Making Heads and Tails of Amphiphile-Induced Distortions in Chiral Nematic Liquid Crystal Fingerprints

Description

The alignment of liquid crystals is uniquely sensitive to the presence of amphiphiles, particularly surfactants, allowing us to use liquid crystals to rapidly detect surfactants and amphiphilic contaminants. In the case of chiral nematic liquid crystals, the transition induces a “fingerprint” texture with a defined periodicity. A question, though, is whether the distorted textures we observe can distinguish between different amphiphiles and in what manner: are these fingerprint textures truly fingerprints for materials of interest?
In this work, we investigate what aspects of amphiphiles contribute to these distortions, using chiral nematics with short pitches (resulting in visible light reflections) and long pitches (which are observable with polarizing optical microscopy). We find that distortions induced by tails lead to more systematically distinguishable differences compared to differences in headgroups, likely owing to the tails directly imparting the distortion on the LC texture, while the headgroups simply affect the distribution of the amphiphiles at the interface. In the terms of short-pitch chiral nematics, this can additionally be manifested in optical signatures which we can quantify though the ratio of the intensities of color channels. This work provides further insights into how we can use liquid crystals for biological sensing applications and what we can ultimately detect with them.

Period	22 Mar 2023 → 24 Mar 2023
Event title	49th German Liquid Crystal Conference
Event type	Conference/symposium
Location	Stuttgart, GermanyShow on map
Degree of Recognition	National