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Capability of stereophonic projection lithography on arbitrarily but gently curved surfaces was demonstrated using plastic spoons as a reticle and specimens to be patterned. It had already been clarified that the patterned area size was drastically enlarged by illuminating the transparent reticle obliquely upward by collimated light from one side. Here, it was confirmed at first that 200 μm line-and-space patterns in 10 mm square area on a flat reticle were stably replicated on Si wafers with large exposure-time and focus margins. Next, reticle patterns on a spoon concave were successfully replicated on convex surfaces of specimen spoons. On the other hand, it was clarified that resist pattern field was distorted in a warped trapezoid, and pattern sizes were also varied similarly. However, because the distortions are regular and systematic, they are probably no problem, if critical overlays are not required. And, the distortions can be compensated by modifying the reticle, if necessary.

Introduction: Intermittent flash glucose monitoring (FGM) and real-time continuous glucose monitoring (CGM) are used to monitor glycemic excursions for 14 days and can demonstrate time in range (TIR), time above range (TAR), and time below range (TBR). The utility of CGM metrics, such as TIR, TBR, and TAR, in diabetics treated with insulin combined with antihyperglycemic drugs is uncertain. Methods: In a cross-sectional and retrospective study, we investigated the relationship between target metrics from CGM/FGM and HbA1c or glucose variabilities in 80 type 1 and 2 diabetic patients receiving insulin treatment with ≥1 injections per day. The proportions of TIR, TAR, and TBR from FGM in relation to HbA1c and coefficient of variation (CV)% in types 1 and 2 diabetics were analyzed. Multivariable analyses were performed regarding the associations of TIR with biochemical factors and glycemic variabilities. TBR was also examined in relation to antidiabetic agents and diabetic type in multiple regression analyses. Finally, the association of retinopathy with FGM-CGM metrics was examined using a logistic analysis. Results: When patients were grouped by sex and diabetic type, significant differences in age, TIR, TBR, high-density lipoprotein cholesterol (HDLC), and insulin dose were detected using Kruskal-Wallis analyses. HbA1c significantly correlated with TIR (p < 0.001) and TAR (p < 0.001) using Pearson’s correlation analysis. TBR significantly correlated with CV% (p < 0.001). Multivariable analysis of TIR showed a significant negative association with HbA1c (p = 0.02). Incretin combined with insulin therapy reduced the TBR proportion significantly according to the multivariate analysis. Retinopathy tended to be related to HbA1c (p = 0.059) and duration (p = 0.078) but not TIR (p = 0.891), according to the logistic analysis. Conclusions: These results demonstrate that CGM metrics reflect glucose control for 2 weeks using TIR. In addition, combined therapy with incretin and insulin therapy is superior for reducing hypoglycemia, based on TBR. Thus, TBR is also useful for monitoring hypoglycemia. However, FGM/CGM metrics do not predict retinopathy accurately.

Stereophonic lithography applying a magic-mirror optics composed of faced parabolic mirrors is proposed. In the magic mirror system, a real image of an object placed on the base of the lower mirror is formed at the aperture center of upper mirror as if an actual object is floating in the air. The image is formed by illuminating the object by the downward light supplied through the upper mirror aperture. In the new optics originated in this research, a lower mirror with an aperture similar to the upper mirror is used, and the object held at the center of the lower mirror aperture is illuminated obliquely by the upward light supplied through the lower mirror aperture. At first, using reflective objects, image formations were demonstrated. When an object was placed at various height of the optical axis, an image almost similar to the object was projected successfully in a wide height range of the object. The size and the height position of the image were almost regularly changed according to the axial height shift of the object. However, image contrasts sufficiently high for the lithographic patterning were not obtained. For this reason, transparent objects were tried next, and the illumination light was adjusted as most of the light rays hit the middle parts of the upper mirror surface. As a result, considerably high-contrast images were formed. Although some distortions were observed in image shapes, feasibility of the new stereophonic projection system was confirmed. The new technology is prospective.

