Browsing by Author "Chang, Chun-Wei"

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Anti-influenza drug discovery
(2007-07-01)
Hsu, John T.-A.
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Hsieh, Hsing-Pang
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Hung, Hui-Chen
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Ju, Yi Wei
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Tseng, Sung-Nain
Anti-Influenza Drug Discovery: Structure-Activity Relationship and Mechanistic Insight into Novel Angelicin Derivatives
(2010-02-25)
Yeh, Jiann-Yih
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Coumar, Mohane Selvaraj
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Horng, Jim-Tong
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Shiao, Hui-Yi
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Kuo, Fu-Ming
By using a cell-based high throughput screening campaign,a novel angelicin derivative 6a was identified to inhibit influenza A (H1N1) virus induced Cytopathic effect in Madin-Darby canine kidney cell culture in low micromolar range. Detailed structure-activity relationship studies of 6a revealed that the angelicin scaffold is essential for activity in pharmacophore B, while meta-substituted phenyl/2-thiophene rings are optimal ill pharmacophore A and C. The optimized lead 4-methyl-9-phenyl-8-(thiophene-2-carbonyl)-furo[2,3-h]chromen-2-one (8g, IC(50) = 70 nM) showed 64-fold enhanced activity compared to the high throughput screening (HTS) hit 6a. Also, 8g was found effective in case of influenza A (H3N2) and influenza B virus strains similar to approved anti-influenza drug zanamivir (4). Preliminary mechanistic studies suggest that these compounds act as anti-influenza agents by inhibiting ribonucleoprotein (RNP) complex associated activity and have the potential to be developed further, Which Could form the basis for developing additional defense against influenza pandemics.
Asymmetries in Porous Membranes: Fabrication of Anodic Aluminum Oxide Membranes with Double-Sized Nanopores and Controlled Surface Properties
(2019-06-13)
Liu, Chih-Ting
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Lin, Yu-Liang
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Chu, Chien-Wei
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Chang, Chun-Wei
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Chiu, Yu-Jing
Recently, anodic aluminum oxide (AAO) membranes with ordered and monodispersed nanopores have attracted significant attention because the pore sizes and lengths of the AAO membranes can be systematically controlled by changing the anodization parameters. Asymmetries of geometry, wettability, charge, and polarity in nanoporous AAO membranes are now highly desired for applications such as drug delivery, membrane filtration, and catalysis. Although the asymmetries in AAO membranes have been widely studied, AAO membranes whose nanopores simultaneously possess more than two asymmetric properties still need to be developed. In this work, we present a simple method to fabricate asymmetric AAO membranes by combining the post-treatments with the three-step anodization method. The asymmetries of the AAO membranes simultaneously possessing larger nanopores with higher hydrophobicity and smaller nanopores with lower hydrophobicity are characterized by scanning electron microscopy, water contact angle measurements, and energy-dispersive X-ray spectroscopy. Using the asymmetric AAO membranes, nanowires of polystyrene and poly(styreneb/ock-dimethylsiloxane) with double-sized diameters are also fabricated via the melt and solvent wetting methods, exhibiting that the AAO membranes with double-sized diameters can be used as the templates for generating double-sized polymer nanowires.
Bamboo-like nanostructures prepared using template-based wetting methods: Molecular arrangements of polyimide and carbon tubes in cylindrical nanopores
(2019-12-17)
Tu, Yi-Hsuan
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Liu, Chih-Ting
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Chu, Chien-Wei
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He, Hung-Chieh
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Chang, Chun-Wei
With excellent mechanical and physical properties, polyimides (PIs) possess diverse applications in different fields. PI-based materials can also be converted to carbon materials by high temperature carbonization processes. The fabrication and properties of PI-based nanomaterials and corresponding carbon nanomaterials, however, have been less investigated, especially the packing behaviors of the polymer chains. In this work, we study the fabrication and characterization of PI nanostructures using the solution wetting (SW) method and the solvent-annealing-induced nanowetting in templates (SAINT) method. Poly(amic acid) (PAA) tubes are first prepared using anodic aluminum oxide (AAO) membranes. After thermal imidization and carbonization processes, PI and carbon tubes can be obtained, respectively. Bamboo-like structures are also observed in the tubes, which can be attributed to the Marangoni effect induced by the gradient of the surface tensions during the solvent evaporation process. Moreover, the laser Raman micro-spectroscopy results show that the packing behaviors of the polymer chains in the nanostructures prepared by the SAINT method are better than those prepared by the SW method, indicating that the solvent annealing process can improve the chain packing while assisting the infiltration of polymer chains in the nanopores.
