Projects / Programmes source: ARIS

Active and complex materials fluidics at microscale

Research activity

Code Science Field Subfield
1.02.01  Natural sciences and mathematics  Physics  Physics of condesed matter 

Code Science Field
P250  Natural sciences and mathematics  Condensed matter: structure, thermal and mechanical properties, crystallography, phase equilibria 

Code Science Field
1.03  Natural Sciences  Physical sciences 
complex fluids, activity, microflow, colloidal swimmers
Evaluation (rules)
source: COBISS
Researchers (1)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  25670  PhD Miha Ravnik  Physics  Head  2013 - 2015  435 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  1554  University of Ljubljana, Faculty of Mathematics and Physics  Ljubljana  1627007  34,059 
Micro-scale activity of materials is today an exciting mechanism at the forefront of research in soft condensed matter and bio-physics, which is capable of exciting new phenomena such as internal motility, swimming of micro-objects, and formation of complex flow profiles. And it is controlling and harnessing this activity into directed actions which is one of the main challenges. In this post-doc project, we propose a novel approach of controllable activity where three central mechanisms affecting the activity –the confinement by geometry, the topological defects, and the colloidal inclusions- will be used for generating the activity and its control. Using advanced numerical modelling with strong ties to collaborating experiments, we will implement in the first Objective, the spherical, toroidal, and other experimentally motivated active cavities to achieve confinement-controllable active flow profiles. In second Objective, active topological defects will be explored as the key- mechanism for topological control of active flows. And in the third Objective, colloidal swimmers made of several micro-particles will be studied in passive anisotropic complex fluids as sources of discrete sources of activity by individual active objects. In active materials, the general activity will be stimulated either by own bulk motility or by the effective activity driven with external fields, which will give a new insight in the microscopic origin of the active flows. We will explore coupled effects of confinement and external fields on the active flow regimes. A particularly biologically relevant research will be to explore mechanisms of localised activity in active patches, where we will focus on the phenomena of active coupling and active synchronisation. Specially application directed research goals will be the concept of “biased” micro-swimming by controlling the anisotropic direction in the fluid and the application of active defects as local micro-pumps, which will give access to local control of the active flow with possible use as novel efficient methods for micromanipulation and micro-control. The central methodological approach of the proposal will be intensive numerical modelling with the Hybrid Lattice Boltzmann method, based on the active nematic fluid model, which is today the central mesoscopic continuum approach to active materials. The project will be implemented in the soft matter group at the Faculty of Mathematics and Physics at the University of Ljubljana, which is renown for highest scientific standards and joint theoretical and experimental work. After the period of mobility, this post-doc project will also serve as a firm basis for direct transfer of knowledge of the fellow from Oxford to Ljubljana (and Slovenia), and will establish the cohesion at bi-lateral and international level. Finally, the wide outreach of the proposed research, the application directed research aims, and strong ties with scientific and general community are a direct commitment to ‘frontier research’ which will be able to create new opportunities for commercialisation of the high-tech research results.
Significance for science
The scientific results of this project encompass a broad study of effects in complex fluids, as affected by confinement, dynamic driving, and external fields. The work –in full collaboration with several groups in Slovenia and internationally- demonstrated among other, the effects of topological defect generation in latter stages of Kibble mechanism, knotting of physical and field knots, stabilisation of a colloidal assembly with quasicrystalline symmetry, and development of nematic droplets as surface sensors for biofibers, which are all cutting edge results at international level. This is reflected in the high-profile publications of these topics (Nature Physics, Nature Materials, 2x PNAS) and multiple (20+) invited presentations at conferences and institutions worldwide. More generally, the developed research results are an interesting contribution at the cross-road between top-level modern soft matter science, light studies, fluidics and applications, which have the potential to grow further into any of these research directions. Finally, this work is a contribution to push forward the concepts of complex fluid dynamics to develop novel materials, novel approaches for microscopically controlling the flow of light, and as a starting point for simulations of complex dynamic phenomena such as protein aggregation
Significance for the country
The results of this project are multilayered in context of contribution to Slovenia. The top level scientific results are a direct contribution to the further establishment of the Slovenian soft matter community as one of the major international centers for the physics of liquid crystals, and more generally complex fluids. Also directly, scientifically, the developed scientific results of this early-stage post-doctoral level project enabled the formation of a young research group around the PI of the project, which is now in the process of further consolidation and growth. Indirectly, this growth of knowledge contributed to a higher level education of students of various level at the University of Ljubljana, and is now one of the sources for future work of several PhD students. The project and its results also indirectly contributed to the development of applied knowledge of simulating complex dynamical phenomena, which is now being transferred into the value-chains and networks of applications to Smart specialisation in Slovenia.
Most important scientific results Annual report 2013, 2014, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2013, 2014, final report, complete report on dLib.si
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