Mi Yuhang, Liu Xiaohu, Gao Zuoxuan, Wang Mengtong, Shi Lihong, Zhang Xiong, Gao Kaifang, Mugisha Euphrem Rwagasore, Yan Wenbo
School of Materials Science and Engineering, Hebei Engineering Laboratory of PFC, Hebei University of Technology, Tianjin 300130, China.
Department of Physics, Tianjin Chengjian University, Tianjin 300384, China.
ACS Appl Mater Interfaces. 2021 Sep 22;13(37):45018-45032. doi: 10.1021/acsami.1c10940. Epub 2021 Sep 5.
So far, microfluidic navigation based on space-charge modulation is limited in a two-dimensional (2D) substrate plane. In this paper, a three-dimensional (3D) photovoltaic water-microdroplet router based on a superhydrophobic LiNbO:Fe crystal is reported. This router employs the repulsive electrostatic force induced by the positive photovoltaic charges generated under focused laser illumination and permits traveling microdroplets to be routed in both in-plane and out-of-plane ways. By analyzing the dynamic process of microdroplet routing, it is found that the microdroplets can gain positive charges through traveling on a superhydrophobic surface and that the positive photovoltaic charges exert an electrophoretic (EP) force on the microdroplets being charged and make them either routed inside the 2D substrate plane or jump out of the 2D plane through electrostatic ballistic ejection. The laser-illumination and microdroplet-size dependence of the deflecting parameters of the in-plane microdroplet routing as well as the jumping trajectory of the out-of-plane routing are investigated. An electrostatic kinetic model is established for both routing ways, and the simulation based on this model predicts well the experimental dependence. A few examples of cascaded free-space microfluidic transportation using the 3D photovoltaic router are demonstrated, showing the potential of this technique in future biological applications.
到目前为止，基于空间电荷调制的微流体导航仅限于二维（2D）衬底平面。本文报道了一种基于超疏水LiNbO:Fe晶体的三维（3D）光伏水微滴路由器。该路由器利用聚焦激光照射下产生的正光伏电荷诱导的排斥静电力，使行进的微滴能够以平面内和平面外的方式进行路由。通过分析微滴路由的动态过程，发现微滴在超疏水表面行进时可以获得正电荷，并且正光伏电荷对被充电的微滴施加电泳（EP）力，使它们要么在二维衬底平面内路由，要么通过静电弹道弹射跳出二维平面。研究了平面内微滴路由的偏转参数以及平面外路由的跳跃轨迹对激光照射和微滴尺寸的依赖性。针对这两种路由方式建立了静电动力学模型，基于该模型的模拟很好地预测了实验依赖性。展示了使用3D光伏路由器进行级联自由空间微流体传输的几个示例，显示了该技术在未来生物应用中的潜力。
