Gim, Min-JunBeller, Daniel A.Yoon, Dong Ki2017-07-242017Gim, Min-Jun, Daniel A. Beller, and Dong Ki Yoon. 2017. “Morphogenesis of liquid crystal topological defects during the nematic-smectic A phase transition.” Nature Communications 8 (1): 15453. doi:10.1038/ncomms15453. http://dx.doi.org/10.1038/ncomms15453.http://nrs.harvard.edu/urn-3:HUL.InstRepos:33490940The liquid crystalline phases of matter each possess distinct types of defects that have drawn great interest in areas such as topology, self-assembly and material micropatterning. However, relatively little is known about how defects in one liquid crystalline phase arise from defects or deformations in another phase upon crossing a phase transition. Here, we directly examine defects in the in situ thermal phase transition from nematic to smectic A in hybrid-aligned liquid crystal droplets on water substrates, using experimental, theoretical and numerical analyses. The hybrid-aligned nematic droplet spontaneously generates boojum defects. During cooling, toric focal conic domains arise through a sequence of morphological transformations involving nematic stripes and locally aligned focal conic domains. This simple experiment reveals a surprisingly complex pathway by which very different types of defects may be related across the nematic–smectic A phase transition, and presents new possibilities for controlled deformation and patterning of liquid crystals.en-USJournal Article2017-07-2410.1038/ncomms15453