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Mekaru H.,Macro Bio Electromechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Takahashi M.,Macro Bio Electromechanical Autonomous Nano Systems Center | Takahashi M.,Japan National Institute of Advanced Industrial Science and Technology
Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films | Year: 2010

The authors have proposed electrical circuits accumulated by injecting electroconductive materials into patterns imprinted on the surface of fibers and weaving the fibers like a mesh. For these circuits, a built-in guide structures, which determine the positions where the fibers are to make contact with each other and exchange pertinent information, must be fabricated on fibers. In the experiments, a concave 21-μm -deep structure to serve as weaving guide was processed on the surface of 90-μm -diameter nylon fibers by thermal imprinting with a plane mold. The guides were made with two types of cross sections: rectangular and arc shaped. The rectangular structure was fabricated by a combination of microelectromechanical systems processing and Ni-electroforming technologies, whereas the arc-shaped structure involved dicing and fine machining operations. These structures on molds were designed to imprint weaving-guide structures on fibers with arrays of poles (20 μm in diameter and 10 μm in height) at their bottom to serve as fixation points for fibers and to make electric contacts after metallization. Both types of molds were made with a two-step structure that could be transferred on fibers in one single stamping operation. In thermal imprint experiments, to speed things up, the contact time was set for 1 s only. In order to compensate for the short contact time, the heating temperature was set at 100 °C, which is 50 °C higher than the glass transition temperature of nylon. Regardless of the type of mold, weaving guides and contact supports were successfully formed on the surface of nylon fibers. Thus, the capability to process complex microstructures by thermal nanoimprinting on the surface of fine fibers was experimentally proven. Moreover, the authors report on the results of the trial run for weaving imprinted nylon fibers to form fabrics. © 2010 American Vacuum Society. Source


Mekaru H.,Macro Bio Electromechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Ohtomo A.,Macro Bio Electromechanical Autonomous Nano Systems Center | Ohtomo A.,Toshiba Machine Co. | And 6 more authors.
Microelectronic Engineering | Year: 2013

We are developing flexible and large-size e-textiles by weaving in a smart fiber. On the surface of the fiber, micro-electro-mechanical-systems (MEMS) structures, electronic circuit patterns, and guide structures for positioning during the weaving process are fabricated. In order to manufacture smart fibers in large quantities, we developed a cylindrical mold with hybrid-layered structures consisting of 260-lmwide macro patterns and several 10-lm-wide patterns fabricated by precise cutting of substrate employing forming tools and 3-D photolithography, and using a micro-patterned flexible photomask. Initially, the polished surface of the cylinder is covered with an electroless-plated Ni-P alloy; and convex structures with rectangular cross-sections and arc shaped convex structures are cut. Next, the surface of the cylinder is coated with a positive-tone photoresist by a dipping process. Ultraviolet (UV) lights are then irradiated on the photoresist through a flexible micro-patterned photomask wrapped around the cylinder; and then the micro-patterns on the photomask are thus transferred onto the cylindrical surface. Next, following a Cu electroplating, hybrid-layered patterns are made that comprise 260-lm-wide macro and several 10-lm-wide microstructures. In the final step, the photoresist is then removed. And moreover, in order to realize high-speed imprinting, the mechanical stiffness of a reel-to-reel thermal imprint system is improved, and the press-force control method is changed. The imprint system is equipped with a completed cylindrical mold; and using the system, a plastic optical fiber (POF) comprising a 240-lmdiameter PMMA core with a 5-lm-thick fluoride clad is imprinted for a demonstration. The cylindrical mold heated up to 50 °C with an infrared lamp, is pushed into the surface of the POF to a depth of 4.5-6.7 lm. As a result, a continuous imprinting on the POF is achieved at an imprint speed of 20 m/min. © 2013 Elsevier B.V. All rights reserved. Source


Mekaru H.,Macro Bio Electromechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Ohtomo A.,Macro Bio Electromechanical Autonomous Nano Systems Center | Ohtomo A.,Toshiba Machine Co. | And 6 more authors.
Microelectronic Engineering | Year: 2011

