A procedure for fabricating collagen gels that contain patterned cavities is described. The fabricated collagen gel consists of cells that are localized at the surfaces of an array of cavities. It was found that an introduction of flow through the collagen and cavities enhanced the exchange of materials between the cavities and the surrounding gel (see Figure). It is believed that this work will enable the in-vitro fabrication of structures that mimic the geometry of epithelial tissues.