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We use Dip-Pen Nanolithography (DPN) to generate monolayer surface templates for guiding pattern formation in spin-coated polymer blend films. We study template-directed pattern formation in blends of polystyrene/poly(2-vinylpyridine) (PS/P2VP) as well as blends of PS and the semiconducting conjugated polymer poly(3-hexylthiophene) (P3HT). We show that acid-terminated monolayers can be used to template pattern formation in PS/P3HT blends, while hydrophobic monolayers can be used to template pattern formation in PS/P2VP blends. In both blends, the polymer patterns comprise laterally-phase separated regions surrounded by vertically separated bilayers. We hypothesize that the observed patterns are formed by template-induced dewetting of the bottom layer of a polymer bilayer during the spin-coating process. We compare the effects of template feature size and spacing on the resulting polymer patterns with predictions from published models of template-directed dewetting in thin films and find the data in good agreement. For both blends we observe that a minimum feature size is required to nucleate dewetting/phase separation. We find this minimum template diameter to be approximately 180 nm in 50/50 PS/P2VP blends, and approximately 100 nm in 50/50 PS/P3HT blends. For larger template diameters, PS/P2VP blends show evidence for pattern formation beginning at the template boundaries, while PS/P3HT blends rupture randomly across the template features.

The ability to bind, assemble, synthesize, and grow technologically relevant materials on a solid surface under mild aqueous conditions is important for many applications including diagnostic biosensors, [1] nanophotonics, [2] and possibly even rapid prototyping. [3] One of the challenges in this regard is the selection and optimization of linking chemistry to bind functional structures to a variety of different technological surfaces such as metals, oxides, and semiconductors. A number of small molecules are routinely used to functionalize surfaces: thiols on gold, silanes on silica or other oxides, and phosphonic acids on metal oxides. Recently, peptides have emerged as a promising class of materials for surface functionalization. By using rapid combinatorial screening techniques, the molecular biomimetic community has already identified a library of peptide sequences with specific affinities for a variety of metals, semiconductors, oxides, and even organic materials like conducting polymers. [4][5][6][7][8][9][10][11][12] Using the tools of molecular biology, these inorganicbinding peptide sequences can be incorporated into proteins, [13] linked with other peptides, [14] conjugated to functional small molecules such as organic dyes, or attached to quantum dots. [15][16][17] The resulting structures can potentially be utilized as molecular building blocks to direct assembly or in situ synthesis of functional inorganic nanostructures. [18][19][20][21] For example, one can imagine using heterobifunctional peptide inks in rapid-prototyping applications on many different surfaces: one end of a functional peptide would bind to a solid surface, while the other end would catalyze growth of another desired inorganic material, all in a site-specific template under the mild conditions typical of biological catalysis. [13,14,18,20,[22][23][24][25] Solid-binding peptides are typically identified by cellsurface or phage-display methods. [26] Although the fundamental mechanism of solid-binding is not fully understood, [27,28] NMR spectroscopy, [29,30] computational modeling, [31,32] and experiments with geometrically constrained peptides/proteins [13] have suggested that the secondary structures of these engineered peptides in solution can play an important role in their solid-binding and selectivity.These factors have the potential to affect the success of peptides in substrate-templated assembly applications. It is known that biomolecules delivered by various printing techniques can denature or adopt other conformations on solid surfaces that differ from their native form in solution. [33][34][35] Biomolecules have been patterned by a wide range of techniques [36,37] including pin printing, inkjet printing, nanoimprint lithography, electron beam (e-beam) lithography, focused ion beam lithography, soft lithography, photolithography, scanning probe microscopy, and dip-pen nanolithography (DPN). [1,[38][39][40][41][42][43][44][45] However, most of these demonstrations did not use biomolecules that were specifically engineered...

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