Hyungoo Kang

Magnetic Micro Actuator Using Interactive Force between Magnetic Elements

In micro electro mechanical system (MEMS) field, there have been used many kinds of actuators. Among them, the magnetic actuator has some advantages. As magnetic micro actuators do not need electric wiring for energy supply, the structure can be simple and be downsized easily. However, the magnetic force would be very small with downsizing, which is the main problem for conventional magnetic actuators. We propose a new type actuator using magnetic interaction force between magnetic elements to solve this matter. This actuator can work even if it gets smaller, because the interaction force is dominant in a microscopic region. We fabricated the actuator by a casting process with photolithography using the SU-8 resist material. Then, the structure was fabricated by casting the mixture of poly(dimethylsiloxane) (PDMS) and a magnetic powder material. The beam type actuator works successfully and also shows interesting behavior. We can control the behavior of this actuator by changing the arrangement of magnetic elements on the structure. We also show theoretical evaluation of the deformation of the present actuator.

Magneto-FEM analysis for micro actuator using array of magnetic elements

This paper reports a magnetic actuator using interaction between micro magnetic elements. It was already reported that the present actuator can work even if the structure was miniaturized to nano-scale. In the present work, simple fabrication process with photolithography and PDMS casting was employed to obtain beam type structures with micro array of magnetic elements on their surface. Two samples with simple grid patterns were prepared for testing. These samples had the same grid pattern but different orientation, which caused directly opposite bending deformation under the same applied magnetic field. We used magneto finite element method (FEM) to explain the behavior of the present actuators.

Improvement of Solid Oxide Fuel Cell by imprinted patterns on eelectrolyte

This paper reports an improved interfacial structure between electrode and electrolyte of Solid Oxide Fuel Cell (SOFC). We employed an imprint process to give fine patterns onto a ceramic electrolyte sheet. The imprint process is a powerful tool to transcribe nano- to micro-patterns on materials. In the present work, a sheet of ceramic compound material was prepared, and micro patterns were given on the sheet. After debinding and sintering, dense ceramic sheet with fine patterns were obtained. We prepared three kinds of electrolyte sheets with different surface patterns using this technique. After applying anode and cathode layers, the three fuel cell samples were assembled to test the cell performance. It was resulted that the finer pattern caused the best performance in the three samples.

Direct laser forming for more complex shaped titanium alloy compacts

Titanium and its alloys have been widely used for various industrial and medical applications because of their excellent characteristics of low density, high corrosion resistance and high biocompatibility. However, it is not easy to produce the complicated shape and precise components with low cost because of their poor workability. Therefore, Direct Laser Forming (DLF) is hoped to be a suitable and advanced powder processing technique. In this paper, DLF technique has been introduced to fabricate more complex shaped Ti-6Al-4V and Ti-6Al-7Nb alloy parts for aerospace and medical applications. The effects of DLF parameters on the morphology of compacts are investigated respectively by fabricating specimens, which have the typical features in the vertical plane, the horizontal plane and 3D coordinate. Eventually, not only the complex shape but also the excellent properties as same as the wrought material were achieved.