Papers by Author: Jae Hwan Kim

Abstract: The application of electroactive polymer devices requires the availability of their properties at various operating conditions. This in turn necessitates a structure-property relationship based on an in-depth understanding of the underlying mechanism responsible for their strain-field response. Cellulose-based Electro-Active Paper (EAPap) has been studied as an attractive Electro Active Polymer (EAP) material for artificial muscles. The feasibility of EAPap material as an actuator/sensor application is greatly dependant on piezoelectric effect. In this paper, converse and di rect piezoelectric ef fect s of Electro-Active Paper materials are studied to characterize piezoelectric effects of EAPap. All experiments were conducted in an environmental chamber that can control temperature and humidity.

Abstract: Electro-Active Paper (EAPap) is attractive for a biomimetic actuator material due to its merits in terms of lightweight, dry condition, large displacement output, low actuation voltage and biodegradability. However, the performance of EAPap actuator is so sensitive to humidity that high humidity is required. We report a robust EAPap actuator that can be activated in room humidity condition. The EAPap is made by dissolving cellulose fibers into a solution using DMAc solvents, and made into a sheet by using casting. Thin electrodes are deposited on the cellulose paper to comprise an EAPap actuator. The fabrication process and the performance evaluation of EAPap are presented in terms of free displacement with respect to frequency and actuation voltage.

Abstract:
Electro-Active Paper (EAPap) materials based on cellulose are attractive for many applications because of their low voltage operation, lightweight, dryness, low power consumption, bio-degradability. The construction of EAPap actuator has been achieved using the cellulose paper film coated with thin gold electrode layers. This actuator showed a reversible and reproducible bending movement. In order to improve both force and displacement of this, efforts are made to construct hybrid EAPap actuators using cellulose paper coated with carbon nanotubes (CNT). To coat the CNT, single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) are dispersed in polyaniline (PANI) matrix, and the solution is coated on the EAPap by using a spin coater. It is expected that the use of CNT can improve the force output by enhancing the stiffness of the hybrid EAPap actuator. Furthermore, the presence of the PANI may improve the actuation performance of the EAPap material. The performance of hybrid EAPap actuators is tested in an environmental chamber in terms of free displacement, blocked force and electrical power consumption. The performance of hybrid actuators is investigated for bio-mimetic applications.

Abstract: A modal strain based damage index is proposed to investigate the damage effects of discrete delaminations in a laminated composite structure. The Fermi-Dirac distribution function is incorporated with an improved layerwise laminate theory to model smooth transition of the displacement and the strain fields at the delaminated interfaces. Modal analysis is conducted to investigate dynamic effects of delamination in a laminated structure and to obtain modal strains. The damage index is calculated based on fundamental modal strains of laminated structures. The damage effects of laminated structures are investigated using arbitrary size, number, location and boundary conditions of discrete delaminations.

Abstract: Cellulose-based Electro-Active Paper (EAPap) has been studied as an attractive electroactive polymer material for artificial muscles due to its low cost, availability, lightweight, large displacement output, low actuation voltage and low power consumption. However, the force output of EAPap is small since paper is so flexible that the bending stiffness is low. In this paper, the cellulose based EAPap material is enhanced by using carbon nanotubes with cellulose paper. Coating of multi-walled carbon nanotubes mixed with polyaniline on EAPap as well as MWNT dispersion in the paper are tried to enhance the force output of the EAPap. The coating process of MWNT/PANI on the EAPap and the dispersion of MWNT in the cellulose paper are explained. The performance of the hybrid EAPap actuators is evaluated in terms of tip displacement, blocking force and electrical power consumption. The power output and the actuator efficiency are improved.

Abstract: A dynamic analysis method has been developed to investigate and characterize the effect due to the presence of discrete single and multiple delaminations of composite laminated structures. The Fermi-Dirac distribution function is combined with an improved layerwise laminate theory to model a smooth transition in the displacement and the strain fields of the delaminated interfaces. In modeling piezoelectric composite plates, a coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. Based on the developed model, the effects of discrete delaminations are quantified by comparing transient responses of composite plates and piezoelectric sensor outputs.

Abstract: This paper introduces the concept of remotely-driven smart actuator utilized by electro-active paper (EAPap). The feature of remotely-driven smart actuator offers unique performance and application capabilities and exploit many of these unique capabilities. Since the microwave-driven actuator does not require carry-on-battery, ultra-lightweight, and distributed micro size actuators can be made. A dipole rectifying antenna (rectenna) array receives the microwave and converts it into a DC power. Recently, cellulose based paper has been came across as an lectroactive paper (EAPap) material so as to be used as artificial muscles for biomimetic insects. Since the power requirement of EAPap is less than the safety limit of microwave power in air, the EAPap actuators can be driven by wireless microwave power. This idea is useful for specific applications that require multifunctional capabilities such as smart skin, ultra-lightweight space structures, micro robots, flapping wing for insect-like flying objects and smart wall paper as well. Current research status along with its issues is addressed including a hybrid actuator of EAPap and conducting polymers that will enhance the performance of the actuator.

Abstract: This paper presents the characterization of Electro-active paper (EAPap). EAPap is a paper that produces large displacement with small force under electrical excitation. EAPap is made with a cellulose paper by constructing thin electrodes on both sides of the paper. When electrical voltage is applied to the electrodes the EAPap produces bending displacement. To be able to apply EAPap in many applications, characterization of EAPap is essential to understand and improve EAPap actuators. The characterization is done in terms of mechanical, electrical and physical tests. Mechanical strain and strength are investigated in sheet level and thermo-mechanical analysis is performed. Electrical resistance and admittance are analyzed to investigate the actuation mechanism. The actuation principle associated with piezoelectric effect is explained. EAPap has merits in terms of lightweight, dry condition, large displacement output, low actuation voltage and low power consumption. The most attractive characteristics of EAPap materials is their application potential for the development of biomimetic systems that are ultra-lightweight, low power, flexible, damage tolerant, noiseless, and agile.