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Smectic Gardening on Curved Landscapes.
Mohamed A Gharbi1, Iris B Liu, Yimin Luo
1Department of Physics, McGill University , Montréal, Québec, Canada.
Langmuir : the ACS Journal of Surfaces and Colloids
|September 24, 2015
Summary
Scientists assembled focal conic domains (FCDs) in liquid crystal films by controlling interface curvature with microposts. This directed assembly method enables the creation of novel optical devices and materials.
Area of Science:
- Materials Science
- Soft Matter Physics
- Liquid Crystals
Background:
- Focal conic domains (FCDs) are defects in smectic-A liquid crystals.
- Their properties, like size and distribution, are influenced by interface curvature and anchoring conditions.
- Potential applications exist in optics and material assembly.
Purpose of the Study:
- To investigate the assembly of FCDs using patterned substrates (micropost arrays).
- To understand how interface curvature (positive, negative, zero Gaussian) affects FCD structure, size, and distribution.
- To explore the molding of FCDs around complex shapes for hierarchical assembly.
Main Methods:
- Utilized micropost arrays with varying shapes and arrangements to control surface topography and Gaussian curvature.
- Imposed positive, negative, or zero Gaussian curvature on the free surface of smectic-A liquid crystal films.
- Characterized FCDs, including their internal structure, defect size, location, and distribution, in relation to surface topography and anchoring strength.
Main Results:
- Successfully assembled arrays of smectic flower patterns by controlling interface curvature.
- Observed that the largest FCDs formed in the thickest film regions, but size distribution was complex due to Apollonian tiling.
- Demonstrated that FCD arrangements near complex microposts were perturbed but became qualitatively similar farther away.
Conclusions:
- Interface curvature is a key factor in directing the assembly and arrangement of FCDs.
- The ability to mold FCDs into hierarchical assemblies offers a pathway for creating new optical devices, such as compound eyes.
- Directed assembly of liquid crystal defects provides a route to advanced material design.
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