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What can Atomic Force Microscopy do for me?

Atomic force microscopy (AFM) is a high-resolution imaging technique that uses a small probe to scan surfaces of materials to provide 3D height information – a landscape.

The probe consists of a ‘tip’, usually an inverted pyramid with base and height of dimensions of < 10 µm and forming a fine point of a certain radius of curvature (< 100 nm), mounted on a cantilever. A laser monitors the position and applied load on the cantilever, controlling the tip-sample interaction. There are many different shapes, sizes and materials for both tips and cantilevers, depending on the application.

The high-resolution capability owes itself to the microscope not requiring the focusing of light or electrons, as with most microscopes, and so features can be resolved that are smaller than the wavelength of light and electrons. Hence, the magnification of AFM is higher than that in electron microscopy. This is achieved by the scanner, which moves the probe, having piezo-electric ceramic crystals that when a voltage is applied across them, produce a small movement, to a staggering accuracy of 0.01 nm!

AFM at Portsmouth

Click to enlarge

The probe can also be pushed into a surface or pulled away from it to gather information on the hardness/stiffness or stickiness (adhesion), which can also be mapped, making AFM far more than just a 3D, high-resolution microscope. Tips can also be chemically or biologically derivatised to obtain meaningful interaction data. Scanning and force measurements can take place ‘in air’ or within the media of interest. Minimal sample preparation is required, as opposed to light and electron microscopies, which can be quite invasive.


So, what can it do for me?

We have had AFM at the University of Portsmouth since 1992, only a few years after they became commercially available, and have scanned a fair number of samples! It’s capable of imaging a variety of surfaces in different environments, with minimal sample preparation and can also measure and map surface properties. Specific examples are shown in the schematic above, and will give you an idea of the things it can achieve.

James Smith
is a Senior Research Fellow at the University of Portsmouth. His current research efforts are mainly focused in the field of bioimaging, particularly using the Atomic Force Microscope. If you would like to know more please contact him or you can chat to him at the 2nd Microscopy Congress where he is speaking.

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Photo of microscope courtesy of James Smith. 

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