Molecular dynamics investigation of pull-in instability in graphene sheet under electrostatic and van der Waals forces

Sha'bani, Farzin,Rash-Ahmadi, Samrand Techno-Press 2021 Advances in nano research Vol.11 No.2

This paper investigates the pull-in instability of graphene sheets. The influence of geometry parameters such as chirality of graphene and length to gap ratio is studied using molecular dynamics (MD). For molecular interactions, the AIREBO potential is used. Furthermore, by applying the electrostatic and van der Waals (vdW) forces, pull-in voltages are calculated. Size effect is estimated, with adding the fringing field effect correction factor to the electrostatic force. In MD simulations, the graphene sheets on the armchair and zigzag structure have been investigated. The results show that the closer the moving electrode to the fixed electrode, the greater the effect of van der Waals force than the electrostatic force. The results also represent that the vdW force and fringing effect on the electrostatic load increases the pull-in deflection and decrease the pull-in voltage. The numerical results of the present study show good agreement with previous analytical and experimental researches.

미세 전극 패턴을 갖는 알루미나 정전척을 이용한 LED용 사파이어 기판 흡착 연구

김형주(Hyung-Ju Kim),신용건(Yong-Gun Shin),안호갑(Ho-Kap Ahn),김동원(Dong-Won Kim) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.4

In this work, handling of sapphire substrate for LED by using an electrostatic chuck was studied. The electrostatic chuck consisted of alumina dielectric, which was doped with 1.2 wt% TiO₂. As the volume resistivity of alumina dielectric was decreased, the electrostatic force was increased by Johnsen-Rahbek effect. The narrower width and gap size of electrode led to the stronger electrostatic force. When alumina dielectric with 3.20×10¹¹Ωㆍ㎝ resistivity and 3 ㎜ width/1.5 ㎜ gap sized electrode was used, the strongest electrostatic force in this work was obtained, which value reached to ~14.46 gf/㎠ at 2.5 ㎸ for 4-inch sapphire substrate. This results show that alumina electrostatic chuck with low resistivity and fine electrode pattern is suitable for handling of sapphire substrate for LED.

증착용 정전척의 기판 크기에 따른 척킹력 및 기판 변형 특성 연구

김성빈,민동균,Seong Bin Kim,Dong Kyun Min 한국반도체디스플레이기술학회 2024 반도체디스플레이기술학회지 Vol.23 No.2

A Electrostatic chuck is a device that fixes the substrate, using the force between charges applied between two parallel plates to attract substrates such as wafers or OLED panels. Unlike mechanical suction methods, which rely on physical fixation, this method utilizes the force of electrostatics for fixation, making it important to verify the adhesion force. As the size of the substrate increases, deformations due to gravity or chucking force also increase, and the adhesion force decreases rapidly as the distance between the chuck and the substrate increases. The outlook for displays is shifting from small to large OLEDs, necessitating consideration of substrate deformations. In this paper, to confirm the deformation of the substrate through various patterns, a simplified 2D model using Ansys' electromagnetic field analysis program, Maxwell, and the static structural analysis program, Mechanical, was utilized to observe changes in adhesion force according to the variation in the air gap between the substrate and the chuck. Additionally, the chucking force was analyzed for the size of the substrate, and the deformation of the substrate was confirmed when gravity and chucking force act simultaneously.

Simulation of droplet generation through electrostatic forces

Rahman, Khalid,Ko, Jeong-Beom,Khan, Saleem,Kim, Dong-Soo,Choi, Kyung-Hyun 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.1

This paper represents the multiphysics simulation of droplet generation of ink containing conductive nano-particles through electrostatic forces on substrate. The main focus is to investigate the phenomena by generating the drops through a nozzle with the help of electrostatic forces. The electrostatic based deposition system has vast application in printed electronics and biotechnology. In electrostatic deposition mechanism for droplet generation, a strong electric potential is applied at the tip of the nozzle; due this electric potential, the liquid containing the nano-particles experience strong electrostatic static forces at the interface with the air (at the tip of the nozzle). When these electrostatic forces exceed the internal (viscous forces) and external forces (surface tension), a deformation takes place which results in the flow of the liquid in the form of droplets. The size of the droplet is dependent on different parameters like applied voltage, properties of the ink, dimension of the nozzle. To have better understanding of this, a numerical simulation was performed based on multi-physics approach. Multiple simulations were performed by changing the position of electrode in nozzle and varying the applied voltage. Droplet size with respect to applied voltage was evaluated; electric field with respect to applied voltage and time for the droplet generation was also evaluated through these simulations. This study will help in better understanding the parameters of droplet generation phenomena and optimal design of the nozzle for the electrostatic inkjet system.

Threshold Voltage Model of Fast-Moving Ball Actuator

홍문표,Jongmo Lee,전철규,윤호원,배병성,한승오 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.2

We clarified underlying physics and thereby developed threshold voltage model of a fast-moving ball actuator (FMBA) for reflective electronic paper display. The proposed threshold voltage model starts from considering all the related forces of Coulomb force, dielectrophoretic (DEP) force, frictional force, and adhesion caused by van der Waals force, where frictional force consists of vertical Coulomb and DEP forces, buoyance, and gravity. Considering 3-dimensional geometric effect, Coulomb and DEP forces were analyzed through numerical simulations while all the remaining forces were analytically modeled. As a result, DEP force, buoyance, and gravity were concluded negligible compared to Coulomb force and van der Waals force. With the simplified threshold voltage model, the required driving voltage of 39.54 V was obtained, which matched well to the measured voltage of 40 V.

