Chul Jin Hwang

An on-chip blood serum separator using self-assembled silica microsphere filter

In this paper, we report a disposable on-chip blood serum separator using self-assembled silica microsphere filter, which can passively separate serum from human blood. A self-assembly packing method was developed for packing silica microspheres through a microfluidic channel on cyclic olefin copolymer (COC) substrate. Using the self-assembled microsphere filter, serum has been successfully separated from diluted human blood. The filters realized in this work are suitable for incorporating into a disposable polymer lab-on-a-chip, which can perform point-of-care testing (POTC) for clinical diagnostics using human blood.

Optical Analysis for Designing a Planar Solar Concentrator Based on Light Guide System

Recently, an optics-based concentrator for solar concentration has been a key issue in development of photovoltaic systems. In the present study, a new, simple, easily producible planar concentrator based on a light guide system is proposed. In this device, solar light is concentrated by microprism optical patterns guiding the light, mainly through total reflection and refraction. The main design variables of the concentrator are the geometric concentration ratio () and the and of the microprism pattern. Ray tracing was simulated using commercial software, SPEOS, and the optical efficiencies of the light guide solar concentrator were predicted in each case. The predicted maximum optical efficiencies are 65.60%, 54.78%, and 46.78%, respectively, for values of 4, 5, and 6. The variation of the optical efficiencies according to , , and the incline angle of the incident light were predicted.

Computer Aided Engineering Design of Powder Injection Molding Process for a Dental Scaler Tip Mold Design

Powder Injection Molding (PIM) has recently been recognized as an advanced manufacturing technology for low-cost mass production of metal or ceramic parts of complicated geometry. With this regards, design technology of dental scaler tip PIM mold, which has complex shape and a slim core pin of 0.6 mm diameter, with the help of computer-aided analysis for powder injection molding process was developed. Computer-aided analysis for dental scaler tip mold was implemented by finite element method with non-Newtonian fluid, modified Cross model viscosity, PvT data of powder/binder mixture. The core deflection analysis of dental scaler tip PIM mold during PIM filling process was also investigated. Compter-aided analysis results, such as filling pattern, weldline formation, and air vent position prediction were investigated and eventually showed good agreements with experimental results.

Fabrication of Partition Wall for Solar Cell by Hot Embossing

Hot embossing technology, one of nanoimprint lithography (NIL) techniques, has been getting attention as an alternative candidate of next generation micro-patterning technologies by the advantages of simplicity and low cost compared to conventional photo-lithographies. For this study of fabrication of partition wall for polymer solar cell, The manufacturing process is made up of three stages as in the following: (i) the stage of lithography process, (ii) the stage of electro-plating process for mold, and (iii) the stage of hot embossing process. As a result, we made 6 inch Ni-mold and hot embossed partition wall for polymer solar cell.

Development of Dental Scaler Tip Mold with Powder Injection Molding Process

With the capability of net shaping for complex 3D geometry, powder injection molding (PIM) is widely used for automotive parts, electronics and medical industry. In this study, an ultrasonic dental scaler tip produced by machining process was redesigned for the PIM process. An injection mold was designed and machined to produce the dental scaler tip by the PIM process. The mold design was aided by CAE analysis. A PIM feedstock was made of SUS316L powder and a wax based binder. The filling balance in the mold was checked by a short shot test with LDPE and the PIM feedstock. Production capability of the PIM process for the dental scaler tip was examined with the mold. Although there were minor problems such as a discoloration around the gate and a flashing at the air vent, the PIM process turned out to be an excellent substitute for machining process to manufacture the ultrasonic dental scaler tip.

A Study on the Birefringence Measurement in Injection Molded Parts Using Two Different Laser Sources and R-G-B Separation of White Light

Recently, injection molded plastic optical products are widely used in many fields, because injection molding process has advantages of low cost and high productivity. However, there remains residual birefringence and residual stresses originated from flow history and differential cooling. The present study focused on developing a technique to measure the birefringence in transparent injection-molded optical plastic parts using two methods as follows: (i) the two colored laser method, (ii) the R-G-B separation method of white light. The main idea of both methods came from the fact that more information can be obtained from the distribution of retardation caused by different wavelengths. The comparison between two methods is demonstrated for the same sample of which retardation is up to 850 nm.