• Elastomers and Composites
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• v.59 no.2
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• pp.73-81
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• 2024

In the field of electronic components, the potting material, which is a part of the electronic circuit package, plays a significant role in protecting circuits from the external environment and reducing signal interference among electronic devices during operation. This significantly affects the reliability of the components. Therefore, the accurate prediction and assessment of the lifespan of a material are of paramount importance in the electronics industry. We conducted an accelerated thermal aging evaluation using the Arrhenius technique on elastic potting material developed in-house, focusing on its insulation, waterproofing, and contraction properties. Through a comprehensive analysis of these properties and their interrelations, we confirmed the primary factors influencing molding material failure, as increased hardness is related to aggregation, adhesion, and post-hardening or thermal-aging-induced contraction. Furthermore, when plotting failure times against temperature, we observed that the hardness, adhesive strength, and water absorption rate were the predominant factors up to 120 ℃. Beyond this temperature, the tensile properties were the primary contributing factors. In contrast, the dielectric constant and loss tangent, which are vital for reducing signal interference in electric devices, exhibited positive changes(decreases) with aging and could be excluded as failure factors. Our findings establish valuable correlations between physical properties and techniques for the accurate prediction of failure time, with broad implications for future product lifespans. This study is particularly advantageous for advancing elastic potting materials to satisfy the stringent requirements of reliable environments.

• Elastomers and Composites
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• v.47 no.4
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• pp.272-281
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• 2012

Flexible/stretchable electronics have recently focused, since their applications extend to emerging flexible displays, sensors, dielectric elastomer actuator and generators, and smart surgical tools. Flexible/stretchable electrodes should be synchronized with employing mechanical deformations of either flexing or stretching modes. Thus, the research area is one of the tough subjects, since the electrodes should keep their basic functions of electrodes under various mode of mechanical deformations. In this review, we discuss the recent development in the preparation and properties of such flexible/stretchable electrodes.

• The Journal of Korea Robotics Society
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• v.1 no.1
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• pp.89-101
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• 2006

Tactile sensation is one of the most important sensory functions for human perception of objects. Recently, there have been many technical challenges in the field of tactile display as well as tactile sensing. In this paper, we propose an innovative tactile display device based on soft actuator technology with ElectroActive Polymer(EAP). This device offers advantageous features over existing devices with respect to intrinsic flexibility, softness, ease of fabrication and miniaturization, high power density, and cost effectiveness. In particular, it can be adapted to various geometric configurations because it possesses structural flexibility, so it can be worn on any part of the human body such as finger, palm, and arm etc. It can be extensively applied as a wearable tactile display, a Braille device for the visually disabled, and a human interface in the future. A new design of the flexible actuator is proposed and its basic operational principles are discussed. In addition, a wearable tactile display device with $4{\times}5$ actuator array(20 actuator cells) is developed and its effectiveness is confirmed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.799-803
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• 2018

We demonstrated memory thin-film transistors (MTFTs) with organic ferroelectric polymer poly(vinylidene fluoride-co-trifluoroethylene) and an amorphous oxide semiconducting indium gallium zinc oxide channel on the elastomeric substrate. The dielectric constant for the P(VDF-TrFE) thin film prepared on the elastomeric substrate was calculated to be 10 at a high frequency of 1 MHz. The voltage-dependent capacitance variations showed typical butterfly-shaped hysteresis behaviors owing to the polarization reversal in the film. The carrier mobility and memory on/off ratio of the MTFTs showed $15cm^2V^{-1}s^{-1}$ and $10^6$, respectively. This result indicates that the P(VDF-TrFE) film prepared on the elastomeric substrate exhibits ferroelectric natures. The fabricated MTFTs exhibited sufficiently encouraging device characteristics even on the elastomeric substrate to realize mechanically stretchable nonvolatile memory devices.

• Composites Research
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• v.32 no.5
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• pp.211-215
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• 2019

The cell culture process under in vitro condition is much different from the actual human body environment. Therefore, in order to precisely simulate the human body environment, a dynamic cell culture device capable of delivering mechanical stimulation to cells is essential. However, conventional dynamic cell culture devices require relatively complicated devices such as tubes, pumps, and motors, and the mechanical stimuli delivered is also simple. In this study, an electro-active polymer actuator as a driving component is introduced to design simply driven dynamic cell culture device without complicated components. The device is capable of delivering relatively complex mechanical stimuli to the cells.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1497-1502
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• 2012

To manufacture a robot hand that essentially mimics the functions of a human hand, it is necessary to develop flexible actuators and sensors. In this study, we propose the design, manufacture, and performance verification of flexible actuators and sensors based on Electro Active Polymer (EAP). EAP is fabricated as a type of film, and it moves with changes in the voltage because of contraction and expansion in the polymer film. Furthermore, if a force is applied to an EAP film, its thickness and effective area change, and therefore, the capacitance also changes. By using this mechanism, we produce capacitive actuators and sensors. In this study, we propose an EAP-based capacitive sensor and evaluate its use as a robot hand sensor.

• Composites Research
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• v.37 no.4
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• pp.247-264
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• 2024

Recent advances in electro-active polymer (EAP) actuators, owing to their flexibility, lightweight, and simple fabrication process, have showcased their high utility across various fields such as soft robotics, biomimetics, wearable devices, and haptic technologies. Moreover, EAP actuators are evolving into smart devices with new functions and characteristics through the integration of functional materials and innovative technologies. This paper categorizes EAPs into ionic EAPs and electronic EAPs. Ionic EAPs include, most notably, ionic polymer-metal composites (IPMCs) and conducting polymers (CPs), while electronic EAPs encompass dielectric elastomer actuators (DEAs), ferroelectric polymer actuators, and the recently introduced hydraulically amplified self-healing electrostatic (HASEL) actuators. Detailed explanations based on the latest research are provided concerning the mechanism, structure, performance improvement strategies, methods for adding functionality, and application areas for each type of actuator.