Nak-Kyu Lee

Development of the Roll Type Incremental Micro Pattern Imprint System for Large Area Pattern Replication

Flexible display has been attracting attention in the research field of next generation display in recent years. And polymer is a candidate material for flexible displays as it takes advantages including transparency, light weight, flexibility and so on. Rolling process is suitable and competitive process for the high throughput of flexible substrate such as polymer. In this paper, we developed a prototype of roll-to-flat (R2F) thermal imprint system for large area micro pattern replication process, which is one the key process in the fabrication of flexible displays. Tests were conducted to evaluate the system feasibility and process parameters effect, such as flat mold temperature, loading pressure and rolling speed. 100 mm × 100 mm stainless steel flat mold and commercially available polycarbonate sheets were used for tests and results showed that the developed R2F system is suitable for fabrication of various micro devices with micro pattern replication on large area.

Research on the Modulating of the Desktop Micro Forming System to Micro Factory

The micro pump module is used in so many MEMS applications, such as medical, fuel cell, display and chemistry fields. The micro pump module is consisted of actuating component, chamber plate, upper/lower fluidic channel plates and thin valve. This micro pump must have a specific performance that is high compressibility and high speed operating response. A polymer thin film is used as a valve component in micro pump module. But this polymer thin film has a low elastic characteristic so cannot operate with high frequency. If this polymer thin valve can be changed to metallic material, thin valve component can operate with high frequency because metal has a high elastic characteristic. As forming components are small in size, forming equipment must also be small in size because the forming die and load must be small. The micro forming press system is high precision forming equipment that can manufacture the precision component. This precision component has a size of several micros to millimeters and precision of sub-micro to micrometer. In this paper, we research about the metallic thin foil valve manufacturing technology to have a high frequency response. This metallic valve has a 30 mum thickness and minimum pattern size of 500 mum. And we develop the miniaturized press system that has a desktop size and a precision compound die set. This compound die set can operate in piercing and blanking process.

Desktop Micro Forming System for Micro Pattern on the Metal Substrate

In this Research, the desktop micro forming manufacturing system has been developed. A micro forming system has been achieved in Japan and its developed micro press is limited to single forming process. To coincide with the purpose to be more practical, research and development is necessary about the press which the multi forming process is possible. Micro patterned metal components are used in so many precision engineering fields. This micro pattern plays an important part in the functional movement of precision module. This micro pattern on the metal component can be made by EDM(Electro Discharge Machining). But this EDM method has low productivity because EDM tools can be worn easily. If another manufacturing process is developed with high productivity, industries can product the competitive goods. So we research on the forming process and system to make micro functional pattern on the metal component.

A Study on the Robust Control of an Inverted Pendulum Using Discrete Sliding-Mode Control

In this paper, discrete sliding mode controller (DSMC) with sliding-like condition is evaluated experimentally the robustness point of view. DSMC was modified to use a pseudo-sliding methodology and a variable sliding gain methodology. DSMC with a pseudo-sliding methodology and a variable sliding gain methodology perfectly eliminate a chattering problem and can control the system use a small control action. The usefulness of the designed DSMC in this paper is demonstrated by the control of an inverted pendulum system and the robustness of DSMC experimentally evaluated for model error. To provide a performance benchmark with respect to robustness, a direct comparison was made against linear quadratic control.

Development of 3D printed biomimetic scaffold for tissue engineering

One of the major challenges in tissue engineering is to mimic nanoarchitecture of native collagen fibrils in human body, as well as to fabricate three-dimensional outer shape to be regenerated. Here, we introduced a novel three-dimensional (3D) fabrication method for biomimetic scaffold by combining 3D printing and electrospinning process with using biocompatible polymers. Electrospun nanofiber construct has been believed to be a promising candidate for the simulation of natural extracellular matrix (ECM) structure. The random and aligned nanofiber mats were prepared for mimicking the nanofibril ECM structure respectively in cartilage and skeletal muscle. Then, they were packed by the 3D printing process. Microscopic pore morphology and macroscopic framework could be finely tuned by 3D printing process. By culturing chondrocyte and C2C12 myoblasts on the developed scaffolds, the each scaffold showed its feasibility for the application to tissue engineering. The hybrid scaffolds containing 3D microscale framework and nanofiber mats entailed both features of mechanical support and nanofibrous topographical guide, and thus could potentially meet the requirements for practical use of tissue engineering scaffolds.

An Experimental Study on Multi-mode Control Methods of Flexible Structure Using PZT Actuator and Modified IMSC Algorithm

In this paper, the modified independent modal space control (IMSC) algorithm, which is a method for reducing the number of actuators, is used for flexible structural vibration control. By comparing the experimental results obtained by the IMSC and modified IMSC algorithm, the performance of those is examined. The performance of the IMSC algorithm is more effective than modified IMSC algorithm in the responses of PZT sensors and the input voltages to PZT actuators. But the IMSC algorithm is limited for many applications since it is needed the number of actuators as many as controlled modes. For this reason, the modified IMSC algorithm is proposed in this paper. That of the modified IMSC algorithm is similar with the IMSC algorithm but there are discontinuous responses because of switching algorithm. Therefore, if the switching algorithm has gradually varying according to shape of control forces, its performance is more effective and applicable than the IMSC algorithm. This paper will provide an essential experimental basis material for that study.

Real-time precision displacement measurement interferometer using the robust discrete time Kalman filter

This paper proposes a robust discrete time Kalman filter (RDKF) for the dynamic compensation of nonlinearity in a homodyne laser interferometer for high-precision displacement measurement and in real-time. The interferometer system is modeled to reduce the calculation of the estimator. A regulator is applied to improve the robustness of the system. An estimator based on dynamic modeling and a zero regulator of the system was designed by the authors of this study. For real measurement, the experimental results show that the proposed interferometer system can be applied to high precision displacement measurement in real-time.