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Hi,
I read about Frequency Modulation AFM in some papers. How can I realise the function of FM-AFM? Is it possible to do this by Open Hardware? Plus, the scanning mode is tapping in liquid, not EFM.
Many thanks,
Zhuoyang
Hi Zhuoyang,
The Open Harware allows you to output the signals necessary to feed a FM detection "box" as well as allows you to use an external signal as "feedback". What you have to provide is any additional electronics required.
Best,
Stefan
Hi Stefan,
Could you please tell me whether the FM is better than AM, especially when scanning biological samples with ultra-high resolution in liquid. Is there any difference of "sensitivity" ? I read two papers scanning the same kind of sample, and it seems the FM image is clearer than AM image.
Thank you!
'Better" will depend on your point of view to a great extend. FM detection certainly does have advantages especially in high Q-environments as the settling time of the lever is greatly reduced when compared to AM detection. In liquids, however, you do have a quite low Q so that advantage vanishes to a great extend. Noise, however, can be reduced and the few data I have seen from japanese groups looked certainly impressive. That being said, I am always somewhat sceptical when I see only a very few publications claiming greatly superior operation. Point is, AM detection works with quite high resolution and is pretty straightforward to operate. Depending on your application that may be all you need. FM in fluids is certainly interesting to develop further.
What exactly is your application?
Hi Stefan，
I am applying AFM to organelle membrane patches. I haven't succeeded in scanning membrane proteins. Successfully engaging SNL probe is just a thing of a few days ago. At present only small protrusions of several hundreds of nm can be distinguished. When zoomed-in to a scan size of less than 100nm on the bilayer membrane, the profile began to fluctuate and almost impossilbe to eliminate. The resulting image looks like being covered by the noise signal. I think further sample preparation optimization such as membrane immobilization is needed rather than scanning condition. Or there is still some skills I don't know. Could you please give me some suggestions?
Zhuoyang,
The profile can fluctuate for several reasons. One being that if your target is very soft, which is true in your case I suppose. By scanning such small of an area your tip interacts quite a long time with the object you are trying to study and can actually potneitally move it around a bit. In this case it often helps zooming out a bit, somewhere to 200-500nm and maybe increase pixel density to allow a later software zoom. Scanning less than 100nm with the 100um Innova scanner in closed might also not get you any benefits considering the closed-loop xy noise level of typically around 0.4nm if I remember that correctly so.