Yuan Xi, Tang Biao, Barman Jitesh, Groenewold Jan, Zhou Guofu
Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute of Electronic Paper Displays South China Academy of Advanced Optoelectronics, South China Normal University Guangzhou 510006 P. R. China
National Center for International Research on Green Optoelectronics, South China Normal University Guangzhou 510006 P. R. China.
RSC Adv. 2020 May 27;10(34):20257-20263. doi: 10.1039/d0ra02405h. eCollection 2020 May 26.
As the most widely used insulator materials in the electrowetting (EW) systems, amorphous fluoropolymers (AFs) provide excellent hydrophobicity, dielectric properties and chemical inertness; however, they suffer from charge trapping during electrowetting with water and the consequent asymmetric phenomenon. In this study, an ultra-thin oil-lubricated AF surface was proposed to release the charge trapping in the dielectric layer and further suppress the polarity-dependent asymmetry during electrowetting. The negative spontaneously trapped charges gathering on the dielectric/water interface with aging time were characterized by various measurements and calculations, which explained the polarity dependence of the asymmetric electrowetting. Approximately symmetric EW curves withstanding water aging were obtained for the oil-lubricated AF surface, confirming the blocking effect on charge trapping induced by the lubricated surface. The improved reversibility of EW with low contact angle hysteresis brought by the oil-lubricated surface was also demonstrated. This study reveals the mechanism behind the asymmetric EW phenomenon and offers an attractive oil-lubricated EW material system for suppressing the charge trapping on the dielectric/water interface, which can significantly improve the manipulation of the EW devices.
作为电润湿（EW）系统中使用最广泛的绝缘材料，非晶态含氟聚合物（AFs）具有出色的疏水性、介电性能和化学惰性；然而，在与水进行电润湿过程中，它们会出现电荷俘获以及随之而来的不对称现象。在本研究中，提出了一种超薄油润滑AF表面，以释放介电层中的电荷俘获，并进一步抑制电润湿过程中与极性相关的不对称性。通过各种测量和计算对随着老化时间在介电/水界面上聚集的负自发俘获电荷进行了表征，这解释了不对称电润湿的极性依赖性。对于油润滑AF表面，获得了经受水老化的近似对称的EW曲线，证实了润滑表面对电荷俘获的阻断作用。还证明了油润滑表面带来的具有低接触角滞后的EW可逆性的改善。本研究揭示了不对称EW现象背后的机制，并提供了一种有吸引力的油润滑EW材料系统，用于抑制介电/水界面上的电荷俘获，这可以显著改善EW器件的操控性能。
