Best Research Prize Awardees

Prize 2015 – Ran Ni (The Netherlands)

Brief CV: Dr. Ni received his B.S. (2005) in Computational Mathematics and M.S. (2008) in Chemical Engineering from Beijing University of Chemical Technology, and Ph.D. in Physics (2012) from Utrecht University (the Netherlands).  From 2012 to 2014, he was a postdoctoral research fellow in a joint program of University of Amsterdam and Wageningen University in the Netherlands. In 2014, he was awarded the NWO VENI fellowship, to start his own independent research. In March 2016, he joined the School of Chemical and Biomedical Engineering in Nanyang Technological University as an assistant professor in Singapore.

The prize was awarded for his work on “Self-propelled colloidal hard spheres


Abstract:  Recent breakthroughs in particle synthesis have enabled the fabrication of artificial colloidal active micro-swimmers that show a high potential for applications in biosensing, drug delivery, etc. By performing computer simulations, we showed that in a simple model system of active colloidal swimmers, i.e. active hard spheres, because of their special dynamics, active hard spheres can tremendously boost the glass transition of the system and crystallise colloidal glasses, as well as mediate tunable long range effective interactions among passive matters. These suggest that active colloidal swimmers can be employed as a novel tool to manipulate the dynamics and assembly of colloidal systems and offer new ways of fabricating functional materials.
Related publications:
Tunable long range forces mediated by self-propelled colloidal hard spheres. Ran Ni, Martien A. Cohen Stuart, and Peter G. Bolhuis, Phys. Rev. Lett. 114 018302 (2015)
Crystallizing hard-sphere glasses by doping with active particles. Ran Ni, Martien A. Cohen Stuart, Marjolein Dijkstra, and Peter G. Bolhuis, Soft Matter 10 6609 (2014)
Pushing the glass transition towards random close packing using self-propelled hard spheres. Ran Ni, Martien A. Cohen Stuart, and Marjolein Dijkstra, Nature Comm. 4 2704 (2013)
Structural signatures of dynamic heterogeneities in monolayers of colloidal ellipsoids. Zhongyu Zheng, Ran Ni, Feng Wang, Marjolein Dijkstra, Yuren Wang, and Yilong Han, Nature Comm. 5 3829 (2014)


Prize 2016 – Amin Doostmohammadi (UK)

Brief CV: Dr. Doostmohammadi obtained his B.Sc. in Mechanical Engineering from the University of Tehran, Iran. In 2015 he earned his PhD degree at the University of Notre Dame, IN, USA, under the supervision of Professor Arezoo Ardekani. His PhD work focused on biological and environmental fluid dynamics (settling of rigid particles, swimming of self-propelled organisms). In 2016, as visiting scholar at Stanford University, CA, USA, he worked on turbulence in mesoscale living systems. Currently, Dr. Doostmohammadi is a postdoctoral research assistant at the Rudolf Peierls Centre of Theoretical Physics, Oxford, UK, working in the research group of Professor Julia Yeomans. His research area encompasses theoretical methods aimed at understanding soft and biological active matter. He developed a unified theory of wet and dry active matter. Moreover, he worked out theoretical tools to explain flow fields generated by cell division. His works shed light on the collective motion of breast cancer cells and show correlations between topological defects and cell extrusion from monolayers. Dr. Doostmohammadi has coauthored 18 papers in peer-reviewed journals, including Soft Matter, Physical Review Letters and Nature Communications.

The prize was offered for his work entitled “Stabilization of active matter by flow-vortex lattices and defect ordering“.

Figure 1: Dynamical behaviours of active nematics in the temperature-friction phase space. TIN denotes the isotropic-nematic transition temperature: above TIN at intermediate frictions we find a novel vortex lattice that entangles an ordered defect array. The blue-red colourmaps represent vorticity fields superimposed by streamlines (black solid lines). The concentration fields are depicted by red-yellow colourmaps. In the mid-lower section, the director field is illustrated by ellipsoids coloured by their orientations. Grey panels show director fields superimposed by topological defects (red circles and yellow triangles correspond to +1/2 and -1/2 defects). (Reproduced from Doostmohammadi A et al., Nature Communications 7 10557 (2016), with permission from Springer Nature under the terms of the Creative Commons Attribution 4.0 International License. )


Abstract: Active systems, from bacterial suspensions to cellular monolayers, are continuously driven out of equilibrium by local injection of energy from their constituent elements and exhibit turbulent-like and chaotic patterns. Here we demonstrate both theoretically and through numerical simulations, that the crossover between wet active systems, whose behaviour is dominated by hydrodynamics, and dry active matter where any flow is screened, can be achieved by using friction as a control parameter. Moreover, we discover unexpected vortex ordering at this wet–dry crossover. We show that the self organization of vortices into lattices is accompanied by the spatial ordering of topological defects leading to active crystal-like structures. The emergence of vortex lattices, which leads to the positional ordering of topological defects, suggests potential applications in the design and control of active materials.
Related publication:
Stabilization of active matter by flow-vortex lattices and defect ordering, Amin Doostmohammadi, Michael F. Adamer, Sumesh P. Thampi and Julia M Yeomans, Nature Communications 7 10557 (2016).
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