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I also got an interesting question from a user: for QNM working properly, we suggest to have a minimum indentation/deformation of 2nm (sometimes ppl misunderstand it as the best indentation for QNM to work), but whether should it have a upper limit? Especially on cells, if indentation is 10s or 100s nm, will the model still fit? Anyone wanna comment
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Thanks for sharing your experience, Alex, it's pretty helpful.
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Hi, Fenny, Your question 1 and 3 are related, if you prefer using Sneddon model, you need to choose cone shaped probes as it assumes so and there won't be front or side angle, but just a cone angle. On cells, we prefer blunt tips instead of sharp tips so you may want to have larger angle probes and in that sense, pyramidal shaped tips are better
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Hi, Benoit, Your procedure sounds on the right track, you may send me the deflection calibration force curve, probe calibration file and the QNM file on the calibrated sample, you may just have overlooked some little issues. My contact is ang.li@bruker-nano.com
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Hi, Brent, Since mica is negative charged and PI of strepavidin is ~5, so if you have strepavidin in an acidic solution, you should be able to direct deposit strepavidin on mica surface through charge interaction. LA
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Hi, Gabriela, Yes, you can get diamond tip suitable for AFM based nanoindentation from BrukerAFMprobes.com, below are the models you can select for your case: http://www.brukerafmprobes.com/category-list.aspx?CategoryID=282 These probes are not considered as consumbles, usually they can last very long time and even the diamond tip break from the cantilever
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Hi, John, Can I just manually update the deflection sens with the contact sens quoted in the spec and thus skip calibrating it? thanks! LA
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Hi, Fenny, After check your file, I found you have two issues with your problem. firstly, the image of RS looks very bad, since your tips have been used to do QNM on cells, I guess it pretty likely has been contaminated and you can't rely on such result for an accurate calibration. Secondly, you can't use this 'absolute method' to calibrate
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Indeed spring constant was not present in the property list, I usually calculated it from Sens.ForceDeflSens (nN/V) and Sens.DeflecSens (nm/V). Maybe a 'point and shoot' analysis function to check single spot values will be quite useful in the analysis software and in real time imaging software, sometimes it will be helpful if we can check the
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Hi, Raphi, Your engage problem could be due to wrong tuning, what were your tuning parameters and what probe and frequency you used? LA