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Support Veeco Probes SNL10s with low amplitude

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BrukerApplications posted on Thu, Mar 4 2010 1:29 PM


I have recently purchased some SNL10s to image some short (100nm) DNA strands. I need to detect whether the DNA strands are bent or straight.

(sausage or banana in the AFM).

I am using a dimension 3100 at the department of chemistry in Cambridge University.

Initially I tried using tap150s in air but these do not seem to have high enough resolution to image the DNA. Is there a tap150 or tap 300 with a sharper tip?

I then tried imaging in fluid using the SNL10s, however I had difficulty increasing the free RMS amplitude above 0.15V. Has anyone else had this problem? Were they able to resolve it? Once I had engaged the set point was about 0.04V and the tip was not still not engaged properly.

The support notes that arrived with the tips showed an excellent image of DNA in fluid with a driving amplitude of about 20mV or thereabouts and the typical RMS with the 'C' cantilever was quoted as 0.3 to 0.6V.

However even with a driving amplitude of the 400mV the best stable RMS amplitude I got was only 0.15V.

Initially my hunch was that the tip isn't mounted properly on the fluid tip holder. However, once the spring is released the tip is being held very firmly. I checked to ensure that the tip of the tip was closer to the surface than the tip holder but there wasn't much in it! Then I thought the laser wasn't aligned on the tip but I am getting a sum signal of around 3.5 - 4 and I was able to see the laser on the tip in the reflection image.

Am I missing something here??? Is there a secret increase amplitude in fluid mode button...?

What is the purpose of the z-modulation? The same example you gave with the tips had the z-modulation disabled, but during an earlier session a colleague managed to increase the amplitude of the SNL10s by enabling the z-modulation. However, when I enabled the z-modulation in a second session the amplitude of the tip stayed low.

Do you have an FAQ/source of info/person I could speak to on phone who can help me with this imaging of DNA in fluid? Perhaps advise on appropriate tips and how to get the best out of the SNL10s. I am envious of your publicity images and wonder why I cannot achieve this quality of image!

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