A bioreactor (200) for cultivating living cells in a liquid medium. In one embodiment, the bioreactor (200) has a substrate (230) having a first surface and an opposite second surface, defining a channel (202) therein, and a plurality of chambers (204) formed in the substrate, wherein each of the plurality of chambers (204) is adapted for receiving cells in a liquid medium and formed with an open end (262), an opposite closed end (264) and side walls, the open end (262) and the closed end (264) defining a depth, d, therebetween for the corresponding chamber (206), the sidewalls defining a width, w, therebetween for the corresponding chamber (206). As such formed, each chamber (206) is in fluid communication with the channel (202) through the open end of the chamber (206), and at least two of the plurality of chambers (206) have depths or widths the same or different form each other.