Room-Temperature Patterning of Nanoscale MoS under an Electron Beam.

Molybdenum disulfide (MoS) is traditionally grown at a high temperature and subsequently patterned to study its electronic properties or make devices. This method imposes severe limitations on the shape and size of MoS crystals that can be patterned precisely at required positions. Here, we describe a method of direct nanoscale patterning of MoS at room temperature by exposing a molybdenum thiocubane single-source precursor to a beam of electrons.

Ultrasmall Designed Plasmon Resonators by Fused Colloidal Nanopatterning.

This work presents a procedure for large-area patterning of designed plasmon resonators that are much smaller than possible with conventional lithography techniques. Fused Colloidal Nanopatterning combines directed self-assembly and controlled fusing of spherical colloidal nanoparticles. The two-step approach first patterns a surface covered with hydrogen silsesquioxane, an electron beam resist, forming traps into which the colloidal gold nanoparticles self-assemble.

Non-invasive paper-based microfluidic device for ultra-low detection of urea through enzyme catalysis.

This work describes the design, fabrication and characterization of a paper-based microfluidic device for ultra-low detection of urea through enzyme catalysis. The microfluidic system comprises an entry port, a fluidic channel, a reaction zone and two electrodes (contacts). Wax printing was used to create fluidic channels on the surface of a chromatography paper.

Superhydrophobic and slippery liquid-infused porous surfaces formed by the self-assembly of a hybrid ABC triblock copolymer and their antifouling performance.

An ABC triblock copolymer based on poly(dimethylsiloxane)-poly(tert-butyl acrylate)-poly(methacrylolsobutyl POSS) is synthesized via combination of SET-LRP and ATRP from a PDMS macroinitiator. The resulting polymer can readily self-assemble into hierarchical structures through a stepwise "bottom-up" strategy, i.e.

Direct Patterning of Zinc Sulfide on a Sub-10 Nanometer Scale via Electron Beam Lithography.

Nanostructures of metal sulfides are conventionally prepared via chemical techniques and patterned using self-assembly. This poses a considerable amount of challenge when arbitrary shapes and sizes of nanostructures are desired to be placed at precise locations. Here, we describe an alternative approach of nanoscale patterning of zinc sulfide (ZnS) directly using a spin-coatable and electron beam sensitive zinc butylxanthate resist without the lift-off or etching step.

Octagonal Wetting Interface Evolution of Evaporating Saline Droplets on a Micropyramid Patterned Surface.

Textured surfaces have been extensively employed to investigate the dynamics, wetting phenomena, and shape of liquid droplets. Droplet shape can be controlled via the manipulation of topographic or chemical heterogeneity of a solid surface by anchoring the three-phase line at specific sites. In this study, we demonstrate that droplet shape on a topographically patterned surface can be modified by varying the concentration of salt potassium chloride (KCl) in the droplet solution.

Second order directed positioning of nanoparticles induced by the main terminal meniscus shape in irregular template cavities.

Directed self-assembly of nanoparticles using topographical templates has demonstrated great capabilities of ordering particles at their maximum packing fraction resulting from template confinement effects and free energy minimization. However, to self-assemble nanostructures at a lower packing fraction with a precise control over particle's positioning is challenging due to the high entropy of such a system. Here, by fabricating templates of irregular cavities together with appropriate choice of solvent, we demonstrate the positioning of 8 nm Au nanoparticles within individual cavities at a low filling factor.

Dispersed Gold Nanoparticle Array Produced by Apoferritins Utilizing Biomineralization and Chemical Conversion.

A new method for producing a dispersed gold nanoparticle (Au NP) array to anchor probe DNAs onto a DNA-sensing electrode has been developed. A homogenous gold sulfide (AuS) core (precursor of Au NP) was biomineralized in the cavity of a mutant apoferritin (K98E) with enhanced negative outer-surface charges. We employed a slow chemical reaction system utilizing a stable cationic gold complex.

Directed self-assembly of sub-10 nm particle clusters using topographical templates.

Directed self-assembly of nanoparticles (DSA-n) is an approach that creates suitable conditions to capture nanoparticles randomly dispersed in a liquid and position them into predefined locations on a solid template. Although DSA-n is emerging as a potential bottom-up patterning technique to build nanostructures using nanoparticles of various sizes, geometries and material compositions, there are still several outstanding challenges. In this paper, we focus on the DSA-n of sub-10 nm particles using topographical templates to guide them into 1D and 2D ordered arrays.

Large Area Directed Self-Assembly of Sub-10 nm Particles with Single Particle Positioning Resolution.

Directed self-assembly of nanoparticles (DSA-n) holds great potential for device miniaturization in providing patterning resolution and throughput that exceed existing lithographic capabilities. Although nanoparticles excel at assembling into regular close-packed arrays, actual devices on the other hand are often laid out in sparse and complex configurations. Hence, the deterministic positioning of single or few particles at specific positions with low defect density is imperative.

Fabrication of Self-Cleaning, Reusable Titania Templates for Nanometer and Micrometer Scale Protein Patterning.

The photocatalytic self-cleaning characteristics of titania facilitate the fabrication of reuseable templates for protein nanopatterning. Titania nanostructures were fabricated over square centimeter areas by interferometric lithography (IL) and nanoimprint lithography (NIL). With the use of a Lloyd's mirror two-beam interferometer, self-assembled monolayers of alkylphosphonates adsorbed on the native oxide of a Ti film were patterned by photocatalytic nanolithography.

Fabrication of biomolecular nanostructures by scanning near-field photolithography of oligo(ethylene glycol)-terminated self-assembled monolayers.

The UV photo-oxidation of oligo(ethylene glycol) (OEG)-terminated self-assembled monolayers (SAMs) has been studied using static secondary ion mass spectrometry, X-ray photoelectron spectroscopy, contact angle measurement, and friction force microscopy. OEG-terminated SAMs are oxidized to yield sulfonates, but photodegradation of the OEG chain also occurs on a more rapid time scale, yielding degradation products that remain bound to the surface via gold-sulfur bonds. The oxidation of these degradation products is the rate-limiting step in the process.

Measurement of the kinetics of photo-oxidation of self-assembled monolayers using friction force microscopy.

The advancement of molecular nanotechnology requires new tools for the characterization of surface chemical reactivity with nanometer spatial resolution. While spectroscopy on sub-100 nm length scales remains challenging, friction force microscopy (FFM) is a promising tool for the characterization of molecular materials, although to date it has been little used in studies of surface reactivity. Here we report the use of FFM to measure the kinetics of photo-oxidation of self-assembled monolayers (SAMs) of alkanethiols adsorbed on gold surfaces.

Friction force microscopy: towards quantitative analysis of molecular organisation with nanometre spatial resolution.

Friction force microscopy (FFM) is a technique based upon scanning force microscopy that provides information on the properties of molecular materials. Continuum mechanics provides models that may be used to conduct quantitative analyses of data. While there are some important unresolved issues associated with the contact mechanics of the tip-sample interaction, there is a growing body of data that demonstrates the sensitivity of FFM to changes in molecular organisation and surface composition.

Nanoscale molecular patterns fabricated by using scanning near-field optical lithography.

Nanometer-scale patterns have been created in self-assembled monolayers by using a scanning near-field optical microscope coupled to an ultra-violet laser emitting light at a wavelength of 244 nm. Sharp, chemically well-defined features with dimensions as small as 40 nm have been created routinely, and on occasions line widths of 25 nm (lambda/10) have been achieved. Because of the wide range of photochemical methods available for surface derivatization, this approach promises to provide a flexible and versatile route to the generation of molecular and biological nanostructures for a wide range of applications.