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Mekaru H.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Ohtomo A.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Ohtomo A.,Toshiba Machine Co. | And 2 more authors.
Microsystem Technologies | Year: 2013

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 μm on the surface of a 250-μm-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 μm. 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. © 2012 Springer-Verlag. Source


Ohtomo A.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Ohtomo A.,Toshiba Machine Co. | Kokubo M.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Kokubo M.,Toshiba Machine Co. | And 6 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2012

The authors succeeded in producing high-speed continuous patterning on the surface of plastic fiber at a feeding speed of 20 m/min by using a system they developed employing thermal roller imprint methodology. In this method, a cylindrical mold with seamless microstructures formed on its surface was used, wherein a plastic fiber is pressed between the cylindrical mold and a backup roller and is then run for imprinting. Here, the movement of the cylindrical mold in the direction of space-change between the mold and the backup roller can be precisely controlled, and the press force during the imprinting can be measured by a load cell located beneath the backup roller. The cylindrical mold and the backup roller are heated up to 250 °C and are rotated synchronously, imparting a forward-linear motion to the plastic fiber and thereby making continuous patterning of microstructures possible. Since the press force feedback system during high-speed imprinting cannot be adequately controlled, the authors devised a scheme where the system memorizes the press positions corresponding to the rotating angles of the cylindrical mold at low feeding speed under a controlled press force. Here, the periodic variation of the center-to-center distance between the cylindrical mold and the backup roller can be measured at set intervals and, by using the memorized relationship between the rotational angle and press position, the position of the cylindrical mold is then moved. Finally, the authors imprinted 50 μm high microstructures onto the surface of the plastic optical fiber whose diameter was 250 μm. As a result, when the press position was fixed, the standard deviation of the press force was 6.86 N; however, this value dropped to 2.80 N when the improved control method was employed. The range of depth variation was 8.0 μm when the press position was fixed, and this number went down to 2.2 μm when the improved control method was employed. © 2012 American Vacuum Society. Source


Mekaru H.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Takagi H.,Macro Bio Electro Mechanical Autonomous Nano Systems Center | Takagi H.,Japan National Institute of Advanced Industrial Science and Technology | And 6 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2011

The authors have developed a novel thermal imprinting method to fabricate microstructures on the surface of plastic optical fibers (POFs) without causing any damage to them. In conventional thermal nanoimprinting using a planar mold, the shape of the molding material is in the form of a film spread on a planar substrate, or the molding material is used in its bulk form. In the case of any 3-dimensional shaped molding material such as in the case of a fiber, the shape becomes susceptible to a certain degree of damage caused by the planar mold. In order to address this problem, we have designed a thermal imprinting method using sliding planar molds. A fiber tightly stretched between two reel stations (for sending and winding of the fiber) is sandwiched between two planar molds facing each other. The fiber is then rolled against the pattern sides of the two planar molds while the rolling motion of the fiber remains synchronized with the sliding motion of the planar molds. The problem of twists in the fiber caused by the sliding planar molds was solved by dynamically rotating the two reel stations to match the rotation of the fiber. To demonstrate this technology, we employed a special electroformed-Ni mold with a mirror image of a string of characters forming the word "MACROBEANS" engraved in the form of a lattice, where the individual characters were composed of diffraction grating structures with 1 and 2 μm of linewidths. Using this mold, the cylindrical surface of a POF made of a 240-μm-diameter polymethyl methacrylate core with a coating of a 5-μm-thick fluoroplastic cladding was thermal-imprinted. From the observation of the imprinted patterns on the POFs, it was verified that the cylindrical surface was patterned without causing any damage to the POF. The height of the convex mold pattern was 1.1 μm, and the depth of the concave imprinted pattern was approximately 1.0 μm. © 2011 American Vacuum Society. Source

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