Jung-Oh Choi

Fabrication and reliable implementation of an ionic polymer–metal composite (IPMC) biaxial bending actuator

Ionic polymer?metal composites (IPMCs) are one of the most popular types of electro-active polymer actuator, due to their low electric driving potential, large deformation range, and light weight. IPMCs have been used as actuators or sensors in many areas of biomedical and robotic engineering. In this research, IPMCs were studied as a biaxial bending actuator capable of smart and flexible motion. We designed and fabricated this bending actuator and implemented it to have a reliable actuating motion using a systematic approach. The resulting device was bar shaped with a square cross section and had four insulated electrodes on its surface. By applying different voltages to these four electrodes, a biaxial bending motion can be induced. To construct this actuator, several fabrication processes were considered. We modified the Nafion stacking method, and established a complete sequence of actuator fabrication processes. Using these processes, we were able to fabricate an IPMC biaxial bending actuator with both high actuating force and high flexibility. Several experiments were conducted to investigate and verify the performance of the actuator. The IPMC actuator system was modeled from experimentally measured data, and using this actuator model, a closed-loop proportional integral (PI) controller was designed. Reference position tracking performances of open-loop and closed-loop systems were compared. Finally, circular motion tracking performances of the actuator tip were tested under different rotation frequencies and radii of a reference trajectory circle.

Cellulose nanofiber assisted deposition of titanium dioxide on fluorine-doped tin oxide glass

Microspores, highly ordered, 300–340 nm thick blocks of titanium dioxide (TiO2) nanoparticles (5–10 nm) were deposited on fluorine-doped tin oxide (FTO) glass by using low concentration of cellulose nanofibers from bacterial origin, through sol–gel process followed by spin coating.

Design and fabrication of a smart flexible structure using Shape Memory Alloy wire (SMA)

The smart structure is broadly applied in various fields. One of main part of smart structure is actuator. To develop smart structure, many kinds of actuators were studied. Shape Memory Alloy (SMA) is one of them. SMA actuator demonstrates large deformation and good repeatability, in spite of hysteresis, it is one of the most generally applied actuator in smart structure. In this research, a smart flexible structure was developed, which is comprise of SMA spring, Polydimethylsiloxane (PDMS) body and Acrylonitrile Butadiene Styrene (ABS) cover. It was developed to be applied to robot as manipulator module showing bending motion. The fabrication of the smart flexible structure is described in this paper. And its performance was tested. Using CCD camera sensor, the bending motion of the smart flexible structure was measured. A coordinate value change of one point of smart flexible structure was measured and the results were analyzed. And a circuit with the pulse width modulation (PWM) controller was designed to control the motion of smart flexible actuator.

In-Situ Characterization of Nano-Structures Fabricated by Focused Ion Beam (FIB) and Nano Particle Deposition System (NPDS)

Nano particle deposition system (NPDS) had been developed for the creation of micro/nano structures with multimaterials in order to develop the micro/nano devices on the basis of specific localized surface on the multilayer. However, micro structures fabricated by NPDS show different mechanical properties when it compared to bulk material because of its porous and uneven deposition structure. To achieve reasonable mechanical properties of the structure fabricated by nanoscale 3D printing system, it requires in-situ mechanical property test method. Herein, a new approach for in-situ nanomechanical characterization system using microforce sensor and nanomanipulator installed in focused ion beam system. In this research, experimental setup for mechanical characterization was developed and mechanical property test was done in Focused Ion Beam (FIB) system. The specimen was fabricated by FIB milling process, then manipulation and compression processes are operated by this characterization system with real time imaging. The test was done for silver microstructures fabricated by NPDS and results show weaker hardness and smaller young’s modulus than bulk material.Copyright