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Hello, I am currently using PeakForce QNM mode for testing soft tissue. The probe for my testing is TAP150A. According to probe geometry and previous paper from Bruker I think I should use value from sneddon channel but when I test on reference sample (young's modulus= 2.7+-0.1GPa) the sneddon modulus is extremely high (around 300GPa). Is this normal? The DMT modulus(around 3GPa) seems quite acceptable, should I use DMT modulus instead?
Thank you
Hi,
1. DMT model is used for the situation where the indentation depth is small compare to the tip radius.
2. Sneddon model is generally used for soft sample. Tip used generally has a radius around 10 nm. To use the Sneddon model, the indentation depth should be >30 nm for accuracy.
3. For the gap between these two model, situation would be more complicated. If you use the force-capture QNM, you can export all the force curves and do your own analysis using your own model.
4. For your measurement, the reference sample has modulus of 2.7 GPa, TAP150A is too soft for it. It will have a very small indentation even for the DMT model. TAP525A should be used and DMT model is a good one.
5. Please send me an email (teddy.huang@bruker.com) so that I can send you a presentation for more details
Thanks,
Teddy