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Direct optical quantification of backflow in a 90 degrees twisted nematic cell
N J Smith1, M D Tillin, J R Sambles
1Sharp Laboratories of Europe Ltd., Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB, England.
Physical Review Letters
|February 28, 2002
Summary
Optical observations reveal backflow during nematic cell relaxation. Fluid flow couples with director reorientation, influencing the director profile and yielding viscosity coefficients.
Area of Science:
- Physics
- Materials Science
Background:
- Nematic liquid crystals exhibit unique optical and fluid properties.
- Understanding director reorientation dynamics is crucial for display technologies.
Purpose of the Study:
- To investigate the transient director profile during the relaxation of a 90-degree twisted nematic cell.
- To observe and analyze the phenomenon of backflow in nematic liquid crystals.
Main Methods:
- Utilized optical guided mode observations to monitor the director profile.
- Analyzed the time-dependent director profiles during the relaxation process.
Main Results:
- Directly observed backflow during the relaxation of a 90-degree twisted nematic cell.
- The midplane director tilt increased, reaching a maximum of 101 degrees at 1.4 ms.
- A 270-degree twisted state with opposite handedness was observed during backflow.
Conclusions:
- Coupling between fluid flow (backflow) and director reorientation drives the observed director profile changes.
- Theoretical models accurately predict experimental results, enabling viscosity coefficient determination.