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Updated: Mar 20, 2026
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High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
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Chirality Detection Using Nematic Liquid Crystal Droplets on Anisotropic Surfaces.
Per Rudquist1, Clarissa F Dietrich2, Andrew G Mark3
1Microtechnology and Nanoscience, Chalmers University of Technology , 412 96 Göteborg Sweden.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 1, 2016
Summary
Researchers developed a simple method to determine the handedness and pitch of chiral liquid crystals. This technique uses tiny droplets to measure twist in nematic liquid crystals (NLCs), even with weak chiral dopants.
Area of Science:
- Materials Science
- Physical Chemistry
- Organic Chemistry
Background:
- Nematic liquid crystals (NLCs) exhibit helical structures when doped with chiral molecules.
- Determining the handedness and pitch of induced twists in NLCs is crucial for understanding chiral induction.
- Existing methods can be complex or lack sensitivity for weak chiral dopants.
Purpose of the Study:
- To develop a simple and highly sensitive method for determining the handedness and pitch of chiral dopants in NLCs.
- To analyze the twist in NLCs induced by weak chiral dopants.
- To demonstrate the effectiveness of the developed method.
Main Methods:
- Utilizing a sessile droplet of chiral-doped NLC (less than 10 nL) on a surface with uniform planar anchoring.
- Observing the hybrid director structure and disclination line formed at the NLC-air interface.
- Analyzing the configuration of the disclination line (S-like or backwards S-like) to determine twist handedness and pitch.
Main Results:
- A simple, highly sensitive method for determining handedness and pitch of induced twist in NLCs was established.
- The method accurately measures extremely large pitch values, up to 10 mm.
- The configuration of the disclination line directly correlates with the sign of the twisting power.
Conclusions:
- The developed droplet method provides an easy and sensitive way to characterize chiral dopants in NLCs.
- This technique is effective even for chiral dopants with very weak twisting powers.
- The study demonstrates the method using 4-cyano-4'-pentylbiphenyl (5CB) doped with mandelic acid.
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