Blending Homopolymers for Controlling the Morphology Transitions of Block Copolymer Nanorods Confined in Cylindrical Nanopores
(2017-06-21)
Cheng, Ming-Hsiang
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Hsu, Yu-Chen
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Chang, Chun-Wei
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Ko, Hao-Wen
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Chung, Pei-Yun
The microphase separation of block copolymers in confined geometries has been widely investigated over the last few decades. The controllability and versatility of the confinement-induced morphologies, however, are still difficult to be achieved because of the limited experimental parameters in the process of fabricating the confined nanostructures. In this work, we study the morphology transitions of lamellae forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanorods confined in the nanopores of anodic aluminum oxide (AAO) templates. The nanorods are formed by solvent-assisted template wetting, and the morphologies are compared to those in the bulk state. By blending PS-b-PDMS with homopolystyrene (hPS), the morphologies of the nanorods can be controlled because of the changes of the effective volume fractions. Special morphology transitions from concentric lamellar morphology, to multihelical morphology, and finally to spherical-like morphology are observed by increasing the weight ratios of hPS. hPS with different molecular weights is also applied to investigate the effect of hPS on the morphologies of the PS-b-PDMS/hPS blend nanostructures. The unusual morphologies are further confirmed by a selective removal process, which also generates nanochannels for possible refilling with functional materials.
Characterization of micro resistance welding with electro-thermal actuator for micro assembly - art. no. 68840G
(2008)
Chang, Chun-Wei
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Hsu, Wensyang
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機械工程學系
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Department of Mechanical Engineering
Optical MEMS devices rely on the micro assembly to achieve re-positioning, such as lifted up micro mirrors and lens and micro resistance welding benefits assembly of optical components. However, the characteristics of micro resistance welding are still unknown. The purpose of this study is to characterize micro resistance welding with electro-thermal actuator for micro assembly. In order to characterize influence of operation parameters on micro resistance welding, important parameters including contact pressure, contact resistance and electrical energy are calibrated. Further, welding strength provide robust join are also measured. The idea of resistance welding is based on generated heat by ohm's law to melt material. From measured results, contact resistance decreases with increasing contact pressure due to increasing contact area. The stronger welding strength can be achieved at a smaller initial contact resistance which means that a larger clamping force could enhance the welding strength. The maximum welding strength is 74.4 mu N at 2.7 Omega. Further, welding energy affects yield significantly. At high welding energy, between 1 to 10 J, the yield can reach 100%. The energy below 0.05 J would not generate adequate heat to weld structure.
Competition Between Effects of Pore Sizes and Annealing Solvents on the Morphology Manipulation of 3D Block Copolymer Nanostructures Using Anodic Aluminum Oxide Templates
(2016-06)
Chu, Chiang-Jui
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Chung, Pei-Yun
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Chu, Chien-Wei
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Cheng, Ming-Hsiang
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Chi, Mu-Huan
In this work, the morphologies of polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures using solvent-induced wetting in the nanopores of anodic aluminum oxide (AAO) templates are investigated. AAO templates with three different pore sizes (approximate to 200, approximate to 60, and approximate to 30 nm) are used in this work to differentiate the effect of confinement and annealing solvents. Different from the results by the traditional wetting methods, two major effects are identified in affecting the morphologies. At larger pore sizes, the morphologies of the nanostructures are mainly affected by the annealing solvent. At smaller pore sizes, however, the morphologies are mainly controlled by the confinement effect (pore sizes).
