Browsing by Author "Chen, Guan-Yu"

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A COMBINED PROCESS OF SILICON SHADOW MASKING AND INKJET PRINTING (SSMP) FOR MAKING GRAPHENE OXIDE AND REDUCED GRAPHENE OXIDE MICROSTRUCTURES FOR SELECTIVE CELL CULTURING APPLICATIONS
(2019-01-01)
Kang, Che-Hao
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Fu, Yu-Min
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Kao, Chin-Chuan
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Yang, Jia-Wei
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Tseng, Ming-Liang
This paper demonstrates a combined process of silicon shadow masking and inkjet printing (SSMP) to fabricate graphene oxide (GO) and reduced graphene oxide (rGO) line features with a width ranging from 20 to 70 mu m on varieties of substrates, such as PDMS, SiO2 , Kapton, etc. for selectively cell (RPE and PC-12 cells) culturing applications. The rGO with an electrical resistance of 33.48k Omega/ is characterized via a printed four point resistivity measurement structure. Owing to the characteristics of low chemical usage, low process temperature and complexity, and high fault tolerance of inkjet printers, the process technique has shown its potential for biomedical applications in terms of flexible cell culturing platform fabrication.
A Forward Collision Avoidance System Adopting Multi-feature Vehicle Detection
(2014-01-01)
Chen, Guan-Yu
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Shen, Po-Chun
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Cho, Chao-Yi
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Vinay, M. S.
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Guo, Jiun-In
This paper presents a vehicle collision avoidance method and it is associated with the exploitation of multiple features based on the AdaBoost classifier result. The proposed system will enhance the precision rate and accuracy of vehicle detection from 72% to 96% using an AdaBoost detection method extracting multiple features in vehicle detection and false alarms are reduced.
A Versatile Method to Enhance the Operational Current of Air-Stable Organic Gas Sensor for Monitoring of Breath Ammonia in Hemodialysis Patients
(2019-04-01)
Yu, Shang-Yu
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Tung, Tin-Wei
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Yang, Hong-Yu
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Chen, Guan-Yu
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Shih, Che-Chi
Point-of-care (POC) application for monitoring of breath ammonia (BA) in hemodialysis (HD) patients has emerged as a promising noninvasive health monitoring approach. In this context, many organic gas sensors have been reported for BA detection. However, one of the major challenges for its integration with affordable household POC application is to achieve stable performance for accuracy and high operational current at low voltage for low-cost read-out circuitry. Herein, we exploited the stability of the Donor Acceptor polymer on the cylindrical nanopore structure to realize the sensors with a high sensitivity and stability. Then, we proposed a double active layer (DL) strategy that exploits an ultrathin layer of Poly(3-hexylthiophene-2,5-diyl) (P3HT) to serve as a work function buffer to enhance the operational current. The DL sensor exhibits a sustainable operational current of microampere level and a stable sensing response even with the presence of P3HT layer. This effect is carefully examined with different aspects, including vertical composition profile of DL configuration, lifetime testing on different sensing layer, morphological analysis, and the versatility of the DL strategy. Finally, we utilize the DL sensor to conduct a tracing of BA concentration in two HD patients before and after HD, and correlate it with the blood urea nitrogen (BUN) levels. A good correlation coefficient of 0.96 is achieved. Moreover, the feasibility of DL sensor integrated into a low-cost circuitry was also verified. The results demonstrate the potential of this DL strategy to be used to integrate organic sensor for affordable household POC devices.
Achieving highly saturated single-color and high color-rendering-index white light-emitting electrochemical cells by CsPbX3 perovskite color conversion layers
(2018-12-21)
Wang, Cheng-Ming
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Su, Yong-Ming
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Shih, Ting-An
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Chen, Guan-Yu
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Chen, Yan-Zhi
Solid-state light-emitting electrochemical cells (LECs) have been thought to be applicable for display and lighting due to their advantages such as simple device architecture, low-voltage operation and compatibility with inert cathode metals. Among the emissive materials of LECs, ionic transition metal complexes (iTMCs) exhibit relatively higher emission efficiency but they show relatively broader emission spectra, resulting in lower color saturation for display application. Here, we demonstrated that by integrating perovskite-based color conversion layers (CCLs) with blue iTMC-LECs, highly saturated green, yellow, red and deep-red and high color-rendering-index (CRI) white LECs can be obtained. The Commission Internationale de l'E'clairage (CIE) 1931 coordinates of the highly saturated single-color LECs are almost on the boundary of the National Television System Committee (NTSC) color gamut, showing their potential application in display. By mixing perovskites of different colors at an appropriate ratio in the CCLs, the white LECs show a CRI >90, which is among the highest reported values, and a correlated color temperature of 2649 K. Hence the proposed technique can also be one of the good candidates for lighting applications. In addition, both the highly saturated single-color and white LECs still exhibit efficient emission for display and lighting applications.
