Fundamentals and Applications of Liquid Drop Interactions with Complex Surfaces

这项拟议的研究是一个独特的项目，旨在了解复杂表面的行为及其与液滴的相互作用。具体地说，它将解决表面上液滴运动的区域，基于液桥的新型光流控器件的制造，以及液滴对复杂(例如编织纺织品)表面的冲击。这项研究可以产生必要的知识，使当今具有战略重要性的先进技术成为可能，例如能源系统(例如高效冷凝器和燃料电池的水管理)、防护纺织品和服装或生物技术(例如聚合酶链式反应机器中的精确点胶)。 将对放置在简单(光滑的疏水或亲水的)或复杂(有图案的)表面上的固定液滴布置在剪切气流中的初始运动进行全面的研究。我们将寻求液滴性质、排列几何和空气速度之间的关系，以实现液滴在表面上的初始运动。通过表面工程策略，我们寻求通过剪切气流，使用带有疏水和亲水区域的有图案的表面，进一步帮助液滴脱落。 掌握有关如何使用液体桥(例如，用于分配和印刷行业)传输液体的基础知识是推进此类工艺的关键。我们将研究非平行表面之间的桥接的复杂情况，以了解表面润湿性和表面之间的二面角在液体转移中的作用。在此过程中，我们将考虑液体属性(表面张力、粘度等)。并对动态和准静态状态进行了研究。我们最近已经证明，通过机械刺激液桥，我们可以制作变焦液体透镜；但为了改善透镜的响应时间，我们将探索液桥在电应力下的形态变化，以开发新型光流控器件(例如变焦柱面透镜)。 将研究多个液滴同时撞击移动表面，目的是了解撞击形态(例如，飞溅限制和静止液滴形状)。此外，对单滴撞击覆盖着一层不相容液体的表面的系统研究将提供有关液滴-薄膜相互作用模式的基本信息，例如薄膜夹带、反弹、飞溅等。首次对液滴冲击机织表面的全面研究将有助于确定最近关于注入液体或超疏水纺织品的保护性质的声明的有效性。 这项提议的核心是为20名不同级别的学生提供培训。他们将通过从事先进成像系统、表面制造和表征以及分析和建模技术的工作，获得加拿大知识经济所需的技能。将通过传播他们的调查结果来磨练沟通技能。

The proposed research is a unique program that seeks to understand the behavior of complex surfaces and their interactions with liquid drops. Specifically, it will tackle areas of drop motion on a surface, fabrication of novel opto-fluidic devices based on liquid bridges, and drop impact onto complex (e.g. woven textile) surfaces. This research can produce the necessary knowledge to enable advanced technologies of strategic importance today, such as, energy systems (e.g. efficient condensers, and water management for fuel cells), protective textile and clothing, or biotechnology (e.g. accurate dispensing in PCR machines). A comprehensive study of incipient motion of sessile drop arrangements placed on a simple (smooth hydrophobic or hydrophilic), or a complex (patterned) surface exposed to a shearing airflow will be done. We will seek relations between drop properties, arrangement geometry and air velocity for incipient motion of drops on a surface. Through surface engineering strategies we seek to further assist the shedding of drops, by a shearing airflow, using patterned surfaces with hydrophobic and hydrophilic regions. Gaining fundamental knowledge about how to transfer liquids using a liquid bridge (e.g. used in dispensing and printing industries) is the key to advance such processes. We will study the complex case of bridges between non-parallel surfaces to understand the role of surface wettabilities, and dihedral angle between surfaces, in liquid transfer. In doing so we will consider liquid properties (surface tension, viscosity, etc.) and study both dynamic and quasi-static regimes. We have recently shown that by mechanically stimulating a liquid bridge, we can make a varifocal liquid lens; but to improve the response time of the lens, we will explore morphological changes of a liquid bridge under an electrical stress to develop novel optofluidic devices (e.g. a varifocal cylindrical lens). Simultaneous impact of multiple drops onto moving surfaces will be studied with the aim of understanding the impact morphology (e.g. splash limits, and resting drop shapes). Also, a systematic study of a single drop impact onto surfaces covered with a thin layer of an immiscible liquid will provide the fundamental information regarding the modes of drop-film interactions, e.g. film entrainment, bouncing, splashing, etc. A first comprehensive study of drop impact onto woven surfaces will allow determining the effectiveness of the claims made recently about protective nature of liquid infused or superhydrophobic textiles. This proposal, at its core, is designed to provide training for 20 students at different levels. They will gain skills needed for Canada's knowledge based economy by working on advanced imaging systems, surface fabrication and characterization, as well as analytical and modeling techniques. Communication skills will be honed through disseminating their findings.