Three-dimensional imaging of helicoidal pitch and structural characterization of cholesteric cellulose nanocrystals suspensions using second harmonic generation microscopy

Thibaut Legat; Wim Thielemans; Yovan de Coene; Thierry Verbiest; Stijn Van Cleuvenbergen

doi:10.1117/12.2677507

29 September 2023 Three-dimensional imaging of helicoidal pitch and structural characterization of cholesteric cellulose nanocrystals suspensions using second harmonic generation microscopy

Thibaut Legat, Wim Thielemans, Yovan de Coene, Thierry Verbiest, Stijn Van Cleuvenbergen

Author Affiliations +

Proceedings Volume 12658, Liquid Crystals XXVII; 1265803 (2023) https://doi.org/10.1117/12.2677507
Event: SPIE Organic Photonics + Electronics, 2023, San Diego, California, United States

Abstract

The chiral nematic phase of cellulose nanocrystals (CNC) in the suspension liquid state is commonly examined using polarized optical microscopy (POM) as it conveniently reveals the cholesteric pitch through fingerprint textures. However, POM has certain limitations, one of which is the requirement for a perpendicular alignment of the chiral axis with the optical axis to achieve accurate measurements. We propose employing SHG microscopy as an alternative technique, offering high-contrast imaging of the chiral nematic phase with inherent 2-photon confocal effect. An IR pulsed femtosecond laser is raster scanned through the microscope, and the cumulative SHG response of the aligned CNC recreates the fingerprint textures. As is shown in this present work, the tight focussing effect of SHG microscope allowed z-scanning to render high contrast 3D models of the structures. Morphological observations and the tracking of defects in 3-dimensional space was made possible.

Conference Presentation

(2023) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Thibaut Legat, Wim Thielemans, Yovan de Coene, Thierry Verbiest, and Stijn Van Cleuvenbergen "Three-dimensional imaging of helicoidal pitch and structural characterization of cholesteric cellulose nanocrystals suspensions using second harmonic generation microscopy", Proc. SPIE 12658, Liquid Crystals XXVII, 1265803 (29 September 2023); https://doi.org/10.1117/12.2677507

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