An Inkjet Printing Technique for Scalable Microfabrication of Graphene-Based Sensor Components
(2020-01-01)
Fu, Yu-Min
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Chou, Meng-Chuin
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Kang, Che-Hao
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Cheng, Yu-Ting
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Wu, Pu-Wei
This paper presents a versatile and precise graphene patterning technique using the combined process of masking and inkjet printing. A graphene-based structure is fabricated by first defining the structural pattern and position using a masking mold, which can be either electroplated copper or deep reactive ion etching (DRIE) silicon shadow mask, followed by inkjet deposition of graphene ink and lift-off. The hybrid technique can realize high-fidelity, high-resolution graphene-based microstructures including free-standing and cantilever beams, four-point resistive measurement structures, and piezoresistive sensing elements with a minimum line width of similar to 20 mu m. Moreover, this method can facilitate the micropatterning of graphene oxide (GO) and reduced graphene oxide (rGO) on substrates such as polydimethylsiloxane (PDMS) and SiO2/Si for selective cell culturing applications. Owing to the characteristics of low chemical usage, low process temperature and complexity, and high fiexibility and fault tolerance of inkjet printing, this technique demonstrates compelling potential for a variety of biomedical applications.
Annealing treatment improves the morphology and performance of photovoltaic devices prepared from thieno[3,4-c]pyrrole-4,6-dione-based donor/acceptor conjugated polymers and CdSe nanostructures
(2011-06-01)
Kuo, Chih-Yin
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Su, Ming-Shi
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Chen, Guan-Yu
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Ku, Ching-Shun
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Lee, Hsin-Yi
We have prepared photovoltaic devices based on blend films of CdSe tetrapods and the donor/acceptor conjugated polymer PDTTTPD, which comprises 2,5-di(thiophen-2-yl) thieno[3,2-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units. The AM1.5 power conversion efficiency (PCE) of a photovoltaic device containing a PDTTTPD/CdSe tetrapod blend (1:9, w/w) that had experienced thermal annealing (130 degrees C, 20 min) was three times greater than that of the corresponding device incorporating the as-prepared PDTTTPD/CdSe tetrapod blend (2.9% vs. 1.0%). Synchrotron X-ray reflectivity revealed that annealing (i.e., removal of pyridine ligands from the surfaces of the CdSe tetrapods) caused the thickness of the PDTTTPD/CdSe tetrapod blend film to decrease (and its average density to increase) relative to that of the as-prepared blend film. Transmission electron microscopy and atomic force microscopy revealed that thermal annealing enhanced the degree of aggregation of the CdSe tetrapods and induced denser morphologies, leading to substantially increased charge transport, which enhanced the PCE of the device.
Cationic Ir-III Emitters with Near-Infrared Emission Beyond 800 nm and Their Use in Light-Emitting Electrochemical Cells
(2019-04-11)
Chen, Guan-Yu
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Chang, Bo-Ren
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Shih, Ting-An
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Lin, Chien-Hsiang
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Lo, Chieh-Liang
Solid-state near-infrared (NIR) light-emitting devices have recently received considerable attention as MR light sources that can penetrate deep into human tissue and are suitable for bioimaging and labeling. in addition, solidstate NIR light-emitting electrochemical cells (LECs) have shown several promising advantages over NIR organic light-emitting devices (OLEDs). However, among the reported NIR LECs based on ionic transition-metal complexes (iTMCs), there is currently no iridium-based LEC that displays NIR electroluminescence (EL) peaks near to or above 800 nm. In this report we demonstrate a simple method for adjusting the energy gap between the highest-occupied molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO) of iridium-based iTMCs to generate NIR emission. We describe a series of novel ionic iridium complexes with very small energy gaps, namely NIR1-NIR6, in which 2,3-diphenylbenzo[g]quinoxaline moieties mainly take charge of the HOMO energy levels and 2,2'-biquinoline, 2-(quinolin-2-yl)quinazoline, and 2,2'-bibenzo[d]thiazole moieties mainly control the LUMO energy levels. All the complexes exhibited NIR phosphorescence, with emission maxima up to 850 nm, and have been applied as components in LECs, showing a maximum external quantum efficiency (EQE) of 0.05% in the EL devices. By using a host-guest emissive system, with the iridium complex RED as the host and the complex NIR3 or NIR6 as guest, the highest EQE of the LECs can be further enhanced to above 0.1%.
