In order to harness the potential of block copolymers to produce nanoscale structures that can be integrated with existing silicon-based technologies, there is a need for compatible chemistries. Block copolymer nanostructures can form a wide variety of two-dimensional patterns, and can be controlled to present long-range order. Here we use the acid-responsive nature of self-assembled monolayers of aligned, horizontal block copolymer cylinders for metal loading with simple aqueous solutions of anionic metal complexes, followed by brief plasma treatment to simultaneously remove the block copolymer and produce metallic nanostructures. Aligned lines of metal with widths on the order of 10 nm and less are efficiently produced by means of this approach on Si(100) interfaces. The method is highly versatile because the chemistry to manipulate nanowire composition, structure and choice of semiconductor is under the control of the user.

Block copolymer thin films can be used as soft templates for a wide range of surfaces where large area patterns of nanoscale features are desired. The cylindrical domains of acid-sensitive, self-assembled monolayers of polystyrene-poly(2-vinylpyridine) block copolymers on silicon surfaces were utilized as structural elements for the production of parallel metal nanowires. Metal ion loading of the P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the protonated P2VP domain. A subsequent brief plasma treatment simultaneously removes the polymer and produces metallic nanowires. The morphology of the patterns can modulated by controlling solution concentration, deposition time, and molecular weight of the block copolymers, as well as other factors. Horizontal metallic nanoarrays can be aligned on e-beam lithographically defined silicon substrates within different shapes, via graphoepitaxy. This method is highly versatile as the procedures to manipulate nanowire composition, dimension, spacing, and orientation are straightforward and based upon efficient aqueous inorganic chemistry.

Lithography techniques are currently being developed to fabricate nanoscale components for integrated circuits, medical diagnostics and optoelectronics. In conventional far-field optical lithography, lateral feature resolution is diffraction-limited. Approaches that overcome the diffraction limit have been developed, but these are difficult to implement or they preclude arbitrary pattern formation. Techniques based on near-field scanning optical microscopy can overcome the diffraction limit, but they suffer from inherently low throughput and restricted scan areas. Highly parallel two-dimensional, silicon-based, near-field scanning optical microscopy aperture arrays have been fabricated, but aligning a non-deformable aperture array to a large-area substrate with near-field proximity remains challenging. However, recent advances in lithographies based on scanning probe microscopy have made use of transparent two-dimensional arrays of pyramid-shaped elastomeric tips (or 'pens') for large-area, high-throughput patterning of ink molecules. Here, we report a massively parallel scanning probe microscopy-based approach that can generate arbitrary patterns by passing 400-nm light through nanoscopic apertures at each tip in the array. The technique, termed beam pen lithography, can toggle between near- and far-field distances, allowing both sub-diffraction limit (100 nm) and larger features to be generated.

Integration of individual nanoparticles into desired spatial arrangements over large areas is a prerequisite for exploiting their unique electrical, optical, and chemical properties. However, positioning single sub-10-nm nanoparticles in a specific location individually on a substrate remains challenging. Herein we have developed a unique approach, termed scanning probe block copolymer lithography, which enables one to control the growth and position of individual nanoparticles in situ. This technique relies on either dip-pen nanolithography (DPN) or polymer pen lithography (PPL) to transfer phase-separating block copolymer inks in the form of 100 or more nanometer features on an underlying substrate. Reduction of the metal ions via plasma results in the high-yield formation of single crystal nanoparticles per block copolymer feature. Because the size of each feature controls the number of metal atoms within it, the DPN or PPL step can be used to control precisely the size of each nanocrystal down to 4.8 AE 0.2 nm.scanning probe lithography | block copolymer micelles | single particle synthesis | nanopatterning N anoparticles exhibit size-dependent photonic, electronic, and chemical properties that could lead to a new generation of catalysts and nanodevices, including single electron transistors, photonics, and biomedical sensors (1-3). In order to realize many of these targeted applications, researchers need ways of synthesizing monodisperse particles while controlling individual particle position on technologically relevant surfaces. The challenge of positioning or synthesizing single sub-10-nm nanoparticles in desired locations is difficult, if not impossible, via current techniques including conventional photolithography (4-7). Scanning probe-based methods such as dip-pen nanolithography (DPN) (8) and polymer pen lithography (PPL) (9) are particularly attractive because inked nanoscale tips can deliver material directly to desired locations on various substrates with high registration and sub-50-nm feature resolution (10). Here we report a unique approach, termed scanning probe block copolymer lithography (SPBCL), which enables one to control individual nanoparticle growth and position in situ by using DPN or PPL to pattern attoliter volumes of metal ions associated with block copolymers in a massively parallel manner over large areas. Reduction of the metal ions via plasma results in the high-yield formation of single crystal nanoparticles per block copolymer feature. Specifically, we demonstrate that pattern dimensions and metal ion concentration dictate the size of each nanoparticle, whose diameter can be controlled with remarkable precision down to 4.8 AE 0.2 nm.To begin, we identified a polymer with two essential properties. The material must transfer from a scanning probe tip to a surface of interest in a controllable way, and it must sequester metal ions which can be used subsequently to make nanoparticles. We evaluated the properties of poly(ethylene oxide)-b-poly(2-vinylpyridine) (PEO-b-P2VP) in thi...

