Viscous flow, Knudsen diffusion, and surface diffusion models are commonly accepted in diffusion inside porous materials and permeation through porous membranes, including polymeric and inorganic materials. However, the permeation equation through subnano?porous membranes is still under discussion. In this contribution, permeation models of gaseous molecules through porous membranes, including gas translation model (GT model) and uniform potential model, are summarized, and then the modified GT model that was recently proposed, was introduced. In addition, Normalized Knudsen?based Permeance (NKP), which was theoretically derived based on the modified GT model, was introduced to the evaluation of pore sizes of porous membranes with sub?nanometer in size.

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Materials used as functional thin films include zeolites, organic polymers, and metal-organic frameworks (MOF), but almost all of these are susceptible to damage by electron beam irradiation. Consequently in comparison to metals or ceramics, using an electron microscope to observe the microstructures of functional films requires substantial effort. In addition, in order to take full advantage of the capabilities of electron microscopes, further technological breakthroughs are needed. On the other hand, the invention of aberration correcting devices has greatly increased the spatial resolution of electron microscopes, and in recent years such functionality has seen rapid improvements. These analysis techniques are thus increasingly useful for carrying out basic research and application development in the field of membrane technology. Based on this, in order to support positively an active environment for research into functional membranes using electron microscopy, which excels in local microstructure analysis, one of the primary conditions is that researchers from many areas of membrane research recognize the need to use electron microscopy. In this study, we plan to use examples of characterization of the most recent zeolite membranes and organic membranes to demonstrate the possibilities of using electron microscopy techniques to characterize the microstructures of functional thin films.

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The applications of streaming potential (SP) measurement to the characterization of porous membranes including microfiltration (MF) and ultrafiltration (UF) membranes were discussed. The SP of the porous membranes will be affected by pore size and ionic strength in addition to the surface charge condition of pores because the thickness of electric double layer (EDL) in the pore will be almost same range as the pore sizes of MF and UF membranes. The zeta potential estimated from SP with Helmholtz -Smoluchowski (H-S) equation is widely used for the index of surface charge condition of pores although the H-S equation does not consider the overlapping of EDLs in the pore. The effect of the overlapping of EDLs in pore on the zeta potential was discussed with wide range of measurements. This behavior of EDL in pore can be used for pore size determination of the porous membranes. The pore size determinations by SP measurements with microscopic model were demonstrated and discussed for MF and UF membranes. The zeta potential can be also used for the characterization of fouling status. The responses of zeta potential to fouling configurations of MF membrane such as adsorption onto pore surface, pore blocking, and cake formation were discussed. It is shown that the change in zeta potential during filtration reflects both the local zeta potential and the location of pressure drop.

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The adsorption measurement methods for porous inorganic membranes such as zeolite membranes were reviewed. The adsorption measurement methods were classified in 5 types (gravimetric methods, volumetric methods, concentration measurement methods, membrane permeation methods and simulation methods). Adsorption on zeolite particles or membranes was usually explained by a Langmuir adsorption type. Selective adsorption of ethanol on a silicalite zeolite membrane was measured by using an adsorption desorption method. Based on the selective adsorption measurements, the permselectivity through the silicalite membrane was found to be due to the adsorption selectivity of ethanol on the silicalite membrane.

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Post-insertion method is now widely used to modify liposomes with poly(ethylene glycol) (PEG) lipids. In this study, we examined the physicochemical properties of surface layers of distearoylphosphatidylethanolamine- PEG2000-modified liposomes composed of distearoylphosphatidylcoline, distearoylphosphatidylglycerol and cholesterol prepared in post-insertion method. Zeta potential measurements showed that the estimated aqueous layer thickness of PEG liposomes increases with increasing concentrations of PEG lipids added. Size exclusion chromatography demonstrated that the incorporation efficiency of PEG lipids into liposomes gradually decreases with increasing addition amount of PEG lipids. Quenching experiments of fluorescence-labeled PEG lipids confirmed that almost all PEG lipids distribute at the outermost layer of liposomes in the post-insertion preparation whereas PEG lipids distribute equally at inner and outer layers of liposomes in the conventional pre-mixed method. By correcting the incorporation efficiency and the outermost distribution of PEG lipids in liposomes, we found that the dependency of increases in aqueous layer thickness of PEG liposomes upon the outermost content of PEG lipids is similar in the both post-insertion and pre-mixed methods. Fluorescence resonance energy transfer measurements suggested that the increasing behavior of aqueous layer thickness is closely correlated with the conformational transition of PEG chains at the liposome surface. These results provide comparative information of the surface properties of PEG-modified liposomes prepared by the post-insertion and pre-mixed methods.

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Orally disintegrating tablet (OD tablet) disintegrates rapidly by penetration of saliva and shear stress and/or pressure in mouth. Therefore, it is easy to swallow this tablet without chewing or taking water together. Recently, OD tablet has become more popular and preferred dosage form from the view point of not only good swallowability to elder patients but also compliance improvement. This dosage form is not novel and has been manufactured in part of the fast disintegrating tablet. To design and formulate OD tablet, it is necessary to take a conflicting balance in performance between sufficient hardness of the tablet and fast disintegrating property in mouth. The content of hydrophobic lubricant in the tablet is one of the important factors which determine such performance of the tablet. Two marketed products are introduced in this report: PYLONICR Tablet (fast disintegrating tablet) and EBASTELR OD Tablet (OD tablet) both of which were designed and formulated based on a common idea to reduce amount of hydrophobic lubricant in a tablet.

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