Azimuthal surface anchoring of a nematic on the patterned azobenzene alignment substrate

Surface anchoring is the key mechanism to control the alignment of liquid crystals. Experimental determination of surface anchoring strength is important for the proper control of alignment. Here we characterize the strength of azimuthal surface anchoring produced by the recently developed photoalignment technique based on plasmonic metamsaks [1]. The measurements use photopatterned arrays of topological point defects of strength +1 and -1 in a nematic liquid crystal. The integer-strength defects split into pairs of defects of half-integer strength with a lower elastic energy cost. The separation distance between the split pair allows one to determine the anchoring extrapolation length by balancing elastic and anchoring forces [2]. The strength of the azimuthal anchoring is directly proportional to the UV exposure time during the photoalignment of the azobenzene layer.
[1] Y. Guo, M. Jiang, C. Peng, K. Sun, O. Yaroshchuk, O. Lavrentovich, and Q. H. Wei, Adv. Mater. 28, 2353 (2016)
[2] T. Turiv, J. Krieger, G. Babakhanova, H. Yu, S. V. Shiyanovskii, Q.-H. Wei, M.-H. Kim, and O. D. Lavrentovich, 651, 1 (2020)