In this chapter, we will discuss how membranes' physical properties affect cells, and we will describe the most employed membrane materials in organs on chip. We will then review the literature on the gut-on-chip as an example of membrane-based OOC. We believe that the gut-on-chip model presents the richest landscape for research due to its primary role in drug metabolism and microbiota-host cross-talk and its relevance in various infectious diseases. For the sake of brevity, in this paper, we will not consider the other OOC models. For a detailed review of all membranebased OOC, we would like to refer to the work of Rahimnejad et al.