Micromètre (appareil de mesure)

Résumé

Le micromètre, ou anciennement « palmer », est un instrument de mesure de longueur. Sous sa forme courante, il est très utilisé en mécanique pour mesurer épaisseurs, diamètres de cylindres (micromètre d'extérieur) ou diamètres d'alésage (micromètre d'intérieur)… De par sa conception, il est moins sujet à déformation que le pied à coulisse, autre instrument classique de mesure de longueur ; sa précision est de l'ordre du 1/100 de mm, alors que les pieds à coulisse se limitent à un affichage au 1/50 de mm, à cause des déformations à la prise de mesure et du principe de lecture lui-même. Les modèles plus récents, numériques, affichent une résolution au 1/1000 de mm (1/100 de mm pour les pieds à coulisse numériques). Historiquement, la vis micrométrique a été inventée par William Gascoigne au et c'est Jean-Laurent Palmer qui en a appliqué le principe à la mesure des petites distances en 1848, d'où son premier nom de « palmer ». Description d'un micromètre d'extérieur Le

Source officielle

https://fr.wikipedia.org/wiki/Microm%C3%A8tre_(appareil_de_mesure)

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Chemical and Optical Identification of Micrometer-Sized 1.9 Billion-Year-Old Fossils by Combining a Miniature Laser Ablation Ionization Mass Spectrometry System with an Optical Microscope

Peter Wurz

2018

Chargement

Fast non-contact surface roughness measurements up to the micrometer range by dual-wavelength digital holographic microscopy

Stéphane Bourquin, Christian Depeursinge, Jonas Kühn, Eduardo Solanas Vilar

We present fast high-roughness and non-contact surface measurements by digital holographic microscopy (DHM). By using single- and dual-wavelength operation modes, coupled with advanced image stitching and non-measured points management methods, the technique enables two-dimensional roughness measurements up to the micrometer (N6). The sample is mechanically scanned over a surface up to 5 × 0.3 mm2 with 17 holograms each acquired in less than 500 µs, the corresponding phase images stitched together by software, and therefore providing multiple profiles measurement in the ISO definition in less than 30 s. The approach is validated by inspection of several different roughness standards and our technique is demonstrated to be in agreement with two existing well-known techniques in the field.

SPIE2010

Chargement

During the last decade, the development of optofluidic chips has become a large field of research. The integration of nano and microstructures with microfluidics layers allowed for the miniaturisation of a number of tools traditionally used in laboratories and optofluidic systems found their main applications in lab-on-a-chip and sensing platforms. At the same time, optical tweezers have become the tool of choice for the trapping and the manipulation of nano and micrometer-sized objects, that can be inert (dielectric or metallic particles) or biological (proteins, bacteria, viruses,...). In this context, nanostructures are the ideal candidate for tweezers miniaturisation, thanks to their ability to strongly confine light in small volumes and hence to generate intense gradient forces. This work reports on the fabrication of an optofluidic chip based on a two-dimensional photonic crystal cavity and on its use in particle and bacteria differentiation. The cavity has a hollow design that maximises the overlap between the confined field and the trapped objects and it supports Self-Induced Back-Action effects that allow for reducing the trapping power (down to few microwatts) and to simultaneously acquire information of the trapped specimen. The system is excited in an end-fire setup and the detection is carried out by recording the light intensity transmitted through the photonic crystal. The fabrication process, that is entirely carried out in the Institue of Physics and in the Center of MicroNanoTechnology cleanrooms, is first detailed. For the cavity design normally used, typical quality factors of 10000 were obtained. Moreover, SU8 mode adaptors were developed to increase the coupling with lensed fibers and a microfluidic membrane presenting two injection channels is proposed for rapid switch between liquids. The trapping and the differentiation of 250 and 500 nm polystyrene is then presented. The differentiation can be achieved qualitatively by direct observation of the transmitted intensity records and quantitatively by the use of histograms and of statistical moments. Finally, the trapping of seven species of living bacteria is shown and their Gram-type is determined by the analysis of the induced transmission increase. This ability to probe the cell wall of bacteria in a fast, label-free and non-destructive way paves the way for applications in biological and biomedical environments.

EPFL2019

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EPFL2019