Fabrication of flexible silicon nanowires by self-assembled metal assisted chemical etching for surface enhanced Raman spectroscopy

A homogenous array of flexible gold coated silicon nanowires was fabricated by the combination of nano spheres lithography and metal assisted chemical etching to obtain highly effective Surface Enhanced Raman Spectroscopy (SERS) substrates. 3D nanostructures with different aspect ratios and well-defined geometries were produced by adjusting the fabrication parameters in order to select the best configuration for SERS analysis. The optimum flexible nanowires with an aspect ratio of 1 : 10 can self-close driven by the microcapillary force under exposure to liquid and trap the molecules at their metallic coated ``fingertips'', thus generating hot spots with ultrahigh field enhancement. The performance of these SERS substrates was evaluated using melamine as the analyte probe with various concentrations from the millimolar to the picomolar range. Flexible gold coated SiNWs demonstrated high uniformity of the Raman signal over large area with a variability of only 10% and high sensitivity with a limit of detection of 3.20 x 10(-7) mg L-1 (picomolar) which promotes its application in several fields such food safety, diagnostic and pharmaceutical. Such an approach represents a low-cost alternative to the traditional nanofabrication processes to obtain well ordered silicon nanostructures, offering multiple degrees of freedom in the design of different geometries such as inter-wire distance, density of the wires on the surface as well as their length, thus showing a great potential for the fabrication of SERS substrates

The Effect of Sustained Compression on Oxygen Metabolic Transport in the Intervertebral Disc Decreases with Degenerative Changes

Intervertebral disc metabolic transport is essential to the functional spine and provides the cells with the nutrients necessary to tissue maintenance. Disc degenerative changes alter the tissue mechanics, but interactions between mechanical loading and disc transport are still an open issue. A poromechanical finite element model of the human disc was coupled with oxygen and lactate transport models. Deformations and fluid flow were linked to transport predictions by including strain-dependent diffusion and advection. The two solute transport models were also coupled to account for cell metabolism. With this approach, the relevance of metabolic and mechano-transport couplings were assessed in the healthy disc under loading-recovery daily compression. Disc height, cell density and material degenerative changes were parametrically simulated to study their influence on the calculated solute concentrations. The effects of load frequency and amplitude were also studied in the healthy disc by considering short periods of cyclic compression. Results indicate that external loads influence the oxygen and lactate regional distributions within the disc when large volume changes modify diffusion distances and diffusivities, especially when healthy disc properties are simulated. Advection was negligible under both sustained and cyclic compression. Simulating degeneration, mechanical changes inhibited the mechanical effect on transport while disc height, fluid content, nucleus pressure and overall cell density reductions affected significantly transport predictions. For the healthy disc, nutrient concentration patterns depended mostly on the time of sustained compression and recovery. The relevant effect of cell density on the metabolic transport indicates the disturbance of cell number as a possible onset for disc degeneration via alteration of the metabolic balance. Results also suggest that healthy disc properties have a positive effect of loading on metabolic transport. Such relation, relevant to the maintenance of the tissue functional composition, would therefore link disc function with disc nutrition

New remeshing applications in resin transfer molding

As resin transfer molding (RTM) is being increasingly used to manufacture composite parts, there is a strong interest to understand the basic physical phenomena that occur at each stage of the process. Modeling and simulation play an important role in the development and optimization of molds production and in devising appropriate resin injection strategies. In general, process simulation requires preprocessing to be carried out carefully to conduct successful, reliable, and reasonably fast calculations. However, it can be time consuming at the early stages of mold design to run several simulations with minor changes only in the geometrical model or in the mesh in order to optimize the mold or some given operating conditions. Unfortunately, in that case the entire mesh has usually to be regenerated. This paper presents applications of a remeshing algorithm to RTM flow simulation. It illustrates how remeshing techniques can be used to enhance the automatic meshing capability by including injection ports and channels along the mold boundaries or along the interior injection lines. Remeshing can also be used to smooth the resin front during mold filling. In the latter case, mesh refinement is based on the flow front without attempting to minimize computational error. By adapting the mesh anisotropy to the flow front during mold filling, the shape of the advancing flow front can be more closely approximated. The first part of this paper describes the remeshing algorithm and the associated anisotropic metric. Then, several examples of metrics are given to provide guidelines for application engineers and illustrate their practical implementation. After introducing the RTM process and recalling the basic equations that govern mold filling, local remeshing of injection ports and runners are presented, followed by the application that minimizes front smearing

Rapport d'activié de mi-parcours projet FAME2

Rapport d'activié de mi-parcours projet FAME

Livrable projet FAME2: Spécifications des adaptations et extensions à effectuer dans XediX pour l'accès aux bases de données génomiques

Livrable projet FAME2: Spécifications des adaptations et extensions à effectuer dans XediX pour l'accès aux bases de données génomique