Actuated MOEMS Micro-Mirror based on PMN-PT Piezoelectric Material.

International audienceThis paper investigates the use of a PMN-PT [001] piezoelectric actuator to be integrated in smart Micro-Opto-Electrical-Mechanicals Systems (MOEMS). Unlike most piezoelectric materials, PMN-PT [001] can generate large-stroke out-of-plane displacement. This is due to its very high longitudinal piezoelectric coefficient of tu to 4500 pm/V. After an introduction on MOEMS actuation and a short description of the Reconfigurable Free Space Micro-Optical Bench (RFS-MoB) in which the studied actuator may be included is presented, a bulk actuator is proposed. FEM simulations are then presented highlighting some tradeoffs : increased displacement with the reduction in size while decreasing the optical aberration. It was observed that for actuators with a smaller surface than 800 x 800 µm2 and 200 µm thick, displacement larger than 325 nm is largely achievable and that the size of the usable area of the actuator varies in size with the applied voltage

Duo-bimorph actuator made of PMN-PT [011] : 3D modeling, development and characterization.

International audienceThis paper reports the development of a duo-bimorph cantilevered actuator made of PMN-PT material and intended for large-stroke micro-scale manipulation. The principle of operation is piezoelectric, but with a series of material-induced particularities: PMN-PT is reputed for its very high piezoelectric and electromechanical coupling characteristics, but exhibits a lower coercive field which prevents driving in a fully bipolar manner. Instead of the uniaxial [001] plate, by using the anisotropic [011] cut, a positive transverse d31 piezoelectric coefficient may be exploited. This allows the extension of the structure with the applied voltage, which is particularly beneficial for micro-gripping. After an introductory part in piezo-materials and duo-bimorph structures, a comprehensive static three-dimensional displacement modeling is provided by means of constitutive matrix equations. The actuator micro-manufacturing is presented, followed by the experimental characterization. Compared to the classical PZT structures, the actuation is increased by a factor of two, up to 600 μm in the transversal plane and up to 20 μm longitudinally. Some perspectives related to 3 DoF (Degrees of Freedom) micro-manipulation tasks are finally approached

Conception, Modélisation, Fabrication et Contrôle des systèmes piézoélectriques en PMN-PT.

This work proposes the use of a novel material, called PMN-PT, that futher aids the miniaturization of complex systems used in different technologies. The work is presented within the collaborative framework of two projects, MIOP and ADMAN. The end-needs account for actuators capable of delivering high displacement, while maintaining system simplicity and reliability. The focus is on the versatility of the PMN-PT piezoelectric material, due to its electro-mechanical properties. The work includes an overview on what influences the electro-mechanical properties focusing on two different, though very potent cuts: anisotropic [011] and longitudinal [001]. They were chosen for generating large displacement and high dynamics with small volume. For PMN-PT[001] a cantilever structure was studied, for which the model was improved taking into account the material specificities. Displacements and forces were found to be superior to a similarly dimensioned PZT actuator, whilst having reduced non-linearities. This is exemplified with a 6 DoF capable microgripper. The PMNPT[001] longitudinal cut based actuator study follows. This is done by using PMN-PT as a simple, easy to integrate, bulk actuator. The findings demonstrate the improvements PMN-PT can bring to micro-spectrometry and image correction with micro-mirror displacement. A bulk PMN-PT micro actuator was integrated into a MOEMS compatible structure and presented.Ce travail propose l’utilisation d’un nouveau matériau, appelé PMN-PT, qui continue aider la miniaturisation des systèmes complexes, utilisés dans des différentes technologies. Le travail est présenté dans le cadre de collaboration entre deux projets, MIOP et ADMAN. Les besoins tien compte que les actionneurs soient capables de délivrer de haute déplacement tout en conservant la simplicité et la fiabilité du système. L’accent est mis sur la polyvalence de ce matériau piézoélectrique, PMN-PT, en raison de ses propriétés électro-mécanique. Le travail comprend un aperçu sur quoi influence les propriétés électro-mécaniques du PMN-PT. L'accent est mis sur deux différentes, mais très puissants coupes: anisotrope [011] et longitudinale [001], choisi pour grand déplacement et haute dynamique avec un volume petit. Pour le PMN-PT[001], une structure de type poutre a été étudié, avec un modèle amélioré pour prendre en compte les spécificités de matériel. Les déplacements et forces ont été trouvés d'être supérieur à un actionneur en PZT, similairement dimensionnée, tandis que avoir des non-linéarités réduites. Ceci est illustré avec une micropince avec 6DDL. L’étude de PMN-PT [001] coupé longitudinal suit. Cette ´etude a été fait en utilisant PMNPT comme un actionneur avec une structure simple, facile à intégrer. Les résultats d´emontrent les améliorations PMN-PT peut apporter à micro-spectrométrie et la correction d’image avec des micromiroir mobiles. Un micro actionneur PMN-PT a été inégré dans une structure compatible avec des MOEMS et présenté

