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Design of micro-confinement for controlled structure formation in non-equilibrium nematic fluids

Presented by: 
Ziga Kos University of Ljubljana
Thursday 16th May 2019 - 10:20 to 10:40
INI Seminar Room 1
Nematic fluids can be designed for a specific purpose by changing their chemical structure, or also by changing the properties of the confinement. I will discuss how the interface between orientational structures in non-equilibrium nematic fluids in microfluidic confinement is affected by the viscoelastic properties of the nematic, flow rate, and shape of the channels [1]. Furthermore, by combining multiple channels into junctions, we were able to create an advanced platform for generation of various topological states, where the strength of the topological singularity in the nematic orientational field is related to the strength of the stagnation point in the junction [2]. The position and strength of the nematic defect can be tuned by the number of channels meeting in a junction and the flow rates through the channels. Flow of confined nematics is of further interest as the nematic structure can allow for the control of the transport properties in porous materials, or the external field-induced modulation of the nematic structure can be designed as a local flow pump, which is a contribution towards using the internal structure of fluids for advanced microfluidic techniques. [1] 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, eaav4283 (2019). [2] 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, E5771 (2017).
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