how is quantitative nanomechanics with AFM: a proof?

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Igor Posted: Tue, Nov 20 2012 10:45 AM

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Dear  SPMwers,

The discussion about "how quantitative mechanics with AFM can be" was here several times. I promised to publish some proof that it can be quantitative. Finally, we published it:
http://pubs.acs.org/doi/abs/10.1021/la302706b .
I hope it is convincing enough that PeakForce QNM and HarmoniX modes can indeed be quantitative.

 If one is ding just doing "regular" AFM indentations, those can also be rather precise (quantitative as absolute (not "relative") ) measurements. This one we demonstrated in:
Dokukin, M., Sokolov, I*. “On the measurements of rigidity modulus of soft materials in nanoindentation experiments at small depth”, Macromolecules,  2012, v.45 (10), p. 4277–4288.

Let us know if you see any weak points in our proofs, and we will try to address those.
Thanks and look forward to hearing your comments/critics/suggestions.
--Igor

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Ang Li replied on Mon, Nov 26 2012 6:12 AM

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Dear Igor,

The abstract looked pretty interesting and thanks for bringing the proof. Is it possible you send me a soft copy of the full text to ang.li@bruker-nano.com, I am very keen to have a comprehensive read of the paper. Thanks!

Ang Li

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Hartmut replied on Mon, Nov 26 2012 6:56 AM

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Dear Igor,

I would be heavily interested in that as well...If you send to Ang, maybe you just could include me in your email header: hartmut.stadler@bruker-nano.com

Unfortunately, if you are outside university, there is often no access to such articles.

One other remark: For operation in air, the NPL in UK did a nice proof as well on polymer samples. Probably you know that paper, the reference is:  Young et al, Meas Sci Technology 22 (2011), 125703.

In that paper, it was described less as a problem of a model, but more like a problem of proper calibration procedure, however they state that the use of other contact mechanics models than the implemented ones might make it even stronger.

One additional note here: We have now a new feature, called PF-capture. This allows to capture an array of up to 256x256 force-curves as well in QNM (like in FV). This would allow some decent offline analysis afterwards.

Hartmut.

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Janne replied on Mon, Nov 26 2012 7:15 AM

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Hartmut, is the PF-capture feature already released? Is it awailable also for PF without QNM on the Catalyst?

Best,

Janne

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Hartmut replied on Mon, Nov 26 2012 10:20 AM

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Hi Janne,

yes, it is released in the latest version 8.15R3. But you need the QNM-option for that.

In the ScanAsyst workspace (standard PF-tapping), the option to change "cature" to "peakforce capture" is not present.

What you anyway can use without QNM-key is quantitative Force Volume, which allows same models to be applied to FV-data as in QNM (conical & spherical geometry for modulus, adhesion, stiffness). That is new as well.

Hartmut.

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Igor replied on Mon, Nov 26 2012 11:23 AM

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Dear Hartmut,

Thanks for your interest. I will send you the PDFs and very keen on your opinion. What we showed is essentially that the issue was not in the model (at least only) but in the excessively high stress that produced by the AFM probe for SMALL indentations.

Best regards,

Igor

P.S. I heard about the software upgrade. this is a dream came real :-). We will definitely try it.

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Hartmut replied on Wed, Nov 28 2012 11:23 AM

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Thanks a lot, Igor.

I have received the pdfs, and will read it very carefully.

Hartmut.