Review of our 2014 AFM course
Last Updated on Wednesday, 14 May 2014 13:58
The 2014 Requimte AFM workshop was held during Easter week, 14th to the 17th of April. The course keeps on growing, and this year we had 15 students attend. Once again, they came from far and wide for the course, and it was great to meet them all. It seems this course really fills a worldwide need, because we had students fly from as far as Malaysia and Washington DC to attend. The other students came from the Czech Republic (lots of them!), Germany, Spain, Portugal, the Netherlands and Poland.
How to measure noise floor on an AFM
Last Updated on Wednesday, 14 May 2014 12:02
While many other procedures are important for full determination of the performance of an AFM instrument, the Z noise floor is often used as a simple parameter to quantify instrument performance, since it indicates the lower limit of what the precision that can possibly be reached in the z axis in that instrument, and is also simple to measure.
It can be essential to know the noise floor of the AFM instrument to assure that high resolution measurements are meaningful. This can be particularly important for measurements of very small features (i.e. < 5nm), and for high resolution force spectroscopy. Measuring the noise floor can also help in optimizing instrument setup and vibration isolation. It is important to know the noise floor when using only the z piezo in the z feedback loop, as well as the noise floor of the z calibration sensor if there is one in the instrument. In most instruments, the noise floor of the z calibration sensor will be much higher than that of the z piezo.
In order to get reproducible results, all scan parameters should be maintained the same when comapring two results. Some factors, such as the PID values vary greatly from instrument to instrument, so the specific values to use cannot be suggested here. In each case, standard values should be established such that a fair comparison can be made.
Note that the procudure below is adapted from general guidelines given in Appendix B, page195 of Eaton and West “Atomic Force Microscopy”. For a outline of a procedure that’s generally applicable to any model of AFM, take a look at the procedure below. Click here to find a specific procedure for measuring the z noise floor on a TT-AFM from AFM workshop.
Book Extract - Bacterial Measurements
Last Updated on Monday, 31 March 2014 15:01
This article contains a small extract from Chapter 7 of “Atomic Force Microscopy”. Chapter 7 contains descriptions of applications of AFM in materials science, chemistry and physics, biology and the life sciences, nanotechnology, and in industry. This short section describes some examples of applications of AFM in bacteriology. References lists, and the second figure can be found in the full book.
AFM is a highly suitable tool to examine bacteria, and has been widely applied to their study. Bacteria are commonly studied by optical microscopy, which can give an overall idea about gross cell morphology (via a two-dimensional projection), and is also useful for cell-counting studies. In comparison, AFM is slower, and thus is less useful for quantitative cell-counting, but allows measurement of a variety of other cellular properties, particularly by nanoindentation and force spectroscopy experiments . In addition, the greatly increased resolution of AFM allows for the imaging of finer details of cell morphology and sub-cellular features such as pili and fimbriae . The three dimensional information from AFM can also be useful in differentiating morphologies which would look the same in optical microscopy . Various other micro-organisms have been studied by AFM such as spores [178, 613–615], fungi [616, 617], including yeasts [171, 618], viruses [287, 619], and others  but here we concentrate on bacteria for the sake of brevity.
Fig. 7.20. Studies of bacterial morphology. Top left: Streptococcus, showing typical linear clusters. Top right: large clusters of Staphylococcus aureus. Bottom left: Salmonella biofilm showing pili-like fimbrial structures. Bottom right: E. coli. All these images were measured in air. Reproduced with permission from  (top left) and  (bottom left). Right hand images the author's own work.
Advertisements on this site
Last Updated on Thursday, 13 March 2014 16:52
Up until now, this website has been funded by Google text adverts that appear on the right of the page. I don’t control what ads appear there, except that I can remove some categories of ads. Beginning soon, I expect to have actual ads from AFM companies appearing there.
The advertisers do not influence any of the other text I write here. Although I do work with some AFM manufacturer’s equipment more than others (and my co-author on the book, Paul West has been owner/CEO of various AFM companies), I do not really favour instruments of one manufacturer over others. I have used many (more than ten) different AFM instruments over the years and this has led me to think that -
ALL AFM instruments can produce great results.
What is necessary to get great results are a certain level of skill on the part of the operator, a good probe, careful sample preparation, patience, use of the right modes and settings, and sometimes, a dash of luck! While newer instruments certainly offer amazing new modes, and in some cases lower noise levels, increased ease of use, or faster scanning, in my experience 99% of AFM could actually be done on just about any instrument. In my teaching, I hope I explain things that are useful to users of all instruments. Furthermore, although I am happy to get new listings, and factual corrections for the “Where to buy instruments” and “Probes” and “Calibration artifacts” pages, I do not accept copy written by the companies for inclusion on those pages. Any inaccuracies, or opinions are mine alone.