基于超疏液表面数字微流控芯片的液滴润湿机理及液滴动力学研究

Digital microfluidics, in which droplets are manipulated on the planar surfaces, have brought many unique advantages compared with traditional channel-based microfluidics. Superlyophobic surfaces, with excellent performances such as high contact angle, low adhesion and low flow resistance to almost any liquid, are proposed as an excellent platform for droplet manipulation in digital microfluidics. Both the motion and evaporation of droplets on digital microfluidic chips are closely related to the wetting mechanisms and droplet dynamic characteristics. Based on our rich research efforts in related areas, we plan to combine experimental observations, theoretical analysis and numerical simulation to explore the wetting mechanisms and droplet dynamics on superlyophobic surfaces. We will analyze the mechanism of the bending three-phase contact line and the pressure stability of superlyophobic surfaces constituted by typical microstructures, clarify the design criteria for superlyophobic surfaces and establish a universal wetting model to predict the contact angle for various liquids on superlyophobic surfaces. Then we will study the precise control of droplet motion on superlyophobic surfaces based on the analysis of forced exerted on droplets and the influence factors on the contact angle hysteresis. We will also adjust the movement of three-phase contact line through tunning the liquid droplet evaporation and condensation to achieve controllable deposition of droplet solute on superlyophobic surfaces. This study will contribute to a thorough understanding of the wetting mechanisms and droplet dynamics on superlyophobic surfaces, and will promote application of superlyophobic surfaces in digital microfluidics, which is of great academic significance and practical importance.

在芯片表面操控液滴的数字微流控系统拥有许多通道微流控系统所不具备的独特优点。超疏液表面对几乎任何液体都具有高接触角、低粘附和低流阻的特性，使其成为在表面操控液滴的数字微流控芯片的绝佳选择。数字微流控系统中液滴的运动、蒸发等问题都与表面的润湿特性和液滴的动力学特性紧密相关，本项目将在课题组多年研究积累的基础上，采用实验观测、理论分析和数值模拟相结合的方法进行深入研究：通过分析超疏液表面三相接触线弯曲的机理和压力稳定性，阐明超疏液表面结构的设计准则，并推导普适的超疏液表面的接触角模型；通过对超疏液表面液滴的受力分析和接触角滞后影响因素的分析，实现超疏液表面液滴运动的精确控制；通过调节液滴的蒸发和冷凝控制液滴三相接触线的移动速度，实现液滴中溶质的可控沉积。本研究将有助于透彻理解超疏液表面液滴润湿机理和液滴动力学特性，并促进超疏液表面在数字微流控系统中的应用，具有重要的学术意义和实用价值。

微流控芯片（Microfluidics）是指将生物、化学和医学等领域的样品前处理、反应、分离和检测等基本操作单元微型化并集成在厘米级的芯片上，通过微尺度的流体操控实现常规生物、化学和医学实验室中各种检测、分析功能的系统。近年来在超疏水表面基础上发展起来的超疏液表面（Superlyophobic surface）非常适合于解决平面微流控芯片的表面清洁、对不同液体的适用性等问题。本项目以基于超疏液表面的平面微流控芯片为背景，针对微流控系统中液滴复杂的运动形式及其力学机理进行了研究。本报告通过理论、实验及数值模拟相结合的方法，对超疏液表面的运动、液滴蒸发等表界面润湿问题进行了深入探讨。从三相接触线、接触角和接触角滞后等角度研究超疏液表面的润湿机理。主要阐明了超疏水上液滴运动相关的几项内容：(1) 具有普适性的超疏液润湿模型； (2) 揭示了超疏液表面微结构对液滴接触线移动的影响机制；(3) 实现了液滴的无损转移。研究阐明了超疏液表面微结构的设计准则，揭示了超疏液表面微结构对液滴运动的影响规律，对于更好地将超疏液表面应用于平面微流控系统具有重要的实际意义。本项目共发表论文10篇，其中SCI检索论文3篇，均发表在Journal of Physical chemistry C, Sensors and Actuators B 等表界面化学、微流控传感器等领域的重要期刊上。另有EI收录会议论文3篇。部分成果获得了中国微米纳米学会年会优秀口头报告等荣誉，且研究成果共申请国家专利5项。本项目还协助培养硕士研究生一名。科研成果数量与质量、学生培养等要求均超出了预期研究计划。