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Resources
Resources
Resources
Let's talk about a fancy microscope.
Introducing...
Atomic Force Microscopy
What is AFM?
What is AFM?
Atomic
A microscope that can "see" atoms.
Force
Forces are felt between the sample and the microscope's probe.
Microscopy
More than a microscope! You can move atoms too!
How does AFM work?
Atomic Force Microscopy (AFM) falls under Scanning Probe Microscopy (SPM).
Unlike light microscopes that use lenses to magnify small objects, SPM uses a very sharp probe to "feel" surfaces.
Zooming in...
Zooming in...
Nano@School CIME
An AFM probe moves along a single line at a time on the sample. By controlling the distance of the probe from the sample, we can measure height changes across that line.
Just like we read text line by line, the probe scans the sample line by line to obtain a 2D map of the surface. Combined with the height information and some image processing, we can generate a 3D map of the sample!
How does the probe "feel" the surface?
The probe is presumably so sharp that there is only one atom (or just a few) at the tip. As the probe moves closer to the sample, this atom feels attractive or repulsive forces from the sample atoms.
Zooming out...
Position Detector
Laser beam
Probe
cantilever-tip assembly
Sample
These attractive/repulsive forces cause part of the probe, the "diving board" that's attached to probe tip, to bend. In technical terms, this bending of the "diving board" is called cantilever deflection.
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The cantilever deflection is measured through an optical detection system. A laser beam is reflected by the back of the probe onto a position detector. When the "diving board" bends, the laser is reflected at a different position in the position detector. This difference in position helps us deduce the surface topography and even measure many other physical properties such as friction.
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A feedback loop controls the cantilever deflection, and hence the distance of the probe from the sample, to track the surface accurately.
How does AFM work?
Why AFM is cool!
Why AFM is cool!
1. AFM can produce atomic-resolution images, going down to the Angstrom scale for atoms.
2. AFM can work in a variety of environments: ambient, vacuum, and even in liquids!
3. Almost any type of sample can be imaged with AFM, from living cells to ceramic surfaces.
4. AFM can measure a multitude of physical properties, from friction to magnetic fields.
5. Just like a finger can push objects, an AFM probe can also push atoms! (Not so easy though...)
Source (Image 2): SPMage Prize, Elizaveta Drozd. A.V. Luikov Heat and Mass Transfer Institute (Belarus), https://www.icmm.csic.es/spmage/spmageview09.php?id=62
Source (Image 1 & 3): https://www.nanosurf.com/en/application/atomic-force-microscopy-images
In short, AFM is super versatile and powerful.
Since its invention in 1985, the Atomic Force Microscope has become a popular instrument used in all fields of science. As its technology continues to be developed, perhaps we may see AFM in classrooms one day.
Structure of a butterfly wing
Lithography on titanium
Some cool images...
A few abnormal red blood cells
Learn more about AFM!
Learn more about AFM!
How AFM Works by Park Systems
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A video series that introduces AFM principles and many different AFM modes.
Scanning Probe/Atomic Force Microscopy by MyScope Microscopy Training
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A module that provides a thorough introduction to AFM. Check out the SPM simulator!
Atomic Force Microscopy by Peter Eaton and Paul West
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A practical introductory textbook to AFM. Comprehensive and easy to read!
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