Key Engineering Materials Vols. 364-366

Abstract: To manufacture the micro parts or micro structures effectively and precisely, a high precision 3-axis micro milling machine is built. All the three axis are driven by linear piezoelectric ultrasonic motors and the slides are supported by cross-roller guide. Investigations are firstly made to analyze the impact of the non-linear characteristics in the servo mechanism on the performance of the servo system. To achieve the positioning and tracking accuracy at sub-micrometer and micrometer level respectively, on one hand, a optical linear encoder with the resolution of 50nm is applied to close the control loop and a high performance DSP based motion control card is used to carried out the reference command. On the other hand, sophisticated control and compensation strategies are also implemented to overcome the non-linear characteristics in the servo system. Positioning and tracking experiments show that, with this well-tuned control system, the positioning and tracking accuracy are ±0.5μm and ±2.4μm respectively. Using this machine, a micro part with 5μm thin-walled structure is machined successfully.

Abstract: An optical non-contact measurement system for micro-scale 3D profiles is developed and analyzed in this research. The core concept of the system is based on Shape-from-Focus method. The methodology and the process of the measurement will be explained in this paper. Briefly, corresponding digital images were taken at different heights with predefined step intervals. The properties of images were enhanced by image processing techniques including discrete Gaussian filtering, histogram equalization and high-boost filtering. Finally, the degree of the focused image was quantified by using Sum-Modified-Laplacian algorithm. The height of each pixel was determined with Gaussian Interpolation. 3D geometry model of the specimens can be reconstructed. This system was verified that it can work on the specimen manufactured by laser beam. Analysis of precision will be revealed and the comparison with other measurement methods will be discussed later.

Abstract: A mura defect detection algorithm for thin-film transistor liquid crystal display (TFTLCD) is developed for automatic detection of mura defects using Discrete Cosine Transform (DCT) principle for background image reconstruction. Detecting blob-mura defects in a LCD panel can be difficult due to non-uniform brightness background and slightly different brightness levels between the defect region and the background. To resolve this issue, a DCT-based background reconstruction algorithm was developed to establish the background image. The background of the inspected images can be first extracted and reconstructed by using the DCT principle and an image filtering strategy. Mura defects can then be detected by the developed segmented strategy. Actual performance of the developed method was evaluated on industrial LCD panels containing natural mura defects.

Abstract: Photonic crystal fibers (PCFs) have recently attracted a great deal of interest because of their unique characteristics and many controllable features. They include a wide range of single mode operation, highly birefringent characteristics (~10-3), high-power light transmission, etc. The field-installable LC connectors tend to be of the larger connector types in the fiber-to-the-home (FTTH) distribution units. In these designs, fibers are clamped inside a splice assembly and are stressed within the connector. In this research, we first developed a novel cam-type mechanism for field-use LC connector. The fiber stress was analyzed via a commercial available finite element program. The stress birefringence distributions of single mode fiber and air-silica based PCFs were calculated by stress photoelastic effect. We further studied the effect of air-hole size on the stressinduced birefringence of PCFs. The results indicate that stress-induced birefringence decreases as air-hole size increase. On the other hand, the birefringence increases as applied clamping force increases on the single mode fiber.

Abstract: Micro-structured optical components (MOCs) show great promise for offering an exciting new degree of freedom and flexibility to optical designers and producers. At present, these micro/miniature components are usually manufactured by large ultra-precision machine tools in tightly controlled environment and the cost of machining is thus very high. In this study, a novel machine with compact structure and flexibility was built, specially used for machining of the MOCs. The key points of the design are given. Fresnel lens, as an example of MOCs, was machined by this machine tool, and the result shows that the form accuracy of the machine tool is in the order of sub-micrometer.

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: 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: In this study, the author uses a novel nanofluid synthesis system to fabricate a TiO2 nanofluid. The improvement of the proposed nanofluid synthesis system focuses mainly on the pressure control system, coolant circulation system, parameter control system and the machine dimension of the original submerged arc nanofluid synthesis system. This helps to achieve an experimental machine with a fabrication condition to produce more stable and finer TiO2 nanofluids with a particle size of good reproducibility. Experiment is proceeded towards 15 sets of TiO2 nanofluid fabricated by the proposed system are tested under the experimental conditions of 250 V, 6 A of peak current, 2μs of discharge pause off time and 15 days of settling time. The experimental results show that the average Zeta potential of TiO2 nanofluids are -54.2 mv, and the difference between the data and the average value of each set is less than 7%. Furthermore, the average particle size is 45.3nm, and the difference between the data and the average value of each set is less than 6%. The fabricated TiO2 particles have an Anatase structure, and in the aspect of roundness measurement, the produced TiO2 has a good roundness of 0.3 nm. Experiment proves that the roundness of the fabricated TiO2 nanoparticles are much better than those fabricated by aerosol methods. Also, the fabricated nanofluid has a high suspension stability.

Abstract: Ultrathin block copolymer films are promising candidates for bottom-up nanotemplates in hybrid organic-inorganic electronic, optical, and magnetic devices. Key to many future applications is the long range ordering and precise placement of the phase-separated nanoscale domains. In this paper, a combined top-down/bottom-up hierarchical approach is presented on how to fabricate massive arrays of aligned nanoscale domains by means of the self-assembly of asymmetric poly (styrene-block-ethylene/butylenes-block-styrene) (SEBS) tirblock copolymers in confinement. The periodic arrays of the poly domains were orientated via the introduction of AFM micromachining technique as a tool for locally controlling the self-assembly process of triblock copolymers by the topography of the silicon nitride substrate. Using the controlled movement of 2- dimensional precision stage and the micro pressure force between the tip and the surface by computer control system, an artificial topographic pattern on the substrate can be fabricated precisely. Coupled with solvent annealing technique to direct the assembly of block copolymer, this method provides new routes for fabricating ordered nanostructure. This graphoepitaxial methodology can be exploited in hybrid hard/soft condensed matter systems for a variety of applications. Moreover, Pairing top-down and bottom-up techniques is a promising, and perhaps necessary, bridge between the parallel self-assembly of molecules and the structural control of current technology.