• Title/Summary/Keyword: Galinstan

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Wearable Force Sensor Using 3D-printed Mold and Liquid Metal (삼차원 프린트된 몰드와 액체 금속을 이용한 웨어러블 힘 센서 개발)

  • Kim, Kyuyoung;Choi, Jungrak;Jeong, Yongrok;Kim, Minseong;Kim, Seunghwan;Park, Inkyu
    • Journal of Sensor Science and Technology
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    • v.28 no.3
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    • pp.198-204
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    • 2019
  • In this study, we propose a wearable force sensor using 3D printed mold and liquid metal. Liquid metal, such as Galinstan, is one of the promising functional materials in stretchable electronics known for its intrinsic mechanical and electronic properties. The proposed soft force sensor measures the external force by the resistance change caused by the cross-sectional area change. Fused deposition modeling-based 3D printing is a simple and cost-effective fabrication of resilient elastomers using liquid metal. Using a 3D printed microchannel mold, 3D multichannel Galinstan microchannels were fabricated with a serpentine structure for signal stability because it is important to maintain the sensitivity of the sensor even in various mechanical deformations. We performed various electro-mechanical tests for performance characterization and verified the signal stability while stretching and bending. The proposed sensor exhibited good signal stability under 100% longitudinal strain, and the resistance change ranged within 5% of the initial value. We attached the proposed sensor on the finger joint and evaluated the signal change during various finger movements and the application of external forces.

A Study on Variable Conductance Radiator using Liquid Metal for Highly Efficient Satellite Thermal Control (인공위성의 고효율 열제어 구현을 위한 액체금속형 가변 전도율 방열판에 관한 연구)

  • Park, Gwi-Jung;Go, Ji-Seong;Oh, Hyun-Ung
    • Journal of Aerospace System Engineering
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    • v.13 no.2
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    • pp.66-72
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    • 2019
  • The observation satellites which uses high heat-dissipating equipment such as synthetic aperture radar (SAR) satellites require a radiator to transmit heat from the equipment into outer space. However, during cold conditions it requires a heater to maintain the temperature of equipment within the allowable minimum limit when it is not in operation. In this study, we proposed a variable conductivity radiator that changes its thermal conductivity value through movement of the liquid metal between two reservoirs based on the temperature condition. This reduces the power consumption of the heater by limiting heat transfer path to the radiator in cold condition, while effectively transferring heat to the radiator during hot condition. The feasibility of the proposed radiator was validated through comparison of the thermal control performance with the conventional fixed conductivity radiator via a thermal analysis.

Evaluation of Sliding Friction Properties of Laser Surface Texturing Dimple Pattern with DLC Coating under GaInSn Liquid Metal Lubricant (액체금속(GaInSn)윤활하에서 DLC(ta-C) 코팅된 레이저 표면 텍스쳐링 딤플패턴의 미끄럼 마찰특성평가)

  • Kwon, Gyubin;Jang, Youngjun;Chae, Younghun
    • Tribology and Lubricants
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    • v.37 no.3
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    • pp.106-111
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    • 2021
  • There are several studies on reducing the friction that occurs on the relative sliding contact surface of moving parts under extreme environments. In particular, a solid lubricated bearing is studied to solve the tribological problem with friction reduction and durability parts using solid lubricants (lead or silver) in a vacuum atmosphere. Galinstan is mainly used as a liquid metal lubricant, but it is inevitable to have limited tribological applications owing to its high coefficient of friction. Many researchers work on surface texturing for surface modification and precision processing methods. To increase durability and low friction, DLC coating with hydrophobicity is applied on the contact surface texture. Therefore, using an untextured specimen, a dimple specimen, and a DLC-coated dimple specimen under liquid metal lubrication, this paper presents the following experimental sliding friction characteristics in the sliding friction test. 1) The average coefficient of friction of the DLC-coated dimple specimen and dimple specimen are lower compared to that of a non-patterned specimen. 2) In the DLC-coated dimple specimens, the average coefficient of friction changes according to the change in the dimple density. 3) DLC-coated dimple specimens with a density of 12.5 have the lowest average coefficient of friction under 41.6 N of normal load and 143.3 RPM.

X-band RADAR Reflected Signal Measurement of Gallium-based Liquid Metal (갈륨에 기초한 액체금속 X밴드 레이더 반사신호 측정)

  • Minhyeok Kim;Sehyeok Kang;Seok-Joo Doo;Daeyoung Kim
    • Journal of the Korea Institute of Military Science and Technology
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    • v.26 no.3
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    • pp.246-251
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    • 2023
  • RADAR(Radio Detection and Ranging) is an important system for surveillance and reconnaissance by detecting a reflected signal which obtains the range from the radar to the target, and the velocity of the target. The magnitude of the reflected signal varies due to the radar cross section of the target, characteristic of the transmission and reception antenna, distance between the radar and the target, and power and wavelength of the transmitted signal. Thus, the RCS is the important characteristic of the target to determine if the target can be observed by the RADAR system. It is based on the material and shape of the target. We have measured the reflection signal of a simple square-shaped (20 × 20 cm) target made of a new material, a gallium-based liquid metal alloy and compared that of well-known metals including copper, aluminum. The magnitude of reflected signal of the aluminum target was the largest and it was 2.4 times larger than that of the liquid metal target. We also investigated the effect of the shape by measuring reflectance of the F-22 3D model(~1/95 ratio) target covered with/without copper, aluminium, and liquid metal. The largest magnitude of the reflected signal measured from side-view with the copper-covered F-22 model was 2.6 times greater than that of liquid metal. The reflectance study of the liquid metal would be helpful for liquid metal-based frequency selective surface or metamaterials.