Ruey Fang Shyu

Realization of fabricating microlens array in mass production

Micro-electro-mechanical system technology offers a wide number of applications for the military, industrial, and consumer markets. The miniaturization of components is a common objective for all studies. Refractive microlens array with density 400 lenses per cm2 are fabricated in three minutes by using hot embossing. The higher accuracy and lower cost of microlens fabrication methods are needed to meet the rapid growth of commercial devices. Higher density of microlens is achievable by a higher density mesh mold. Microlens diameters of 250-380 micrometers are shaped with various molds. Focal lengths of 185-225 micrometers are obtained by changing compression pressure and working temperature which are discovered in this experiment. Molding temperature effects on the surface tension in lens material as explored is essential. From accuracy of microlens arrays are less than Rt 0.1 micrometers that adapt to the form accuracy of the lenses. This article describes a mass fabricating method for microlens array by using hot embossing and the experimental results show its feasibility for practice.

A New Method to Fabricate Polymer Waveguides

Polymer waveguides were successfully fabricated by a new method, which was incorporated with a micromolding process. The refractive index of the UV polymer used in these experiments was changed by an extremely low electric field. The experiment of the near field measurement with end fire coupling had shown that the light had been totally restricted inside the core layer of the waveguide. This process is easy and simply for mass production of any shape of polymer waveguides.

Manufacturing of a micro probe using supersonic aided electrolysis process

In this paper, a practical micromachining technology was applied for the fabrication of a micro probe using a complex nontraditional machining process. A series process was combined to machine tungsten carbide rods from original dimension. The original dimension of tungsten carbide rods was 3 mm; the rods were ground to a fixed-dimension of 50 mum using precision grinding machine in first step. And then, the rod could be machined to a middle-dimension of 20 mum by electrolysis. A final desired micro dimension can be achieved using supersonic aided electrolysis. High-aspect-ratio of micro tungsten carbide rod was easily obtained by this process. Surface roughness of the sample with supersonic aided agitation was compared with that with no agitation in electrolysis. The machined surface of the sample is very smooth due to ionized particles of anode could be removed by supersonic aided agitation during electrolysis. Deep micro holes can also be achieved by the machined high-aspect-ratio tungsten carbide rod using EDM process. A micro probe of a ball shape at the end was processed by proposed supersonic aided electrolysis machining process.

Fabrication of polymer waveguides using a molding process

Polymer waveguides are successfully fabricated by a simple method, which is incorporated with a lithography-galvanic LIGA-like and micromolding process. The refractive index of the UV polymer used in these experiments is changed by an extremely low electric field. The measured propagation loss is 0.32 dB/cm for 1.3 m and 0.30 dB/cm for 1.55 m. This process is easy, simple, and suitable for mass production.

Parametric Study of Spherical Micro-lens Array

This study presents a concept to fabricate micro-lens devices using high-aspect-ratio lithography, extra-hardness electroplating, and hot embossing processes. A bath of electroplating electrolyte will be formulated to fabricate micro-optics mold inserts with extra-hardness Ni-Co alloy. It is a novel method to increase the life of the mold insert during fabricating micro-lens devices. With this high hardness, the mold inserts can resist high abrasiveness and wearness so as to extend the mold cycle life and reduce the idle time of replacing mold plates during fabrications. Therefore, the process of fabrications of micro-lens can be more cost-effective. In this study, parametric effects of reflow time, and temperature on micro-lens profiles will be characterized and discussed. Finally, the optical properties such as focal length of developed micro-lens will be measured and tested.

Transducing Mechanical Forces Using a Polymer Optical Grating Sensor

A new means of transducing mechanical force using a diffractive Bragg grating based polymeric sensor is presented. The diffraction gratings are successfully fabricated on a polydimethylsiloxane (PDMS) polymer using the holographic interference and micromolding technique. The micro MTS tensile test incorporated with the Raman experiment showed that a relationship between the load and the observed diffraction pattern shift could be obtained. The results show an excellent correlation between the optical measurements and load with a sensitivity of 0.05N.

