Effect of buffer materials on thermal imprint on plastic optical fiber

We are advancing the development of a smart fiber using a plastic optical fiber (POF) as a fibrous substrate with micro-electro-mechanical-systems (MEMS) patterned on its surface. We employed hot embossing and thermal nanoimprinting techniques for patterning on the surface of POF, although, no work has so far been reported on the molding characteristic of POF. And moreover, achieving any high quality imprinted patterns on POFs has also proven to be difficult. We have been studying the effect of molding on POFs under various heating temperatures and press depths by sandwitching the POF between patterned face of a mold and a buffer material. When a soft buffer material with its hardness less than that of the polymethyl methacrylate (PMMA) core of a POF fiber was used, a reasonable patterning on the clad layer covering the surface of the POF was achieved without any sign of deformation of PMMA core. On the other hand, when the hardness of a buffer material happened to be equal to, or higher than that of the PMMA core, then deep concave pattern could be processed by purposefully deforming the POF. We successfully transferred a pseudo MEMS pattern with a width of 20 mu m on the surface of a 250-mu m-diameter POF. Also, under another kind of optimized molding conditions combined with buffer material, we fabricated an arc-shaped weaving guide structure on POF with the weaving guide's bottom width of 300 mu m. The investigation of the molding characteristic of POF by examining any change in the cross-sectional shape is a unique one. The experimental results thus obtained, add significantly to the database for the processing of a fibrous substrate by thermal deformation.