OLED 증착용 정전척 개발을 위한 척킹력 분포와 변화 특성 연구

민동균,임충환,김성빈 한국반도체디스플레이기술학회 2023 반도체디스플레이기술학회지 Vol.22 No.3

The electrostatic chuck is a technology that uses electroadhesion to attach objects and is widely used in semiconductor and display processes. This research conducted Maxwell by varying parameters to examine the distribution and variations of chucking force in a bipolar-type ESC. The parameters that were changed include the material properties of the dielectric layer and attachment substrate, applied voltage to the electrode, and the gap and width between the electrodes. The analysis results showed that as the relative permittivity of the dielectric layer and substrate increased, the chucking force also increased, with the relative permittivity of the substrate having a greater impact on the chucking force. And increasing the applied voltage led to an increase in both the chucking force and its rate of change. Lastly, as the gap between the electrodes increased, the chucking force rapidly decreased until a certain distance, after which the decrease became less significant. On the contrary, increasing the electrode width resulted in a rapid increase in the chucking force until a certain width, beyond which the increase became less pronounced, eventually converging to a chucking force of 1700 Pa. This paper is expected to have high potential for the development and research of ESC for OLED deposition.

쿨롱 타입 정전척의 유한요소해석

최재석(Jae Seok Choi),홍상준(Sang-Joon Hong),유정훈(Jeonghoon Yoo),김태현(Tae-Hyun Kim),이성진(Sung Jin Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

This research tries to compute the attractive force between Coulomb type electrostatic chuck(ESC) and liquid-crystal display(LCD) panel using the finite element analysis and confirms the influence of the air gap upon the attractive force. The air gap exists between LCD panel and the dielectric layer of the ESC and its thickness is below a few hundreds nanometers. The attractive force acting on perpendicular direction to the ESC can be obtained by applying the force calculation method, called the Maxwell stress tensor. In conclusion, the modeling of the air gap is essential to derive the attractive force of the ESC.

Simulation and Experimental Research on Shape Adjustment of Membrane Reflector Antenna (MRA) Combined with Electrostatic Forces and Boundary Cable Forces

Wang Zhong,Yongzhen Gu,Shunji Zhang,Qinggang Zhang 한국항공우주학회 2024 International Journal of Aeronautical and Space Sc Vol.25 No.2

The membrane reflector antenna (MRA) possesses significant advantages, such as being light in weight and having a large storage ratio. As a result, it is considered one of the critical forms of space-borne antennas. However, the MRA faces a challenge in that it is easily impacted by thermal loads in space, and there is a lack of effective shape adjustment means. To address this issue, a bidirectional adjustment method has been proposed utilizing electrostatic forces and boundary cable forces. Firstly, the mechanical analysis model of the MRA, including the cable-membrane-truss structure, is constructed based on the energy variation principle. Then the calculation formula of electrostatic forces has been deduced considering the change in the distance between the membrane reflector surface and the membrane control surface. The update process of electrostatic forces has also been presented. Finally, an optimization model of the shape adjustment of the MRA has been established, with electrode voltages and boundary cable forces as design variables and the surface accuracy of the membrane reflector as the optimization goal. Simulation examples have been conducted under three types of temperature loads, and a 10:1 scaled experimental prototype has been used to verify the effectiveness of the shape adjustment method.

정전력 질감제시장치의 평가를 위한 손끝 마찰시험기 개발

신현덕(Hyunduk Shin),강정구(Jeonggoo Kang),최윤정(Yoonjeong Choi),김희원(Heewon Kim),류제하(Jeha Ryu) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11

This paper presents a finger pad friction tester for evaluation of tactile displays that modulate surface friction via electrostatic force. Normal force control of this instrument is performed with a balance beam by placing weights on the beam. A finger supporter which is designed for easy finger rest and hold is moved by motorized linear stage. Reciprocating frictional force tests are carried out between a finger pad and an electrostatic tactile display. In this test, the sinusoidal wave is applied to the display by varying frequency. The results obtained with the use of our tester are in agreement with the recent study. Therefore, the developed finger pad friction tester is capable of frictional force tests for evaluation of electrostatic tactile display.

자유 표면 유동의 정전기력 제어에 관한 수치해석

이유섭(You-Seop Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

This paper presents numerical studies of electrostatically-driven free surface flows using the COMSOL Multiphysics. Electrostatic forces are calculated by a weak formulation of the Maxwell stress tensor. Fluid interfaces are tracked with the Level Set Method. The numerical method is first validated with the leaky-dielectric model of Melcher and Taylor on the electro-capillary cellular flow. Second, the Taylor cone formation is simulated to investigate drop ejection phenomena for an electrostatic inkjet head. It is found that hydrophobic surface wetting conditions are beneficial for a better and earlier drop ejection. It is suggested that Marangoni flow can be used to control the electro-capillary flow and vice versa.