Browsing by Author "Chang, Po-Yi"

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Laser Polymer Tattooing: A Versatile Method for Permanent Marking on Polymer Surfaces
(2019-12-01)
Chang, Po-Yi
;
Bruntz, Adele
;
Vidal, Loic
;
Vetter, Pierre-Alain
;
Roudot, Patrick
A versatile and efficient method for the permanent marking of polymer surfaces that combines inkjet deposition and near-infrared (NIR) laser curing is investigated. The NIR laser treatment forces the ink particles to migrate into the upper layers of the polymer. This results in the fixation of a permanent grayscale image that can be applied to various polymers, such as polypropylene, which is widely used in industry but still difficult to mark. The physiochemical processes induced by laser curing are investigated by electronic and optical microscopy. The dependence of the thickness of the deposited ink and the laser power on the contrast of marking are also studied. A mechanism implying fast laser-induced melting of the polymer surface followed by displacement of carbon nanoparticles by convection is proposed. Finally, a comparison of the aging properties of samples prepared by this process and standard UV ink is proposed to illustrate the interesting nature of this new polymer marking process. Integrating the ink under the surface of the polymer, as in a skin tattooing procedure, by laser curing is an efficient way to generate permanent images on polymer surfaces.
Near-Infrared Laser-Annealed IZO Flexible Device as a Sensitive H2S Sensor at Room Temperature
(2020-06-03)
Chang, Po-Yi
;
Lin, Ching-Fu
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Rouphael, Samer El Khoury
;
Huang, Ting-Hsuan
;
Wu, Chang-Mao
A metal-oxide material (indium zinc oxide [IZO]) device with near-infrared (NIR) laser annealing was demonstrated on both glass and bendable plastic substrates (polycarbonate, polyethylene, and polyethylene terephthalate). After only 60 s, the sheet resistance of IZO films annealed with a laser was comparable to that of thermal-annealed devices at temperatures in the range of 200-300 degrees C (1 h). XPS, ATR, and AFM were used to investigate the changes in the sheet resistance and correlate them to the composition and morphology of the thin film. Finally, the NIR-laser-annealed IZO films were demonstrated to be capable of detecting changes in humidity and serving as a highly sensitive gas sensor of hydrogen sulfide (in ppb concentration), with room-temperature operation on a bendable substrate.
On substrate behavior of flexible displays subjected to torque
(2011-08-01)
Lee, Y. C.
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Liu, T. S.
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Chang, Po-Yi
;
Ku, Yi-Sha
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機械工程學系
In contrast to liquid-crystal displays (LCDs) and light-emitting-diode (LED) displays, flexible displays allow deformation. Therefore, it is worth studying the deformation of substrates in flexible displays. In this work, an analytical derivation is carried out for the torsion behavior of flexible substrates. Comparisons are made between deflection results of linear and non-linear elasticity analyses for substrates subject to four corner forces and torque, respectively. They show that when deflection becomes large, torques or forces needed for unit deformation also increase. Simulation results also show that when the substrate aspect ratio of length/width in display sizes increases, displays are easier to deform under torsion. In addition, polyethylene terephthalate (PET) substrates subject to torque are compared with polyethylene naphthalate (PFN) substrates. Finally, in experiments a fringe-reflection method and a four-step phase-shifting technique were carried out to validate the proposed non-linear model.
Vertical organic transistors withstanding high voltage bias
(2015-04-13)
Chang, Po-Yi
;
Peng, Shao-Fu
;
Chao, Yu-Chiang
;
Lin, Hung-Cheng
;
Zan, Hsiao-Wen
Vertical organic transistors withstanding high voltage bias were realized with an insulating silicon monoxide layer obliquely deposited on both the surface of the base electrode and sidewalls of the vertically oriented cylindrical nanopores. No noticeable insulating layer can be observed on the emitter electrode at the bottom of the cylindrical nanopores. The leakage current between the electrodes was suppressed and an operating voltage as high as 15V was obtained. An on/off current ratio of 10(3)-10(4) and an output current density of 5-10 mA/cm(2) were achieved. (c) 2015 AIP Publishing LLC.