Fundamentals and Applications of Liquid Drop Interactions with Complex Surfaces

提出的研究是一个独特的程序，旨在了解复杂表面的行为及其与液滴的相互作用。具体来说，它将处理表面上的水滴运动区域，基于液体桥的新型光流体装置的制造，以及水滴对复杂表面（例如编织纺织品）的冲击。这项研究可以产生必要的知识，使今天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），保护性纺织品和服装，或生物技术（例如，在PCR机器中精确分配）。将对暴露在剪切气流中的简单（光滑疏水或亲水）或复杂（图案）表面上的无基液滴排列的初始运动进行全面研究。我们将寻求液滴在表面上的初始运动的性质、排列几何和空气速度之间的关系。通过表面工程策略，我们寻求通过剪切气流进一步帮助液滴脱落，使用带有疏水和亲水区域的图案表面。获得关于如何使用液体桥转移液体的基本知识（例如用于点胶和印刷工业）是推进此类过程的关键。我们将研究非平行表面之间桥的复杂情况，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，我们将考虑液体的性质（表面张力、粘度等），并研究动态和准静态状态。我们最近展示了通过机械刺激液体桥，我们可以制造一个变焦液体透镜；但为了提高透镜的响应时间，我们将探索电应力下液体桥的形态变化，以开发新型光流体器件（如变焦圆柱透镜）。将研究多个液滴对移动表面的同时冲击，以了解冲击形态（例如飞溅限制和静止液滴形状）。此外，对单滴撞击覆盖有一层不混溶液体的表面的系统研究将提供关于滴膜相互作用模式的基本信息，例如膜夹带、弹跳、飞溅等。一项关于水滴对织物表面冲击的首次全面研究将允许确定最近关于液体注入或超疏水纺织品保护性质的声明的有效性。该提案的核心是为20名不同级别的学生提供培训。他们将通过研究先进的成像系统、表面加工和表征以及分析和建模技术，获得加拿大知识型经济所需的技能。沟通技巧将通过传播他们的发现得到磨练。

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.