This work describes a comparison of biocompatible membranes to encapsulate gas sensors in the human intestinal tract. The goal is to identify semipermeable materials that allow intestinal gases to pass through the membrane while also separating them from other intestinal contents. Important aspects of this study are the membranes’ chemical resistance to gastric acid and their gas permeability. Chemical resistance was assessed by submerging selected membranes in artificial gastric acid. Surface structure of membrane samples before and after the acid treatment was compared using scanning electron microscopy and signs of degradation were documented. To characterize the membranes in terms of their gas permeability, an experimental setup was developed to measure average airflow through the membranes. A constant pressure of 7 kPa was applied across the membrane and flow rate Q of air was measured over a predefined surface area A. This evaluation marks the first step in the development of an ingestible capsule for in-vivo analysis of intestinal gases.

From the Proceedings of the 1975 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - April 11-12, 1975, Tempe, Arizona / In direct (normal, forward) osmosis water automatically flows through a semipermeable membrane from a "source" solution of low concentration to a "driving" solution with higher solute content. The process requires a membrane which is impermeable to the solutes; hydrostatic pressure differences are not directly involved and can be set equal to zero. In principle, direct osmosis is a low -technology, low-power consumption method for reducing the water volume of industrial effluents or liquid agricultural products, and for reclaiming brackish irrigation water. In the latter application the driving solution may utilize fertilizer as a solute; the source solution is drainage that contains harmful salt components. This type of operation has been experimentally demonstrated. This paper summarizes basic physical principles and introduces some quantitative design factors which must be understood on both a fundamental and on an applications level.