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Trinity Physicist Finds New Way to Pack Spheres Efficiently

New collaborative research has revealed the most efficient method to date for packing spherical objects into a cylinder.  Dr Ho-Kei Chan, a Research Fellow from the Foams and Complex Systems research group at Trinity’s School of Physics, has developed an algorithm for sphere packing which finds an arrangement in which the spheres fit as densely as possible into the cylinder provided, an issue that has a broad range of applications. 

The theoretical study, which was recently reported in the journal Physical Review E and featured in ScienceNow of Science Magazine, could have a number of practical applications on both the macro and the nano scale.  Microfluidics researchers could benefit from the research when they are packing drug-delivery bubbles into tiny capillary tubes, material scientists could benefit when creating multi-walled nanotubes with nanospheres inside, and manufacturers when looking for more efficient shipping options for virtually anything spherical.

The research findings show that achieving the densest arrangement of spheres depended on having the right form or template at the bottom of the cylinder.  Previous attempts used flat bottomed cylinders, which nevertheless meant the spheres might shift out of alignment and into a less dense configuration.  Chan introduced a novel algorithm for obtaining the right template and showed that the densest packing can simply be constructed by depositing spheres one by one into the cylinder.  Chan’s method works only for situations in which the ratio of the cylinder’s diameter to the sphere’s diameter is less than 2.7013, which are however very common.  If this ratio increases the algorithm becomes more complex, a problem that Chan is currently trying to solve based on further simulation results (to be published in Physical Review E) from Dr Adil Mughal of Aberystwyth University in Wales.

Follow up work in the Foams and Complex Systems research group includes experiments with ball bearings and soap bubbles.  The group recently attracted international attention for the solution of another packing problem, namely the laboratory realisation of the Weaire-Phelan structure which is famed for being the architectural design of the Beijing’s National Aquatics Centre.  Chan hopes that his spiral-like sphere packing will one day be employed in architecture.

Born in Hong Kong, Dr Chan obtained a first class BSc (Hons) in Engineering Physics from the Hong Kong Polytechnic University in 2002 and then a PhD in Nonlinear and Liquid Crystal Physics from the University of Manchester in 2007, followed by a few years of post-doctoral research experience in Hong Kong, America and eventually Ireland. Dr Ho-Kei Chan has been a Research Fellow in the Foams and Complex Systems research group of Trinity’s School of Physics since September 2009. He won a UK Government’s Overseas Research Students Award in 2004 and a Government of Ireland EMPOWER Postdoctoral Fellowship in 2010. To date he has published peer-reviewed scientific papers in various domains of condensed matter research including sphere packing, soft matter physics (liquid crystals, foams), and conduction problems (electrical, thermal).  For more information on studying or researching at Trinity College Dublin see www.tcd.ie/international.