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Hello,
I use a Dimension Icon with PF-QNM and I have some samples that have modulus in the range of the PS standard but have domains of softer material also. When using PF-QNM (relative method), keeping a consistent peak force set-point will result in deforming the sample more in the softer areas, and hence the tip radius would be larger than what was calibrated for a smaller deformation depth in PS. Is it best to reduce the PF set-point during the scan to keep the deformation depth consistently matched to what was used on a reference sample, or adjust the radius to a larger value, or something else to get the most accurate modulus values in both regions?
I suppose this question can be asked about scanning the PS-LDPE standard too. If I use this to calibrate the tip radius, should I reduce the PF set-point over the LDPE areas to keep the deformation 2 nm?
How large of a modulus range can be accurately mapped with the same probe?
Thank you,
Lauren
Hi, Lauren,
Generally speaking, you got different deformation on the mixed sample and you just need to use different tip radius corresponding to the particular deformation for the modulus calculation. Though ideally it would be the best if you can control the deformation depth rather than the force for the most accurate measurement.
For the particular case of PS-LDPE, it is possible to get a relatively consistent modulus results on both polymers using the same tip, but it is not recommended for the mixed samples with modulus difference more than one order.
For mixed samples with modulus more than one order, you may need to decide which one is more of interest and use the corresponding reference sample calibrated parameters (such as the setpoint for particular deformation). So a multi step method may need to apply to the mixed sample with very different modulus, each step measures only one component with corresponding reference sample, the results of the other components may not be accurate and need seperate measurements.
Ang Li
Thanks for the response Ang. Just to clarify, if both polymers are similar enough (within one order), than holding the setpoint and radius constant should still allow for accurate measurement of the two moduli because their deformation should not be too different?
Thanks,
Yes, you can use the mean value of the whole image for tip radius estimation and update the modulus channel using image math, it should give you a slightly better result than fixing the setpoint to achieve 2nm deformation on one of the component.