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Scanning probe microscopic imaging can be complicated by the capillary force of water meniscus formed in air between the tip and the sample. Water menisci between a tungsten and Pt/C-coated mica and their dynamic behavior have been directly visualized by environmental scanning electron microscopy. Rapid scan secondary electron micrographs give information in the 100 nm range. We found that static models are not appropriate to describe to shape of a meniscus when the tip is moving across the sample. The surface structure and its properties influence the affinity of the meniscus thus causing a varying capillary force that may exhibit a vertical and a lateral component as well. Our experimental data indicate that the Kelvin equation also holds for microscopically small water menisci

In this study, the effect of powder cellulose (PC) and 2 types of microcrystalline cellulose (MCC 101 and MCC 301) on pellet properties produced by an extrusion/spheronization process was investigated. The different investigated types of cellulose displayed different behavior during the extrusion/spheronization process. Pure PC was unsuitable for extrusion, because too much water was required and the added water was partly squeezed during the extrusion process. In contrast, MCC 101 and MCC 301 were extrudable at a wide range of water content, but the quality of the resulting products varied. In the extrusion/spheronization process, MCC 101 was the best substance, with easy handling and acceptable product properties. The properties of the extrudates and pellets were determined by Fourier transform (FT) Raman spectroscopy and environmental scanning electron microscopy (ESEM). FT-Raman spectroscopy was able to distinguish between the original substances and also between the wet and dried extrudates. The particle sizes of the raw material and of the extrudates were determined by ESEM without additional preparation. For MCC, the size of the resulting particles within the extrudate or pellet was smaller. However, in the extrudates of PC, changes in particle size could not be observed.

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