A bottom-up framework for the nanoscale origins of ice formation and adhesion on structured surfaces

结冰是自然界中经常遇到的问题，对人类的许多活动都有不利的影响。特别重要的是粗糙表面上的冰的形成，这也是化学上不均匀的。表面粗糙度和成分极大地影响结冰行为，从而影响冰的粘附性，这对除冰很重要。通过更好地了解实际表面上的冰形成，可以采取适当的步骤来避免在生命受到威胁或机器在冰冻温度下遇到故障时结冰。这项工作的主要目标是制定基于科学的最佳抗冰性能指南（最大冻结延迟和最小冰粘附）。该研究将光谱工具与液体细胞扫描透射电子显微镜（STEM）和原位冷冻冷却相结合，研究了具有纳米级粗糙度的表面上的结冰，以及从可湿性到不可湿性的成分。该方法采用石墨烯液体电池（GLCs），其包裹有不同润湿性和大小的纳米颗粒。glc可以通过电子显微镜（纳米级分辨率）对水中包裹的纳米颗粒悬浮物进行动态观察，并通过精确的温度控制，使其成为实时查询结冰动力学的真空密闭容器。在不同的冷却条件下，通过调节GLC样品的温度来控制冰的形成。平行原位纳米尺度光谱方法量化了纳米颗粒在冻结期间和冻结后的冰/水质量比和周围结构，作为原子薄壁石墨烯电池中颗粒尺寸、润湿性和约束的函数。另一方面，宏观实验使用与纳米实验相似的具有化学性质和特征长度织构的表面来确定宏观冻结延迟和冰的粘附强度。通过将宏观尺度的冰性质与纳米尺度的动力学参数相关联，该项目制定了最佳抗冰性能或易于除冰的指导方针。这项研究为现有仪器无法获得的多相输运空间机制提供了高质量的实验数据，也为验证和推进模拟纳米尺度多相系统的模型开辟了新的视野。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Icing is frequently encountered in nature and has adverse consequences on many human activities. Of particular importance is ice formation on rough surfaces, which are also chemically inhomogeneous. Surface roughness and composition drastically influence icing behavior, and consequently, ice adhesion, which is important for ice removal. By developing a better understanding of ice formation on realistic surfaces, appropriate steps can be taken to avert icing in situations where lives are threatened or when machines encounter trouble operating in freezing temperatures. The main goal of the work is to produce science-based guidelines for optimal anti-icing performance (maximum freezing delays and minimal ice adhesion). Using spectroscopic tools in conjunction with liquid-cell scanning transmission electron microscopy (STEM) and in-situ cryo-cooling, the research examines icing on surfaces having nanoscale roughness and compositions from wettable to non-wettable. The methodology employs graphene liquid cells (GLCs) with encapsulated nanoparticles of varying wettabilities and sizes. The GLCs allow electron microscope (nm-scale resolution) dynamic observations of encapsulated nanoparticle suspensions in water, and with precise temperature control, they become vacuum-tight vessels for interrogating icing kinetics in real time. Ice formation is controlled by modulating the GLC sample temperature under various cooling scenarios. Parallel in-situ nanoscale spectroscopic methods quantify the ice/water mass ratio and structure around the nanoparticles during and after freezing, as a function of particle size, wettability and confinement in the atomically-thin-walled graphene cell. The macroscopic experiments, on the other hand, use surfaces with chemistry and characteristic length texture similar to the nanoscopic experiments, to determine macro freezing delays and ice adhesion strength. By correlating the macroscale ice properties with the nanoscale kinetic parameters, the project produces guidelines for optimal anti-icing performance or easy ice removal. The research, by generating high-quality experimental data for a spatial regime of multiphase transport that has been inaccessible by existing instrumentation, also opens new horizons for validating and advancing models simulating nanometer-scale multiphase systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.