Polymer waveguide couplers based on metal nanoparticle-polymer nanocomposites.

In this work Au nanoparticles (AuNPs) are incorporated into poly(methyl methacrylate) (PMMA) waveguides to develop optical couplers that are compatible with planar organic polymer photonics. A method for growing AuNPs (of 10 to 100 nm in size) inside the commercially available Novolak resist is proposed with the intention of tuning the plasmon resonance and the absorption/scattering efficiencies inside the patterned structures. The refractive index of the MNP-Novolak nanocomposite (MNPs: noble metal nanoparticles) is carefully analysed both experimentally and numerically in order to find the appropriate fabrication conditions (filling factor and growth time) to optimize the scattering cross section at a desired wavelength. Then the nanocomposite is patterned inside a PMMA waveguide to exploit its scattering properties to couple and guide a normal incident laser light beam along the polymer. In this way, light coupling is experimentally demonstrated in a broad wavelength range (404-780 nm). Due to the elliptical shape of the MNPs the nanocomposite demonstrates a birefringence, which enhances the coupling to the TE mode up to efficiencies of around 1%.

Arrays of templated TiO2 nanofibres as improved photoanodes for water splitting under visible light.

Arrays of TiO2 nanofibres (NFs) were successfully prepared by template sol-gel synthesis, using track-etched polycarbonate membranes as structure directing agent. The control of the sol-gel kinetic was crucial in order to homogeneously fill the pores with a continuous framework. For this reason acetylacetone was added to the sol-gel mixture as chelating agent. The band edge positions of TiO2 NFs were determined by a Mott-Schottky plot and diffuse reflectance analysis. The results support the presence of trace dopants which can act favorably with respect to the photoelectrochemical properties. The TiO2 NFs array showed enhanced photoelectrochemical activity both under UV light and visible light when used as photoanodes for the water splitting reaction.

Motor Unit Tracking Using High Density Surface Electromyography (HDsEMG) . Automated Correction of Electrode Displacement Errors.

INTRODUCTION: This article is part of the Focus Theme of Methods of Information in Medicine on "Biosignal Interpretation: Ad-vanced Methods for Neural Signals and Images". OBJECTIVES: The study discusses a technique to automatically correct for effects of electrode grid displacement across serial surface EMG measurements with high-density electrode arrays (HDsEMG). The goal is to match motor unit signatures from subsequent measurements and by this, achieve automated motor unit tracking. METHODS: Test recordings of voluntary muscle contractions using HDsEMG were performed on three healthy individuals. Electrode grid displacements were mimicked in repeated recordings while measuring the exact position of the grid. A concept of accounting for translational and rotational displacements by making the projection of the recorded motor unit action potentials is first introduced. Then, this concept was tested for the performed measurements attempting the automated matching of the similar motor unit action potentials across different trials. RESULTS: The ability to perform automated correction (projection) of the isolated motor unit action potentials was first shown using large angular displacements. Then, for accidental (small) displacements of the recording grid, the ability to automatically track motor units across different measurement trials was shown. It was possible to track 10 -15% of identified motor units. CONCLUSIONS: This proof of concept study demonstrates an automated correction allowing the identification of an increased number of same motor unit action potentials across different measurements. By this, great potential is demonstrated for assisting motor unit tracking studies, indicating that otherwise electrode displacements cannot always be precisely described.