Fabrication strategies the combines top-down and bottom-up techniques are actively researched to create topographic features that are beyond the capability of individual techniques. Prominent examples are the guided (or directed) self-assembly of various polymer building blocks such as nanoparticles, block copolymers, polymer blends, and simply homopolymers. A variety of hierarchical structures has been demonstrated, with length scales defined by both the top-down lithographic techniques as well as the physical principles that govern the bottom up assembly. Dewetting of thin viscous polymer films on chemically, topographically or combined chemico-topographic substrates have been extensively explored. It offers a low-cost way to engineer complex meso- and nano-scale structures over large area. To date, all these topographic substrates are elastic and remain intact during the dewetting process, and thus the assembled structures are directly evolved from the polymer in contact with or confined by the patterned substrates.
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