Research tools for understanding soft wetting

申请人打算研究液体在软表面上的动态润湿行为。软材料对迎面而来的液滴的反应方式是不平凡的，与刚性表面有显著的不同。软材料在设计拒液自清洁和防污表面方面表现出很有前途的潜力，并提供优于传统微/纳米结构或液体注入表面的几个优点，包括在广泛的操作范围内的可靠性和长期耐用性。然而，在理解软表面对液滴的动态响应方面的科学努力相对较少。在本研究中，申请人打算寻求动态软润湿中两个基本问题的答案。首先，液滴在与软表面初始接触时如何扩散，其次，当液滴撞击软变形表面时会发生什么？这两种现象本质上都是瞬态的，典型的持续时间只有几秒钟。最近，申请人在实验室中安装了双波长反射干涉对比显微镜（DW-RICM）系统，该系统专门设计用于探测液滴与软表面的复杂相互作用，通常发生在纳米级。静态润湿的初步实验表明，这种技术在获得有价值的见解润湿行为的潜力。申请人的研究小组还开发了内部图像处理算法来解释实验数据。然而，由于其内置的CCD摄像头，DW-RICM本质上限于以低帧速率成像（所需视场的最大值为60 fps），严重限制了其在捕捉瞬态润湿动态方面的适用性。申请人打算通过用两个高速摄像机替换DW-RICM的现有检测系统来克服这一瓶颈。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，从底部拍摄软表面上液滴的瞬时润湿行为（扩散和冲击）。每一个捕获的动态干涉签名所产生的表面照明与双波长系统中存在的两个激光源之一。另一个高速摄像机（申请人的实验室中已经可用）将与系统集成，以捕获侧视图，从而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软润湿的基本理解的界限，并创造实际应用的机会，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，这一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.