Leaves of an obscure plant “oxalis deppei” are so hydrophobic that showered water droplets are almost completely repelled and hardly remained on their surfaces. For this reason, surface configurations were investigated. On the live leaves, there formed protrusions somewhat similar to those observed on lotus leaves which are well known as super hydrophobic leaves. However, in winter, it was found that even dead leaves were hydrophobic also. Because leaf tissues were shriveled and dried half, heights of protrusions with sizes of 20-50 μm were low, and undulations of surfaces were gentle and smooth, and pitches of undulations were as large as 30-70 μm. It was thought that such gentle lens-like protrusions would be probably formed on versatile stainless-steel plates using lithography and wet chemical etching. For this reason, arrays of protrusions with a size of 20 μm, a pitch of 35 μm, and heights of 6-7 μm were formed, and change of hydrophobic properties were investigated. As a result, the hydrophobic properties were effectively improved by forming even such gentle and smooth protrusions. It was also clarified that contact angles were improved almost in proportion to etched depths.

A new stereophonic projection lithography applying a parabolic magic mirror system was proposed. An aperture was also opened at the bottom of lower mirror, and a transparent reticle was placed in place of a reflective object article used in the conventional magic mirror system. Toward the transparent reticle, illumination light was irradiated obliquely upward from the bottom. Thus, images of curved reticle patterns were projected at the aperture center of the upper mirror, and 200 μm line-and-space resist patterns were actually printed on a silicon wafer when a flat reticle was used. On the other hand, it was clarified by tracing light rays in the meridional plane that the resolution depended on the field size, the extent of used mirror parts, and the defocus. It is considered that aimed 50 μm patterns will be printable if the illumination system is improved. The new method is feasible and hopeful.

A new lithography optics designed and fabricated for printing 300-μm patterns on inside surfaces of pipes with an inner diameter of 10 mm and a length of 300 mm was investigated. Such patterning is required for giving textures to heat pipes, graving bearing grooves, and fabricating electrode and wiring patterns on inside surfaces of pipes. Although the pattern size is far larger than those used for semiconductor device fabrication, patterning onto non-flat surfaces in narrow spaces has hardly been researched anywhere else. Here, a linear optical fiber array composed of 500-μm fibers with squared ends were used for leading exposure light from light emitting diodes and designating pattern shapes. Then, the fiber array end was contacted to the inlet of a taper-conduit, and the pattern shapes were reduced in 1/2.25 at the outlet of the conduit. The conduit was composed of densely contacted fine optical fibers, and each fiber diameter was gradually reduced in the longitudinal direction keeping each fiber position invariably. The reduced pattern shapes were projected by a ratio of 1.25/1 using a simple convex lens on the inside surface of a pipe. Here, the performances of the projection optics were investigated by printing patterns on wafers used temporarily in place of the inside wall of a pipe. As a result, hole and linear space patterns with sizes or widths of approximately 300 μm were successfully formed.

It was verified that a lenticular lens array with a fine pitch of 100 μm was effective for improving resolution and clearness in switching of two images. Lenticular lens array patterns of negative resist SU-8 were fabricated on a 240-μm thin quartz plate, and they were directly used as lenticular lens arrays. The patterns were printed using 1:1 projection lithography under largely defocused conditions using a reticle with 50-μm line-and-space patterns. Because pattern images were made vague by the defocus, connected humpbacked patterns with a pitch of 100 μm were continuously formed without spaces. Cross section profiles of the patterns were almost circular, and the curvature radius was controllable in a range between 60 and 130 μm by adjusting exposure time. In the case of picture switching using conventional lenticular lens arrays with 40-100 lenses per inch, stitching lines appeared considerably clear between divided picture elements, and discontinuous steps were observed at inclined parts of figures. However, when the 100-μm pitch lens arrays were used, stitched steps became far finer and smoother, and scenes without notable stitching lines were obtained. Steps and discontinuities at inclined parts of figures were especially improved. Thus, fine pitch lenticular lens arrays are effective, and the new method for printing lenticular lens patterns would be useful for fabricating original molds of lenticular lens arrays.

A new fabrication method of micro-lens arrays with element lens diameters of 20-50 μm was developed in the past research. In the method, epoxy micro-lens arrays are replicated using concave resist patterns as molds. In this paper, resist mold pattern profiles were investigated again in detail, and model curves to be fitted to pattern cross sections were looked over again. As a result, it was found that cross section curves of resist mold patterns were very accurately modeled by decomposing each curve into three parts of a central circular concave arc, a peripheral circular convex arc, and a tangential line connecting them. For this reason, using the new fitting curves, how parallel light rays incident in an element lens were refracted at the lens surface, and concentrated in a spot were investigated. It was clarified by the ray trace that parallel light rays were efficiently concentrated in a considerably small light spots by grace of the tangential line parts. Next, the ray trace results were compared with the experimental results. A micro-lens array fabricated under the same conditions was illuminated by a parallel light ray flux. As a result, the position where the traced rays were concentrated almost coincided with the position obtained experimentally. The diameters of concentrated light spots estimated by the ray trace also almost coincided with the actually observed ones. Thus, optical characteristics of microlens arrays fabricated by the new method were adequately qualified. The new method will be useful.