COMPARISON OF CUTOFFS BETWEEN LAZY WALKS AND MARKOVIAN SEMIGROUPS
(2013-12-01)
Chen, Guan-Yu
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Saloff-Coste, Laurent
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應用數學系
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Department of Applied Mathematics
We make a connection between the continuous time and lazy discrete time Markov chains through the comparison of cutoffs and mixing time in total variation distance. For illustration, we consider finite birth and death chains and provide a criterion on cutoffs using eigenvalues of the transition matrix.
Computing cutoff times of birth and death chains
(2015-07-18)
Chen, Guan-Yu
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Saloff-Coste, Laurent
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應用數學系
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Department of Applied Mathematics
Earlier work by Diaconis and Saloff-Coste gives a spectral criterion for a maximum separation cutoff to occur for birth and death chains. Ding, Lubetzky and Peres gave a related criterion for a maximum total variation cutoff to occur in the same setting. Here, we provide complementary results which allow us to compute the cutoff times and windows in a variety of examples.
Crystalline conjugated polymer containing fused 2,5-di(thiophen-2-yl)thieno[2,3-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units for bulk heterojunction solar cells
(2011-01-01)
Chen, Guan-Yu
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Cheng, Yu-Hsin
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Chou, Yi-Jen
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Su, Ming-Shin
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Chen, Chia-Min
A new conjugated polymer, PDTTTPD, comprising 2,5-di-(thiophen-2-yl)thieno[3,2-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units, exhibits high crystallinity and excellent thermal stability. A device incorporating PDTTTPD and [6,6]-phenyl-C(71)-butyric acid methyl ester (1 : 1, w/w) exhibited a power conversion efficiency of 5.1%.
Crystalline conjugated polymer containing fused 2,5-di(thiophen-2-yl)thieno[2,3-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units for bulk heterojunction solar cells
(2011-01-01)
Chen, Guan-Yu
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Cheng, Yu-Hsin
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Chou, Yi-Jen
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Su, Ming-Shin
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Chen, Chia-Min
A new conjugated polymer, PDTTTPD, comprising 2,5-di-(thiophen-2-yl)thieno[3,2-b]thiophene and thieno[3,4-c]pyrrole-4,6-dione units, exhibits high crystallinity and excellent thermal stability. A device incorporating PDTTTPD and [6,6]-phenyl-C(71)-butyric acid methyl ester (1 : 1, w/w) exhibited a power conversion efficiency of 5.1%.
Current Conjugation Methods for Immunosensors
(2018-05-01)
Li, Zeyang
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Chen, Guan-Yu
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生物科技學系
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生醫工程研究所
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Department of Biological Science and Technology
Recent advances in the development of immunosensors using polymeric nanomaterials and nanoparticles have enabled a wide range of new functions and applications in diagnostic and prognostic research. One fundamental challenge that all immunosensors must overcome is to provide the specificity of target molecular recognition by immobilizing antibodies, antibody fragments, and/or other peptides or oligonucleotide molecules that are capable of antigen recognition on a compact device surface. This review presents progress in the application of immobilization strategies including the classical adsorption process, affinity attachment, random cross-linking and specific covalent linking. The choice of immobilization methods and its impact on biosensor performance in terms of capture molecule loading, orientation, stability and capture efficiency are also discussed in this review.
Cutoffs for product chains
(2018-11-01)
Chen, Guan-Yu
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Kumagai, Takashi
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應用數學系
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Department of Applied Mathematics
We consider products of ergodic Markov chains and discuss their cutoffs in total variation. Our framework is general in that rates to pick up coordinates are not necessary equal, and different coordinates may correspond to distinct chains. We give necessary and sufficient conditions for cutoffs of product chains in terms of those of coordinate chains under certain conditions. A comparison of mixing times between the product chain and its coordinate chains is made in detail as well. Examples are given to show that neither cutoffs for product chains nor for coordinate chains imply others in general. (C) 2018 Elsevier B.V. All rights reserved.
