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现象，对人类的许多活动都有不良影响。特别重要的是在粗糙的表面上结冰，这些表面在化学上也是不均匀的。表面粗糙度和成分极大地影响结冰行为，从而影响结冰粘附性，这对除冰非常重要。通过更好地了解现实表面上的结冰情况，可以采取适当的步骤，在生命受到威胁或机器在冰冻温度下操作遇到困难的情况下避免结冰。这项工作的主要目标是为最佳防冰性能(最大冻结延迟和最小冰粘附性)制定基于科学的指导方针。利用光谱工具，结合液晶盒扫描电子显微镜(STEM)和原位冷冻冷却，该研究检查了具有纳米级粗糙度的表面上的结冰情况，以及从可湿到不可湿的成分。该方法使用具有不同润湿性和大小的封装纳米颗粒的石墨烯液体电池(GLC)。GLC可以用电子显微镜(纳米级分辨率)动态观察包裹在水中的纳米颗粒悬浮液，并通过精确的温度控制，成为实时询问结冰动力学的真空密闭容器。在不同的冷却方案下，通过调节GLC样品的温度来控制结冰。平行的原位纳米光谱方法量化了冻结过程中和冻结后纳米颗粒周围的冰/水质量比和结构，作为原子薄壁石墨烯单元中颗粒尺寸、润湿性和限制的函数。另一方面，宏观实验使用与纳米实验相似的具有化学成分和特征长度纹理的表面来确定宏观冻结延迟和冰的粘合强度。通过将宏观尺度的冰特性与纳米尺度的动力学参数相关联，该项目为优化抗冰性能或轻松除冰提供了指导方针。这项研究通过为多相传输的空间体系生成高质量的实验数据，为验证和推进模拟纳米级多相系统的模型开辟了新的视野。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.