Research tools for understanding soft wetting

申请人打算研究液体在柔软表面上的动态润湿行为。软质材料对迎面而来的液滴的反应方式是非平凡的，与刚性表面有很大不同。软质材料在设计防液自清洁和防污表面方面具有很大的潜力，与传统的微/纳米结构或液体注入表面相比，软质材料具有许多优势，包括在广泛的工作范围内的可靠性和长期耐用性。然而，在了解软表面对液滴的动态响应方面的科学努力相对较少。在这项研究中，申请人打算寻求动态软润湿的两个基本问题的答案。首先，液滴最初接触到柔软的表面时是如何扩散的；其次，当液滴撞击到柔软的可变形表面时会发生什么？这两种现象本质上都是短暂的，通常持续时间只有几秒钟。最近，申请人在实验室安装了双波长反射干涉对比显微镜（DW-RICM）系统，该系统专门用于探测液滴与软表面的复杂相互作用，通常发生在纳米尺度上。静态润湿的初步实验表明，该技术在获得润湿行为的宝贵见解方面具有很大的潜力。申请人的研究小组还开发了一种内部图像处理算法来解释实验数据。然而，由于其内置的CCD相机，DW-RICM本质上被限制在低帧速率下成像（所需视场最大60 fps），严重限制了其在捕获瞬态润湿动态方面的适用性。申请人打算用两台高速摄影机取代DW-RICM现有的探测系统，以克服这一瓶颈。这将使成像速率提高到160,000 fps，使用户能够以所需的时空精度探测润湿动态。这两台相机将协同工作，从底部拍摄液滴在柔软表面上的瞬态润湿行为（扩散和冲击）。每一个捕获的动态干扰特征产生的表面照明与两个激光源之一存在于双波长系统。另一个高速摄像机（已在申请人的实验室中提供）将与系统集成，以捕获侧视图，以获得动态交互的整体描述。从这项研究中产生的见解将扩大对软润湿的基本理解的界限，并为实际应用创造机会，特别是在制药和食品包装行业，最终推动加拿大经济向前发展。此外，这个最先进的系统一旦投入使用，将提供给加拿大各地的界面科学界。

The applicant intends to investigate the dynamic wetting behaviour of liquids on soft surfaces. The way a soft material responds to an oncoming droplet is non-trivial and significantly different from rigid surfaces. Soft materials exhibit promising potential in designing liquid-repellent self-cleaning and anti-fouling surfaces and offer several advantages over the conventional micro/nanostructured or liquid infused surfaces, including reliability in a wide range of operational spectrum and long-term durability. However, scientific endeavour on understanding the dynamic response of a soft surface towards a droplet is relatively scarce. In this research, the applicant intends to seek answers to two fundamental questions in dynamic soft wetting. First, how does a droplet spread upon its initial contact with soft surfaces and second, what happens when a liquid droplet impinges on a soft deformable surface? Both of these phenomena are intrinsically transient, with a typical duration of only a few seconds. Recently the applicant has installed a Dual Wavelength Reflection Interference Contrast Microscopy (DW-RICM) system in the lab, designed specifically for probing the complex interaction of liquid droplets with soft surfaces, often occurring at nanoscale. Preliminary experiments on static wetting have indicated the promising potential of this technique in gaining valuable insights on wetting behaviour. An in-house image processing algorithm has also been developed by the applicant's research group to interpret the experimental data. However, with its in-built CCD cameras in place, DW-RICM is intrinsically restricted to image at a low frame rate (maximum 60 fps for the required field of view), severely limiting its applicability in capturing the transient wetting dynamics. The applicant intends to overcome this bottleneck by replacing the existing detection system of DW-RICM with two high-speed cameras. This will revamp the imaging rate to 160,000 fps, enabling the users to probe the wetting dynamics with desired spatiotemporal accuracy. These two cameras will work in tandem to image transient wetting behaviour (spreading and impact) of liquid drops on soft surfaces from the bottom. Each one captures the dynamic interference signature generated by surface illumination with one of the two laser sources present in the dual-wavelength system. Another high-speed camera (already available in the applicant's lab) will be integrated with the system to capture the side view for obtaining a holistic description of the dynamic interaction. The generated insights from this study will expand the boundaries of fundamental understanding of soft wetting and create opportunities for practical application, especially in the pharmaceutical and food packaging industries, ultimately propelling the Canadian economy forward. Additionally, this state-of-the-art system will be made available to the interface science community across Canada once commissioned.