Nanofabrication strategies are becoming increasingly expensive and equipment-intensive, and consequently less accessible to researchers. As an alternative, scanning probe lithography has become a popular means of preparing nanoscale structures, in part owing to its relatively low cost and high resolution, and a registration accuracy that exceeds most existing technologies. However, increasing the throughput of cantilever-based scanning probe systems while maintaining their resolution and registration advantages has from the outset been a significant challenge. Even with impressive recent advances in cantilever array design, such arrays tend to be highly specialized for a given application, expensive, and often difficult to implement. It is therefore difficult to imagine commercially viable production methods based on scanning probe systems that rely on conventional cantilevers. Here we describe a low-cost and scalable cantilever-free tip-based nanopatterning method that uses an array of hard silicon tips mounted onto an elastomeric backing. This method-which we term hard-tip, soft-spring lithography-overcomes the throughput problems of cantilever-based scanning probe systems and the resolution limits imposed by the use of elastomeric stamps and tips: it is capable of delivering materials or energy to a surface to create arbitrary patterns of features with sub-50-nm resolution over centimetre-scale areas. We argue that hard-tip, soft-spring lithography is a versatile nanolithography strategy that should be widely adopted by academic and industrial researchers for rapid prototyping applications.

Poly(methyl methacrylate) (PMMA) has been modified via a dc pulsed oxygen plasma for different treatment times. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), optical profilometer, zeta potential, and advancing contact angle measurements. The measured advancing contact angles of water decreased considerably as a function of discharge. Several oxygen-based functionalities (carbonyl, carboxyl, carbonate, etc.) were detected by XPS, while zeta potential measurements confirmed an increase in negative charge for the treated PMMA surface. Evaluating the correlation between the concentration of polar chemical species and zeta potential, we found that increase in surface hydrophilicity results from the coeffect due to incorporation of oxygen functional groups and creation of charge states. The electrical double layer (EDL) effect was also considered in contact angle interpretation by introducing an additional surface tension term into Young's equation. We also found that EDL contribution to the solid-liquid interfacial tension is negligible and can be safely ignored for the systems considered here.

The ability to control the placement of individual protein molecules on surfaces could enable advances in a wide range of areas, from the development of nanoscale biomolecular devices to fundamental studies in cell biology. Such control, however, remains a challenge in nanobiotechnology due to the limitations of current lithographic techniques. Herein we report an approach that combines scanning probe block copolymer lithography with site-selective immobilization strategies to create arrays of proteins down to the single-molecule level with arbitrary pattern control. Scanning probe block copolymer lithography was used to synthesize individual sub-10-nm single crystal gold nanoparticles that can act as scaffolds for the adsorption of functionalized alkylthiol monolayers, which facilitate the immobilization of specific proteins. The number of protein molecules that adsorb onto the nanoparticles is dependent upon particle size; when the particle size approaches the dimensions of a protein molecule, each particle can support a single protein. This was demonstrated with both gold nanoparticle and quantum dot labeling coupled with transmission electron microscopy imaging experiments. The immobilized proteins remain bioactive, as evidenced by enzymatic assays and antigen-antibody binding experiments. Importantly, this approach to generate single-biomolecule arrays is, in principle, applicable to many parallelized cantilever and cantilever-free scanning probe molecular printing methods.dip-pen nanolithography | scanning probe lithography | single molecule array | gold nanoparticles | protein nanoarray P rotein immobilization on solid substrates with nanoscale control has been utilized in a variety of applications, including chip-based bioassays (1), proteomics (2, 3), drug discovery (3), and cellular biology studies (4). In cellular biology research, the ability to fabricate protein nanostructures on surfaces has enabled the study of many basic cellular functions including growth, signaling, and differentiation (4-7). For combinatorial molecular biology, the miniaturization of protein nanoarrays allows for smaller and higher density chips and the need for smaller sample volumes; in certain cases, this can translate into diagnostic systems with higher sensitivity and the ability to track disease and biological processes more efficiently (2, 3). The ability to site-specifically isolate single biomolecules can also facilitate molecular level studies of such structures (8, 9). Therefore, being able to nanofabricate biomolecular features at a resolution of 10 nm or less is of significant interest because this length scale approaches the dimensions of single protein molecules and offers an opportunity to address many previously unexplored biological phenomena.The use of dip-pen nanolithography (DPN) (4, 10) for the generation of arrays of biomolecules either by a direct deposition of proteins (11-13) or indirect methods (14, 15), through DPN writing of patterns followed by capture of proteins onto the patterns, has been widel...

Block copolymers can be used to template large arrays of nanopatterns with periodicities equal to the characteristic spacing of the polymer. Here we demonstrate a technique capitalizing on the multilayered arrangement of cylindrical domains to effectively double the pattern density templated by a given polymer. By controlling the initial thickness of the film and the solvent annealing conditions, it was possible to reproducibly create density doubled lines by swelling the film with solvent until bilayers of horizontal cylinders were obtained. This process was also demonstrated to be compatible with graphoepitaxy.