The Nanoscale World

Stiffness of nanoparticles

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Top 500 Contributor
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Martin G. posted on Tue, Nov 15 2016 9:17 AM

Dear all,


I performed measurements of some polymer nanoparticles (PLGA, size cca 50 nm, on air, on silica) and it appears that they are as stiff (DMTModulus channel) as their silicon substrate, which is almost certainly not true. Does anyone have any explanation? Are they so small that the tip actually senses the substrate underneath?

Here are printscreens of height and modulus, as well as the original datafile.

PS: I tried to measure Force-Volume in order to try a different way of determining stiffness, but I ran into another set of problems as described here.

thanks for any advice  Martin

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Top 10 Contributor
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Hi Martin,

I assume you're using DMT model and the absolute method for this measurement. 

This model is based on the contact mechanism between the tip and the sample. It is the Hertzian model with considering the adhesion force. The Hertzian model assumes "an elastic sphere of radius R indents an elastic half-space to depth d, and thus creates a contact area of radius a=(Rd)^0.5". 

You have nanoparticles with radius of ~25 nm. The measurement accuracy will be challenging, especially when the tip is blunt. What kind of probe did you use?



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