Mechanical adhesion of SIO2 thin film on a polymeric substrate under compressive stress

International audienceTo ensure good adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, quantification of adhesion is performed by analyzing SiO2 buckle morphologies generated under compressive stress. This adhesion test was chosen for its representativeness of defects observed in real life. Interfacial toughness can be determined by applying Hutchinson & Suo model. This analytical model involves accurate value of elastic modulus Ef of SiO2 thin film. Small dimensions at stake make characterization of elastic modulus challenging. First part of the study focuses on using both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus. Results showed significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films with different intrinsic stresses was also investigated and suggests that higher density of SiO2 thin film leads to higher elastic modulus. Compression tests resulted in formation of straight-sided buckles that evolve into telephone cords upon unloading. Numerical simulation and Digital Image Correlation were implemented to ensure homogeneous strain of substrate and favor regular distribution of buckles. Values of energy release rates of SiO2 / Hardcoat range from 2.7 J/m² to 8.9 J/m², depending on moduli values found on wafer or lens substrate

A new minimally invasive heart surgery instrument for atrial fibrillation treatment : first in vitro and animal tests.

International audienceThe paper presents a new robotic system for beating heart surgery. The final goal of this project is to develop a tele-operated system for the thoracoscopic treatment of patients with atrial fibrillation. The system consists of a robot that moves an innovative end-effector used to perform lines as in the Cox-Maze technique. This device is an electrode mesh that is introduced in the thorax through a trocar and is deployed inside the left atrium, where it can create selective ablation lines at any atrial region, using radio frequency. The current version of the umbrella has 22 electrodes. Using visual feedback from an ultrasound based navigation system, the surgeon can choose which electrodes on the mesh to activate. Once the umbrella is in contact with the endocardium of the left atrium, at the expected position, the surgeon activates the chosen electrodes sequentially. The umbrella can then be moved to another position. In vitro and in vivo animal tests have been carried out in order to test and improve the instrument, the robotic system and the operative procedure

FE simulation of interfacial delamination between SiO2 thin film and polymeric substrate

International audienceOphthalmic lenses are made of plastic polymeric substrates usually coated with functional treatments composed of 5 to 15 layers, ranging from micrometers to nanometers. Each of these interfaces may lead to delamination due to poor adhesion, and therefore affect the vision and comfort of wearers. The interface between the anti-reflective stack and the hardcoat is particularly sensitive because of chemical and mechanical contrast of its materials. To better understand mechanisms that lead to loss of adhesion between the SiO2 anti-reflective layer deposited on the anti-scratch hardcoat, compression experiments are performed to induce buckling of SiO2 layer. A Finite Element Model is developed to refine characterization of interfacial properties. Simulation of buckling phenomenon and delamination of SiO2 layer under compressive stress is proposed. Interfacial properties between SiO2 layer and hardcoat are modeled using cohesive elements following a traction separation law. Geometry of buckle yielded by the model is compared against experimental results to adjust the numerical model and access interfacial properties

Le radeau des cimes au Parc national de Masoala (Madagascar). Première partie : éléments pour un inventaire des Lépidoptères

Grâce à l'expédition Radeau des Cimes 2001, de nombreuses espèces de Lépidoptères peuvent être rajoutées aux inventaires faunistiques de la presqu'île de Masoala, encore très incomplets. Des papillons et quelques chenilles ont été collectés pendant cinq semaines (principalement en novembre) dans la région de Tampolo, mais aussi dans celle d'Andranobe, au sud d'Ambanizana. Un certain nombre de chenilles ont été élevées avec succès, notamment celle d'une noctuelle, apparemment non décrite (Herminiinae) et la chenille jusque-là inconnue du Sphingidae Rhagastis lambertoni (Clark). A partir de nids d'un Hypsoides sp. (Notodontidae Thaumetopoeinae; espèce peut-être nouvelle), divers insectes ont été obtenus, dont un Cosmopterigidae et un Phycitinae (Pyralidae) vraisemblablement des espèces nouvelles pour la science. Au moins 23 espèces de Bombycoïdes (dont le Sphingidae Hipparion melichari Haxaire) ont pu être capturées - en octobre-novembre 2001 - dans la région de Tampolo. En comparant l'efficacité de trois pièges lumineux similaires, mais installés, l'un sur le Radeau des Cimes, les deux autres sous celui-ci, dans le sous-bois, on peut avancer l'hypothèse selon laquelle la plupart des Sphinx nocturnes tendraient à voler au-dessus de la canopée. Une première liste des Sphingidae de Masoala est proposée. Parmi les Rhopalocères, 65 espèces de Rhopalocères ont été distinctement aperçues (p. ex. Smerina manoro (Ward) - Nymphalidae) ou capturées. Trois Hesperiidac sont signalés pour la première fois de Masoala: Perrotia howa (Mabille), P. silvestralis (Viette) et Borbo ratek (Boisduval). (Résumé d'auteur

