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Cleri F.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
International Journal of Plasticity | Year: 2012

We present a continuum model describing the extreme plastic behavior of nanostructured materials with covalent bonding, drawing inspiration both from recent experiments on Si nanowires, and atomic-scale molecular dynamics simulations. Building on the observations of such works it is proposed that deformation in a nanostructure made of randomly oriented nanocrystals embedded in an amorphous layer, proceeds by transferring the deformation energy to and from three distinct regions: a crystalline phase, corresponding to the bulk-like interior of each nano grain; a constrained amorphous phase, the percolative connecting network between different nano grains; and a defect accumulation zone, a thin shell surrounding each nano grain, where matter is turned from one phase into another. We formulate a free energy functional to describe the energy balance among the phases under steady non-equilibrium loading conditions. Strain and stress partial differential equations are derived, which are solved numerically to follow the evolution of the concentrations of the material phases, and the overall mechanical response of the system at constant input of external work. Matter transport is also included in the model, to account for stress-assisted diffusion, leading to accretion and non-constant volume and mass of the nanostructure during the mechanical deformation. A remarkable agreement with recent experiments on Si nanowires under extreme tensile deformation is obtained. © 2012 Elsevier Ltd. All rights reserved. Source


Arscott S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

This short review focuses on the application of SU-8 for the microchip-based approach to the miniaturization of mass spectrometry. Chip-based mass spectrometry will make the technology commonplace and bring benefits such as lower costs and autonomy. The chip-based miniaturization of mass spectrometry necessitates the use of new materials which are compatible with top-down fabrication involving both planar and non-planar processes. In this context, SU-8 is a very versatile epoxy-based, negative tone resist which is sensitive to ultraviolet radiation, X-rays and electron beam exposure. It has a very wide thickness range, from nanometres to millimetres, enabling the formation of mechanically rigid, very high aspect ratio, vertical, narrow width structures required to form microfluidic slots and channels for laboratory-on-a-chip design. It is also relatively chemically resistant and biologically compatible in terms of the liquid solutions used for mass spectrometry. This review looks at the impact and potential of SU-8 on the different parts of chip-based mass spectrometry-pre-treatment, ionization processes, and ion sorting and detection. © 2014 the Partner Organisations. Source


Arscott S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Applied Physics Letters | Year: 2013

Wetting of sessile bubbles on various wetting surfaces (solid and liquid) has been studied. A model is presented for the apparent contact angle of a sessile bubble based on a modified Young's equation - the experimental results agree with the model. Wetting a hydrophilic surface results in a bubble contact angle of 90°whereas using a superhydrophobic surface one observes 134°. For hydrophilic surfaces, the bubble angle diminishes with bubble radius whereas on a superhydrophobic surface, the bubble angle increases. The size of the plateau borders governs the bubble contact angle, depending on the wetting of the surface. © 2013 AIP Publishing LLC. Source


Devos A.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
Ultrasonics | Year: 2015

The aim of this paper is to review the various laser-wavelength effects reported in the field of ultrafast acoustics (UA). First observed by chance in 1999, a wavelength change can indeed have a strong effect on the signal detected in UA. After the physical origin of the effect was clarified and from a systematic exploration we established that all the opto-acoustic mechanisms acting in UA are influenced by the laser-wavelength. From that we suggested original applications of UA to fundamental and applied physics. So emerged a new field, now referred as Colored Picosecond Acoustics or APiC. © 2014 Elsevier B.V. All rights reserved. Source


Giordano S.,CNRS Institute of Electronics, Microelectronics and Nanotechnology
International Journal of Solids and Structures | Year: 2013

In this work we consider a cylindrical structure composed of a nonlinear core (inhomogeneity) surrounded by a different nonlinear shell (matrix). We elaborate a technique for determining its linear elastic moduli (second order elastic constants) and the nonlinear elastic moduli, which are called Landau coefficients (third order elastic constants). Firstly, we develop a nonlinear perturbation method which is able to turn the initial nonlinear elastic problem into a couple of linear problems. Then, we prove that only the solution of the first linear problem is necessary to calculate the linear and nonlinear effective properties of the heterogeneous structure. The following step consists in the exact solution of such a linear problem by means of the complex elastic potentials. As result we obtain the exact closed forms for the linear and nonlinear effective elastic moduli, which are valid for any volume fraction of the core embedded in the external shell.© 2013 Elsevier Ltd. All rights reserved. Source

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