T.L. Yang

Fibers and conductive films using silver nanoparticles and nanowires by near-field electrospinning process

The silver nanowires (AgNWs) and silver nanoparticles (AgNPs) were synthesized. With near-field electrospinning (NFES) process, fibers and thin films with AgNPs and AgNWs were fabricated. In the NFES process, 10 k voltage was applied and the AgNPs and AgNWs fibers can be directly orderly collected without breaking and bending. Then, the characteristics of the fibers were analyzed by four-point probe and EDS. The conductive film was analyzed. When the thickness of films with AgNWs and AgNPs was 1.6 µm, the sheet resistance of films was 0.032Ω/sq which was superior to that of the commercial ITO. The transmissivity of films was analyzed. The transmissivity was inversely proportional to sheet resistance of the films. In the future, the fibers and films can be used as transparent conductive electrodes.

Design of Elliptic Reflective LED Surgical Shadowless Lamps Using Mathematical Optical Tracing Algorithms

Traditional surgical shadowless halogen lamps are generally designed as projection type with many light bulbs, which can produce not only mercury pollution but also heat radiation that are serious problems to patient. The study utilized Runge-Kutta methods and mathematical algorithms to design and optimize the freeform lens. The LED (light-emitting diode) was adopted to replace the traditional halogen lamp. A uniform lens was designed and fabricated based on the energy conservation. At first, the light field of LED is concentrated through the freeform lens to improve the optical efficiency. Second, the three-shell elliptic curves are applied to the reflective surgical shadowless lamps, where only few LED chips are needed. Light rays emitting from different directions to the target plane can achieve the goal of shadowless. In this study, the LED’s luminance flux is 1,895 lm. The shadow dilution on the target plane is 54%. (central illuminance) is 114,900 lux, and the is 57% which is higher than the regulation by 7%, whereas the power consumption is only 20 W. The energy of reflective surgical shadowless lamps can save more than 50%, compared with the traditional projective one.

Study of selective laser melting process for cubic models with various porosities

Additive manufacturing (AM) has the advantages of fabricating complex models for application. In this study, cube structure with various porosity is manufactured by AM of selective laser melting (SLM). CAD software is used to create the micro porosity of sample models from 60 %~80 %. The models are printed by Ti-6Al-4V powders. The morphology of the printed porous structures are examined by OM and SEM. Results show that only minor geometric deviation between the designed CAD pattern and the printed samples.

Study of freeform lens for UV-LEDs exposure system with reflector for uniform irradiance

In this study, UV-LED (ultraviolet light emitting diode) is developed for photolithography industry. Since the accuracy of the degree of cross linking and sidewall profile could be affected by intensity of UV light dosage, this research proposes optical design and fabrication of freeform lens with reflector coated on the light source element of UV-LED for exposure systems. Based on the law of conservation of energy and Snells law method, a free-form lens is designed in the study. The optical distribution intensity of the freeform lens with reflector layer was determined by using commercial optical simulation FRED software. The experimental results show that the average irradiance and uniformity on the target plane with 60 degree reflector layer were 8.7mW/cm2 and 86.9%, respectively. The irradiance and uniformity were higher than that of freeform lens without reflector, 7.8mW/cm2 and 87%, respectively. Therefore, the results show that the freeform lens with reflector was demonstrated to obtain 97.5% average normalized cross correlation (NCC) between the simulation and experimental measurement of UV-LEDs exposure system. Through this design of reflection of UV-LED light source, the intensity and uniformity can be enhanced significantly.

Investigation of optimal silver nanowires film as conductive wires for LED

In the study, the Polyol reduction process was used to fabricate silver nanowires (AgNWs). In the experiment, the ratio of PVP/Ag, silver seed, AgNO3 and the amount of ethylene glycol (EG) were adopted to design orthogonal array with a constant temperature and heating time and the synthesis parameters of AgNWs were obtained. Therefore, the optimal AgNWs solution was obtained, followed by centrifuging to obtain AgNWs which were used to fabricate AgNWs film. The scanning electron microscope (SEM), Fourier Transform Infrared Spectroscope (FTIR), Energy Dispersive Spectrometer (EDS) and four-point probe were used to measure the sheet resistant and transmittance of AgNWs film. Moreover, the AgNWs film was adopted to be the conductive wires of LED. From the experiment results, the synthesis parameter of 15ml EG, 0.01g AgCl, ratio 2 of PVP/Ag and 0.22g AgNO3 could be used to fabricate optimal AgNWs with 45nm average diameter, 5μm average length and aspect ratio of 110. The sheet resistance and transmittance of film fabricated by centrifuged AgNWs was 0.1252 Ω/sq and 70%, respectively. Furthermore, the luminance of LED with conductive wires made of AgNWs film was better than that made of commercial silver plastic. In the future, the AgNWs film can be broadly applied to the conductive films of touch electric products, LCD display and solar panels.