Piezoelectric 3D actuator for micro-manipulation based on [011]-poled PMN-PT single crystal

International audienceThis paper sets forth to study and demonstrate the usability of an emerging piezoelectric material, called Lead Magnesium Niobate–Lead Titanate (PMN–PT), as a potential actuator for dexterous micro-manipulation. For this purpose, a generic structure called a duobimorph cantilever is studied. The proposed design takes advantage of a specific transverse elongation property of the PMN-PT poled in the [011] crystalline direction. A static 3D analytical model is presented, that links the applied voltage signals to the displacement and blocking force along each axis. Experimental characterization is conducted on 21.0 × 0.6 × 0.41 mm3 cantilevers to validate the analytical 3D model. The transverse and longitudinal displacement range (not counting end-effectors) is over 460 μm and 40 μm respectively, while still generating high forces typically in the range of 16.5–48.2 mN, values which are significantly higher than in the case of regular Lead Zirconate Titanate (PZT) ceramics. Results also show that PMN-PT has a good linearity, i.e. a very low hysteresis in the range of 2.8–6%, which is around 5 times lower than in the case of PZT. Next, in order to test the potential of this material for micro-manipulation devices, a pair of duobimorph cantilevers is used to build a microgripper. This device is used to conduct a 3D pick-and-place exercise without assistance from external motorized stages. A number of six useful Degrees of Freedom (DoF) are thus achieved, which is a novelty for cantilevered piezoelectric grippers. The results prove that PMN-PT is a great candidate for precise motion generation while still generating large displacement, which is a key factor for any Micro Electro Mechanical Systems (MEMS) implementation. Furthermore, PMN-PT of [011] type particularly can be used in complex, yet more compact, multi-DoF micro-manipulation applications

Size-dependent Analysis and Experiments of Bulk PMN-PT [001] Piezoelectric Actuator for MOEMS Micro-Mirrors.

International audienceThis paper presents the modeling, fabrication, FEM simulation and validation of a PMN-PT [001], bulk micro-actuator intended dor integration in smart Micro-Opto-Electrical-Mechanicals Systems (MOEMS). Unlike the majority of piezoelectric materials, PMN-PT [001] has the ability to generate large-stroke out-of-plane actuation ; this is due to its high longitudinal piezoelectric coefficient of up to 4500 pm/V. After an introduction on MOEMS actuation, a concise modeling is given. The FEM simulations are then presented, highlighting actuation-induced shape specificities. The focus is placed on planar displacement and on possible shape generation. Actuation reached values as high as 680 nm for a 200 µm tick layer. Spherical shape generation was also studied. After presenting the fabrication of a basic piezo-patch mirror, the experimental verification is provided, outlining the influence of the contact interface size and nature

Design of Anti-HIV Ligands by Means of Minimal Topological Difference (MTD) Method

Molecular modeling and MTD methods are useful tools to assess both qualitative(SAR) and quantitative (QSAR) chemical structure-biological activity relationships. The 1-[(2-hydroxiethoxi)-methyl]-6-(phenylthio)thymine congeners (HEPT ligands) show in vitroanti-viral activity against the type-1 human immunodeficiency virus (HIV-1), which is theetiologic agent of AIDS. This work shows an extensive QSAR study performed upon a largeseries of 79 HEPT ligands using the MTD and HyperChem molecular modeling methods.The studied HEPT ligands are HIV reverse-transcriptase inhibitors. Their geometries wereoptimized and conformational analysis was carried out to build the hypermolecule, whichallowed applying the MTD method. The hypermolecule was used for space mapping of thereceptor’s interaction site. The obtained results show that there are three 3D molecular zonesimportant for the anti-HIV biological activity of the HEPT ligands under study