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Dear community,
I am working on plastic samples with stiffnesses around 2 GPa and use PeakForce QNM in air to analyze them at the nanoscale. Now I was wondering how important moisture concerns are for the correct interpretation of the measured data. So far, I keep my samples in a dry environment until I measure them; however, I have no idea whether this is necessary or wise. Sometimes my samples show surprisingly strong adhesion and I was wondering if this could have to do with moisture?!
So, I would like to ask the experts here: What do you know about the importance of moisture for PeakForce QNM measurements?
Best regards, Dietmar Haba
Hi Dietmar,
Moisture can have a great influence on the adhesion characteristics, but so can electrostatic charge. I wonder if you see that strong adhesion because your samples are charged. Did you try mounting your samples using conductive stickty taps or similar? Do you use a polonium source or similar above your sample?
Stefan
Dear Stefan,
Now that is interesting. I didn't ever think of the significance of elecrostatic charging. This might become even worse by drying, right? My samples are nonconductive so I doubt that conductive sticky tapes might help. So far I use glue to fix my samples. But no, I do not use any Polonium source. What would that be for?
I am even less confident of the correctness of my adhesion data now that I think of the electrostatic charging. Shouldn't the tip somewhat act as a grounding and remove the electrostatic charging?
Best regards, Dietmar
It might not be an issue with your samples but its worthwhile keeping in mind. Yes, very dry atmosphere would make the effect more pronounced. Conductive carbon tape helps for sure. for discharging you could use something like this: http://www.company7.com/staticmaster/products/staticmaster.html The insert has a small strip in it that when placed close to the tip-sample area will help eliminating static. There are fancier devices but this one works just fine for most applications.
Regards,
Tanks for your helpful advices. I will use conductive tapes from now on and I will stop drying my samples. Nevertheless, I wonder how to assure that what I measure is not just a moisture effect. I will store my samples under the same conditions; I hope that the effects are reduced that way.
I would not stop drying my samples. If you image them in ambient conditions however they will be affected by your environment. That is why we offer a glove-box for critical experiments like lithium battery research that requires defined atmosphere.
Hi, Stefan,
Hmm... Well, then I'll go on drying them, but I'll use the brush you recommended or something similar. My experiments should not be very critical, so I don't think that a glove-box is necessary.
Thanks a lot, Dietmar
Just to clarify: You only need the replaceable cartridge not the whole brush. Inside the cartridge is the strip with the polonium for ionizing the air. A decent photo store should have that.