This article provides an overview of various patterning methodologies, and it is organized into three major sections: generation of patterns, replication of patterns, and three‐dimensional patterning. Generation of patterns from scratch is usually accomplished by serial techniques that are able to provide arbitrary features. The writing process can be carried out in many different ways. It can be achieved using a rigid stylus; or a focused beam of photons, electrons, and other energetic particles. It can also be accomplished using an electrical or magnetic field; or through localized add‐on of materials such as a liquid‐like ink from an external source. In addition, some ordered but relatively simple patterns can be formed by means of self‐assembly. In replication of patterns, structural information from a mask, master, or stamp is transferred to multiple copies with the use of an appropriate material. The patterned features on a mask are mainly used to direct a flux of radiation or physical matter from a source onto a substrate, whereas a master/stamp serves as the original for replication based on embossing, molding, or printing. The last section of this article deals with three‐dimensional patterning, where both vertical and lateral dimensions of a structure need to be precisely controlled to generate well‐defined shapes and profiles. The article is illustrated with various examples derived from recent developments in this field.

Platinum nanowires of approximately 100 nm in length and approximately 5 nm in diameter have been synthesized by reducing H(2)PtCl(6) with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP) and a trace amount of Fe(3+) or Fe(2+). The wires were generated at the final stage of the synthesis, which involved the formation of several intermediate species. The Fe(3+) or Fe(2+) ions had dual functions in the synthesis: they induced aggregation of Pt nanoparticles into larger structures that served as the nucleation sites, and they greatly reduced the reaction rate and supersaturation level to induce anisotropic growth. The reaction mechanism was studied by X-ray photoelectron spectroscopy (XPS) and UV-vis spectral analysis. The Pt nanowires could be readily separated from the surfaces of the agglomerates by sonication and obtained as pure samples by centrifugation.

No abstract

A new form of edge lithography, edge spreading lithography (ESL), has been demonstrated and applied to the formation of coinage metal rings. In this process, alkanethiols are delivered from a flat PDMS stamp to the surface of a metal film through a two-dimensional array of spherical silica colloids. The thiols further spread on the metal surface, forming highly ordered SAMs in the form of a ring pattern. Following lift-off of beads, the pattern in the SAMs can be transferred into the metal film through wet chemical etching, with SAMs serving as the resist. The dimensions of the rings can be readily controlled by several parameters such as the beads diameter, the concentration of the thiol solution, and the contact time between the stamp and the silica beads.

The patterning of a surface using microcontact printing (μCP) generally employs a hydrophobic micropatterned stamp made from poly(dimethylsiloxane) (PDMS) to place ink molecules on a surface with spatial control. We present a simple procedure to hydrophilize PDMS stamps based on the O2 plasma oxidation of PDMS (referred to as PDMSox) and the grafting of poly(ethylene oxide) silanes (PEO−Si) to the oxidized surface. The wetting properties of a PDMSox surface derivatized with PEO having none, one, or two silanes and having chains with 7−70 EO units are inspected. All PDMSox surfaces treated with PEO−Si are hydrophilic and have advancing and receding contact angles of ∼40° and ∼30°, respectively. These surfaces remain hydrophilic for periods longer than 7 days, which saves having to hydrophilize stamps freshly prior to their usage. In particular, grafting a PEO having two triethoxysilane end groups and a molecular weight (MW) of 3400 g mol-1 enables inking and microcontact printing a polar Pd/Sn catalyst for electroless deposition (ELD) from a stamp to an amino-functionalized glass surface. The printed pattern of colloids has high accuracy and contrast, as reflected by the selective ELD of NiB in the printed regions of the glass. The same stamp can be reused for many cycles of inking and printing without degradation of the quality of the final NiB patterns. The hydrophilic layer provided by the grafted PEO molecules is, in some cases, not sufficiently thick to incorporate and print enough polar ink to form a complete monolayer of cysteamine, for example, onto printed Au substrates. Oxidizing a planar PDMS surface through a mask permits the patterning of PEO onto PDMSox. It then becomes possible to ink the stamp with proteins either by depositing proteins from solution onto the areas left underivatized with PEO or by printing proteins in the PEO-derivatized areas only. The proteins on the planar PDMS/PDMSox-PEO surface in turn are microcontact printed with high accuracy onto glass. This work may help expand μCP to applications in which it is desirable to use polar inks or proteins.