Nanofluidic Energy Absorption of Metal-Organic Frameworks

智能材料具有高效、可控的能量吸收特性，是下一代冲击、振动和爆炸防护技术工程中的关键一步。例如，这种材料技术可以为士兵和警察提供防弹衣或防弹衣，提供比以往任何时候都更好的保护。同样，它可以防止在运动和车辆碰撞中对人体造成伤害，或者提高舒适性，降低作为防振减震材料的维护成本。然而，为了设计防护系统，工程师们目前只有一个非常有限的工具箱，这些工具箱基于几十年前开发的能量吸收机制，如材料的塑性变形、结构的屈曲、聚合物阻尼等。这些机制很有用，但在能量吸收密度(即单位质量容量)、响应速度方面存在重要的内在限制，并且大多数机制不能重复使用或控制以应对不同的加载条件。这些阻碍了充分发挥吸收能量造福社会的潜力。最近纳米科学的兴起使人们得以开发新的方法，并首次想象出令人兴奋的新表演。该研究金的目标是通过利用涉及纳米材料化学和物理的多学科方法，为能量吸收和保护系统的新纪元奠定基础。其创新之处在于，通过以可控的方式将不润湿的液体机械挤压到极小的空间中，利用了一种全新的能量吸收现象。这些空间将被制造得如此之小，以至于液体，例如水，必须分裂成水分子才能进入并流动到里面，因此在这个过程中可以吸收大量的机械能。一种名为金属有机骨架(MOFS)的海绵状多孔材料将被使用，它提供了这种类型的小孔。它们的孔径为纳米级，即十亿分之一米，与水或其他液体分子的大小相当。这一想法具有开创性，因为它有可能解除目前能量吸收系统的主要限制，例如实现前所未有的效率、可重用性和可控性。人们可以设计纳米级的液体入侵和挤压行为，以实现预期的性能，如可重复使用，甚至可以通过施加外部刺激来实时控制它们的性能：它可以提供针对不同情况和个人身体条件定制的保护，而不是简单的被动屏蔽。申请人开发了新的实验技术，对系统施加和测量突然冲击，复制那些在实际影响中经历的冲击，这也允许就地描述材料特征和应用物理刺激。通过对不同结构和性质的材料系统进行实验，该研究会旨在充分了解液体分子如何在密集的压力波下在MOF内作为一种灵活和可控的纳米限制进行传输。它有可能给能量吸收材料带来革命性的变化，并增强我们对MOF力学和纳米流体的知识。从长远来看，这将反过来使工程和社会的许多部门受益。

Smart materials possessing efficient and controllable energy absorption characteristics are a critical step forward in the engineering of next-generation protection technologies against impact, vibration, and blast. For instance, such materials technology can provide soldiers and police with body armours or bomb suits that offer better protection than ever before. Similarly, it can prevent human body injuries in sports and vehicle crashes, or enhance comfort and reduce maintenance costs used as vibration-proof damping materials. However, in order to design protection systems, engineers currently only have a very limited toolbox based on energy absorption mechanisms developed decades ago, such as plastic deformation of materials, buckling of structures, polymer damping, etc. These mechanisms are useful but have important intrinsic limitations in energy absorption density (i.e. capacity per unit mass), response rate, and most of them cannot be reused or controlled to cope with varying loading conditions. These hinder the delivery of the full potential of energy absorption for the benefit of society. The recent rise of nanoscience has allowed novel approaches to be developed and exciting new performances to be imagined for the first time. The objective of the fellowship is to lay the foundations of a new era in energy absorption and protection systems by leveraging a multidisciplinary approach engaging the nanoscale material chemistry and physics. The underpinning novelty is to exploit a fundamentally new energy absorption phenomenon through the process of mechanically squeezing non-wetting liquid into extremely small spaces in a controllable way. These spaces will be made so small that the liquid, for example, water, must split into water molecules to be able to enter and flow inside, and therefore a substantial amount of mechanical energy can be absorbed during this process. A sponge-like porous material called Metal-Organic Frameworks (MOFs) will be used which provides these kinds of small pores. Their pore size is at the nanoscale, i.e. one-billionth of a metre, comparable to the size of water or other liquid molecules. The idea is ground-breaking as it has the potential to lift the current major limitations of energy absorption systems, e.g. to achieve unprecedented efficiency, reusability, and controllability. One can design the nanoscale liquid intrusion and extrusion behaviours to achieve desired performances such as reusability, or even control their performance in real-time by applying external stimuli: rather than simply being a passive shield, it can provide protection that is customized for different situations and individual's body conditions. The applicant has developed novel experimental techniques to apply and measure sudden shocks onto the system that replicate those experienced in practical impact, which also allows in-situ material characterisation and the application of physical stimuli. With experiments on material systems of different structures and properties, the fellowship aims to fully understand how liquid molecules transport under intensive pressure waves inside MOFs as a flexible and controllable nanoconfinement. It has the potential to revolutionize energy absorption materials and enhance our knowledge of MOF mechanics and nanofluidics. This will in turn benefit many sectors of engineering and society in the long term.