Alteration of superconductivity of suspended carbon nanotubes by deposition of organic molecules

We have altered the superconductivity of a suspended rope of single walled carbon nanotubes, by coating it with organic polymers. Upon coating, the normal state resistance of the rope changes by less than 20 percent. But superconductivity, which on the bare rope shows up as a substantial resistance decrease below 300 mK, is gradualy suppressed. We correlate this to the suppression of radial breathing modes, measured with Raman Spectroscopy on suspended Single and Double-walled carbon nanotubes. This points to the breathing phonon modes as being responsible for superconductivity in carbon nanotubes

Silicon NANO-ESI Emitters for Mass Spectrometry: A Mixed Micromechanical and Microfluidic Design

International audienc

A new optimal design method for electrostatically actuated silicon-based MEMS: Application to a micro-gripper with large stroke and high force resolution

Conference of 1st International Conference on Engineering and Applied Sciences Optimization, OPT-i 2014 ; Conference Date: 4 June 2014 Through 6 June 2014; Conference Code:108723International audienceThe design of Micro Electro Mechanical Systems (MEMS) is often based on the use of costly trial and error method which depends highly on the technical skills of the involved engineers. The drawback of such a procedure is to lead to sub-optimal designs and poor performance at the end. Some research works on dedicated optimization tools have begun a few years ago. The present paper deals with the development of a dedicated optimal design tool for monolithic MEMS, fabricated using the Silicon On Insulator (SOI) process. This tool is an evolution of a previously developed heuristic method, using a multi-objective evolutionary algorithm and a compliant building blocks library. It has been adapted and implemented in the MEMS design software called FlexIn SOI (Flexible Innovation for SOI), which account for the anisotropic elastic behavior of the Single Cristal Silicon material for the Finite Element evaluation of the fitness functions involved in the optimization process. To illustrate the usefulness of this tool, the automatic optimal design of a monolithic microgripper has been investigated. Here, the micro-fabrication process resolution is defined as an optimization constraint. Five dedicated objective functions have been considered to quantify real performances of the gripper, and also to be able to consider the use recommendations of associated inter-digital actuators and sensors. At the end of the optimization process, the nonlinear comb-drive actuator stiffness has been considered to select an electromechanically stable solution among Pareto front. This solution has been prototyped and characterized. It showed very outstanding performances regarding state-of-the-art micro-grippers [1], thus validating the proposed optimal design method

Contact modelling by the finite element method : Application to the piezoelectric motor

The operating principle of the piezoelectric motor is based upon various physical phenomena, among which one could mention the acoustic vibration and the friction between the stator and the rotor. In our laboratory a finite element code called ATILA has been developed. ATILA is efficient to perform static, modal or harmonic analysises for elastic structures. During the last two decades, the contact modeling drew the attention of numerous research groups, suggesting numerical approach by the finite element. However, most of these numerical studies require heavy programming techniques. In this paper we suggest an algorithm in order to treat the problem of contact with or without friction. This algorithm is based on a technique of mathematical simple programming using the method of static condensation. Finally, an application to the piezoelectric motor is presented. The present study focused on the interface between the stator and the rotor, where the acoustic energy is converted into the spinning of the rotor through the friction mechanism. The contact algorithm presented in this paper allows the contact surface, the normal and tangential stresses to be determined as a function of the interface parameters. The results are validated by comparing with piezoelectric motor experimental data

Tip-matter interaction measurements using mems ring resonators

We have previously reported on a new concept of Atomic Force Microscope (AFM) probes using bulk-mode silicon resonators [1]. We report here measurements of interaction between a surface and the vibrating tip of the resonator. In particular, the tip oscillation amplitude versus the probe-sample distance has been acquired for various surface materials. These experiments give access to the electrical response of the resonator regarding the tip-surface interaction and represent a first step towards force spectroscopy using MEMS resonators based probes. This work paves the way to the integration of such probes in an AFM set-up using the resonator output signal as the AFM feedback control signal