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

Lead Research Organisation: University of Nottingham
Department Name: Sch of Physics & Astronomy


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.

Planned Impact

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.


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Baldwin KA (2018) Magnetic Levitation Stabilized by Streaming Fluid Flows. in Physical review letters

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Baldwin KA (2015) The Inhibition of the Rayleigh-Taylor Instability by Rotation. in Scientific reports

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Cheng T (2016) High temperature MBE of graphene on sapphire and hexagonal boron nitride flakes on sapphire in Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena

Description We have applied magnetic levitation to create conditions for studying suspensions of particles under effective weightless conditions on Earth. This technique has allowed us to investigate for the first time the full 3-dimensional flow around vibrated particulates without the complications of boundary effects. We have found that a pair of spheres will attract each other and can spontaneously orbit each other under vibration.

Using magnetic levitation to levitate microlitre volumes of liquid we have demonstrated that the vibrational frequencies and spectral widths of the mechanical oscillations of viscoelastic droplets of polymer solutions can be used to extract values of the frequency-dependent storage and loss moduli.

We have made a significant step towards understanding the
behaviour of a novel, neutrally-buoyant swimmer: two connected spheres propelled by their relative motion. Through experiments and
simulations, the existence of a critical streaming Reynolds number above which relative motion induces swimming of the dimer has been discerned.

We have used diamagnetic levitation to study the development and behaviour of Drosophila melanogaster in a simulated micro-gravity and a 2g environment (twice Earth's gravity).  Previous studies on board the International Space Station had shown that the motility of fruit flies (Drosophila melanogaster) increases in microgravity, compared with motility on the ground. However, flight preparation procedures made it difficult to implement control experiments that could be used to verify these results. Our experiments in magnetic levitation show conclusively that the behaviour of the flies are indeed significantly altered in weightlessness.

We have developed a novel experimental method, using magnetic forces to induce Rayleigh Taylor instability in a two-fluid system. Using this novel technique, we have studies the stabilising effect of rotation on the Rayleigh-Taylor instability. We show that rotation suppresses large scale unstable corrugations of the interface and can significantly inhibit the growth of the instability.
We have use magnetic levitation to manufacture solid wax figures of the equilibrium shapes of a spinning liquid droplet, which we call artificial tektites. We have shown that these wax forms are of benefit in validating numerical models of these shapes. the long-standing discrepancy between Lord Rayleigh's theory for the charge required to fission a liquid droplet, and experimental observations.
We used diamagnetic levitation to investigate the shapes and the stability of free, electrically-charged and rapidly rotating liquid droplets.
By studying these droplets, we circumvent criticisms of the experimental methods used in previous experiments. Our result, that charged droplets become unstable to fission at Rayleigh's predicted limit, is important for several areas of science and technology. Droplet fission is the key process used in electrospray ionisation, deposition and in ink-jet printing and fuel injection. Instabilities of charged metal clusters have been explained using Rayleigh's theory. Bohr invoked the model of a liquid droplet to explain fission of the atomic nucleus, referencing Rayleigh's limit. The data from our experimental realisation of this model, a classical liquid droplet endowed with angular momentum, mass, electric charge and surface tension, is an important addition to the understanding of these aforementioned processes.

Invited talks and seminars have been given by R. J. A. Hill at the JET Nuclear Fusion Centre, Culham, Oxford (Sept 2009), International Conference on Magnetoscience, Nijmegen, Netherlands (October 2009), Physics Department, Loughborough University (January 2010), University of Greenwich (May 2011), French Embassy, London (November 2011) and as the Keynote Talk at the International Workshop on Materials Analysis and Processing in Magnetic Fields, Okinawa, Japan (2014); University of Bayreuth, July 2017; at the International Meeting of the Japanese Magnetoscience society Japan Nov 2016; and on Equilibrium shapes & stabilty of charged and spinning liquid drops, Intl. conference on Materials Processing in Magnetic fields, Brown University RI, June 2016; and the University of Surrey Nov 2017.
Exploitation Route We anticipate that our work on levitated granular suspension will open up new ways for manipulating and ordering granular suspensions in a non-invasive way. As such, our work will interest researchers from the fields of hydrodynamics, granular materials and dynamic self-assembly. Our work will also be of interest to researchers investigating novel uses of strong magnetic fields, or to those using the space station to create weightless conditions e.g. for studying crystal growth.

