Papers by Author: Jeou Long Lee

Abstract: This study characterizes warpage of a micro-injection molded micro electrical fan using the Michelson interference method. This study conducts experiments to analyze different polymers-polypropylene (PP), polyamide (PA), acrylonitrile-butadiene styrene (ABS), ABS+ polycarbonate (PC), and polyoxymethylene (POM)-process parameters, such as mold temperature, injection temperature, injection pressure, injection time, packing time, and packing pressure, for a micro electrical fan. To obtain the optimum result (minimum warpage), this study assesses the effect (warpage) of each material on micro-injection molding. PA plastic is the very suitable material for micro electrical fan with Michelson interference analysis on micro-injection molding.

Abstract: The purpose of this research is to find the optimal design for biodegradable polymer microneedle patches. Based on the mechanical properties of different skin layers and the failure criterion of the material, this research designs a microneedle of four types and three sizes, then discusses the insertion force and the variation of stress during the process of PLA microneedle insertion into skin by numerical simulation. This research uses the dynamic finite element software ANSYS / LS-DYNA to simulate the processing for PLA microneedle inserts into skin. The master microneedle array was fabricated by the MEMS process. This research uses PDMS to fabricate the mould for microneedles. Finally, a biodegradable polymer polylactic acid (PLA) microneedle patch was fabricated using a PDMS mould micro hot embossing method.

Abstract: This paper proposes a solid freefrom fabrication (SFF) technology for fabricating hydroxyapatite(HA)-silica ceramics, which can generate porous three-dimensional physical objects. The HA powder and the silica are mixed with water into slurries form as raw materials. The slurries are paved by a scraper to from a thin layer which is selective scanned by a laser beam according to the cross-section of a 3D model. The HA particles are embeded in the sintered silica matrix to form green parts via a suitable range of process parameters. The benefits of this process are: bio-ceramic parts can be built by lower laser energy and faster fabricating speed. Following a subsequence heat treatment process has been developed to optimize the crystallization process and to increase the strength of the sintered parts. The parts were analyzed by an Atomic Force Microscope (AFM) to determine the surface roughness. The results obtained indicate that the proposed process was possible to generate multilayer, overhanging, and porous structure with brittle property but sufficient integrity for handling prior to post-processing. It was possible to produce the porous structure from the proposed hydroxyapatite-silica ceramics, which had a greater potential for possible bone scaffolds fabrication.

Abstract: Nano-porous anodic alumina oxide (AAO) templates are fabricated by anodizing method. The average diameter of nano-porous anodic alumina is 200 nm. The molded plastic thin film (Polycarbonate, PC) with nano-structure is fabricated by AAO as mold insert for nanoimprint. This research discusses the surface property of molded plastic thin film for different processing parameters (embossing temperature, embossing pressure, embossing time, de-molding temperature) on nanoimprint. The original contact angle of PC material without nano-structrue is about 78.2°. The contact angle of molded PC with nano-structrue is about 115.5°. The contact angle of molded plastic film (PC) with nano-structure is larger than that without nano-structure. The hydrophilic property of PC material has changed to hydrophobic property. A significant advantage of the fabrication process employed in this work is that it can create the good surface modification of plastic thin film.

Abstract: In this work, skeletons of micro aerial vehicle are fabricated by precision injection molding. The Taguchi method is adopted to identify the important factors that govern the shrinkage of MAV skeletons. The results indicate that the most significant factor in the shrinkage of a skeleton formed by precision injection molding is the mold temperature.

Abstract: This study succeeds to replicate a micro-feature by ultrasonic nanoimprint. The conjunction effect of the pressure and the ultrasonic vibration enables flowing of plastic into a more precise micro-feature of the metal mold. The longitudinal wave generated by an ultrasonic system of the frequency 35KMz and output power 900W. The micro-feature of the Ni mold insert used in the experiment is a groove shape. The groove’s width is 49 µm and its depth is 25 µm. The PMMA, PC and PP are chosen with the replication materials. This study also discusses the replication properties of plastic film by different processing parameters (delay pressure, fusion pressure, embossing pressure, delay time, fusion time and embossing time).

Abstract: The influence of surfactant CTAB (cetyl trimethyl ammonium bromide) on electrodeposited nickel layer has been investigated in this research. Our result shows that CTAB added in the electrolysis bath can effectively remove the hydrogen to obtain a smoother nickel layer. The effect of CTAB on the surface roughness is also significant. It may be ascribed to the adsorption of CTAB on the electrode surface which results in a hindering effect in the electrodeposition process. Increasing the concentration of CTAB, the grain size of nickel deposit was reduced and the microhardness of the nickel deposit was therefore improved. The hardness of the metal layer can be promoted to 450 Hv when 300 ppm CTAB is added.

Abstract: In this study, a Ni-P alloy electroforming nanostructure material with low surface roughness and low internal stress was developed by using a pulse current. Square-wave cathodic current modulation was employed to electrodeposit ultrafine-grained Ni-P films from an additivefree Sulfamate nickel bath. The effect of various factors, such as peak current density, duty cycle and pulse frequency on the roughness and internal stress were investigated. Pulse current significantly influences the microstructure of Ni-P alloys. The internal stress and roughness of Ni-P alloys increased as peak current density increased, but the internal stress of Ni-P alloys decreased as duty cycle decreased.

Abstract: This research first indicates the melt front delay of wedge-shaped lightguiding plate of backlight module on micro injection molding. This research fabricated the patterns of mold insert of lightguiding plate by photo etching process. The micro-facture of lightguiding plate was manufactured by micro injection molding. The lightguiding plate of backlight module was used for the PMMA material. The single parameter method was used to discuss the flatness and replication properties for different processing parameters (mold temperature, melt temperature, packing pressure, packing time and injection pressure). The results show that there are melt front delays due to the slow injection velocity, the low temperature induced by the little effect of shear heating, the high viscosity, the large flow resistance and the slow flow velocity. The mold temperature is the most important factor for the flatness and the replication of micro-feature of liughtguiding plate. Lower mold temperature induces better flatness properties. The surface roughness of micro-facture of lightguiding plate is 8.8 nm on micro injection molding for this work.