Controlled Assembly of Polymer-Tethered Gold Nanorods via a Rayleigh-Instability-Driven Transformation: Implications for Biomedical Applications
(2019-05-01)
Chiu, Tang-Yao
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Cheng, Ming-Hsiang
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Chang, Chun-Wei
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Ko, Hao-Wen
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Chen, Jiun-Tai
We study the assembly and morphology transformation of gold nanorods tethered with polystyrene ligands (AuNRs@PS). The AuNRs@PS nanotubes are first fabricated in the nanopores of anodic aluminum oxide (AAO) templates by the solution wetting method. When the samples are thermally annealed, the Rayleigh-instability-driven transformations of the nanostructures are triggered by the decrease of the interfacial energies between the nanotubes and the inner air cylinders. Four different morphologies are identified: nanotubes (I), undulated structures (II), Rayleigh-instability-induced structures (III), and nanorods (IV). The morphology diagrams of the AuNRs@PS structures using different thermal annealing temperatures and times are also made, showing that the morphology transformation rates are higher at higher annealing temperatures. This work has implications to be applied in different fields such as biomedical applications.
Controlled self-assemblies of polystyrene-block-polydimethylsiloxane micelles in cylindrical confinement through a micelle solution wetting method and Rayleigh-instability-driven transformation
(2017-08-28)
Ko, Hao-Wen
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Higuchi, Takeshi
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Chang, Chun-Wei
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Cheng, Ming-Hsiang
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Isono, Komei
Block copolymer micelles have been extensively discussed for many decades because of their applications, such as lithography and drug delivery. However, controlling the morphologies of nanostructure assembly using block copolymer micelles as building elements remains a great challenge. In this work, we developed a novel route to induce micelle assembly in confined geometries. Polystyrene-block-polydimethylsiloxane (PS-b-PDMS) micelle solutions were used to prepare micelle nanostructures, and the critical parameters affecting the morphologies were determined. Micelle nanorods, micelle nanospheres, and multi-component nanopeapods were prepared by wetting anodic aluminum oxide (AAO) templates with micelle solutions. Rayleigh-instability-driven transformation was discovered to play an important role in controlling the morphologies of the micelle nanostructures. This study not only proposes a versatile approach to preparing block copolymer micelle nanostructures, but it also provides deeper insight into the controlling factors of block copolymer micelle morphologies in cylindrical confinement.
Curved block copolymer nanodiscs: structure transformations in cylindrical nanopores using the nonsolvent-assisted template wetting method
(2019-11-07)
Lin, Yu-Liang
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Cheng, Ming-Hsiang
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Chang, Chun-Wei
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Chu, Chien-Wei
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Liu, Chih-Ting
In this work, we study the structure transformations of cylinder-forming polystyrene-block-polydimethylsiloxane (PS31k-b-PDMS14.5k) confined in cylindrical nanopores. PS-b-PDMS nanotubes, nanospheres, and curved nanodiscs are ingeniously prepared by a facile template wetting strategy using anodic aluminum oxide (AAO) templates. Quantitative analyses of the structure transformations from nanospheres to curved nanodiscs are also conducted, showing that the lengths of the curved nanodiscs can be controlled by adjusting the annealing temperature and time. Furthermore, the PDMS domains of the nanostructures can be selectively etched using HF solutions, generating porous PS nanostructures. This work not only offers versatile routes to prepare block copolymer nanostructures with controlled shapes but also provides a deeper understanding of the structure transformation of block copolymers in confined geometries.
