• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.339-342
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• 1999

The equation of output voltage from the PVDF was derived. When impact force applied to the PVDF films of cantilever beam and one-end fixed, other-end supported beam structure, output voltage equation induced. Experimental output voltages by falling ball agreed quite well with induced theoretical data. This PVDF film showers to be in high possibility in a warning system of abnormal pulse rate and breathing, and in detecting impact force and/or mechanical energy.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.462-465
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• 2009

Cellulose based electro-active paper (EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. Beside of the natural abundance, cellulose EAPap is fascinating with its biodegradability, lightweight, high mechanical strength and low actuation voltage. An actuating mechanism of EAPap is revealed to be the combination of ion migration effect and piezoelectricity. EAPap can generate the electrical current and voltage when the mechanical stress applied due to its electro-mechanical characteristics. In this paper, we investigated the feasibility of EAPap as a mechanical strain sensor.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.671-679
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• 2018

Finite element analyses are carried out to understand the piezoelectric behaviors of ZnO nanowires. Three different types of ZnO nanowires, with aspect ratios of 1:2. 1:31, and 1:57, are analyzed for uniaxial compression, pure bending, and buckling. Under the uniaxial compression with a strain of $1.0{\times}10^{-4}$ as the reference state, it is predicted that all three types of nanowires develop the same magnitude of the piezoelectric fields, which suggests that longer nanowires exhibit higher piezoelectric potential. However, this prediction is not in agreement with the experimental results previously reported in the literature. Such discrepancy is understood when the piezoelectric behaviors under bending and buckling are considered. When only the strain field due to bending is present in bending or buckling, the antisymmetric nature of the through-thickness stain distribution indicates that two piezoelectric fields, the same in magnitude and opposite in sign, develop along the thickness direction, which cancels each other out, resulting in a zero net piezoelectric field. Once additional strain contribution due to axial deformation is superposed on the bending, such field cancelling is compensated for due to the axial component of the piezoelectric field. Such numerical predictions seem to explain the reported experimental results while providing a guideline for the design of nanowire-based piezoelectric devices.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.314-316
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• 2011

This paper develops a spectral element model for the composite beams with a surface-bonded piezoelectric layer from the governing equations of motion. The governing equations of motion are derived from Hamilton's principle by applying the Bernoulli-Euler beam theory for the bending vibration and the elementary rod theory for the longitudinal vibration of the composite beams. For the PZT layer, the Bernoulli-Euler beam theory and linear piezoelectricity theory are applied. The high accuracy of the present spectral element model is evaluated through the numerical examples by comparing with the finite element analysis results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.73-76
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• 2007

Electro-Active paper (EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It is made by cellulose that is abundant material in nature. EAPap is fascinating with its biodegradability, lightweight, large displacement, high mechanical strength and low actuation voltage. Actuating mechanism of EAPap is known to be the combined effects of ion migration and piezoelectricity. However, the electromechanical actuation mechanisms are not yet to be established. This paper presents the modeling of the actuation behavior of water infused cellulose samples and their composite dielectric constants calculated by Maxwell-Wagner theory. Electro-mechanical forces were calculated using Maxwell stress tensor method. Bending deflection was evaluated from simple beam model and compared with experimental observation, which result good correlation with each other.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.9
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• pp.915-921
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• 2009

Cellulose based electro-active paper(EAPap) is considered as a new smart material which has a potential to be used for biomimetic actuators and sensors. Beside of the natural abundance, cellulose EAPap is fascinating with its biodegradability, lightweight, high mechanical strength and low actuation voltage. When the external stress is applied to EAPap, it can generate the electrical output due to its piezoelectric property. Using piezoelectric behavior of EAPap, we studied the feasibility of EAPap as mechanical strain sensor applications and compared to commercial strain sensor. By measuring the induced output voltage from the thin piezoelectric cellulose EAPap under static and dynamic force, we propose cellulose EAPap film as a potential strain sensor material.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.12
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• pp.1179-1183
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• 2007

Electro-Active paper(EAPap) is a new smart material that has a potential to be used in biomimetic actuator and sensor. It is made by cellulose that is abundant material in nature. EAPap is fascinating with its biodegradability, lightweight, large displacement, high mechanical strength and low actuation voltage. Actuating mechanism of EAPap is known to be the combined effects of ion migration and piezoelectricity. However, the electromechanical actuation mechanisms are not yet to be established. This paper presents the modeling of the actuation behavior of water infused cellulose samples and their composite dielectric constants calculated by Maxwell-Wagner theory. Electro-mechanical forces were calculated using Maxwell stress tensor method. Bending deflection was evaluated from simple beam model and compared with experimental observation, and which result in good correlation with each other.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.727-730
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• 2005

Cellulose based Electro-Active Papers (EAPap) is very promising material due to its merits in terms of large bending deformation, low actuation voltage, ultra-lightweight, and biodegradability. These advantages make it possible to utilize applications, such as artificial muscles and achieving flapping wings, micro-insect robots and smart wall papers. This paper investigates the in-plane strains of EAPap under electric fields, which are useful for a contractile actuator application The preparation of EAPap samples and the in-plane strain measurement system are explained, and the test results are shown in terms of electric field, frequency and the oriental ions of the samples. The power consumption and the strain energy of EAPap samples are discussed. Although there are still unknown facts in EAPap material, this in-plane strain may be useful for artificial muscle applications.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.43-53
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• 2021

Dynamic behavior of piezoelectric ZnO nanowires is investigated using finite element analyses (FEA) on FE models constructed based on previous experimental observations in which nanowires having aspect ratios of 1:2. 1:31, and 1:57 are obtained during a hydrothermal process. Modal analyses predict that nanowires will vibrate in lateral bending, uniaxial elongation/contraction, and twisting (torsion), respectively, for the three ratios. The natural frequency for each vibration mode varies depending on the aspect ratio, while the frequencies are in a range of 7.233 MHz to 3.393 GHz. Subsequent transient response analysis predicts that the nanowires will behave quasi-statically within the load frequency range below 10 MHz, implying that the ZnO nanowires have application potentials as structural members of electromechanical systems including nano piezoelectric generators and piezoelectric dynamic strain sensors. When an electric pulse signal is simulated, it is predicted that the nanowires will deform in accordance with the electric signal. Once the electric signal is removed, the nanowires exhibit a specific resonance-like vibration, with the frequency synchronized to the signal frequency. These predictions indicate that the nanowires have additional application potential as piezoelectric actuators and resonators.