Diamagnetic levitation for studies of fluids and granules in weightless conditions, and for interdisciplinary science

当物体失重时，它们的行为如何？这是一个吸引了一代又一代科学家的问题，也激发了普通公众的想象力。为了解决这个对太空旅行至关重要的问题，人们在宇宙飞船、绕地球运行或自由落体中进行了实验。抗磁悬浮是一种很有前途的技术，它利用电磁铁产生的强大磁场来模拟地球轨道上的失重条件。它允许水和生物有机体等抗磁性物质漂浮在磁铁上方。这些材料受到磁场的排斥，但强度太小，通常不会被注意到，不像铁那样被磁场强烈吸引。就像离心力平衡轨道宇宙飞船的重量一样，抗磁力与悬浮物体上的重力相反，所以它就像在太空中漂浮一样。1863年，高原受到启发，在酒精混合物中漂浮的旋转油滴上进行实验，以模拟地球的形状。他认识到，将水滴聚集在一起的表面张力，可以模拟引力将行星或恒星聚集在一起的行为。后来人们意识到，带电液滴的表面张力也可以模拟原子核内结合核子的力。我将用DL来研究高原做不到的事情：一滴自由悬浮在太空中的水滴。我将研究利用这一点来发现天文物体和原子核行为线索的可能性。通过研究水滴的振动，我还将获得它的表面张力。这种非接触式测量技术将使非常活跃的液体和过冷液体的研究成为可能。我还将研究悬浮的“雨滴”如何在电场中振动、扭曲和破碎，这会影响雷暴的行为，并想象分解时从雨滴中喷出的小水滴的喷雾。后一种过程在从液体中提取生物分子进行分析、为约翰·芬赢得2002年诺贝尔奖以及彻底探索新的药物方面起到了重要作用。颗粒材料无处不在，从小行星到玉米片。了解颗粒的动力学在许多行业都很重要，例如食品和制药，以及研究许多自然过程，例如山体滑坡。在失重状态下，颗粒总是悬浮在液体中。振动液体使颗粒移动并自组织成三维图案，这是由液体围绕颗粒运动引起的。我将对悬浮颗粒进行实验，以研究颗粒和液体之间的相互作用；这些知识最终将导致地球和太空中颗粒材料的控制和开发方面的重大改进。通过与其他研究人员的合作，我还将探索如何将数字语言应用于更广泛的主题。我将使用它来精确测量生物组织在强磁场中的磁化程度，这对医学磁共振成像至关重要。在传统方法中，样品容器的磁化会给测量带来很大的不确定度。由于悬浮样品不需要容器，因此我们避免了这种复杂情况。我将研究漂浮的气体饱和液体中气泡的成核和生长，这将直接有助于我们对水肺事故中的减压病(“弯曲症”)的理解。通过将液体悬浮起来，我们可以观察到不断增长的气泡，而不会脱离其成核点并漂离。我还将研究如何利用强磁场在悬浮液中构建中空管状蛋白质结构的网状结构，这可以形成纳米级电路的模板或细胞生长的“支架”。

How do objects behave when they are weightless? This is a question that has fascinated generations of scientists and captured the imagination of the general public. To address this question of fundamental importance for space travel, experiments are performed in space-craft, orbiting the Earth, or in free-fall. Diamagnetic levitation (DL) is a promising technique that uses a powerful magnetic field generated by an electromagnet, to simulate the weightless conditions in orbit, on the Earth. It allows diamagnetic materials, such as water and biological organisms, to levitate above the magnet. These materials are repelled from the magnetic field, but too weakly to notice ordinarily, unlike iron for example, which is strongly attracted to the field. Just as the centrifugal force balances the weight of an orbiting spaceship, the diamagnetic force opposes the force of gravity on a levitated object, so that it floats as though in space. In 1863, Plateau was inspired to experiment on a spinning drop of oil, floated in an alcohol mixture, to model the Earth's shape. He recognised that surface tension, holding the drop together, could model the action of gravity holding a planet or star together. It was later realised that the surface tension of an electrically-charged drop could also model the forces binding nucleons inside an atomic nucleus. I will use DL to study what Plateau couldn't: a drop suspended freely in space. I will investigate the possibility of using this drop to discover clues to the behaviour of both astronomical objects and the atomic nucleus. By studying vibrations of the drop, I will also obtain its surface tension. This non-contact measurement technique will enable the study of very reactive liquids and supercooled liquids.I will also study how levitated 'rain' drops vibrate, distort and shatter in electric fields, which influences the behaviour of electrical storms, and image the spray of small droplets that issue from the drop upon break-up. The latter process is important in extracting biological molecules from liquids for analysis, winning John Fenn a Nobel Prize in 2002, and revolutionising the search for new medicinal drugs.Granular materials are everywhere, from asteroids to cornflakes. Understanding the dynamics of the granules is important in many industries, e.g. food and pharmaceutics, and in studying many natural processes, e.g. landslides. In zero-gravity, granules are always suspended in the liquid. Vibrating the liquid causes granules to move and self-organise into three-dimensional patterns, caused by the motion of the liquid around the grains. I will perform experiments on levitated granules to investigate the interactions between the grains and the liquid; such knowledge should ultimately lead to significant improvements in the control and exploitation of granular materials on Earth and in space. By collaborating with other researchers, I will also explore how DL can be applied to a broader range of topics. I will use it to obtain precise measurements of the magnetisation of biological tissues in a strong magnetic field, fundamentally important for medical magnetic resonance imaging. In conventional methods, the magnetisation of the sample container introduces significant uncertainty into the measurement. Since a levitated sample does not require a container, we avoid this complication. I will study the nucleation and growth of bubbles in levitating gas-saturated liquids, directly benefitting our understanding of, e.g. decompression sickness ('the bends') in SCUBA accidents. By levitating the liquid, we can observe the growing bubble without it detaching from its nucleation site and floating away. I will also investigate how a strong magnetic field can be used to construct a mesh of hollow tubular protein structures in levitating solutions, which could form templates for nano-scale electric circuits or 'scaffolds' for cell growth.