Abstract: A process and extrusion die for making capillary channel structures having one or more intrastructure capillary channels. The process includes feeding a flowable, molten polymer composition through an extrusion die having an annular base orifice from which a plurality of capillary channel wall orifices radially extend. The extrusion die has a gas inlet port located interior to the annular base orifice. Simultaneous with feeding the polymer composition through the extrusion die's annular base and capillary channel wall orifices a gaseous stream is directed through the gas inlet port in the same direction as the flow of molten polymer composition. Subsequent to exit of the polymer composition from the extrusion die, the capillary channel structure is drawn to a desired size and cooled.