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

La microscopia a forza atomica o AFM genera un'immagine utilizzando una nanosonda per fornire informazioni topografiche su un campione con risoluzione nanometrica.
Mentre un microscopio ottico può ingrandire fino a 1000X, il potenziale di ingrandimento dell'AFM è fino a 1.000.000X.
L'AFM è in grado di creare immagini di campioni sia fissi che vivi, consentendo di catturare processi cellulari dinamici come la dinamica dell'actina.
La nanosonda AFM è attaccata all'estremità di un cantilever flessibile e insieme scansionano il campione. La sonda segue i contorni della superficie del campione, muovendosi su e giù, spostando il cantilever.
In un tipo di AFM, un raggio laser è puntato verso il cantilever e, mentre si muove, si muove anche il riflesso del laser.
Un fotorilevatore sensibile alla posizione registra la deflessione del raggio laser.
I dati vengono inviati a un computer dove il software può elaborarli per generare un'immagine tridimensionale della superficie del campione.

<ol>
	<li>Casuso, Ignacio, Felix Rico e Simon Scheuring. "AFM biologico: da dove veniamo, dove siamo, dove possiamo andare". Journal of Molecular Recognition 24.3 (2011): 406-413.</li>
	<li>Garcıa, Ricardo e Ruben Perez. "Metodi di microscopia dinamica a forza atomica". Rapporti di scienza delle superfici 47.6-8 (2002): 197-301.</li>
</ol>

microscopia a forza atomica

Atomic Force Microscopy

La microscopia a forza atomica (AFM) è un tipo di microscopia a scansione di sonda in grado di analizzare i dettagli topografici di vari campioni come ceramica, vetro, polimeri e campioni biologici. L'AFM offre una risoluzione oltre 1000 volte maggiore rispetto al sistema di imaging ottico. Le immagini generate dall'AFM sono profili di superficie tridimensionali, che offrono un vantaggio rispetto alle immagini piatte e bidimensionali di altre tecniche di imaging.

La sonda AFM

La sonda è considerata il cuore di qualsiasi configurazione AFM e comprende il gruppo cantilever e punta. Le sonde sono la parte sostituita più comunemente su questo tipo di microscopio perché la costante interazione con i campioni consuma la punta. Pertanto, la scelta del materiale per la sonda dipende dalle proprietà del campione. Le sonde al silicio, utilizzate per analizzare campioni duri, sono più rigide e più affilate delle sonde al nitruro di silicio, che sono più adatte alla scansione di campioni più morbidi. Queste punte affilate sono prodotte utilizzando incisione elettrochimica o nanotubi di carbonio per un'analisi più accurata.

Modalità di imaging dell'AFM

Nell'AFM, la topografia superficiale viene studiata utilizzando l'interazione tra la punta della sonda e la superficie del campione. Esistono due modalità di imaging principali: una modalità statica, denominata anche modalità di contatto, e una modalità dinamica.

Nella modalità statica o a contatto, la punta della sonda è in continuo contatto con la superficie del campione. Quando la punta si trascina sulla superficie, le forze repulsive tra il campione e la punta determinano la flessione del cantilever, che viene registrata. L'intera superficie del campione viene scansionata avanti e indietro su entrambi gli assi x e y, la cosiddetta scansione raster, mentre il movimento verticale del cantilever registra l'asse z, generando così un'immagine 3D.

Nella modalità dinamica, la sonda oscilla appena sopra la superficie del campione, avvicinandosi ma senza toccarla. Le forze attrattive e repulsive determinano la variazione della distanza tra la punta e il campione, influenzando l'ampiezza dell'oscillazione del cantilever. Questo feedback viene registrato per costruire la topografia superficiale del campione.

Microscopia a forza atomica

La microscopia a forza atomica (AFM) è un tipo di microscopia a scansione di sonda in grado di analizzare i dettagli topografici di vari campioni come ceramica, vetro, ...

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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

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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JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Atomic Force Microscopy for Surface Mapping

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