Mechanical adhesion of SiO2 thin films onto polymeric substrates

Quantification of adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick polymeric coating was performed by analysing the SiO2 buckle morphologies generated under compressive stress. Impacts of mechanical properties of SiO2 layers, as well as a surface pretreatment on adhesion, are shown. Interfacial toughness of both configurations are assessed using the Hutchinson and Suo model, which involves buckle dimensions determined in situ by an optical profilometer, and elastic modulus Ef, of the SiO2 thin films, characterised by nanoindentation. The surface pretreatment led to initiation of buckling at a higher strain. The same trend is observed for a layer with a lower stiffness and residual stress

Understanding mechanisms of adhesion of SiO2 thin films evaporated on a polymeric substrate

A better understanding of mechanisms of adhesion between a 200 nm thick silicon dioxide layer and a 4.5 µm thick polymeric hardcoat is indispensable for an efficient adhesion at the interface. To reach this purpose, focus is placed on two axes: finding an applicable and effective method to quantify adhesion and in parallel, characterizing mechanical properties of materials composing the system. The second axis is needed to obtain data to feed modeling codes, enabling a better analysis of the adhesion experiment. Modulus of modified Si02 was found to be roughly 20% higher than reference Si02, by nanoindentation. AFM experiments showed no difference between modified and reference Si02• Currently, an investigation to detect cracks at the interface of interest for micro-tensile test is ongoing. Adhesion tests, such as micro-compression will be performed as well

Mechanical adhesion of SIO2 thin film on a polymeric substrate under compressive stress

To ensure good adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, quantification of adhesion is performed by analyzing SiO2 buckle morphologies generated under compressive stress. This adhesion test was chosen for its representativeness of defects observed in real life. Interfacial toughness can be determined by applying Hutchinson & Suo model. This analytical model involves accurate value of elastic modulus Ef of SiO2 thin film. Small dimensions at stake make characterization of elastic modulus challenging. First part of the study focuses on using both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus. Results showed significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films with different intrinsic stresses was also investigated and suggests that higher density of SiO2 thin film leads to higher elastic modulus. Compression tests resulted in formation of straight-sided buckles that evolve into telephone cords upon unloading. Numerical simulation and Digital Image Correlation were implemented to ensure homogeneous strain of substrate and favor regular distribution of buckles. Values of energy release rates of SiO2 / Hardcoat range from 2.7 J/m² to 8.9 J/m², depending on moduli values found on wafer or lens substrate

Adhesion characterization of SiO2 thin films evaporated onto a polymeric substrate

To ensure good adhesion between a 200 nm thick silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, focus is placed on two axes: characterizing mechanical properties of materials composing the system and in parallel, finding an applicable and effective method to quantify adhesion. Small dimension of SiO2 thin film makes it challenging to accurately characterize it. Hence the use of both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus Ef; taking into account limitations and uncertainty associated with each technique. Elastic modulus of SiO2 thin film determined by nano-indentation is roughly 50 GPa on a wafer substrate and 15 GPa on a lens substrate. As for AFM, modulus measured is approximatively 56 GPa on a wafer substrate and 22 GPa on a lens substrate. This highlights significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films under different intrinsic stresses was also investigated. Results suggest that higher density of SiO2 thin film leads to higher elastic modulus. To quantify adhesion, micro-tensile and micro-compression tests were performed. Micro-tensile experiments give ultimate shear strengths of hardcoat-substrate interface ranging from 9 to 14 MPa. Values of energy release rates of SiO2 / Hardcoat, range from 0.1 J/m² to 0.5 J/m², depending on moduli values found on wafer or lens substrate

FE simulation of interfacial delamination between SiO2 thin film and polymeric substrate

Ophthalmic lenses are made of plastic polymeric substrates usually coated with functional treatments composed of 5 to 15 layers, ranging from micrometers to nanometers. Each of these interfaces may lead to delamination due to poor adhesion, and therefore affect the vision and comfort of wearers. The interface between the anti-reflective stack and the hardcoat is particularly sensitive because of chemical and mechanical contrast of its materials. To better understand mechanisms that lead to loss of adhesion between the SiO2 anti-reflective layer deposited on the anti-scratch hardcoat, compression experiments are performed to induce buckling of SiO2 layer. A Finite Element Model is developed to refine characterization of interfacial properties. Simulation of buckling phenomenon and delamination of SiO2 layer under compressive stress is proposed. Interfacial properties between SiO2 layer and hardcoat are modeled using cohesive elements following a traction separation law. Geometry of buckle yielded by the model is compared against experimental results to adjust the numerical model and access interfacial properties

Diagnostic du Projet d'agglomération franco-valdo-genevois de 2ème génération

Ce document répond à l’exigence de base 3 (EB3) de la directive pour l’examen et le cofinancement des projets d’agglomération de deuxième génération (DETEC, ARE, 2010). Le rapport présente une analyse de l’état actuel et des tendances de développement dans l'agglomération franco-valdo-genevoise et fait ressortir, pour tous les domaines (urbanisation, transport et environnement) les principales forces et faiblesses de l’agglomération. En lien avec les tendances de développement, il identifie les opportunités, les menaces et les besoins d’action. Ce document est l'annexe 1 du dossier de Projet d'agglomération 2012