Modify force parameters when calculating Young modulus from Force-Volume curve

Martin G. posted on Tue, Nov 15 2016 7:34 AM

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Dear all,

I measured some soft nanoparticles in force-volume mode and now I try to calculate Young's modulus from the force curves. Before actual fitting ("Indentation" procedure), I need to modify Deflection sensitivity ("Modify force parameters") to a value I determined after the measurement. However, I find that it has fatal influence on the shape of the curve. Namely, it bends the curve backwards, which makes no physical sense (my interpretation of the bent curve, if it described reality, would be, that the surface actively bulges out as soon as the tip touches it).

Curve shapes for deflection sensitivity values of 10, 80 and 150 are here. It can be seen that the higher the value, the more bent the curve is. We can assume that the real, measured value of deflection sensitivity is 150.

So, which of the following is/are true?

1) it is not possible to modify deflection sensitivity in this case for reasons I dont understand (which is...?)

2) modifying deflection sensitivity should be theoretically possible, but there is a bug in NanoScope that makes the result invalid.

3) the results I get are actually ok (why?)

Thanks a lot for your thoughts and advice.