"Include surface forces" in Young's Modulus modeling

ChrisZiemba posted on Sun, Sep 15 2013 1:36 AM

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Hello,

I'm using a Multimode with a IIIa controller and 5 um diameter glass ball tips to measure the Young's modulus of biofilm samples. I'm trying to use NanoScope Analysis V. 1.40 software to crunch the numbers. I'm using the linearization model, but I can't figure out what the "include surface forces" option means. I looked through the help file and it only says:

"Including Adhesion Force means that calculations are performed based on forces relative to the adhesion force. Otherwise, calculations are performed on absolute force values."

This makes it sound to me like the Young's modulus is being standardized (divided by or scaled to) the amount of surface forces. I don't understand why anyone would want to do that though. Instead of "relative", does it mean "ignoring adhesion forces"? 

Can someone please explain to me exactly what the implication of the "include surface forces" option is in the model? Is it correct to fit my minimum line in the model to the force value that stabilizes far from the surface (absolute zero) as in the below curve? 

If this software indeed is just calculating a Hertz fit and ignoring the surface force interactions (which may be acceptable for my less quantitative purposes) does bruker offer another software package I can use to automatically calculate the Young's modulus using alternative models which include surface adhesion? 

Thank you very much for your help,

Chris