Polymer inking as a micro- and nanopatterning technique

A polymer inking technique was developed to form micro- and nanopatterns on a substrate. In this process, a polymer thin film is spin coated on a patterned mold. After contacting the substrate at a suitable temperature and pressure, the polymer on the protruded surfaces of the mold is transferred to the substrate and a positive image of the mold is obtained. A selective surface treatment method has been developed to improve the edge smoothness of the inked pattern. During selective surface treatment, the protruded surfaces of the mold are first treated with a flat poly(dimethylsiloxane) stamp impregnated with a silane that has medium surface energy. The mold is then immersed into the solution of another silane with very low surface energy to treat the trenches of the mold. Because the surface energy of the sidewalls is lower than that on the protrusions, polymer dewetting from the sidewalls is promoted, which makes the polymer film discontinuous along the edges of patterns. Therefore, inked polymer patterns from the protrusions of the mold show very smooth edges and smaller dimensions compared to that of the mold. The dimension change of the inked pattern is dependent on the selection of polymer materials. It was found that patterns inked from poly(carbonate) showed larger dimension shrinkage $(∼75%)$ compared to that from poly(methyl methacrylate) $(∼30%).$ This offers a viable approach to obtain predictable submicrometer features using a mold with much larger feature sizes.