Construction of a Prediction Model for an Acceptable T-Shape Tube Product in Magnesium Alloy Hydro-Forming

The finite element method in conjunction with abductive neural network is applied to predict an acceptable T-shape product of which the minimum wall thickness and the protrusion height being fulfilled the industrial demand in the magnesium alloy hydro-forming. AZ31 magnesium alloy circular tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanically auxiliary force from the punch to fabricate a qualified T-shape tubing product. Finite element software is adopted to investigate the forming characteristics of T-shape tube forming, by changing process parameters such as punch velocity, hydraulic pressure, fillet radius of the die and tool-workpiece interface friction etc. to investigate the material flow of tube forming, and the variations of wall thickness and protrusion height. And the neural network method in turn is applied to synthesize the data sets obtained from the numerical simulations and a prediction model for an acceptable T-shape tube product in magnesium alloy hydro-forming is thus constructed. From the prediction model, a suitable range of the process parameters variation for producing those qualified T-shape tubes that may be accepted in industrial applications can thus be identified.Copyright

Fabrication of Eyeball-Like Spherical Micro-Lens Array for Optical Fiber Coupling

Batch-fabrication of eyeball-like spherical micro-lens not only reduces micro assembly cost, but also replaces conventional ball-lenses or costly GRINs (Gradient Reflective Index) without sacrificing performance. Compared to the conventional micro-lenses made in a half-spherical geometry, the eyeball-like micro-lens is a sphere, which allows focusing light in all directions on the substrate surface, thus providing application flexibility for optical applications. The current eyeball-like spherical micro-lens is made using photoresist SU-8. This work develops a batch process at low temperature by spin-coating SU-8 on a surface of silicon wafer. The SU-8 thick film is patterned by UV lithography to form an array of holes for holding eyeball-like spherical micro-lens. The fabrication process employs bulk micromachining to fabricate an array of nozzles on the silicon wafer. Next, this process pours viscous SU-8 into the cavity of silicon wafer and presses it through the nozzle before reflow. The eyeball-like spherical micro-balls form by balancing between surface tension and cohesion. Varying the amount of SU-8 pressed through the nozzle controls the diameter of the balls. This paper designs a pattern with a 3 × 3 lens-array with a numerical aperture of about 0.38. Diameters range from 60 to 500 um. Optical measurements indicate a diameter fluctuation within 3% and an optical insertion loss is below 2.5dB with a wavelength of 635nm in a single-mode fiber (SMF). Therefore the eyeball-like spherical micro-lens is capable of increasing coupling efficiency.Copyright

Forming Rule Construction for Hourglass-Like Tube Hydroforming with Magnesium Alloy

The objective of this study is to construct the forming rule for hourglass-like tube with magnesium alloy during hydro-forming and offer the analysis results as a guideline for magnesium alloy forming in industry. AZ31 magnesium alloy circular tube is used as the billet material for hydro-forming with hydraulic pressure as the main forming power combined with the mechanical auxiliary force from the punch to fabricate the hourglass-like tubing products. A finite element based code is utilized to investigate the forming characteristics of hourglass-like tube forming, by changing process parameters such as punch velocity, hydraulic pressure gradient and tool-workpiece interface friction etc. to investigate the material flow of tube filling, wall thickness variations, and stress and strain distributions. And the abductive network is in turn applied to synthesize the data sets obtained from the numerical simulations. Consequently, a quantitative prediction model is developed for the relationships among the process variables, corner radius and minimum tube thickness in the process of hourglass-like tube hydro-forming with magnesium alloy. The results show that proper mechanical force can help material flow, prevent large strain deformation from falling into the area of negative strain hardening rate, enhance the magnesium alloy to become easy in forming and make tube fitting may to be formed successfully.

P‐68: Optical Tapered Array in Light‐Guide Plate Fabrication for Enhancing Backlighting Brightness

Optical tapered array fabrication for new light-guide plate molding technology and assembly to a LED backlighting module are presented. The UV proximity printing method was used by controlling exposure dosage resulting tapered array patterns. Various tapered angles of micro-cone pit patterns can be fabricated using this method. The practical application in the 1.8-inch LED backlight module, the luminance can achieve at 4300 cd/m2 with 83% uniformity by using three LEDs. Optical simulation result also showed with the optimum tapered structure with 30° angle, a higher bright backlighting module can be implemented.