apparatus for forming and fibrillating a molten polymeric film into nanofibers consisting of a plurality of two - phase flow spinning nozzles arranged in a substantially liner array each nozzle into nanofibers including one or more first input orifices for a process gas ; one or more second input orifices for a polymer melt ; a flow channel including two or more channel walls and a monotonically decreasing flow area wherein the process gas and polymer melt are combined into a stratified two phase flow with the polymer melt formed into a film on one or more of the channel walls ; and one or more channel exit openings , each exit opening including an edge at which the process gas reaches sonic velocity or less and where the edge is configured to fibrillate the polymeric film into a stream of nanofibers .