In this article, I’m going to talk about what not to do in AFM. I’ll list 4 mistakes that are common in AFM use, which if you avoid, will certainly improve your results!
Using standard settings.This is possibly the worst mistake you can make. AFM imaging is a highly adaptable technique. It’s able to image very large samples of tens of microns with extremely rough topography, or make tiny image sof extremely smooth samples, with subnanometer features. There is no standard setting which will get good images of all samples. You need to be able to adapt the imaging settings based on the response from the instrument. Optimal AFM imaging is attained through an iterative process! If you don’t know how to optimise imaging of the AFM, I highly recommend revising chapter 4 of my book, “Atomic Force Microscopy”.
Interpreting image artifacts as image features. It’s important to know which features in your image come from your sample, and which are image artifacts. Learning this can save you some major embarrassment, and a lot of time!
|Example of image showing imaging artifacts. being able to spot and correct these artifacts is a crucial skill for an AFM operator.|
- Trying to image dirty or contaminated samples. Sample preparation is the first, and most important part of an AFM experiment. If your sample has a layer of contaminant covering the the part you are interested in imaging, it will make your job almost impossible. Prepare your sample so that it only contains things you want to image.
- “Optimising” your imaging for a nice-looking amplitude (or deflection) image. I was amazed to find people do this. Amplitude and deflection images are made up of the error signal in AFM. The less contrast here is in the error signal, the more accurate your height image is. So, if you optimise imaging to produce a nice-looking high-contrast image in amplitude, you are decreasing the accuracy of your height image!
Avoid these pitfalls and your AFM work should be hassle-free! For help avoiding them I recommend reading my book, “Atomic Force Microscopy”, soon to be released in paperback!
All text and images copyright 2018 Peter Eaton, AFMHelp.com
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There are a wide variety of technique available to make these kind of measurements nowadays, however, microscopy is often used, because it is a direct technique (some other techniques measure properties related to size), and because it’s also possible to measure shape at the same time. The size of nanoparticles is extremely important for their properties, and ideally a technique to measure nanoparticle size will have sub-nanometer resolution.
Apart from microscopy, light-scattering techniques are probably the most common techniques used. The method of dynamic light scattering, or DLS; is extremely popular and used in thousands of labs worldwide. A newer method based on laser light scattering, called nanoparticle tracking analysis, or NTA, is currently growing in popularity.
In our project, we prepared nine samples; these we made up of nanoparticles composed of three different, and commonly used materials, a metal, an oxide (silica), and a polymer. We examined each materials in two different sizes, and also tested the ability of each method to distinguish between different populations in mixed samples.
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"Atomic Force Microscopy by Peter Eaton and Paul West is the manual that should accompany any AFM."
Prof. Othmar Marti, University of Ulm
Peter Eaton and Paul West share a common passion for atomic force microscopy. However, their involvement with atomic force microscopes are from very different perspectives. Over the past 10 years Peter used AFM's as the focal point of his research in a variety of scientific projects from materials science to biology. Paul, on the other hand, is an instrument builder and has spent the past 25 years creating microscopes for scientist and engineers. Together Peter and Paul have created an insightful book on the theory, practice and applications of atomic force microscopes. This book serves as an introduction to scientists and engineers that want to learn about these fascinating devices, and as a reference book for expert AFM users.
The book was published on the 25th March 2010. It can be found at Amazon.com, Amazon.co.uk, Barnes and Noble, and all major book stores. Click the image on the right to go straight to the amazon page for the book. There is also a Kindle Version of the book available. If you are affiliated to subscribing institution, then you may be able to access it via Oxford Scholarship Online.
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|Bart showing his results|
Our atomic force microscopy training course for 2017 ran in April, between the 10th and the 13th. Once again, the course was a great success, and all the places were filled. In this post, I quote some of the the feedback we got from some of me of the attendees, as well as some of the images they produced. In this edition, the highlight (for me) was the talk from Prof. Bart Hoogenboom, from UCL.
Bart demonstrated some amazing results in AFM, and gave some real inspiration as to what AFM can achieve.
|Phase image of E. coli cells|
Once again, we had a good mix of students. They came from Wales, Portugal, Switzerland, the Netherlands, and Germany. We had PhD students, AFM technicians, lecturers, post-doctoral fellows and industrial researchers. It's always great to have such a wide range of opinions and nationalities!
As usual, we began with the basics of AFM, including instrumentation, modes, and fundamental concepts. Then the more fun parts, how to prepare samples, tips and tricks for running the instruments, and how to process and analyse the data.Most of the students prepared samples, and they all ran the instruments and processed and analysed image files. Based on the feed back, the students thought the course very worthwhile.
"I liked the course a lot. I think it's well-adapted to people with no AFM experience, and it seems it works well also for experienced users"
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AFM Manufacturer list
The following is a simple alphabetical list of, hopefully, all the AFM manufacturers in the world. If you have any additions to make, get in touch via the contact form. For AFM probes, look at the SPM Probes list, and for reference samples, see the SPM References list.
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