A maskless exposure system was developed utilizing a commercial LCD video-projector.Only the projection optics was changed to a camera lens for macro-photography.The system is very simple, and has a small desk-top size of 300iÂ?400iÂ?500mm3.Patterns with a minimum width of 14µm were smoothly printed in 14.3iÂ?10.7mm2 field.The new lithography tool was fabricated by an expenditure of only Â?500,000Â?Â?3500. A very simple and low-cost maskless exposure tool with a desk-top size was developed for applying to fabrications of various micro electro mechanical systems (MEMS) and bio-devices. A commercial projector with three liquid crystal display (LCD) panels of red, green, and blue colors was utilized as it was, except attaching a macro-lens for a camera after removing the magnification optics of the original projector. Therefore, the sizes were as small as 300 wideiÂ?400 deepiÂ?500 high mm3, and the system was fabricated at a very small expense (Â?500,000Â?Â?3500). Pixel pitches on the LCD panel were 8.5µm, and the 7.4-µm square pixels were projected onto a wafer in a magnification ratio of 1.65. Efficient pixel numbers were 1024iÂ?768, and the exposure field sizes were 14.3iÂ?10.7mm2. Using the system, isolated line patterns with a width corresponding to one pixel size of approximately 14µm, and 1:1 lines-and-spaces (L&S) patterns with a width of two pixel sizes of 28µm were stably printed. Not only line patterns in orthogonal directions, but also radial oblique patterns were clearly and smoothly printed, and complicated arbitrary patterns were also printed. These projection ratio and pattern widths were decided considering the present applications to fabrications of micro-fluidic devices and lens arrays. If smaller patterns are required, the minimum pattern size and the projection ratio are conformably changed in principle. Because arbitrary patterns designed on a personal computer are directly printed on a wafer, preparations of expensive reticles are not necessary. Accordingly, besides the system cost and footprint are drastically saved, working expenses are much saved.

Mixing processes of two liquids were investigated by visualizing the mixing when they were simultaneously injected in a micro-mixer with lithographically fabricated Y-shape flow paths, and the mixing phenomena was analyzed in detail. To visualize the mixing, flows were observed by an optical microscope, and a clearly detectable chemical reaction was utilized. As the two liquids, a transparent aqueous solution of a strong alkali and a phenolphthalein ethanol solution were used. When they were simultaneously injected in Y-shape flow paths of a micro-mixer, they flowed at first in parallel along the joined path as laminar flows. This is because the Reynolds’ number became very small caused by the narrow flow-path widths of 50-100 μm. However, because two liquids were always contacted at the boundary, they were gradually mixed by diffusion, and the color of the mixed parts changed to vivid red. For this reason, it was able to measure the diffusion distance from the flow path center. Because the flow speeds were much faster than the diffusion speeds, the area colored in red did not depend on the time but depended on the distance from the joint point. It was known that the distance from the joint point corresponded to the time for mixing the liquids by the diffusion. It was clarified that the diffusion distance x was proportional to the square root of the diffusion time t or the distance from the joint point. The calculated diffusion coefficient D was (0.87-1.00)×10-9 m2/s.

Printing of thick resist patterns with a high aspect ratio and vertical side walls was investigated. Such resist patterns are required for using as molds of electroplating, and patterning feasibility in a small field of 2 mm square was verified in the past researches. However, it is necessary to print patterns homogeneously in an exposure field with a practical size of larger than 10 mm square, for example. As profiles of resist patterns for the use of electroplating molds, rectangular cross-sections are preferable. For this reason, patterns were printed in the negative resist SU-8 with a thickness of 50 μm using an exposure system with a field size of 15 mm square. Before using the thick SU-8, the best focus position of the exposure system was investigated. To find out the best focus position, line and space (LS) patterns were printed using a positive resist OFPR-800 with a thickness of approximately 1 μm. The focus position where patterns were most clearly formed on the wafer was decided to be the focus origin, and defocuses were controlled by moving wafers downward. Next, 50-μm LS patterns were printed in 50-μm thick SU-8. As a result, LS patterns with rectangular cross sections and a height of 40 μm were obtained when the defocus and the exposure time were set at 2000 μm and for 70 seconds, respectively. It was demonstrated that patterns with rectangular cross sections were printed in 3x5 mm2 exposure fields.