We are developing a woven fabric of micro-electro-mechanical-systems (MEMS) where smart fibers are woven to make large-size flexible devices. MEMS structures and electric circuits are formed on the surface of individual fibers to serve as smart fibers where they can function as sensors and actuators. Moreover, when smart fibers are inter-woven it becomes necessary to process electric contact and physical positioning guides on the surfaces of warp and woof fibers. To transfer various patterns on the surface of a fiber at high speed, a batch process by thermal nanoimprinting is pursued. We then developed a new-type roller nanoimprint system to precisely transfer fine patterns from a plane mold onto the curved surface of a fibrous substrate. In this system, a fiber is sandwiched by two molds and rolls under the traction force of sliding molds traveling in opposite directions. At the end of their travel the molds are separated. The molds are moved in directions opposite to their previous directions of travel. This brings the molds back to their inital positions. Then, the fiber is moved by a preset distance using a reel-to-reel feeder. A new cycle starts again. With this method, 5-μm-width square and 5-μm-diameter circular dotted patterns with 10 μm pitch were successfully transferred onto a 250-μm-diameter plastic optical fiber (POF) covering its full surface. Moreover, we succeeded in a continuous molding on the entire curved surface of 1.6 m long POF using a reel-to-reel feeder as a batch processing operation with a pitch of 16 mm by a repetition of roller-imprinting for 100 times. No significant difference was observed when the shapes and depths of the imprinted patterns obtained from the first imprinting were compared with those of obtained from the 100th imprinting. © 2011 Elsevier B.V. All rights reserved. Source


Mekaru H.,Macro Bio Electromechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Ohtomo A.,Macro Bio Electromechanical Autonomous Nano Systems Center | Ohtomo A.,Toshiba Machine Co. | And 6 more authors.
Microelectronic Engineering | Year: 2012

We developed a reel-to-reel imprint system using a cylindrical mold that could continuously process a uniform-depth microstructure on the surface of a fibrous substrate. A fiber coming out from a sending reel was placed between two rotating heated cylindrical molds under a moderate press-force, and was then fed into a receiving reel. The two cylindrical molds rotated in opposite directions to each other while synchronized with the rotations of the two reels that moved the fiber from the sending reel to the receiving reel. The cylindrical molds comprised 100-mm-diameter metal cylinders covered with a Ni electroless-plated layer on which convex mold patterns were fabricated using a high-precision machining tool. The system was equipped with a press-force control mechanism capable of adjusting the gap between the two cylindrical molds in rapid response to any variation in the press-force as detected by a load cell. This mechanism suppresses any fluctuation in the press-force that may occur due to any error made during the assembling of the cylindrical mold. This setup can also make continuous imprinting possible under a constant force. By adjusting the cylindrical mold's position within a 74-μm-wide range, the fluctuation of the press-force can be reduced from 33 to 3 N. Furthermore, as a demonstration, a plastic optical fiber (POF) in a diameter of 250 μm was sent at speeds of 1 m/min and 5 m/min; and by a continuous imprinting process, 260-μm-wide rectangle-shape, and 145-μm-radius arc-shape concave microstructures were formed on the surface of the POFs. When the sending speeds were 1 and 5 m/min, the maximum standard deviations of the imprinted depths were estimated to be 0.52 and 0.14 μm, respectively. These values fell within 17% of the POF's diameter variations of 3 μm. The imprinted fibrous substrate will be used as fibers that constitute e-textiles; and the imprinted concave microstructures will be used as weaving guides to fix the contact positions between warps and wefts. © 2012 Elsevier B.V. All rights reserved. Source


Mekaru H.,Macro Bio Electromechanical Autonomous Nano Systems Center | Mekaru H.,Japan National Institute of Advanced Industrial Science and Technology | Koizumi O.,Macro Bio Electromechanical Autonomous Nano Systems Center | Koizumi O.,Japan National Institute of Advanced Industrial Science and Technology | And 4 more authors.
Microelectronic Engineering | Year: 2010

For the next generation of micro-electro-mechanical-systems (MEMS) with flexibility and large size, we are developing new kinds of MEMS that will be woven fabric of "on-fiber-devices". An on-fiber-device is realized by thin-film-coating, patterning, and etching on the surface of a thin fiber that is then transformed into fiber-shaped device to make MEMS such as sensors and actuators. These on-fiber-devices that themselves are in shape of fibers are woven and criss-crossed resulting in new devices with novel functions. The contact points, interconnecting the woven fibers are designed to be fixed with respect to each other where they can make electrical contacts as necessary. We have developed a thermal nanoimprint technology to fabricate weaving guide structures supporting electric contact points on the surface of a thin fiber. The cross-sectional shape of the weaving guide structure was made to be rectangular, and arrays of cylinder poles of 5, 10 and 20 μm in diameters were arranged as supporting structures for making electrical contacts with the bottom of the weaving guide structure. A mold for this purpose required a two-step structure capable of imprinting weaving guide structure, and the contact points on the surface of a fiber in one stamping operation. Such a mold was fabricated by combining MEMS processing with Ni-electroforming technology. Four kinds of guide structures with depths of 20, 30, 40 and 50 μm were processed by adjusting the dry-etching during the making of a Si master. Using these electroformed-Ni molds, these different weaving guide structures, each with a set of 5-, 10- and 20-μm diameter cylinder poles were transferred onto a 90-μm diameter nylon fiber by thermal imprinting. © 2009 Elsevier B.V. All rights reserved. Source

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