介电层表面纳米织构化及其电润湿行为影响研究

Study on Surface Nanotexturization of Dielectric Layer and Its Effect on the Electrowetting Behavior

为了更好地调控液滴的形状,探讨了纳米织构化介电层表面的电润湿行为.采用刻蚀和软压印方法在导电基底上实现了紫外光固化聚合物(NOA61)介电层的纳米织构;搭建了实验平台,观察对比了厚度相同而形貌不同的介电层表面的电润湿响应.结果表明,平整光滑介电层在电压较低时表现为不可逆的电润湿响应,当方波电压大于200V时则表现为可逆的电润湿响应;网格纳米织构介电层的可逆转变临界电压为350V,而纳米锥织构介电层则在高达500V以上直至产生接触角饱和现象也仍保持不可逆的电润湿响应;几种介电层的饱和接触角趋于一致.之所以水滴在纳米织构化的介电层表面发生了不可逆的Wenzel接触模式润湿转变,是由于水滴在电场下与织构微观表面之间具有较高的粘滞作用.

In order to better manipulate the droplet shape, the effect of surface nanotexturization of die-lectric layer on the electrowetting behavior was studied. In this study, etching and soft nanoimprinting lithography approaches were used to achieve nanotextured dielectric layer on conductive substrate. Meanwhile, experimental platform was established to investigate the electrowetting （EW） effect, and the EW response was compared of several UV-curable polymer （NOA61） dielectric layers with the same thickness but different morphologies. The result shows that, when a square-wave voltage with lower amplitude of 200 V is applied, the flat smooth dielectric layer demonstrates irreversible electrowetting behavior, while it reveals reversible electrowetting response when the applying voltage increased above 200 V. In contrast, grid nanotexture dielectric layer shows a critical voltage of 350 V for reversible tran sition, while nanocone textured dielectric layer keeps irreversible response even up to 500 V until it rea- ches contact angle saturation. Furthermore, the eventual saturation for all samples will become the same for various dielectric layers with the same thicknesses. The irreversible electrowetting may be attributedto the transition of Wenzel contact mode occurring on the surface textured dielectric layer surface, which will trigger a large adhesion between the droplet and the microscopic surfaces of nanotexture.