An improved micro injection molding technique for grating devices

In this research, we propose a mass production method of gratings integrated with micro channels (GIMC) by means of an improved micro injection molding technique. The GIMC can be used together with a waveguide layer as a biochip in bio-medical assays. In the improved micro injection molding technique of this work, we fabricate an injection mold of gratings through the use of a nanoimprint and photolithography processes. The injection mold of gratings is composed of a hybrid inorganic/organic sol-gel material and stainless steel substrate. The grating pattern of a commercial epoxy grating (EG) is first transferred to a PDMS mold of grating (PMG) via a casting process, and then the PMG is used to imprint the sol-gel material. After exposure, the sol-gel material will solidify and is used as a part of the injection mold. COC (Cyclic olefin copolymer), because of its high luminous transmission and melt flow index, is used to inject the 1800 line/mm period and 100nm depth grating integrated with a 30μm height micro channel at 110°C mold temperature. From the measured results, it is noted the structure of the sol-gel mold of grating remains intact after 1000 times of injection. The diffraction-efficiency uniformity among the grating array elements of COC 3 x 3 grating arrays is better than 97%.