Effect of Nonsolvent on the Formation of Polymer Nanomaterials in the Nanopores of Anodic Aluminum Oxide Templates
(1970-01-01)
Lee, Chih-Wei
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Wei, Tzu-Hui
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Chang, Chun-Wei
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Chen, Jiun-Tai
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應用化學系
"We study the effect of nonsolvent on the formation of polymer nanomaterials in the nanopores of porous templates. Water (nonsolvent) is added into a poly (methyl methacrylate) (PMMA) solution in dimethylformamide (DMF) confined in the nanopores of an anodic aluminum oxide (AAO) template. Water forms a wetting layer on the pore wall and causes the PMMA solution to be isolated in the center of the nanopore, resulting in the formation of PMMA nanospheres or nanorods after the solvent is evaporated. The formation of the polymer nanomaterials induced by nonsolvent is found to be driven by the Rayleigh-instability-type transformation. Without adding the nonsolvent, PMMA chains precipitate on the walls of the nanopores after the solvent is evaporated, and PMMA nanotubes are obtained."
Experimental investigation and characterization of micro resistance welding with an electro-thermal actuator
(2009-02-01)
Chang, Chun-Wei
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Yeh, Cheng-Chi
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Hsu, Wensyang
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機械工程學系
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Department of Mechanical Engineering
Resistance welding is a common scheme of assembly on the macro scale by pressing together two workpieces with current passing through them to generate joule heating at the contact region due to high contact resistance. However, micro assembly by resistance welding is seldom reported. Here, resistance welding with an electro-thermal microactuator to assemble micro Ni structures is experimentally investigated and characterized. The bent-beam electro-thermal microactuator is designed to provide the necessary displacements and pressing forces. The two-mask metal-based surface micromachining process is adopted to fabricate the micro Ni structures. The calibrated initial contact resistance is shown to decrease with increasing contact pressure. Furthermore, stronger welding strength is achieved at a smaller initial contact resistance, which indicates that a larger clamping force would enhance the welding strength as large as 3.09 MPa (74.4 mu N) at a contact resistance of 2.7 Omega here. The input welding energy is also found to be a critical factor. In our tests, when welding energy is below the threshold limit of 0.05 J, the welding trials all fail. For the energy between 0.05 J and 1 J, there is a transition from a lower yield of 33.3% to a higher yield of 58.3%. At high welding energy, between 1 and 10 J, 100% yield is achieved. With the demonstration and characterization of micro resistance welding by the electro-thermal microactuator, the scheme proposed here would be helpful in the automation of micro assembly.
Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application
(2009-07-01)
Sahoo, Kartika Chandra
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Lin, Men-Ku
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Chang, Edward-Yi
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Lu, Yi-Yao
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Chen, Chun-Chi
We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160-200 nm and a height of 140-150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen.
Fabrication of Core-Shell Polymer Nanospheres in the Nanopores of Anodic Aluminum Oxide Templates Using Polymer Blend Solutions
(2015-07-01)
Ko, Hao-Wen
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Chi, Mu-Huan
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Chang, Chun-Wei
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Chu, Chien-Wei
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Luo, Ke-Hsuan
Spherical core-shell structures have been widely investigated in recent years, and they can be used for various applications, such as drug delivery, biological labeling, and batteries. Although many methods have been developed to prepare core-shell structures, it is still a great challenge to fabricate core-shell structures in the nanoscale with well-controlled morphologies and sizes. In this work, we present a simple method to fabricate core-shell polymer nanospheres consisting of polystyrene (PS) cores and poly(methyl methacrylate) (PMMA) shells. The nanostructures are prepared by a solution-based template wetting method. After the nanopores of anodic aluminum oxide (AAO) templates are wetted sequentially by PS/PMMA blend solutions and water, the core-shell nanostructures can be formed. The formation process is related to the Rayleigh-instability-type transformation. Selective removal techniques are also used to confirm the morphologies of the core-shell nanostructures.