Dimmable sunlight-like organic light emitting diodes with ultra-high color rendering index
(2016-05)
Wu, Jin-Han
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Chi, Chien-An
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Chiang, Chang-Lin
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Chen, Guan-Yu
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Lin, Yi-Ping
We propose novel dimmable sunlight-like white organic light-emitting diodes that were fabricated using three luminophores to form an emitting spectrum similar to black body radiation at 2250 K with ultra-high color rendering index (CRI) value of 91, which nearly remained the constant at various luminance values ranging from 100 to more than 2500 cd/m(2) at Commission Internationale de l\'Eclairage chromaticity coordinates of (0.51, 0.41). Introducing charge modification layers suppressed the energy transfer between the emitting material layers and increased the probability of carrier recombination. Moreover, we reveal that covering long-wavelength ranges played a vital role in achieving high CRI values; the CRI values of a spectrum artificially shifted toward a long-wavelength direction (from 610 to 620 nm) remained constant, whereas those of a spectrum shifted toward a short-wavelength direction (from 610 to 600 nm) dropped to 79. (C) 2016 Elsevier B.V. All rights reserved.
Dynamic Local Contrast Enhancement for Advanced Driver Assistance System in Harsh Environments
(2014-01-01)
Hsu, Sheng-Wei
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Chen, Guan-Yu
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Shen, Po-Chun
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Cho, Chao-Yi
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Guo, Jiun-In
This paper presents a Dynamic Local Contrast Enhancement (DLCE) method, which can strengthen the image quality in most of inclement weather conditions. This improves unnatural image over-enhancement, reduce noise, make image more saturated, and can be applied on foggy day and night. DLCE reaches 50 fps D1 resolution and 120 fps CIF resolution on ATOM 1.6GHz in TREK-668 embedded platform.
Effects of tuning the applied voltage pulse periods on the electroluminescence spectra of host-guest white light-emitting electrochemical cells
(2018-07-21)
Wu, Ming-Lun
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Chen, Guan-Yu
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Shih, Ting-An
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Lu, Chin-Wei
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Su, Hai-Ching
Solid-state white light-emitting electrochemical cells (LECs) are potential candidates in solid-state lighting due to their promising advantages of simple device structure, low-voltage operation and compatibility with inert cathode metals. Adjusting the correlated color temperature (CCT) of background illumination is highly desired for modern smart lighting systems. In this work, a novel technique to tune the CCT of electroluminescence (EL) from white LECs is proposed. Color tuning is based on adjusting the applied voltage pulse period on the host-guest white LECs and the working mechanism is illustrated. A shorter voltage pulse period is insufficient to completely charge the capacitive LEC device and thus the effective voltage applied on the device is lower. Since the host-guest energy level offsets favor carrier trapping, a lower effective applied voltage results in a more pronounced guest emission, rendering redder white EL with a lower CCT. On the other hand, a longer voltage pulse period facilitates more complete charging and the effective voltage applied on the white LEC is higher. A higher bias facilitates direct exciton formation on the host molecule and subsequent partial host-guest energy transfer generates bluer white EL with a higher CCT. By tuning the voltage pulse period from 0.2 to 20 ms, the CCT of EL resulting from white LECs ranges from 2482 to 5723 K. The CCT tuning range is sufficient for general lighting applications. In contrast to color tuning of white LECs under constant-voltage driving, in which >10 x brightness enhancement is accompanied by higher-CCT white EL, the discharging halfperiod in pulse-voltage driving provides relaxation time to turn off the device and reduces the average brightness of the white LECs driven under a longer voltage pulse period. Therefore, similar brightness can be achieved for white EL with different CCTs. No additional optical filtering device is needed for this novel color tuning technique and it has potential for use in solid-state lighting.
Efficient and Saturated Red Light-Emitting Electrochemical Cells Based on Cationic Iridium(III) Complexes with EQE up to 9.4 %
(1970-01-01)
Yu, Guang-Xiang
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Lin, Chien-Hsiang
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Liu, You-Xuan
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Yi, Rong-Huei
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Chen, Guan-Yu
Solid-state light-emitting electrochemical cells (LECs) have several advantages, such as low-voltage operation, compatibility with inert metal electrodes, large-area flexible substrates, and simple solution-processable device architectures. However, most of the studies on saturated red LECs show low or moderate device efficiencies (external quantum efficiency (EQE) <3.3 %). In this work, we demonstrate a series of five red-emitting cationic iridium complexes (RED1--RED5) with 2,2 '-biquinoline ligands and test their electroluminescence (EL) characteristics in LECs. The Commission Internationale de l ' Eclairage (CIE) 1931 coordinates for the LECs based on these complexes are all beyond the National Television System Committee (NTSC) red standard point (0.67, 0.33). The maximal EQE of the neat-film RED1-based LECs reaches 7.4 %. The reddest complex, RED3, is doped in the blue-emitting host complex, BG, to fabricate host-guest LECs. The maximal EQE of the host-guest LECs (1 wt % complex RED3) reaches 9.4 %, which is among the highest reported for the saturated red LECs.
