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

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.

This research proposal consists of several projects, including studies of diamagnetically-levitated water and granular materials, and of magnetically-aligned bio-compatible nanostructures, each of which have potential benefits to society and the economy. Potential benefits of some aspects of the proposed work will only be realised in the long term, whilst others could see benefits in the immediate future (~3 years). For projects that have possible economic impacts in the near term, I have sought Project Partners from outside the host institute, and collaborators from within, to begin exploiting the outcomes immediately. For projects with longer-term economic benefits, the immediate impact will be made by disseminating the work in internationally-recognised journals. 1 A novel non-contact technique for obtaining the surface tension of a liquid from the oscillation frequencies of levitated liquid droplets could find immediate use in studying, for example, highly reactive liquids, supercooled liquids, or liquids in which it is important to minimise contamination. With the cooperation of Project Partners, we will seek to open up this technique to the wider academic community and to industry. 2 I expect studies of the stability of a rapidly spinning electrically charged drop to benefit academics investigating the stability of rapidly spinning atomic nuclei. One potential long-term benefit of this work is in improving understanding of nuclear fission processes, with impact on nuclear energy. 3 Studies of the deformation and break-up of electrically charge-polarised levitated droplets will benefit understanding of electro-spray processes used to extract bio-molecules from liquids for analysis. These studies will also shed light on the behaviour of rain drops in storm clouds, with benefits for meteorology. 4 Studying granular dynamics in weightless shaken fluids will improve understanding of a new mechanism for self-assembly of granular structures. There are also longer-term potential benefits for the control and exploitation of granular materials in space. 5 Magnetically aligned bio-compatible nanostructures could find use as 'scaffolding' for growing biological cells. This could find applications in promoting and directing re-growth of damaged nerve fibres or in retinal repair. 6 Precise measurements of tissue magnetic susceptibility using a novel containerless levitation technique will assist in the biological interpretation of MRI scans, benefitting our understanding of neuro-degenerative diseases. 7 Studies of bubble nucleation in diamagnetically levitated liquids could benefit understanding of decompression illness, caused by bubbles forming in tissues and blood. They are also highly relevant in, e.g., the study of explosive volcanic eruptions caused by magma degassing, and for the preparation of carbonated drinks. 8 Demonstrating the ability to perform experiments on liquids requiring weightlessness, using a superconducting magnet on the ground will have benefits for the space industry, since these experiments can be performed at reduced cost, and more conveniently, compared to experiments in spacecraft and parabolic flights. For more details of the impact of this work, please see the attached 2-page Impact Plan and Case for Support.