Investigation of the internal structure of flax fibre cell walls by transmission electron microscopy

The development of the use of flax fibre as reinforcement of eco-friendly composite materials requires a good knowledge of its hydrothermal and mechanical behaviours. To this end the fibre internal structure must be finely investigated. Transmission electron microscopy was used to analyse the morphology of the fibre cell walls in terms of the arrangement of the layers and their thickness. Thus, an alternative eco-friendly staining method, based on oolong tea extract was successfully implemented. The results reveal an arrangement at the nanoscale slightly different from the classical four layer model encountered in the literature: the inner layer includes three to four sub-layers. The cell walls comprises two outer layers of relative thickness of about 10 %, a middle layer of about 70 % and a group of thinner layers (called sub-layers) that are contiguous to the lumen with relative thickness of about 20 %

Key Parameters for Detectivity Improvement of Low Noise Anisotropic Magnetoresistive Sensors Made of La 2/3 Sr 1/3 MnO 3 Single Layers on Vicinal Substrates

International audienceThe current trend in magnetoresistive sensors development is to increase the sensitivity of single sensing elements by using multilayer structures and to design them into arrays. Such arrays are designed to compensate the excess low frequency noise of individual elements, which limits their magnetic resolution. Here, we report the modeling, design, and fabrication of single layer anisotropic magnetoresistive (AMR) sensors using low noise epitaxial La2/3Sr1/3MnO3 (LSMO) oxide thin films deposited on vicinal SrTiO3 substrates. The fabrication process is simple, and the operation of the sensor is based on a step-induced uniaxial magnetic anisotropy, described using the Stoner–Wohlfarth model. A coherent magnetization reversal process is observed by magneto-optical Kerr effect imaging. A good agreement between experimental data and the expected sensor response confirms the correct operation of the device. Three main fabrication parameters, namely the vicinal angle of the substrate, the deposition temperature, the thin film thickness, and their effects on film anisotropy field and device detectivity have been studied. Detectivity levels as low as 1.4 nT Hz–1/2 at 1 Hz and 240 pT Hz–1/2 in the white noise region are achieved with a single Wheatstone bridge element operating at 310 K. Compared to GMR and AMR sensors, these results are promising for further development and for their use as single layer LSMO low field AMR sensors, including applications as implantable biomedical devices