Lithographical patterning on the surface of a fine pipe with a thin wall is required for fabricating three-dimensional micro-parts. For this reason, a new exposure system for printing patterns on a cylindrical pipe by synchronous rotary scan-projection exposure was developed. Using the exposure system, stent-like resist patterns with a width of 251 μm were printed on a surface of stainless-steel pipe with an outer diameter of 2 mm. The exposure time was 30 s. Next, the patterned pipe was chemically etched. As a result, a stent-like mesh pipe with a line width of 230 μm was fabricated. It was demonstrated that the new method had a potential to be applied to fabrications of stent and other cylindrical micro-parts.

Recently, it is required to develop a method for fabricating cylindrical micro-components in the field of measurement and medical engineering. Here, electrolytic etching of fine stainless-steel pipes patterned by laser-scan lithography was researched. The pipe diameter was 100 μm. At first, a pipe coated with 3-7 μm thick positive resist (tok, PMER P LA-900) was exposed to a violet laser beam with a wavelength of 408 nm (Neoark,TC20-4030-45). The laser beam was reshaped in a circle by placing a pinhole, and irradiated on the pipe by reducing the size in 1/20 using a reduction projection optics. Linearly arrayed 22 slit patterns with a width of 25 μm and a length of 175 μm were delineated in every 90-degree circumferential direction. That is, 88 slits in total were delineated at an exposure speed of 110 μm/s. In the axial direction, patterns were delineated at intervals of 90 μm. Following the pattern delineation, the pipe masked by the resist patterns was electrolytically etched. The pipe was used as an anode and an aluminum cylinder was set as a cathode around the pipe. As the electrolyte, aqueous solution of NaCl and NH4Cl was used. After etching the pipe, the resist was removed by ultrasonic cleaning in acetone. Although feasibility for fabricating multi-slit pipes was demonstrated, sizes of the etched slits were enlarged being caused by the undercut, and the shapes were partially deformed, and all the pipes were snapped at the chuck side.

Two dimensional code marks are often used for the production management. In particular, in the production lines of liquid-crystal-display panels and others, data on fabrication processes such as production number and process conditions are written on each substrate or device in detail, and they are used for quality managements. For this reason, lithography system specialized in code mark printing is developed. However, conventional systems using lamp projection exposure or laser scan exposure are very expensive. Therefore, development of a low-cost exposure system using light emitting diodes (LEDs) and optical fibers with squared ends arrayed in a matrix is strongly expected. In the past research, feasibility of such a new exposure system was demonstrated using a handmade system equipped with 100 LEDs with a central wavelength of 405 nm, a 10×10 matrix of optical fibers with 1 mm square ends, and a 10X projection lens. Based on these progresses, a new method for fabricating large-scale arrays of finer fibers with squared ends was developed in this paper. At most 40 plastic optical fibers were arranged in a linear gap of an arraying instrument, and simultaneously squared by heating them on a hotplate at 120°C for 7 min. Fiber sizes were homogeneous within 496±4 μm. In addition, average light leak was improved from 34.4 to 21.3% by adopting the new method in place of conventional one by one squaring method. Square matrix arrays necessary for printing code marks will be obtained by piling the newly fabricated linear arrays up.

SUMMARY Precise microcoils and mesh pipes with outer and inner diameters of 100 μm and 60 μm were fabricated using laser-scan lithography and electrolytic etching. Non-magnetizable stainless-steel (SUS304) pipes were coated with resist films, and helical patterns were delineated using a laser-scan exposure system. Positive resist PMER P-LA900 was used for fabricating microcoils, and negative resist PMER N-CA3000 was used for fabricating micromesh pipes. Mesh patterns were formed by doubly delineating helical patterns coiled in opposite directions each other. Widths of resist patterns used for fabricating mesh patterns were also controlled by stitching two helical patterns. Because space widths of coils and sizes of mesh holes became larger than space widths and hole sizes of resist patterns caused by undercut in etching process, widths of resist patterns were adjusted by considering the undercut depths. As a result, pipe specimens were suitably etched in a solution of sodium chloride and ammonium chloride in water, and microcomponents with homogeneous widths were successfully fabricated.