Optics11 CHIARO NANOINDENTER, User Manual, Page: 37 / 65

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Suitable probe tip size
Choosing an appropriate tip size is related to the structure of the sample and the kind of
experiment one wishes to perform. When measuring the global elasticity of a sample, a larger tip
would be more suitable, since the applied and recorded force of each indentation would effectively
average over a larger area than for a small tip. For measuring small spatial features or a very rough
sample, a smaller tip could be more suitable. Tip size should be carefully considered when working
with porous materials: to determine the overall structural properties of a porous material, select a
tip size several times larger than the largest pore. For examining local features within one pore,
select a tip size that is several times smaller than the pore diameter.
Adhesion
Adhesion between a sample and the indentation tip could interfere with the find-surface procedure
or affect the measurement result. Three solutions for measuring adhesive samples can be provided:
(1) immerse the sample in a liquid (2) to passivate the sample using some sort of non-adhesive
coating, for example bovine serum albumin (BSA), or in case this is not possible (3) use the
‘Adhesion mode’, to be adjusted in the Piuma software’s ‘Advanced’ tab within the Option’ menu,
to pull the cantilever free from the surface to a desired height and duration after the surface has
been detected using the find-surface function (Figure 19).