Arrays of Nano-Electromechanical Biosensors Functionalized by Microcontact Printing

The biofunctionalization of nanoelectromechanical structures is critical for the development of new classes of biosensors displaying improved performances and higher-level of integration. We propose a modified microcontact printing method for the functionalization and passivation of large arrays of nanocantilevers in a single, self-aligned step. Using fluorescence microscopy and resonant frequency measurements, we demonstrate (1) the bioactivity and the anti-fouling property of deposited antibodies and BSA molecules and (2) the preservation of the nanostructures' mechanical integrity.Comment: 20 pages, 5 figure

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Finite element modeling of abradable materials – Identification of plastic parameters and issues on minimum hardness against coating's thickness

Abradable materials are used to decrease the gas consumption of aircraft engines by minimizing the gap between the blade tips and the stator. The key idea consists in using the blades themselves to machine the gap on the abradable coating. The best compromise between soft and hard coating properties has to be reached to avoid blades wear and prevent coating erosion by gas flux and particles. The plastic parameters of abradable coating were identified by using an optimization process directly connected to FEA. The first order optimization method (conjugate gradient strategy + golden section algorithm) was applied to achieve the optimal solution. A good agreement was found between experimental and numerical results. The plastic parameters were used to study the hardness variability of abradable materials with the coating thickness. Surprisingly, a minimum hardness value was found while it was expected that hardness should be always decreasing with thickness. It has been demonstrated that this minimum is produced by the boundary conditions influence on hardness measurement. This research work was completed within the Seal-Coat project funded by the European Commission under the FP5 Growth Program

Modelling route for abradable coatings

International audienceImproving sealing between rotating and stationary parts in aerospace gas turbines significantly increases engine performance by improving thermal efficiencies. To reach this aim, abradable seals are being incorporated into turbine casings. With an abradable seal, the blade tips incur into the shroud, thereby reducing the gap between the rotor and the coating to a minimum. These coatings are generally multiphase materials applied by thermal spray techniques and consisting in a combination of metallic matrix and additional dislocator phases with a controlled amount of porosity. The sealing effectiveness requires a combination of properties that are usually optimised empirically with thermal spray coatings generally made up from a range of two-phase powder mixtures. The present study intends to initiate a theoretical approach for the study of these materials aiming at developing a prediction strategy for structure improvement. Image analyses and finite element calculations were used to examine the effect of phase morphology on the mechanical behaviour of two reference abradable systems, namely AlSi-hBN and NiCrAl-Bentonite for compressor stages. Scanning Electronic Microscopy (SEM) was used to obtain a series of micrographs for coating characterisation. These micrographs were then treated to create equivalent images based on geometrical description of the inherent morphology. The resultant reduced images are used to carry out finite element calculations, in order to determine the mechanical properties of each coating. It is believed that this approach provides consistent results and is believed to be a reliable starting point for further coatings design