Fabrication of Multicomponent Polymer Nanostructures Containing PMMA Shells and Encapsulated PS Nanospheres in the Nanopores of Anodic Aluminum Oxide Templates
(2015-03-01)
Ko, Hao-Wen
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Chi, Mu-Huan
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Chang, Chun-Wei
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Su, Chun-Hsien
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Wei, Tzu-Hui
Multi-component polymer nanomaterials have attracted great attention because of their applications in areas such as biomedicine, tissue engineering, and organic solar cells. The precise control over the morphologies of multi-component polymer nanomaterials, however, is still a great challenge. In this work, the fabrication of poly(methyl methacrylate)(PMMA)/polystyrene (PS) nanostructures that contain PMMA shells and encapsulated PS nanospheres is studied. The nanostructures are prepared using a triple solution wetting method with anodic aluminum oxide (AAO) templates. The nanopores of the templates are wetted sequentially by PS solutions in dimethylformamide (DMF), PMMA solutions in acetic acid, and water. The compositions and morphologies of the nanostructures are controlled by the interactions between the polymers, solvents, and AAO walls. This work not only presents a feasible method to prepare multi-component polymer nanomaterials, but also leads to a better understanding of polymer-solvent interactions in confined geometries.
Fabrication of Polymer Nanopeapods in the Nanopores of Anodic Aluminum Oxide Templates Using a Double-Solution Wetting Method
(2014-08-12)
Chen, Jiun-Tai
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Wei, Tzu-Hui
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Chang, Chun-Wei
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Ko, Hao-Wen
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Chu, Chien-Wei
Although one-dimensional polymer nanomaterials can be prepared by approaches such as the template method, the control over the morphologies of one-dimensional polymer nanomaterials containing multiple components is still a great challenge. In this work, we investigate the formation of polymer nanopeapods using a novel double-solution wetting method in the nanopores of anodic aluminum oxide (AAO) templates. A polystyrene (PS) solution in dimethylformamide (DMF) is first introduced into the nanopores of the AAO templates. Then a second polymer solution of poly(methyl methacrylate) (PMMA) in acetic acid is infiltrated into the nanopores. Because of the stronger interaction between acetic acid and aluminum oxide than that between DMF and aluminum oxide, the PMMA solution preferentially wets the pore walls of the templates and the PS solution is isolated in the center of the nanopores. After the evaporation of the solvent, peapod-like PS/PMMA nanostructures are obtained, where the shell and the core are composed of PMMA and PS, respectively. The compositions of the polymer nanopeapods are confirmed by removing PS or PMMA selectively. The formation mechanism of the nanostructures is related to the Rayleigh-instability-type transformation and further studied by changing experimental parameters such as the polymer concentration or the polymer molecular weight. This work not only provides a simple approach to prepare multicomponent polymer nanomaterials with controlled morphologies and sizes, but also contributes to a deeper understanding of polymer solvent-interactions in confined geometries.
From Block Copolymer Nanotubes to Nanospheres: Nonsolvent-Induced Morphology Transformation Using Porous Templates
(2018-11-27)
Chang, Chun-Wei
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Tu, Yi-Hsuan
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Luo, Ke-Hsuan
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Chen, Jiun-Tai
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交大名義發表
Block copolymer nanostructures have attracted great attention because of the wide range of applications such as sensors and drug delivery. The fabrication of block copolymer nanostructures with controlled morphologies and sizes, however, is still challenging. Here, we study the fabrication of nanotubes and nanospheres of polystyrene-block-polybutadiene (PS-b-PBD) using anodic aluminum oxide (AAO) templates. When PS-b-PBD solutions in N-methyl-2-pyrrolidone are introduced into the nanopores of the AAO templates applying the traditional solution wetting method, PS-b-PBD nanotubes can be obtained. When PS-b-PBD solutions in the nanopores are in contact with a nonsolvent, acetic acid, PS-b-PBD nanospheres are formed. Two possible mechanisms are proposed to discuss the formation of the nonsolvent-driven morphology transformation, including the Rayleigh-instability-type transformation mechanism and the nucleation and growth mechanism. The effect of the polymer concentrations on the internal morphologies of the PS-b-PBD nanostructures is discussed; at higher concentrations, PS-b-PBD nanocapsules can also be prepared. Furthermore, core-shell PS-b-PBD/polymethylmethacrylate nanospheres can be fabricated using this strategy with polymer blend solutions. This work not only demonstrates a simple strategy to control the morphologies of block copolymer nanostructures but also deepens the understanding of the interactions between polymer solutions and solvents.
