Tuning the effective coupling of an AFM lever to a thermal bath

Fabrication of Nano-Electro-Mechanical-Systems (NEMS) of high quality is nowadays extremely efficient. These NEMS will be used as sensors and actuators in integrated systems. Their use however raises questions about their interface (actuation, detection, read out) with external detection and control systems. Their operation implies many fundamental questions related to single particle effects such as Coulomb blockade, light matter interactions such as radiation pressure, thermal effects, Casimir forces and the coupling of nanosystems to external world (thermal fluctuations, back action effect). Here we specifically present how the damping of an oscillating cantilever can be tuned in two radically different ways: i) through an electro-mechanical coupling in the presence of a strong Johnson noise, ii) through an external feedback control of thermal fluctuations which is the cold damping closely related to Maxwell's demon. This shows how the interplay between MEMS or NEMS external control and their coupling to a thermal bath can lead to a wealth of effects that are nowadays extensively studied in different areas

CXCL10 and ILâ 6: Markers of two different forms of intraâ amniotic inflammation in preterm labor

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137580/1/aji12685_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137580/2/aji12685.pd

Caractérisation des Interactions entre une Microsphère et une Surface Métalliques aux Echelles Nanométriques.

MEMS and NEMS (Micro and Nano Electro-Mechanical Systems) presently undergo a wide development within the framework of the Nanomechanics. The efficient operation of these MEMS / NEMS requires the control and knowledge of fundamental interactions between surfaces separated by distances of the order of 100 nm to 1 micron. At this scale, dominant forces can have different origins (van der Waals, Casimir effect, electrostatic, magnetic...). This thesis presents an experimental study by AFM of the electrostatic and Van der Waals/Casimir interactions between a microsphere and a metallic surface. First, characterisation of the sensors that is based on a microsphere glued onto a cantilever beam is presented. Sensitivity of our measurements determined by noise analysis is shown to provide us with a resolution in the subpiconewton range. In static mode (i.e. cantilever deflection measurement), we have precisely measured capacitive forces of the order of few dozens of piconewton in the 100 to 500 nanometer range. We have also measured and quantified the cantilever deflection effects on the determination of the sphere-surface distance. By dynamic measurements (cantilever as an oscillator at resonance), we studied the coupling between the oscillator mechanically or thermally excited and a surface under the influence of Casimir effect. Finally, dynamic mode measurements allowed us to study dissipation mechanisms associated to long range interactions. For example, we have observed the damping induced by electromechanical coupling.Les MEMS et NEMS (Micro et Nano ElectroMechanical Systems) connaissent un développement important notamment dans le cadre de la Nanomécanique. Le bon fonctionnement de ces MEMS/NEMS est soumis au contrôle des interactions de surfaces séparées par des distances de l'ordre de 100 nm à 1 Μm. A cette échelle, les forces dominantes peuvent être de nature variée (Van der Waals, Casimir, électrostatique, magnétique,...). Ce travail de thèse est consacré à l'étude expérimentale par AFM des interactions électrostatiques et de Van der Waals/Casimir entre une microsphère et une surface d'or. Une attention particulière a été apportée à la préparation et à la caractérisation des sondes (microsphère collée sur un microlevier). Ensuite, à partir de l'analyse du bruit et de la sensibilité du système de mesure, nous avons pu montrer notre capacité à mesurer des forces faibles avec une résolution inférieure au piconewton. Par une détection statique, nous avons mesuré précisément des forces capacitives de l'ordre de quelques dizaines de piconewton et pour des distances comprises entre 100 et 500 nm. Nous avons mesuré et quantifié les effets de la déflexion du microlevier sur la détermination de la distance sphère-surface. Par des mesures dynamiques, nous avons étudié le couplage entre un oscillateur (sphère-microlevier) excité mécaniquement ou thermiquement et une surface sous l'effet de la force de Casimir. Enfin, les mesures en mode dynamique, nous ont permis d'aborder l'étude des mécanismes de dissipation associés aux interactions à longue distance. Nous avons ainsi observé la dissipation par couplage électromécanique

Caractérisations des interactions entre une microsphère et une surface métalliques aux échelles nanométriques

Les MEMS et NEMS (Micro et Nano ElectroMechanical Systems) connaissent un développement important notamment dans le cadre de la Nanomécanique. Le bon fonctionnement de ces MEMS/NEMS est soumis au contrOle des interactions de surfaces séparées par des distances de l'ordre de 100 nm à 1 micromètre. A cette échelle, les forces dominantes peuvent être de nature variée (Van der Waals, Casimir, électrostatique, magnétique,...). Ce travail de thèse est consacré à l'étude expérimentale par AFM des interactions électrostatiques et de Van der Waals/Casimir entre une microsphère et une surface d'or. Une attention particulière a été apportée à la préparation et à la caractérisation des sondes (microsphère collée sur un microlevier). Ensuite, à partir de l'analyse du bruit et de la sensibilité du système de mesure, nous avons pu montré notre capacité à mesurer des forces faibles avec une résolution inférieure au piconewton. Par une détection statique, nous avons mesurée précisément des forces capacitives de l'ordre de quelques dizaines de pico newton et pour des distances comprises entre 100 et 500 nm. Nous avons mesuré et quantifié les effets de la déflexion du microlevier sur la détermination de la distance sphère-surface. Par des mesures dynamiques, nous avons étudié le couplage entre un oscillateur (sphère-microlevier) excité mécaniquement ou thermiquement et une surface sous l'effet de la force de Casimir. Enfin, les mesures en mode dynamique, nous ont permis d'aborder l'étude des mécanismes de dissipation associés aux interactions à longue distance. Nous avons ainsi observé la dissipation par couplage électromécanique.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Non parabolic capacitive coupling in an AFM based microsystem at the picoNewton level

