Dynamics of complex fluids

We study the dynamics of complex fluids, particularly the dynamics of various liquid crystalline phases, active fluids and their coupling with external fields (electric, optic, pressure). We explore the dynamics of generation and annihiliation of topological defects in nematics and the role of backflow in annihilation dynamics. We developed a mesoscopic continuum numerical model to investigate the structural properties of flow and orientational field. Using complex geometries and external fields, we achieve non-equilibruim stable topologically protected states in long microcapillaries and microfluidic junctions, and investigate the cross talk between defects in molecular orientation field and velocity field in nematic microfluidics. The main motivation is to develop novel liquid crystal structures for applications in photonics, optics, colloidal suspensions and as sensors.

Selected papers

  • V. P. Patil, Z. Kos, M. Ravnik, and J. Dunkel, Discharging dynamics of topological batteries, Phys. Rev. Research 2, 043196 (2020). [Link] [PDF].

  • S. Čopar, Ž. Kos, T. Emeršič, U.Tkalec, Microfluidic control over topological states in channel-confined nematic flows, Nat. Comm. 11 59 (2020) [Link] [PDF].

  • T. Emeršič, R. Zhang, Ž. Kos, S. Čopar, N. Osterman, J. J. de Pablo, and U. Tkalec, Sculpting stable structures in pure liquids, Sci. Adv. 5, 2 (2019) [Link] [PDF].

  • L. Giomi, Ž. Kos, M. Ravnik and A. Sengupta Cross-talk between topological defects in different fields revealed by nematic microfluidics , Proc. Natl. Acad. Sci., 114, 29 (2017). [Link] [PDF].

  • J. Aplinc, S. Morris and M. Ravnik Porous nematic microfluidics for generation of umbilic defects and umbilic defect lattices, Phys. Rev. Fluids, 1, 023303 (2016). [Link] [PDF].

  • A. Sengupta, U. Tkalec, M. Ravnik, J. M. Yeomans, C. Bahr and S. Herminghaus Liquid Crystal Microfluidics for Tunable Flow Shaping, Phys. Rev. Lett., 110, 048303 (2013). [Link] [PDF].

  • D. Svenšek, H. Pleiner and H. R. Brand Phase winding in chiral liquid crystalline monolayers due to Lehmann effects, Phys. Rev. Lett., 96, 140601 (2006). [Link] [PDF].

  • C. Blanc, D. Svenšek, S. Žumer and M. Nobili Dynamics of nematic liquid crystal disclinations: The role of the backflow, Phys. Rev. Lett., 95, 097802 (2005). [Link] [PDF].