Papers by Author: Jae Do Nam

Abstract: A novel electrically conductive adhesives (ECAs) with solder particle have been developed. The kinetics of the curing reaction were investigated using isothermal differential scanning calorimeter (DSC). The dynamic DSC scans were also conducted to investigate the temperature dependant curing degree. The temperature dependant viscosity characteristic of polymer was investigated using rheometer. The wetting characteristic of two solders on two kinds of metals were investigated using an optical microscope. It was found that developed resin material showed good fluxing capacity against Sn-Bi solder on Ni/Au and the wetting angles was about 24º.

Abstract: In this paper, we present a multilayered and arrayed flexible sensor made of Polyvinylidene Fluoride (PVDF), which can detect contact normal forces as well as positions. Since the sensor is flexible enough to be adapted to arbitrarily curved three-dimensional surfaces, it can be employed as the fingertip sensor of the robot hand, contact sensors for robot manipulators etc. The sensor displays enhanced characteristic features in terms of ease of fabrication, high spatial resolution and cost-effectiveness. We propose a new design of the sensor that can be fabricated without adopting sophisticated processing technique as well as with improved spatial resolution. In addition, an electronic hardware for signal processing using a DSP chip has been proposed and, its effectiveness is validated experimentally.

Abstract: Flexible and thin conductive films of poly(3,4-ethylenedioxythiophene) (PEDOT) on PET substrate were obtained by an in- situ vapor-phase polymerization (VPP) method using ferric toluene sulfonate as an oxidant. The addition of epoxy acrylate resin used as a binder to provide adhesive strength between PEDOT and PET also afforded the possibility of the surface patterning through UV exposure. The electrical and optical properties of the conductive PEDOT films were characterized by UV-Vis spectroscopy and conductivity measurement. Surface resistance below 150./sq. was achieved for 100 nm thick films with UV-vis-spectrum transparency exceeding 80%. The combination of these properties makes the films highly suitable for numerous device applications.

Abstract: A novel core-shell material composed of closely packed gold shells on poly (divinylbenzene) (PDVB) cores was fabricated via the reduction of a gold complex. PDVB beads (2-5 +m) were synthesized by precipitation polymerization. The surface of the PDVB beads was modified by three different methods, viz. sulfonation, chloromethylation, and thiolation. The modification of the surface of the PDVB beads was designed to allow the facile attachment of the gold layer onto the PDVB cores. The gold seeding layer was initially formed on the modified PDVB cores by the chemical reduction of a gold-phenanthroline complex. The subsequent growing reactions of NH2OH and HAuCl4 increased the gold coverage to more than 90%. The structure of the PDVB/Au core-shell material was characterized by SEM, XPS, and FT-IR.

Abstract: This paper presents a new design of an artificial muscle actuator called tube-spring actuator (TSA) that is fabricated with dielectric elastomer. The new actuator construction includes two steps: the first is that a cylindrical actuator is manufactured with dielectric elastomer with multi-layer lamination process. Then a compressed spring is inserted to inside the tube as the second step of the process. The inner spring is used to maximize the axial deformation while constraining the radial contraction. This design enables effective linear actuation with largest amount strain. The monitored strain of active length is up to 15 percents. The manufactured actuator is applied to a robot hand as an example of the actual application.

Abstract: Melt processable plasticized cellulose diacetate (CDA) was prepared using triacetin (TA) as a plasticizer and its mechanical properties were characterized. The processability of the plasticized CDA was further enhanced by using a small amount of epoxidized soybean oil as a secondary plasticizer. The glass transition temperature of the plasticized CDA was observed at 50°C lower than that of the virgin CDA and the incorporation of 5 % of ESO also resulted in an additional 20°C decrease in the Tg value. In order to obtain practical processing conditions, a plasticizer content of more than 20 wt % should be used.

Abstract: As ElectroActive Polymers (EAPs) attract keen attentions from various engineering fields, they have been proven more beneficial over the traditional electromagnetic transducers. In the present paper, a new polymeric material that could be adopted for a dielectric elastomer actuator is introduced. The proposed synthetic rubber produces larger deformation at higher energy efficiency compared to previously known dielectric elastomers. A method for the material synthesis and a set of comparative testing of the material to the existing material are to be mentioned in the present work. In addition, benefits of actuators made with the proposed material are discussed.

Abstract: Many publications have demonstrated advantages of smart polymer actuators over the traditional electromagnetic transducers. One of the most significant contributions of the polymers might be their soft actuation mechanism. Hence unlike the traditional actuators, there is morphological freedom for actuator construction that benefits production of either small scale complex mechanisms or human-like applications. Although many different actuation paradigms of polymer actuators presented in previous publications, no significant contributions are made for the actual industrial applications. A noble idea for acquiring controllable actuation is antagonistic drive mechanism of dielectric elastomer. The mechanism provides fairly accurate controllable motion and relatively large actuation forces. A strong dependency to pre-strain of the polymer is however one of the major constraints of the actuator driving mechanism. A detailed characterization of pre-strain effects should be done for the successful construction of the actuators. Hence an experimental and theoretical consideration about mutual effects of pre-strain and actuator performance is to be presented in the present work.

Abstract: Smart polymer based actuators have demonstrated various benefits over the traditional electromagnetic or piezoelectric-material actuators. One of the most significant contributions of the polymers is its soft actuation mechanisms. Hence morphological freedom for actuator construction benefits production of either small scale complex mechanisms or human-like applications. Although many actuation paradigms of polymer actuators are presented in various publications, no significant contributions are made for investigation of modeling and control methods of the material. In the present work, a smart polymer based actuator is constructed. It is then modeled and analyzed for feasible control scheme selection.

Abstract: The fabrication of dry type conducting polymer actuator was presented. In the preparation of actuator system, nitrile rubber (NBR) was used as a base material of the solid polymer electrolyte. Thin films of NBR (150-200μ m) were prepared by compression molding process. The conducting polymer, poly (3,4- ethylenedioxythiophene) (PEDOT) was synthesized on the surface of NBR by chemical oxidation polymerization technique, and the room temperature ionic liquid, 1-ethyl-3- methylimidazolium bis (trifluoromethyl sulfonyl) imide (EMITFSI) was introduced into the composite film. The ionic conductivity of new type solid polymer electrolyte as a function of the immersion time and the cyclic voltammetry responses and the redox switching dynamics of PEDOT in NBR/ionic liquid solid polymer electrolyte were studied. The displacement of actuator was measured by laser beam radiation.