Capacitive coupling is most commonly used in NEMS/MEMS or in Scanning Probe Techniques to either induce a displacement or to detect an external interaction applied to the micro/nanosystem. A parabolic elastic deformation of the sensor signs a capacitive interaction as the applied voltage is varied. In this paper, we present detailed force measurements performed in the submicron range with a picoNewton sensitivity, and using a UHV AFM and a silicon microlever equipped with a metallized microsphere,. A complete treatment of the sensor sphere/plane geometry enables one to detect quantitatively a V4 departure from the parabolic behaviour. This shows that using this setup allows to detect the increased deformation of a lever much before the mechanical instability. More importantly, this effect must be carefully taken into account if sphere/plane absolute separations are to be quantitatively measured on the basis of electrostatic calibration. To our knowledge, this behaviour in AFM is reported for the first time. We believe that it is relevant for the description of NEMS/MEMS behaviour. Moreover, it provides a method to accurately measure the lever spring constant without any direct contact

A MEMS-based high frequency x-ray chopper

International audienc

Nanoscale stripe arrays templated on Moiré patterns in graphite

Large areas of nanoscale stripe arrays were produced by drop casting silica nanoparticle solutions on highly oriented pyrolytic graphite surfaces at room temperature and imaged with atomic force microscopy. The alignment of the striped areas always reflected the threefold symmetry of the graphite surface. Two different patterns were observed, with different coverages, line separations and mutual orientation, being offset by 30°. Measurement of the relative angles and separations of the line patterns showed a very good match with an underlying Moiré pattern, resulting from the rotation of the top graphene layers. Closer-spaced lines were attributed to the zig-zag direction of the Moiré pattern whereas wider-spaced lines belonged to the armchair direction. The different abundance and apparent difference in long-term stability suggested that stability was governed by the number of reactive vertices per unit area as opposed to the number of vertices per line-length. Whilst sequential images recorded over several days revealed long term stability of all zig-zag arrays, attachment and detachment of single nanoparticles was observed. By contrast, arrays aligned in the armchair direction appeared and vanished collectively, suggesting condensation and evaporation of a fluid of nanoparticles floating on the surface

Casimir Force Contrast Between Amorphous and Crystalline Phases of AIST

Phase change materials (PCMs) can be rapidly and reversibly switched between the amorphous and crystalline state. The structural transformation is accompanied by a significant change of optical and electronic properties rendering PCMs suitable for rewritable optical data storage and non-volatile electronic memories. The phase transformation is also accompanied by an increase of the Casimir force of 20 to 25% between gold and AIST (Ag5In5Sb60Te30) upon crystallization. Here the focus is on reproducing and understanding the observed change in Casimir force, which is shown to be related to a change of the dielectric function upon crystallization. The dielectric function changes in two separate frequency ranges: the increase of absorption in the visible range is due to resonance bonding, which is unique for the crystalline phase, while free carrier absorption is responsible for changes in the infrared regime. It is shown that free carriers contribute ≈50% to the force contrast, while the other half comes from resonance bonding. This helps to identify PCMs that maximize force contrast. Finally it is shown that if this concept of force control is to be employed in microelectromechanical devices, then protective capping layers of PCMs must be only a few nanometers thick to minimize reduction of the force contrast.

Nanoscale stripe arrays templated on Moiré patterns in graphite

Large areas of nanoscale stripe arrays were produced by drop casting silica nanoparticle solutions on highly oriented pyrolytic graphite surfaces at room temperature and imaged with atomic force microscopy. The alignment of the striped areas always reflected the threefold symmetry of the graphite surface. Two different patterns were observed, with different coverages, line separations and mutual orientation, being offset by 30°. Measurement of the relative angles and separations of the line patterns showed a very good match with an underlying Moiré pattern, resulting from the rotation of the top graphene layers. Closer-spaced lines were attributed to the zig-zag direction of the Moiré pattern whereas wider-spaced lines belonged to the armchair direction. The different abundance and apparent difference in long-term stability suggested that stability was governed by the number of reactive vertices per unit area as opposed to the number of vertices per line-length. Whilst sequential images recorded over several days revealed long term stability of all zig-zag arrays, attachment and detachment of single nanoparticles was observed. By contrast, arrays aligned in the armchair direction appeared and vanished collectively, suggesting condensation and evaporation of a fluid of nanoparticles floating on the surface