The Nanoscale World

Stiffness measurement

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Dani posted on Mon, Feb 2 2015 4:51 AM

Hello

Is it possible to perform stiffness measurements of a polymer using standard AFM? I ve got a Multimode veeco with only SCM and CAFM modules. DO I need extra modules?

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Answered (Not Verified) Igor replied on Thu, Feb 5 2015 9:10 PM
Suggested by Bede Pittenger

It depends. You can use just force-volume mode ( Macromolecules,  2012, v.45 (10), p. 4277–4288 ) or the additional Peak-Force QNM (Langmuir,  2012, 28 (46), pp 16060–16071).

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You could also use a ramp array if you don't care much about mapping.  The XY spacing won't be very accurate with the Multimode, but that isn't usually a big problem.  You can use Nanoscope Analysis indentation view to analyze the individual curves (this can be automated if you have a lot of them).

--Bede

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Dani replied on Mon, Feb 9 2015 4:58 AM

Thank you for your answers. Is the QNM mode an additional software? Does it require special tips? I m also a bit concerned as my polymer has a very low Young's modulus (15-100KPa) and as far as I understood, the QNM measurements have to be carried out in contact mode and not tapping mode. Is this the case? Thanks!

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Answered (Not Verified) Igor replied on Mon, Feb 9 2015 2:37 PM
Suggested by Bede Pittenger

>Is the QNM mode an additional software?

Yes.

>Does it require special tips? I m also a bit concerned as my polymer has a very low Young's modulus (15-100KPa) 

Yes, blind probes, if you want to measure the modulus. 

> and as far as I understood, the QNM measurements have to be carried out in contact mode and not tapping mode.

No, it is not. It is an oscillation but non-resonant  mode. The issue is not just the potential destruction of the sample (it is a sort of trivial and can easily be avoided). The problem is the keeping the stress below the linearity limit. Otherwise, you measure something but not modulus. 

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