Abstract: The present invention relates to a biofabricated Active Microfluidic Membrane (AMM) in a microfluidic network of a microfluidic device and a method for the in situ biofabrication of such a microfluidic network. More specifically, the invention relates to devices exhibiting (and methods of) positioning (i.e., erecting, modifying or removing a membrane matrix in situ in a microchannel of a microfluidic network of a microfluidic device. In one embodiment, the membrane comprises a single type of matrix constituent, such as chitosan, alginate, etc. Alternatively, the membrane may be composed of two or more matrix constituents, which may be integrated into one another or layered adjacent to one another.