Apparatus and Methods are provided for a microfabricated fluorescence activated cell sorter based on a switch for rapid, active control of cell routing through a microfluidic channel network. This sorter enables low-stress, highly efficient sorting of populations of small numbers of cells (i.e., 1000-100,000 cells). The invention includes packaging of the microfluidic channel network in a self-contained plastic cartridge that enables microfluidic channel network to macro-scale instrument interconnect, in a sterile, disposable format. Optical and/or fluidic switching forces are used alone or in combination to effect switching.