Ethanol is widely used in our daily life, including in ingredient liqueurs, medicines, cosmetics, and so on. Aqueous solutions containing high concentrations of ethanol are also used as hand sanitizers. Such sanitizers are discharged from a bottle as liquid, mist, gel, or foam. Foams are generally stabilized by the adsorption of a surfactant at the air/liquid interface; however, the stabilization of foams containing high concentrations of ethanol in aqueous solutions is very challenging. In this short review, we focus on the foam stability of an aqueous solution containing a high concentration of ethanol (60 vol.%) under the combined addition of an anionic surfactant, a long-chain alcohol, and an inorganic electrolyte. The key conclusion of this work is that the addition of these materials in the aqueous ethanol solution results in an increased surface viscosity, leading to an enhanced foam stability. This finding is expected to provide a new platform for formulating foam-type hand sanitizers with high concentrations of ethanol.

Rich foam is one of the most important characteristics of cosmetic detergents. Although many studies have been performed on the visual and physical aspects of foam, such as "foamability" and "foam stability", the scientific origins of the sensory values that foam provides, such as "pleasant", “comfortable, fresh and mild feel", are not well understood. To understand what factors are at work when foam is applied and spread on hair and skin, we investigated the rheological properties of foam, focusing on its adhesion to several solid substrates with different properties. The results suggest that the fluidity of foam on solid surfaces is highly dependent on the properties of the solid surface and the thin water film on the surface.

It is known that the basic value of a makeup remover is its ability to remove makeup and deliver the resulting feeling of freshness. Additional consumer needs to heighten the product experience include putting no burden on the skin during removal, not dripping during use, being easy to wash off, and so on. It has been assumed that a foamy makeup remover would be a strong candidate to address these issues. However, a foam-type remover has been impossible to create previously since makeup contains a considerable amount of hydrophobic solids, such as hydrophobized powders, waxes, and film formers. These ingredients break up the foam by intruding into its membrane.
We have succeeded in hybridizing an anion/amphoteric surfactant mixture into a bicontinuous microemulsion (BME) phase, which is known to have an excellent ability to remove makeup. The solution forms dense foam by dispensing it from a pump foamer, achieving a highly effective foam-state makeup remover for the first time. Furthermore, we found an interesting phenomenon whereby makeup is spontaneously dissolved upon contact with the foam-state remover. This phenomenon is caused after moderate foam breaking upon contact with makeup, leading to a supply of surfactant molecules from the air/remover interface to the makeup/remover interface, followed by a flow of water, resulting in makeup removal.
By this novel function of foam, achieved by the foam-state BME phase, a novel makeup remover that fulfills all the consumer needs listed above was successfully developed.

Foam separation can separate and remove dissolved substances from an aqueous solution together with surfactants. When bubbles are introduced into a solution using a device, an adsorption monolayer of surfactant (including amphiphilic substances) is formed at the bubble surface. The bubbles float to the interface while adsorbing substances and become foams. The substances are concentrated with accompanying the drainage progresses during the rise of the foam in the long tube, and the substances in the aqueous solution are separated as foam. The removal mechanism is adsorption between the surfactant and the substance at the gas-liquid interface, and is often based on electrostatic interaction. Regarding the removal of metal ions, it was found that there is a correlation between the size of the hydrophilic group of the surfactant and the crystal ionic radius of the metal ion. Studies of ionic dye removal in foam separation systems have shown that ionic dyes can be removed using surfactants with opposite charges. On the other hand, amphoteric surfactants can remove both anionic and cationic dyes. Finally, I report on a study in which the foam separation method is applied to cleaning organs for the purpose of decellularization.