Our studies of swimming motion are relevant to the understanding of motion of microscopic biological and artificial 'robots' - a hot topic of current interest to an interdisciplinary field that includes physics, biology, chemistry, fluid dynamics, and engineering. These studies are relevant to efforts to develop microscopic swimming robots for medical applications.

Our work on the Rayleigh Taylor instability addresses a fundamental fluid dynamical instability prevalent in many systems, manifesting in numerous astrophysical, atmospheric and geophysical phenomena, including in inertial confinement fusion. There are many situations in which it is desirable to supress this instability, for example in inertial confinement fusion.
Our new technique opens up the possibility to study this fundamental fluid system under rotation. The relevance of this work to natural processes, academic and technological problems will draw interest from many areas of physics, engineering and technology.

Our artificial tektites are of benefit in validating numerical models of the equilibrium shapes of spinning liquid drops, which are important to nuclear physicists studying the stability of atomic nuclei, and astrophysicists studying the shapes of rotating astronomical bodies including asteroids, stars and black holes. The technique also offers the first reproducible way to investigate the formation of tektites---small stones formed from molten rock flung out of asteroid impacts---in the laboratory, which has already captured the attention of geophysicists.
Our investigations of the vibrations of liquid levitated drops are a significant step forward in our ability to measure the rheological properties of polymer solutions where the sample volumes are small (microlitres to millilitres).

Our work on the behaviour and development of fruit flies under magnetic levitation addressed a question of key importance for future space missions: how do biological organisms respond to the absence of gravity?
In addition to the findings of our experiments, the protocols and experimental techniques we developed will be applied by future researchers who use, or plan to use, diamagnetic levitation to explore weightless effects on living organisms. We anticipate that our demonstration of this technique will encourage other researchers to use diamagnetic levitation to explore the effects of reduced, enhanced and micro-gravity on a wider range of living organisms.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Energy,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

URL http://www.nottingham.ac.uk/~ppzlev
Description We anticipate that the results of our work will be used in areas beyond academia. For example, our work on the Rayleigh Taylor instability is directly relevant to efforts to generate power by nuclear fusion. These findings will take some time to be exploited commercially however. In microgravity research, vital for the future space industry, our experiments showing the promise of magnetic levitation as a 'ground-based facility' for microgravity research are already becoming well-known. We have used our research several times in public outreach, aimed particularly at encouraging young people to take an interest in science and engineering. For example, we have produced youtube videos (www.sixtysymbols.com) on the physics of swimming and on electrically charged liquids. We have also produced a video on our research on the equilibrium shapes of spinning liquid droplets 'artificial tektites' : https://www.nottingham.ac.uk/news/pressreleases/2015/january/levitation-recreates-natures-dumbbells.aspx RJAH has given interviews on the topic of the behaviour of fruit flies and seedlings in space on popular science radio shows in the USA (Science Friday on NPR http://www.sciencefriday.com/videos/what-happens-when-you-levitate-flies-2/) and Canada (Quirks and Quarks, CBC, http://www.cbc.ca/player/play/2192776713 ), on local BBC radio in the UK, on local student radio, on Russian national TV, for several popular science magazines (SPACE.com, Discovery News- Discovery Channel, COSMOS Magazine, Popular Mechanics, Wired.com), and given public lectures on the subject, organised by the British Science Association, University of Nottingham and the Maxwell Society (King's College London). News stories about this research were also covered by national newspapers, The Mail, Independent, Telegraph, Metro, and Huffington Post.
Impact Types Cultural,Societal,Economic