a) Cells of a single type are cultured as a monolayer on a planar rigid (e.g., glass) or flexible (e.g., PDMS) substrate on one side of a microfluidic channel through which medium is perfused. (b) Cells of two types are cultured in direct juxtaposition by micropatterning ECM adhesive islands within the microfluidic chamber that preferentially support one cell population (e.g., hepatocyte). These cells are delivered first, and the empty spaces are then filled with the second cell population (e.g., fibroblast). (c) Cells in a tissue construct engineered with ECM are cultured in a microfluidic channel. In this example, microcontact printing of ECM in a linear pattern on a thin PDMS layer coated over the substrate is used to orient muscle cells to create an anisotropic muscle tissue layer. When parts of the PDMS film are released from the substrate, they bend up when the cells contract, allowing measurement of cell contraction forces under flow35.