HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

A multiphysics model for capacitive micromachined ultrasonic transducers (CMUTs) is developed taking into account the main sources of nonlinearities in the case of circular plates. The equation of motion is reduced to an asymmetric Duffing equation which is solved using the harmonic balance method coupled with the asymptotic numerical method. Multiple-valued solutions, indicating the occurrence of jump phenomena, are observed numerically and confirmed experimentally on measured frequency responses of micro-machined CMUTs based on anodic bonding of a SOI wafer on a glass wafer. This purely numerical approach allows designers to control the resonator bifurcation topology by tuning the design parameters and thus gives the possibility of driving the CMUT beyond its critical amplitude. As a consequence, the CMUT performances can be enhanced in terms of bandwidth and generated acoustic power.

In this paper, we present construction, fabrication and characterization of an electrostatic MOEMS vertical microscanner for generation of an optical phase shift in array-type interferometric microsystems. The microscanner employs asymmetric comb-drives for a vertical displacement of a large 4x4 array of reference micromirrors and for in-situ position sensing. The device is designed to be fully compatible with Mirau configuration and with vertical integration strategy. This enables further integration of the device within an "active" multi-channel Mirau micro-interferometer and implementation of the phase shifting interferometry (PSI) technique for imaging applications. The combination of micro-interferometer and PSI is particularly interesting in the swept-source optical coherence tomography, since it allows not only strong size reduction of a system but also improvement of its performance (sensitivity, removal of the image artefacts). The technology of device is based on double-side DRIE of SOI wafer and vapor HF releasing of the suspended platform. In the static mode, the device provides vertical displacement of micromirrors up to 2.8µm (0 -40V), whereas at resonance (fo=500 Hz), it reaches 0.7 µm for only 1VDC+1VAC. In both operation modes, the measured displacement is much more than required for PSI implementation (352nm peak-to-peak). The presented device is a key component of array-type Mirau micro-interferometer that enables the construction of portable, low-cost interferometric systems, e.g. for in vivo medical diagnostics.

No abstract

An extension of classical laminate theory to the anelastic domain is proposed. It is based on numerical methods which describe the laminate's response to mechanical loading not analytically but step by step. This approach is applied to a behaviour model of a non linear viscoelastic layer and its application to multiaxiaI creep tests on filament wound tubes ± 55°is discussed.