Name: atomic force microscopy for surface mapping
Uploaded: 2023-04-30T12:00:37.000Z
Duration: 1 min 8 s
Channel: JoVE

La microscopie à force atomique ou AFM génère une image à l’aide d’une nanosonde pour fournir des informations topographiques sur un échantillon avec une résolution nanométrique.
Alors qu’un microscope optique peut grossir jusqu’à 1000X, le potentiel de grossissement de l’AFM est jusqu’à 1 000 000X.
L’AFM peut créer des images d’échantillons fixes et vivants, ce qui lui permet de capturer des processus cellulaires dynamiques tels que la dynamique de l’actine.
La nanosonde AFM est fixée à l’extrémité d’un cantilever flexible et, ensemble, elles scannent l’échantillon. La sonde suit les contours de la surface de l’échantillon, se déplaçant de haut en bas, ce qui déplace le porte-à-faux.
Dans un type d’AFM, un faisceau laser est dirigé vers le cantilever et, lorsqu’il se déplace, la réflexion du laser se déplace également.
Un photodétecteur sensible à la position enregistre la déviation du faisceau laser.
Les données sont envoyées à un ordinateur où un logiciel peut les traiter pour générer une image tridimensionnelle de la surface de l’échantillon.

<ol>
	<li>Casuso, Ignacio, Felix Rico et Simon Scheuring. « AFM biologique : d’où nous venons - où nous sommes - où nous pouvons aller. » Journal de reconnaissance moléculaire 24.3 (2011) : 406-413.</li>
	<li>Garcıa, Ricardo et Ruben Perez. « Méthodes de microscopie à force atomique dynamique. » Rapports scientifiques de surface 47.6-8 (2002) : 197-301.</li>
</ol>

microscope à force atomique

Atomic Force Microscopy

La microscopie à force atomique (AFM) est un type de microscopie à sonde à balayage qui peut analyser les détails topographiques de divers spécimens comme la céramique, le verre, les polymères et les échantillons biologiques. L'AFM offre une résolution plus de 1 000 fois supérieure à celle du système d'imagerie optique. Les images générées par l'AFM sont des profils de surface tridimensionnels, offrant un avantage par rapport aux images plates et bidimensionnelles provenant d'autres techniques d'imagerie.

La Sonde AFM

La sonde est considérée comme le cœur de toute configuration AFM et comprend l’ensemble cantilever et pointe. Les sondes sont la pièce la plus couramment remplacée sur ce type de microscope car l'interaction constante avec les échantillons utilise la pointe. Le choix du matériau de la sonde dépend donc des propriétés de l’échantillon. Les sondes en silicium, utilisées pour analyser des échantillons durs, sont plus rigides et plus pointues que les sondes en nitrure de silicium, mieux adaptées à l'analyse d'échantillons plus mous. Ces pointes acérées sont produites par gravure électrochimique ou par nanotubes de carbone pour une analyse plus précise.

Modes D'imagerie de L'AFM

En AFM, la topographie de la surface est étudiée en utilisant l'interaction entre la pointe de la sonde et la surface de l'échantillon. Il existe deux modes d'imagerie principaux : un mode statique, également appelé mode contact, et un mode dynamique.

En mode statique ou contact, la pointe de la sonde est en contact continu avec la surface de l'échantillon. Lorsque la pointe glisse sur la surface, les forces répulsives entre l'échantillon et la pointe entraînent une flexion du cantilever , qui est enregistrée. La surface entière de l'échantillon est numérisée d'avant en arrière sur les axes x et y, appelé balayage raster, tandis que le mouvement vertical du porte-à-faux enregistre l'axe z, générant ainsi une image 3D.

En mode dynamique, la sonde oscille juste au-dessus de la surface de l’échantillon, se rapprochant de la surface sans la toucher. Les forces attractives et répulsives déterminent la variation de distance entre la pointe et l'échantillon, affectant l'amplitude de l'oscillation en porte-à-faux. Ce retour d'information est enregistré pour construire la topographie de surface de l'échantillon.

Microscope à Force Atomique

La microscopie à force atomique (AFM) est un type de microscopie à sonde à balayage qui permet d’analyser les détails topographiques de divers spécimens comme la céramique, le verre, ...

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atomic force microscopy for surface mapping

Atomic force microscopy is used to map the surface details of materials. It can examine ceramics, glass, polymers, and biological samples. The method gives far more resolution than an optical imaging system and produces three-dimensional surface profiles instead of flat 2D images.

The probe is the key part of an AFM setup. It includes the cantilever and tip assembly, and it is also the part that is replaced most often. Constant contact with samples wears down the tip, so probe choice depends on the sample being scanned. Silicon probes are stiffer and sharper, which makes them useful for hard samples. Silicon nitride probes are better for softer samples.

AFM tips can be made with electrochemical etching or with carbon nanotubes to improve accuracy. The microscope reads surface topography by tracking how the probe tip interacts with the sample surface. This interaction is recorded as the probe scans across the surface.

AFM uses two main imaging modes. In static mode, also called contact mode, the tip stays in continuous contact with the surface. As it drags across the sample, repulsive forces bend the cantilever, and that bending is recorded. The sample is scanned back and forth in the x- and y-axes, which is called raster scanning, while the vertical motion of the cantilever records the z-axis and builds a 3D image.

In dynamic mode, the probe oscillates just above the sample surface. It comes close to the surface without touching it. Attractive and repulsive forces change the distance between the tip and the sample and affect the oscillation amplitude. That feedback is then used to construct the surface topography.

Atomic Force Microscopy for Surface Mapping

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Atomic force microscopy is used to map the surface details of materials. It can examine ceramics, glass, polymers, and biological samples. The method gives far more resolution than an optical imaging system and produces three-dimensional surface profiles instead of flat 2D images. The probe is the key part of an AFM setup. It includes the cantilever and tip assembly, and it is also the part that is replaced most often. Constant contact with samples wears down the tip, so probe choice depends...

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key terms and concepts

Learn how atomic force microscopy maps surfaces, why probe choice matters, and how contact and dynamic modes build detailed 3D images of samples.

Atomic Force Microscopy for Surface Mapping | JoVE K12

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Atomic Force Microscopy for Surface Mapping

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