본 연구에서는 비전도성 매질 내에서 전도성 액적의 접촉 충전 현상에서 전극 표면의 소수성 코팅이 액적의 충전 거동에 미치는 영향을 분석하였다. 동일한 실험장치에서 전극 코팅 종류를 변화시키고, 각 코팅 조건에서 액적의 크기와 전기장의 세기를 변화시켜 전하량의 변화를 분석하였다. 연마만을 진행한 전극에서의 실험을 대조군으로 설정하여 소수성 코팅으로 Teflon과 Thiol 코팅을 적용하여 액적 충전 실험을 진행하였다. Teflon 코팅 전극은 대조군 대비 접촉각

이 약 10° 증가하였으나 충전 성능이 90% 수준을 보였으며 충전량의 편차도 더 크게 나타났다. 이에 반해 Thiol 코팅 전극은 접촉각이 약 21° 증가하여 가장 높은 소수성 특성을 나타냈으나 양극에서의 전하 충전이 거의 일어나지 않는, 기존 액적 접촉 충전 현상에서 보고된 적 없는 특이한 현상이 발견되었다. Thiol 코팅이 보이는 특이한 충전 거동은 Thiol 코팅의 강한 표면 전하에 기인한 것으로 추정되나 추후 추가적인 연구를 통한 확인이 필요할 것으로 판단된다.

실험결과를 토대로 ECD 실험에 사용되는 전극 표면에 소수성 코팅을 진행해야 할 경우, Teflon 코팅을 적용하는 것은 가능하나 Thiol 코팅의 경우, 우수한 소수성 특성에도 불구하고 접촉 충전 거동 및 충전량의 급격한 변화로 전극의 소수성 코팅으로는 적합하지 않은 것으로 판단된다.

In this study, the effect of hydrophobic coating of electrode surface on the charging behavior of droplets in the contact charging phenomenon of conductive droplets in a non-conductive medium was analyzed. In the same experimental device, the type of electrode coating was changed, and the change in charge amount was analyzed by changing the size of the droplet and the intensity of the electric field under each coating condition. The experiment on the electrode that was only polished was set as the control group, and the droplet charging experiment was conducted by applying Teflon and Thiol coatings as hydrophobic coatings. The Teflon-coated electrode showed an increase in the contact angle of about 10° compared to the control group, but the charging performance was at the level of 90%, and the deviation of the charging amount was also larger. In contrast, the thiol-coated electrode showed the highest hydrophobic characteristics with a contact angle increase of approximately 21°, but a peculiar phenomenon that has

not been reported in the existing droplet contact charging phenomenon was found, in which almost no charging occurred at the anode. The peculiar charging behavior exhibited by the thiol coating is presumed to be due to the strong surface charge of the thiol coating, but confirmation through additional research is necessary in the future. Based on the experimental results, if a hydrophobic coating is to be applied to the electrode surface used in the ECD experiment, it is possible to apply a Teflon coating. However, in the case of a thiol coating, although the hydrophobic properties are very excellent, it is not suitable as a hydrophobic coating for the electrode due to the rapid change in contact charging behavior and charging amount.

Droplet, Contact charging, Coating, Electrode surface

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