The Small Business Technology Transfer Research (STTR) Phase I project will control the shape of microextruded polymers (microprofiles) using a sheath fluid at the exit of the extruder. Microprofiles are defined as continuous filaments having a non-circular cross-section with precision microfeatures and a mean diameter of 100 microns or less. In the standard polymer extrusion process, the boundary condition at the free surface of the extrudate is not controlled after the polymer exits the die. Consequently, the free deformation of the extrudate subjected to the combined effects of die swell and surface tension contributes to significant shape distortion of the extruded profile. In the proposed technology, the use of a low-viscosity fluid with closely matched surface tension as that of the polymer extrudate, will help suppress the shape change of the cross-section caused by different mechanisms. The proposed technology will provide an efficient method to produce precision polymeric micro-size profiles for various applications including the medical field. For example, these microprofiles can be used as functional filaments in artificial kidneys and artificial capillary vein networks. Filaments with highly non-circular cross-sections are also needed in the polymer composites industry to improve the integrity of the composite via mechanical interlocking with the polymer matrix.
