Toric focal conic domains (TFCDs) film is one of the most common defect structures frequently shown in smectic A (SmA) phase with free surface, showing the hexagonal array of indentations.
A TFCD film consisting of sublimable molecules shows morphological transformation during thermal sintering at SmA phase. When the sample was kept at 130 ºC for 120 h in air, sublimation of the original film with a hexagonal array of indentations results in partial removal of the smectic layers, shown in the figure taken by scanning electron microscopy (SEM). The edges of remaining partial layers are seen in the Figure as sharp bright curved lines connecting the interiors of the neighboring TFCDs.
An intriguing feature of the resulting morphology is an Udumbara flower-like formation, representing a vertical stalk centered at the symmetry axis of the original TFCD and capped by a tiny sphere. The region around the stalks closer to the TFCD periphery, shows a much stronger degree of sublimation removal of the material in this region is deeper than in the interstitial regions between the TFCDs with flat SmA layers.
Currently, we have reported a series of morphological transformation with SmA films under several sintering conditions, showing a variety of layering structures and also we are engaging in combining the effects of thermal sublimation/condensation with external stimuli to paves the way for new approaches to control soft morphologies at micron and submicron scales.
Jury comment: an unconventional view on toric focal conic domains. Thermally sintered smectics suggest the way to make "real" three dimensional structures.
