Recently, technology using microbubbles has been studied for water purification. However, the mechanism and physical parameters of the purification process have not yet been sufficiently clarified. The purpose of this study is to clarify the physical parameters of microbubbles that influence water purification. Firstly, we measured and analyzed the purifying performance using various millimeter-sized bubbles, and we obtained the equilibrium constant of the pollutant adsorbed on the bubble surface from the experimental results. Secondly, we experimented with purifying the polluted water using microbubbles and clarified that the purification performance of microbubbles agreed with that theoretically expected using the equilibrium constant obtained in the preparatory experiment. We assume that an important parameter affecting adsorption on the surface of microbubbles is the equilibrium constant in the chemical potential. Because the equilibrium constant is derived from the surface chemical potential, it is equal to the bulk chemical potential of the liquid. In the microbubbles diameter (70 mm) range in this study, we have found that the most significant factor determining the adsorption is the surface area. The surface tension of microbubbles is not significant factor.

In this paper, we report the development of a new surface mount structure for optical communication devices using micro-electro-mechanical system (MEMS) technologies. We have designed and fabricated a silicon submount by wet anisotropic micromachining techniques. We have surveyed the main design parameters of this submount as an example against optical and thermal effects by computer simulations and experiments. We have mounted a light-emitting diode (LED) for plastic optical fiber (POF)-based optical communication systems on the silicon submount and evaluated the optical and thermal properties of this submount, indicating that the radiation half width at full maximum (HWFM) angle of the LED decreased from 60 to 40°. Additionally, we have observed a 60% reduction in the thermal resistance of the LED while keeping its thermal reliability.