‘Fairy Chimney’‐Shaped Tandem Metamaterials as Double Resonance SERS Substrates

A highly tunable design for obtaining double resonance substrates to be used in surface‐enhanced Raman spectroscopy is proposed. Tandem truncated nanocones composed of Au‐SiO₂‐Au layers are designed, simulated and fabricated to obtain resonances at laser excitation and Stokes frequencies. Surface‐enhanced Raman scattering experiments are conducted to compare the enhancements obtained from double resonance substrates to those obtained from single resonance gold truncated nanocones. The best enhancement factor obtained using the new design is 3.86 × 10⁷. The resultant tandem structures are named after “Fairy Chimneys” rock formation in Cappadocia, Turkey.     

A frontal Delaunay quad mesh generator using the L ∞ norm

In a recent work, a new indirect method to generate all‐quad meshes has been developed. It takes advantage of a well‐known algorithm of the graph theory, namely the Blossom algorithm, which computes in polynomial time the minimum cost perfect matching in a graph. In this paper, we describe a method that allows to build triangular meshes that are better suited for recombination into quadrangles. This is performed by using the infinity norm to compute distances in the meshing process. The alignment of the elements in the frontal Delaunay procedure is controlled by a cross field defined on the domain. Meshes constructed this way have their points aligned with the cross‐field directions, and their triangles are almost right everywhere. Then, recombination with the Blossom‐based approach yields quadrilateral meshes of excellent quality. Copyright © 2013 John Wiley & Sons, Ltd.     

On‐Surface Synthesis of 8‐ and 10‐Armchair Graphene Nanoribbons

Armchair graphene nanoribbons (AGNRs) with 8 and 10 carbon atoms in width (8‐ and 10‐AGNRs) are synthesized on Au (111) surfaces via lateral fusion of nanoribbons that belong to different subfamilies. Poly‐para‐phenylene (3‐AGNR) chains are pre‐synthesized as ladder ribbons on Au (111). Subsequently, synthesized 5‐ and 7‐AGNRs can laterally fuse with 3‐AGNRs upon annealing at higher temperature, producing 8‐ and 10‐AGNRs, respectively. The synthetic process, and their geometric and electronic structures are characterized by scanning tunneling microscopy/spectroscopy (STM/STS). STS investigations reveal the band gap of 10‐AGNR (2.0 ± 0.1 eV) and a large apparent band gap of 8‐AGNRs (2.3 ± 0.1 eV) on Au (111) surface.     

An alternative desirability function for achieving ‘six sigma’ quality

To achieve high process yields or ‘six sigma’ quality, engineers often need to evaluate and optimize processes that are characterized by multiple quality characteristics. Existing desirability functions weigh together multiple objectives but they have a number of limitations. Most importantly, available desirability functions do not explicitly account for the combined effect of the mean and the dispersion of the quality characteristic. Therefore, it is easy to incur excessive expenditures or unknowingly to fail to achieve targeted yields. In this paper, a desirability function is proposed that addresses these limitations. This function conservatively estimates the ‘effective yield’ under assumptions described in the ‘six sigma’ literature. We use an arc‐welding application to illustrate how the proposed desirability function can yield a substantially higher level of quality as well as a more accurate assessment of the process capability than available alternatives. We suggest that the proposed desirability function should be used to facilitate multicriterion optimization when dispersion data are available. Copyright © 2003 John Wiley & Sons, Ltd.     

Oberflächen‐ und Dünnschichtanalytik – unverzichtbares Werkzeug für Schichtentwicklung und ‐produktion

Surface and thin film analysis – indispensable tool for coating development and ‐production Development and production of thin films for functional coating on special materials is unalterable combined with a permanent quality control and therefore use of sophisticated analysis and measurement techniques. The field of interest is belonging to all steps of the production chain, starting with the characterization of the substrate surface (e. g. glass, plastics), followed by polishing and cleaning processes up to depth profiling of complex multilayers. The typical analyses are focused onto topographical and chemical features and their influence onto the product functionality. The use of surface and thin film analytics for problem oriented characterization is demonstrated by a few examples, which deal with surface roughness, contamination, impurities and dopand profiles as well as composition variations in the surface near region.     

