Browsing by Author "Shih, Teng-Kai"

Now showing 1 - 9 of 9

A novel method for fabrication of self-aligned double microlens arrays
(2007-04-15)
Ho, Jeng-Rong
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Shih, Teng-Kai
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Cheng, J. W. John
;
Sung, Cheng-Kuo
;
Chen, Chia-Fu
Based on the excimer laser microdrilling and the spin coating scheme, a new fabrication method of polymeric, double microlens arrays on a thin plastic pedestal sheet is proposed in this study. On each through hole on the pedestal sheet, a double microlens pair, consisting of two microlenses with different parabolic surfaces, is sited. The two microlenses of each pair are located respectively on both ends of the through hole and arranged surface to surface and automatically share a common lens principal axis. The fabricated microlens arrays are made of PMMA that are formed on a PMMA pedestal sheet with thickness of 100 mu m. The diameter and height for the microlens on one layer are of 150 mu m and 28 mu m, respectively, and they are correspondingly of 130 mu m and 24 mu m on the other layer. Experimental results demonstrate that the double microlens arrays have a better focusing property than the single-layer mircolens array. Simulation results indicate that, simply by changing the thickness of the pedestal sheet, the present fabricated double microlens arrays can serve the purposes for light collimating and diffusing. Due to its inherent simplicity in fabrication, the present method has high flexibility for making double microlens arrays with different lens configurations and various lens refractive indices. The facts that precise alignment and all processing steps are performed in ambient and at low temperature render the proposed approach a potential low-cost method for fabrication of double microlens arrays. (c) 2006 Elsevier B.V. All rights reserved.
Fabrication of optical gratings by shrinkage of a rubber material
(2008-06-30)
Shih, Teng-Kai
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Ho, Jeng-Rong
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Liao, Hung-Yu
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Chen, Chia-Fu
;
Liu, Chueh-Yang
Ordered wavy surface structures generated by deposition of a metal thin film on a pre-stretched PDMS plate were fabricated and its potential application for optical gratings was proposed. The orientation of the generated structures was always perpendicular to the pre-stretched direction and the pitch of the structure could be adjusted ranging from 4.5 mu m to 6.8 mu m by controlling the strength of the pre-stretched strain and the thickness of the surface metal film. Based on these periodic structures, various optical gratings were demonstrated. With a slight modification of the fabrication scheme, gratings with different orientations can be fabricated on both sides of the PDMS plate, the double-sided gratings, could be fabricated. It is believed the current method has the potential for the fabrication of a large-scale diffractive grating at lower costs. (C) 2007 Elsevier B.V. All rights reserved.
Fabrication of optical reflectors by using of elastomer with self-organized undulations
(2008-08-01)
Wang, Jui-Hao
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Shih, Teng-Kai
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Chen, Chia-Fu
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Chen, Kuang-Chung
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Chen, Chien-Chung
Back-surface diffusive reflectors have been widely applied in many optical systems to promote the efficiency used in system. In this work, we propose a novel way to fabricate a soft diffusive reflector by using of silicone (polydimethylsiloxane, PDMS). High-reflectance substrates were first fabricated by mixing nanoscaled TiO2 powders with PDMS polymers, and then microscale wave-like undulations were spontaneously developed after the substrates were dipped into H2SO4/HNO3 solutions. After optical examination, a TiO2/PDMS plate comprising microscale undulations, which can surely serve as a reflector, could reflect and diffuse light effectively. Besides, all fabrication processes can be executed in the ambient environment and at low temperature. This proposed method has a potential for mass production in the future. (c) 2008 Elsevier B.V. All rights reserved.
Fabrication of PDMS (polydimethylsiloxane) microlens and diffuser using replica molding
(2006-11-01)
Shih, Teng-Kai
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Chen, Chia-Fu
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Ho, Jeng-Rong
;
Chuang, Fang-Tzu
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材料科學與工程學系
This paper reports the fabrication method of PDMS (polydimethylsiloxane) microlens array based on the replica molding process, casting a liquid PDMS into concave microlens molds. Concave microlens molds were fabricated through spin-coating processes suspended a liquid PMMA film on the micro-drilled hole, leading to the formation of the special curvature. Then, PDMS microlens arrays and diffusers were fabricated by replica molding and discussed in this study. The fabricated microlenses have both good surface roughness and high-quality optical properties. Therefore, diffusers were fabricated by two-step replica molding. A high-intensity He-Ne laser beam was uniformly spread through diffusers. Experimental tests demonstrated that all PDMS elements are successfully fabricated by replica molding process and operated during optical measurement. (c) 2006 Elsevier B.V. All rights reserved.
