Integration of liquid crystals into microfluidic sensors

2024-9
Özşahin Işılak, Ayşe Nurcan
Liquid crystals (LCs) are the oily state of liquid matter that possess anisotropy and unique optical properties. The LC interfaces, which are known for their multifunctional responsiveness, are applied in fundamental and applied research areas such as colloidal assembly, sensing and diagnostics, optics and photonics, release, and material synthesis. Besides successful and promising applications, the employed stagnant LC systems possess limitations in adaptations for continuous and automated high-throughput applications. We designed a microfluidic channel platform in which a stable LC flow was maintained while in contact with aqueous phases. The preferential wetting of the LC and aqueous phases was maintained at chemically heterogeneous microchannel interfaces, and these pathways defined the stable LC-water soft interface. For such a system, we demonstrated that the LC-water interfaces were stable up to a certain pressure across the interfaces. The low and high flow velocities affected the LC alignment. The flow configurations were operated as co-current and counter-current in our microchannel designs. We observed that the shear induced from both bulk phases had a direct impact on the LC director configurations near the aqueous interface, and the strain of the LC mesogens was modulated by this shear effect at this responsive interface. We demonstrated the response of the LC-aqueous interface for both homogeneous and heterogeneous interfacial adsorbates. The results presented in this thesis show that the soft-interface LC flow microchannel platforms are promising and meet the fundamental needs of continuous and autonomous, high-throughput analysis by offering convenience in fabrication, operation, and quantification.
Citation Formats
A. N. Özşahin Işılak, “Integration of liquid crystals into microfluidic sensors,” M.S. - Master of Science, Middle East Technical University, 2024.