Synthesis and characterization of sensor microparticles templated from cholesteric liquid crystals

Date

2020-9

Author

Avşar, Deniz Işınsu

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Structural coloring in nature, especially the crystalline ordering and responsive characteristics of those found in chameleon skins has inspired us to fabricate artificial photonic materials for sensor applications. In the first part of this study, we employed cholesteric liquid crystals (CLCs) for templated synthesis of polymeric particles with periodic structures that allow visible light to undergo Bragg reflection and performed characterization studies to understand the optical appearance and the internal structure of the polymeric particles to be used as sensors. In the second part, we tested their response against volatile organic compounds (VOCs) and quantified the optical response by including colorimetric imaging. We demonstrated that the particles were responsive against toluene with detection limits, surprisingly in the order of 100 ppm. Then, we investigated the response characteristics and determined the critical role of the liquid crystal elasticity in the response of particles upon VOCs exposure. We found that such a high sensitivity was achieved due to the critical steps we followed during the CLC-templated synthesis of particles that resulted in the storage of an elastic energy in the anisotropic polymer network. In addition to the sensor tests, we presented our efforts to design particle-assisted sensor chips that allow easy integration into wearable optical devices for easy and reliable online tracking of VOC concentrations. The results proved that sensors developed from the CLC-templated particles can be used multiple times without a significant loss of sensitivity and offered rapid, sensitive and battery-free detection.

Subject Keywords

Cholesteric Liquid Crystals, Structural Coloring, Elastic Energy, Optical Gas Sensor, Vocs

URI

https://hdl.handle.net/11511/69291

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

D. I. Avşar, “Synthesis and characterization of sensor microparticles templated from cholesteric liquid crystals,” M.S. - Master of Science, Middle East Technical University, 2020.