Enhanced Cell Capture on Functionalized Graphene Oxide Nanosheets through Oxygen Clustering
(2017-02)
Bardhan, Neelkanth M.
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Kumar, Priyank V.
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Li, Zeyang
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Ploegh, Hidde L.
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Grossman, Jeffrey C.
With the global rise in incidence of cancer and infectious diseases, there is a need for the development of techniques to diagnose, treat, and monitor these conditions. The ability to efficiently capture and isolate cells and other bio-molecules from peripheral whole blood for downstream analyses is a necessary requirement. Graphene oxide (GO) is an attractive template nanomaterial for such biosensing applications. Favorable properties include its two-dimensional architecture and wide range of functionalization chemistries, offering significant potential to tailor affinity toward aromatic functional groups expressed in biomolecules of interest. However, a limitation of current techniques is that as-synthesized GO nanosheets are used directly in sensing applications, and the benefits of their structural modification on the device performance have remained unexplored. Here, we report a microfluidic-free, sensitive, planar device on treated GO substrates to enable quick and efficient capture of Class-II MHC-positive cells from murine whole blood. We achieve this by using a mild thermal annealing treatment on the GO substrates, which drives a phase transformation through oxygen clustering. Using a combination of experimental observations and MD simulations, we demonstrate that this process leads to improved reactivity and density of functionalization of cell capture agents, resulting in an enhanced cell capture efficiency of 92 +/- 7% at room temperature, almost double the efficiency afforded by devices made using as-synthesized GO (54 +/- 3%). Our work highlights a scalable, cost-effective, general approach to improve the functionalization of GO, which creates diverse opportunities for various next-generation device applications.
Enhanced Osteogenic Differentiation of Stem Cells on Phase-Engineered Graphene Oxide
(2018-04-18)
Yang, Jia-Wei
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Hsieh, Kuan Yu
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Kumar, Priyank V.
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Cheng, Sheng-Jen
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Lin, You-Rong
Graphene oxide (GO) has attracted significant interest as a template material for multiple applications due to its two-dimensional nature and established functionalization chemistries. However, for applications toward stem cell culture and differentiation, GO is often reduced to form reduced graphene oxide, resulting in a loss of oxygen content. Here, we induce a phase transformation in GO and demonstrate its benefits for enhanced stem cell culture and differentiation while conserving the oxygen content. The transformation results in the clustering of oxygen atoms on the GO surface, which greatly improves its ability toward substance adherence and results in enhanced differentiation of human mesenchymal stem cells toward the osteogenic lineage. Moreover, the conjugating ability of modified GO strengthened, which was examined by auxiliary osteogenic growth peptide conjugation. Overall, our work demonstrates GO's potential for stem cell applications while maintaining its oxygen content, which could enable further functionalization and fabrication of novel nano-biointerfaces.
Graphene Oxide-Based Biosensors for Liquid Biopsies in Cancer Diagnosis
(2019-12-01)
Chen, Shiue-Luen
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Chen, Chong-You
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Hsieh, Jason Chia-Hsun
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Yu, Zih-Yu
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Cheng, Sheng-Jen
Liquid biopsies use blood or urine as test samples, which are able to be continuously collected in a non-invasive manner. The analysis of cancer-related biomarkers such as circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), microRNA, and exosomes provides important information in early cancer diagnosis, tumor metastasis detection, and postoperative recurrence monitoring assist with clinical diagnosis. However, low concentrations of some tumor markers, such as CTCs, ctDNA, and microRNA, in the blood limit its applications in clinical detection and analysis. Nanomaterials based on graphene oxide have good physicochemical properties and are now widely used in biomedical detection technologies. These materials have properties including good hydrophilicity, mechanical flexibility, electrical conductivity, biocompatibility, and optical performance. Moreover, utilizing graphene oxide as a biosensor interface has effectively improved the sensitivity and specificity of biosensors for cancer detection. In this review, we discuss various cancer detection technologies regarding graphene oxide and discuss the prospects and challenges of this technology.