Hydrogel samples in our lab are prepared in a special way and we're limited to 20 micron cubes. We can produce 100 of them fairly easily, and 1000 over the course of a day. However, this yields only 10-100 nanograms of material, which can be difficult to work with.
To measure porosity, we're currently using TEM followed by image analysis (e.g. binarization, Euclidian distance transform, skeletonization). We fix the hydrogel in glutaraldehyde since unmodified hydrogel can't survive a high vacuum. This gives usable data, but we're looking for something a bit better. One alternative I'm exploring is NMR cryoporometry, though a couple thousand of our cubes would be required.
Are there other techniques available that could be used on very small samples to determine both total porosity and pore size distribution for pore sizes ranging from 5-60 nanometers?
Dear Michelson
Did you manage to get the SEM data or surface area analyses along with pore size distribution etc.?
Perhaps, positron annihilation technique could help to determine porosity.
Yours
R. Mitdank
I had never heard about positron annihilation, but it's a very interesting technique from what I just read. Thank you Rudiger.
Irfan, unfortunately SEM does not have the resolution necessary to measure pore size. Our standard now, which is decent but hard to interpret, is TEM ultrathin sections stained with heavy elements.
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