contact line. This is also verified by DCLL using PS/PMMA blend in ethyl acetate as well. In that case, more soluble PMMA deposits first near the contact line compared to marginally less soluble PS in the solvent.