Hierarchical hybrid nanostructures: controlled assembly of polymer-encapsulated gold nanoparticles via a Rayleigh-instability-driven transformation under cylindrical confinement
(2016-01-01)
Ko, Hao-Wen
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Chang, Chun-Wei
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Chi, Mu-Huan
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Chu, Chien-Wei
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Cheng, Ming-Hsiang
We develop a novel route based on the solution wetting method using anodic aluminum oxide (AAO) templates to fabricate hierarchical hybrid nanostructures assembled from polystyrene-encapsulated gold nanoparticles (Au@PS NPs). Hybrid nanostructures including nanotubes and nanospheres can be reliably prepared, in which the spatial arrangement of the Au@PS NPs is determined by the pore diameters of the templates and the molecular weights of the thiol-ended polystyrene (PS-SH) ligands. In particular, the Rayleigh-instability-driven transformation plays a key role in the formation of the hybrid nanospheres.
InAlAs/InGaAs metamorphic high electron mobility transistor with Cu/Pt/Ti gate and Cu airbridges
(2007-05-01)
Chang, Chun-Wei
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Chen, Po-Chou
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Lee, Huang-Ming
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Chen, Szu-Hung
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Sahoo, Kartik Chandra
The use of a Cu/Pt/Ti Schottky contact structure and Cu-based airbridges for high-frequency metamorphic high electron mobility transistor (MHEMT) is successfully developed. The material characteristics of the Cu/Pt/Ti Schottky contact on i-InAlAs were studied. Judging from the results of the X-ray diffraction analysis, Auger electron spectroscopy, and transmission electron microscopy, the Cu/Pt/Ti Schottky contact structure on InAlAs was very stable after annealing at 350 degrees C. However, after 400 degrees C annealing, the reaction of copper with the layers underneath started to occur and formed the Cu4Ti phase. The Cu-metallized MHEMT using the proposed Cu/Pt/Ti T-gate structure and Cu-based airbridges has a saturated drain current of 673 mA/mm and a maximum transconductance of 750 mS/mm. The gate to drain breakdown voltage measured was 14.5 V at a gate reverse current of -1 mA/mm. The device also demonstrated a cutoff frequency F-t of 90 GHz and a maximum frequency of oscillation F-max of 165 GHz. An MHEMT with a Au/Pt/Ti gate was fabricated and compared with an MHEMT fabricated with the proposed Cu/Pt/Ti gate. These two kinds of MHEMTs showed similar F-t and F-max. These results demonstrate that the Cu/Pt/Ti T-gate and Cu-based airbridges can be used for MHEMT fabrication with excellent electrical characteristics.
Mechanism of microstructure evolution for the Cu/Ta/GaAs structure after thermal annealing
(2007-04-01)
Chang, Chun-Wei
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Lee, Huang-Ming
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Chen, Chang-You
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Chang, Li
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Chang, Edward Y.
The diffusion behavior and microstructure evolution of Cu/Ta/GaAs multilayers after thermal annealing are investigated and the mechanism is proposed. A thin 30 nm tantalum layer was sputtered as a diffusion barrier to block Ga and As diffusion into the Cu layer. From the results of sheet resistance measurement, X-ray diffraction analysis, Auger electron spectroscopy and transmission electron microscopy, the Cu/Ta films on GaAs were found to be very stable up to 500 degrees C without Cu migration into GaAs. After annealing al 550 degrees C, the interfacial mixing of Ta with GaAs substrate occurred, resulting in the formation of TaAs2, and the diffusion of Ga through the Ta layer formed the Cu3Ga phase at the Cu/Ta interface. After annealing at 600 degrees C, the reaction of GaAs with Ta and Cu formed TaAs and Cu3Ga owing to Ga migration and interfacial instability.