Fabrication of soft reflective microoptical elements using a replication process
(2008-01-01)
Shih, Teng-Kai
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Ho, Jeng-Rong
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Wang, Jui-Hao
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Chen, Chia-Fu
;
Liu, Chueh-Yang
This paper reports the fabricated method and optical performance of soft, reflective elements with nonspherical surface. Based on excimer laser microdrilling and spin coating processes, a PMMA film suspended on microdrilled holes was used as a concave mold. Then, a high-reflectance material, mixed PDMS rubber polymers with TiO2 nanoscale powders, was cast on the PMMA mold. Finally, both of concave and convex elements could be fabricated through soft replica molding processes and these elements could directly reflect light without the deposition of metal coatings. Therefore, we proposed a model regarding a flexible cable with its weight suspended on fixed points to explain the formation mechanism of PMMA molds. With the change of diameters of microholes and thicknesses of PMMA films, the suspended height of films was surely controllable. Therefore, the curvature radiuses and shapes of these aspherical elements also depended on the diameters of microholes and the thicknesses of PMMA films. Experimental results demonstrated that soft reflective elements have good surface qualities and high-quality optical properties. Besides, all fabrication steps can be executed in ambient environment and at low temperature, the proposed method has a potential for mass production. (C) 2007 Elsevier B.V. All rights reserved.
One-step fabrication of surface-relief diffusers by stress-induced undulations on elastomer
(2009-09-01)
Wang, Jui-Hao
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Chen, Chia-Fu
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Ho, Jeng-Rong
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Shih, Teng-Kai
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Chen, Chien-Chung
In this study, we demonstrated that microscale surface undulations induced by acid treatment could serve as the surface relief on diffusers coated with a layer of PDMS polymer. Since the orientation of undulations was found to be always disordered, these undulations would scatter light uniformly. The periodicity of the undulations could be adjusted by the control of duration of the dipping of the elastomer into H(2)SO(4)/HNO(3) solutions and by the volume ratio of H(2)SO(4)/HNO(3) the solution, resulting in the modulation of diffusing ability of diffusers. The optical properties, transmittance, and light diffusivity, were characterised. This proposed approach offers potential for mass production of surface-relief diffusers. In addition, the proposed method allows the creation of undulations on arbitrary substrates. (C) 2008 Elsevier Ltd. All rights reserved.
Optical diffusers based on silicone emulsions
(2009-12-01)
Wang, Jui-Hao
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Lien, Shui-Yang
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Ho, Jeng-Rong
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Shih, Teng-Kai
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Chen, Chia-Fu
The present study provides an experimental approach for fabricating optical diffuser films based on silicone emulsions. The silicone emulsion consisting of silicone polymer (Sylgard 184) and NaCl aq. solution was used as the optical material of diffusers, wherein NaCl aq. solution was severed as surfactant to stabilize the emulsions. After stirring mechanically, microscaled water drop with various sizes distributed randomly in silicone polymer, wherein water drop was used as scattering diffusion particles. To modulate the volume of NaCl aq. solution, the diffusing performance of diffusers could be change by different amount drop particles. Thereafter, an optical examination was carried out to characterize optical properties, transmittance. and light diffusivity of volumetric diffuser films. (C) 2009 Elsevier B.V. All rights reserved.
Study of leading factors in formation of surface wavy structures on a rubber material
(2006-12-15)
Shih, Teng-Kai
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Chen, Chia-Fu
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Ho, Jeng-Rong
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Liu, Chueh-Yang
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Chuang, Fang-Tzu
Wavy structures are often observed on the surface of a rubber material (polydimethylsiloxane, PDMS) covered with a thin metallic film. In this study we demonstrate that the orientation, periodicity, location of formation, and range of periodicity of the wavy structures can be regulated by three leading factors including the surface pattern, substrate hardness and the thickness of the metallic film. Results show the orientation of the wavy structures can be adjusted by the location, shape and size of the surface patterns. Enhancement of the substrate hardness can prevent forming random wavy structures. The thickness of surface metallic film significantly influenced the periodicity of the structures. Experimental results revealed an increase of the thickness of surface Au film by 50 nm, the periodicity was increased roughly by 1 mu m. A compound structure, combining longitudinally preset patterns and transversely induced wavy structures, and a parallel wavy structure fabricated, respectively, by suitable arrangement of pattern configurations and adjustment of substrate hardness were demonstrated. The relatively simple approaches proposed here show the potential application in fabrication of designated complicate structures. (c) 2006 Elsevier B.V. All rights reserved.
Topographic control on silicone surface using chemical oxidization method
(2007-10-15)
Shih, Teng-Kai
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Ho, Jeng-Rong
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Chen, Chia-Fu
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Whang, Wha-Tzong
;
Chen, Chien-Chung
The paper describes a wet process for modifying the surface of polydimethylsiloxane (PDMS) using H2SO4/HNO3 solutions. The oxidation on the surface of PDMS was confirmed by the examinations of Fourier transform infrared spectrometry (FTIR), contact angle of water drop and X-ray photoelectron spectroscopy (XPS). The hydrophobic surface of pristine PDMS was not only changed to hydrophilic, but also formed wrinkles on it after chemical modification. Bilayer systems, stiff oxidized PDMS layers were capped on soft PDMS foundations, would generate easily compressive stresses due to the large difference in volumetric contraction rates and led to form wrinkles on the surface. Experimental results demonstrated the periodicity of wrinkles was controllable by controlling the duration of oxidation. Therefore, wrinkles could be arranged orderly by the guidance of external forces before oxidization. The potential technology for generating and ordering wrinkles on the PDMS surface is valuable in the applications of pressure sensors, biology, micro-optics and nano-/micro-fabrication in the future. (C) 2007 Elsevier B.V. All rights reserved.