Browsing by Author "Kao, Fu-Jen"

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Assessment of ESD Robustness in High Power Light-Emitting Diodes
(2010)
Yang, Shih-Chun
;
Lin, Pang
;
Fu, Han-Kuei
;
Wang, Chien-Ping
;
Chen, Tzung-Te
The capability of high-power nitride-based light-emitting diodes (HPLED) to withstand electrostatic discharge (ESD) is very important key index due to the horizontal structure of the insulating property of the sapphire substrate. However, it is difficult to real-time monitor the damage caused by the ESD stress because it occurred in a very short period. Current-voltage (I-V) curves and electroluminescence (EL) spectrum were applied to study the change during the series ESD stress. Time-resolved optical beam induced current (TR-OBIC) was used to analyze the characteristics of the delay time between normal region and the defect point caused by ESD stress. Transmission electron microscopy (TEM) was used to compare to the difference in the distribution of damage region and investigate the failure modes. During the series ESD stresses, V-shaped pits suffered from the high electrical field and the distance from multi-quantum well (MQW). The bottom of V-shaped defect would be one of index to assess the ESD endurance of LED chips.
Current Developments for Taiwanese Women in Physics
(2015)
Hsu, Shih-Ying
;
Ho, Mon-Shu
;
Lin, Jauyn Grace
;
Hu, Shu-Fen
;
Chiu, Ya-Ping
Statistics for 2002 to 2012 show that the percentage of women among graduates in physics and astronomy has not changed much in the Republic of China in Taiwan. Women comprise about 15% of graduates with bachelor\'s degrees in physics and astronomy, 17% of those with master\'s degrees, and 12% of doctorates. The number of female faculty members has increased slightly during this time frame but overall has stayed at approximately 11%.
Dynamic photopatterning of cells in situ by Q-switched neodymium-doped yttrium ortho-vanadate laser
(2014-01-01)
Deka, Gitanjal
;
Okano, Kazunori
;
Kao, Fu-Jen
;
前瞻跨領域基礎科學中心
;
Center for Interdisciplinary Science
Cellular micropattering has been increasingly adopted in quantitative biological experiments. A Q-switched pulsed neodymium-doped yttrium ortho-vanadate (Nd:YVO4) laser directed in-situ microfabrication technique for cell patterning is presented. A platform is designed uniquely to achieve laser ablation. The platform is comprised of thin gold coating over a glass surface that functions as a thermal transducer and is over-layered by a cell repellant polymer layer. Micropatterns are engraved on the platform, subsequently exposing specific cell adhesive micro-domains by ablating the gold-polymer coating photothermally. Experimental results indicate that the proposed approach is applicable under culture conditions, viable toward cells, and has a higher engraving speed. Possible uses in arraying isolated single cells on the platform are also shown. Additionally, based on those micro-patterns, dynamic cellular morphological changes and migrational speed in response to geometrical barriers are studied to demonstrate the potential applications of the proposed approach. Our results further demonstrate that cells in narrower geometry had elongated shapes and higher migrational speed than those in wider geometry. Importantly, the proposed approach will provide a valuable reference for efforts to study single cell dynamics and cellular migration related processes for areas such as cell division, wound healing, and cancer invasion. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
In situ laser micropatterning of proteins for dynamically arranging living cells
(2013)
Okano, Kazunori
;
Matsui, Ai
;
Maezawa, Yasuyo
;
Hee, Ping-Yu
;
Matsubara, Mie
This study shows the modification of the surface of polymer-layered glass substrates to form biofunctional micropatterns through femtosecond laser ablation in an aqueous solution. Domains of micrometer size on a substrate can be selectively converted from proteinphobic (resistant to protein adsorption) to proteinphilic, allowing patterning of protein features under physiological aqueous conditions. When femtosecond laser pulses (800 nm, 1 kHz, 200-500 nJ per pulse) were focused on and scanned on the substrate, which was glass covered with the proteinphobic polymer 2-methacryloyloxyethylphosphorylcholine (MPC), the surface became proteinphilic. Surface analysis by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveals that the laser ablates the MPC polymer. Extracellular matrix (ECM) proteins were bound to the laser-ablated surface by physisorption. Since femtosecond laser ablation is induced under physiological aqueous conditions, this approach can form micropatterns of functional ECM proteins with minimal damage. This method was applied to pattern collagen, laminin, and gelatin on the substrate. Removal of an ECM protein from the substrate followed by replacement with another ECM protein was achieved on demand at a specific location and time by the same laser ablation method. Living cells adhered to the fabricated domains where ECM proteins were arranged. The modification of patterning during cell culture was used to control cell migration and form arrays of different cells.