Superplastic diffusion bonding of γ-TiAl-based alloy

With laser surface melting and conventional heat treatment, superplastic diffusion bonding of TiAl alloy samples was carried out. Three different microstructure, i.e. fully lamellar structure, fine dendritic structure and refined equiaxed structure are used and their effects on bonding quality were investigated, and the bond quality was assessed by shear test at room temperature. Sound bonds could be achieved at 900 °C by laser surface modification or by laser surface modification and pre-bond heat treatment at 1000 °C for 60 min, which is lower than conventional diffusion bonding temperature. The bonds were also post-bond heat treated at 1200 °C for 30 min, which improved the bond quality in all cases. The best shear strength of the bonds is greater than 80% of that of base metal.     

Corrosion behaviour of cold‐rolled aluminium AA8015‐alloy in natural seawater at 0.18 μm surface roughness

Aluminium is one of the most produced and used metals globally, second to ferrous metals. Its good corrosion resistance is one of the reasons for its heavy usage in typical applications, such as in marine applications. Electrochemical corrosion study of cold‐rolled aluminium AA8015‐alloy at 0.18 μm surface roughness in natural seawater was explored. The aluminium AA8015‐alloy utilized in this study was cold rolled in a reversible Achenbach cold rolling mill in four pass schedules to a thickness gauge of 1.2 mm. A surface roughness of 0.18 μm with three cold mounted samples was achieved on an automated grinding/polishing machine using 320 grit, 800 grit, and 1200 grit SiC paper. Electrochemical corrosion experiments were conducted on the samples in natural seawater using a computer‐controlled potentiostat in an open polarization cell set‐up at room temperature. The corrosion behaviour on surface morphologies of the samples was observed by high mega pixel camera and scanning electron microscope. Findings reveal asymmetric polarization curves for all the samples and energy dispersive X‐ray spectrometry elemental analysis shows the existence of insoluble substrate complexes formed on the surfaces. Consequently, the scanning electron microscope analysis confirms localised corrosion in the mode of pitting.     

Creating “Smart” Surfaces Using Stimuli Responsive Polymers

Surfaces modified with stimuli‐responsive polymers (SRPs) dynamically alter their physico‐chemical properties in response to changes in their environmental conditions. The triggered control of interfacial properties provided by immobilized SRPs at the solid–water interface has application in the design of biomaterials, regenerable biosensors, and microfluidic bioanalytical devices. In this article, we briefly summarize recent research in this area, followed by two recent examples of research from our laboratory on stimuli‐responsive surfaces. First, we present a new assay to quantify the phase transition behavior of SRPs at the solid–water interface. This assay, which is based on the distance‐dependent colorimetric properties of gold nanoparticles, provides a technically simple and convenient method to determine the effect of different variables on the lower critical solution temperature (LCST) behavior of SRPs at the solid–water interface. Second, we show that stimuli‐responsive surfaces can be created by the immobilization of an elastin‐like polypeptide (ELP), a thermally responsive biopolymer, on a glass surface. We exploit the phase transition of the ELP at a surface to reversibly address an ELP fusion protein to a surface. This method, which we term thermodynamically reversible addressing of proteins (TRAP), enables the reversible, spatio‐temporal modulation of protein binding at the solid‐liquid interface, and will enable the realization of new bioanalytical applications.     

Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter

Microfluidic fluorescence‐activated cell sorters (μFACS) have attracted considerable interest because of their ability to identify and separate cells in inexpensive and biosafe ways. Here a high‐performance μFACS is presented by integrating a standing surface acoustic wave (SSAW)‐based, 3D cell‐focusing unit, an in‐plane fluorescent detection unit, and an SSAW‐based cell‐deflection unit on a single chip. Without using sheath flow or precise flow rate control, the SSAW‐based cell‐focusing technique can focus cells into a single file at a designated position. The tight focusing of cells enables an in‐plane‐integrated optical detection system to accurately distinguish individual cells of interest. In the acoustic‐based cell‐deflection unit, a focused interdigital transducer design is utilized to deflect cells from the focused stream within a minimized area, resulting in a high‐throughput sorting ability. Each unit is experimentally characterized, respectively, and the integrated SSAW‐based FACS is used to sort mammalian cells (HeLa) at different throughputs. A sorting purity of greater than 90% is achieved at a throughput of 2500 events s^?1. The SSAW‐based FACS is efficient, fast, biosafe, biocompatible and has a small footprint, making it a competitive alternative to more expensive, bulkier traditional FACS.