Papers by Author: Chih Wei Wu

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: The development of homoepitaxial films for advanced device applications has been studied, but high growth rate and diamond film quality have not yet been explored. In the current study, high quality homoepitaxial diamond films were grown on type Ib (100) HPHT synthetic diamond substrate by hot-filament chemical vapor deposition. The reactant gases were mixed by CH4 and H2 with small amounts of N2 (500 to 3000 ppm). Besides, a bias system was used to assist diamond film deposition. The pyramidal crystals on diamond surface can be suppressed and high quality diamond film of FWHM (Full Width at Half Maximum) = 10.76 cm-1 with high growth rate of 8.78 ± 0.2 μm/ hr was obtained at the condition of adding 1000 ppm nitrogen. At the bias voltage of -150 V, the pyramidal crystals can also be suppressed and high quality diamond film of FWHM = 10.19 cm-1 was obtained. With nitrogen addition above 2000 ppm, diamond film was partly doped and some sp2 structures appeared. These homoepitaxial diamond films were characterized by optical microscopy and micro-Raman spectroscopy.

Abstract: This paper presents an innovative fabrication of a large-area silicon mold with microstructures. Conventional techniques capable of manufacturing a large size mold pose severe challenges in making microstructures. In contrast, semiconductor process is limited in its wafer scale. This paper shows a new approach to achieve a large beyond-wafer-size silicon mold with alignment microstructures using two-direction passive alignment recombining techniques. Anisotropic bulk-micromachining technique, laterally joined of (111) silicon crystal planes, passive-alignment methods are the key to fabricate a large-area silicon mold. The area of each small silicon plate is 2.9cm2. Therefore, four small silicon plates with microstructures were recombined as a large-area square silicon mold. The optical fibers were placed into V-grooves on small silicon plates to make sure of microstructures alignment, minimum tilting and rotation angles between plates during the recombining process. The gap, height difference, and aligning accuracy of microstructures between joined silicon plates were able to achieve 8μm, 0.902μm and 20μm, respectively. Moreover, the rotation and tilting angles could be lowered to 0.0622 degree and 0.002 degree, respectively. Microstructures on the large-area silicon mold are faithfully reproduced by polydimethylsiloxane (PDMS). Finally, a 16.8 cm x 12.6 cm silicon mold was fabricated using twelve 4.2cm x 4.2cm silicon plates. It is believed that the novel technique will give an impact and create a highly value-added technology to the precise mold manufacturing.

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: A novel nutrient sensor using liquid core waveguide technique is reported, implementing Teflon AF 1601S coated microchannels. Straight PDMS microchannels replicated from a master were coated with Teflon AF 1601S and sealed with a Teflon AF 1601S coated Pyrex 7740 wafer. It formed a liquid core waveguide with a low index of refraction channel in which a high index aqueous solution was flowed. Light generated by a fiber-coupled tungsten halogen lamp propagated by total internal reflection to the end of the channel where the light was detected using a CCD array spectrometer. There is a dramatic difference between channels with and without a Teflon coating. The absorbance response of this sensor varies linearly with concentration. This innovative technique provides a potentially low-cost and high efficient approach to fill the inspection technology gap between in-situ and laboratory analyses. It is believed that the novel process is expected to give an impact to the aqueous inspection and to create a highly value-added technology in optical test, measurement industry.

Abstract: Many technologies, such as Radio Frequency Identification (RFID), have been developed to keep pace with rapid changes in society. Additionally, an RFID tag can be integrated with a sensor or actuator (a smart RFID), they can comprise a sensitive wireless network. The potential and utility of smart RFID techniques have increased dramatically. However, based on the distinctive characteristics of RFID and sensors/actuators, they cannot be combined simultaneously using commercial RFID techniques and materials such as poly phenylene sulfide (PPS). Conversely, smart RFID systems will be exposed to harsh environments, including temperature variations, salt corrosion, and violent impact. The current polymeric RFID packaging technique cannot withstand severe environmental conditions for a long period. This study presents a novel integrated packaging technique for sensors and RFID that is fully compatible with the complementary metal-oxide-semiconductor (CMOS) processes to identify the limitations of traditional RFID packaging methods. After several tests in harsh environments, such as strength, corrosion resistance, thermal stress, and simulated washing, the RFID and sensor operated normally. Therefore, the novel encapsulation process for RFID integrated with a sensor overcomes the bottleneck of conventional RFID packaging techniques. The potential of this novel technique is significant and provides a new approach as it achieves high performance and at a low cost. Furthermore, the proposed new technique should prove very useful in applications as smart RFID areas.

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.