Label-free characterization of collagen fibers in cancerous esophagus tissues using ratiometric nonlinear optical microscopy
(1970-01-01)
Chen, Wei-Chung
;
Chen, Yu-Jen
;
Lin, Shih-Ting
;
Hung, Wei-Han
;
Chan, Ming-Che
A quantitative analytical method to discriminate among the various types of cancerous esophagus tissue is essential for accurate cancer staging. This paper reports on the use of ratiometric nonlinear optical microscopy to reveal the ratio of two-photon excited fluorescence (TPEF) to second harmonic generation (SHG) and forward to backward (F/B) SHG from single collagen fibers only in submucosa of esophageal squamous cell carcinoma. This makes it possible to accurately differentiate among the four stages of esophageal cancer, providing results that are in good agreement with histopathology. Furthermore, it is confirmed by polarization-dependent SHG that the varied SHG response in esophageal cancer tissues is mainly from the shrinkage in diameter of collagen fibers instead of the collagen triple helixes altered by cancer cells. Based on the results of TPEF/SHG and F/B SHG ratio, they can cooperatively improve the precision of diagnostics on esophageal cancer and could be transferred to other types of cancer diseases with changed collagen fibers. Impact statement The issue of classifying esophageal cancer at various developmental stages is crucial for determining the optimized treatment protocol for the patients, as well as the prognosis. Precision improvement in staging esophageal cancer keeps seeking quantitative and analytical imaging methods that could augment histopathological techniques. In this work, we used nonlinear optical microscopy for ratiometric analysis on the intrinsic signal of two-photon excited fluorescence (TPEF) and second harmonic generation (SHG) from single collagen fibers only in submucosa of esophageal squamous cell carcinoma (ESCC). The blind tests of TPEF/SHG and forward (F)/backward (B) SHG were demonstrated to compare with the histology conclusion. The discussion of sensitivity and specificity was provided via statistical comparison between the four stages of esophageal cancer. To the best of our knowledge, this is the first study of using these two ratios in combination for staging ESCC.
Laser-Assisted Control of Protein Adsorption for Dynamically Arranging Viable Cells
(2013)
Okano, Kazunori
;
Matsui, Ai
;
Maezawa, Yasuyo
;
Matsubara, Mie
;
Hosokawa, Yoichiroh
Polymers and proteins covering glass surface were ablated by femtosecond laser pulses under physiological aqueous condition. The prepared micropatterns of proteins were confirmed by fluorescence imaging and their cell adhesion characteristics was demonstrated.
Metabolic variation of HeLa cells migrating on microfabricated cytophilic channels studied by the fluorescence lifetime of NADH
(2014-01-01)
Deka, Gitanjal
;
Okano, Kazunori
;
Masuhara, Hiroshi
;
Li, Yaw-Kuen
;
Kao, Fu-Jen
We report a novel method for studying cellular migration in vitro. Cytophilic microdomains were formed on a cytophobic substrate by laser ablation. HeLa cells were grown on those domains until confluence, and then channels were formed to guide cellular migration. Two-photon excitation fluorescence-lifetime imaging of NADH revealed metabolic variation among migrating and nonmigrating cells.
Multiphoton microscopy for skin wound healing study in terms of cellular metabolism and collagen regeneration
(2014-01-01)
Deka, Gitanjal
;
Okano, Kazunori
;
Wu, Wei-Wen
;
Kao, Fu-Jen
;
前瞻跨領域基礎科學中心
Multiphoton microscopy was employed to study normal skin wound healing in live rats noninvasively. Wound healing is a process involving series of biochemical events. This study evaluates the regeneration of collagen and change in cellular metabolic activity during wound healing in rats, with second harmonic generation (SHG) and fluorescence lifetime imaging microscopy (FLIM), respectively. In eukaryotic cells ATP is the molecule that holds the energy for cellular functioning. Whereas NADH is an electron donor in the metabolic pathways, required to generate ATP. Fluorescence lifetime of NADH free to protein bound ratio was evaluated to determine the relative metabolic activity. The FLIM data were acquired by a TCSPC system using SPCM software and analyzed by SPCImage software. Additionally, polarization resolved SHG signals were also collected to observe the changes in optical birefringence and hence the anisotropy of regenerated collagens from rat wound biopsy samples. Mat lab programming was used to process the data to construct the anisotropy images. Results indicated that, cells involved in healing had higher metabolic activity during the first week of healing, which decreases gradually and become equivalent to normal skin upon healing completes. A net degradation of collagen during the inflammatory phase and net regeneration starting from day 5 were observed in terms of SHG signal intensity change. Polarization resolved SHG imaging of the wound biopsy sample indicates higher value of anisotropy in proliferative phase, from day 4th to 8th, of wound formation; however the anisotropy decreases upon healing.