Microfluidic control over topological states in channel-confined nematic flows

Čopar, Simon (author), Kos, Žiga (author), Emeršič, Tadej (author), Tkalec, Uroš (author)

Compared to isotropic liquids, orientational order of nematic liquid crystals makes their rheological properties more involved, and thus requires fine control of the flow parameters to govern the orientational patterns. In microfluidic channels with perpendicular surface alignment, nematics discontinuously transition from perpendicular structure at low flow rates to flow-aligned structure at high flow rates. Here we show how precise tuning of the driving pressure can be used to stabilize and manipulate a previously unresearched topologically protected chiral intermediate state which arises before the homeotropic to flow-aligned transition. We characterize the mechanisms underlying the transition and construct a phenomenological model to describe the critical behaviour and the phase diagram of the observed chiral flow state, and evaluate the effect of a forced symmetry breaking by introduction of a chiral dopant. Finally, we induce transitions on demand through channel geometry, application of laser tweezers, and careful control of the flow rate.

• Language: English
• Keywords: nematic liquid crystals, microfluidics
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics; MF - Faculty of Medicine
• Publication status: Published
• Publication version: Version of Record
• Year: 2020
• Number of pages: 10 str.
• Numbering: Vol. 11, art. 59
• PID: 20.500.12556/RUL-128776
• UDC: 532.5
• ISSN on article: 2041-1723
• DOI: 10.1038/s41467-019-13789-9
• COBISS.SI-ID: 3400804
• Publication date in RUL: 28.07.2021

Record is a part of a journal

• Title: Nature communications
• Shortened title: Nat. Commun.
• Publisher: Nature Publishing Group
• ISSN: 2041-1723
• COBISS.SI-ID: 2315876

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 02.01.2020

Secondary language

• Language: Slovenian
• Keywords: nematski tekoči kristali, mikrofluidika