Speaker
Description
Cholesteric phases are liquid crystals in which a helical twist can be induced by the presence of a chiral agent. This twist, with a periodicity or pitch (p), can be frustrated under geometrical confinement comparable to p. Under those conditions, skyrmions can be formed if the material undergoes an instability. Skyrmions are topologically protected solitonic-like structures [1-3], formed by the spatial discordance in the orientation of the molecules of the liquid crystal, forming a torus in which the principal axis of the molecules turns 180o. Skyrmions behave as quasi-particles and can be driven by the action of a modulated AC electric field [1-3]. However, the directionality of their motion has, so far, only been in-situ controlled using complex optical systems [3]. In our work, we study the propulsion of skyrmions under modulated AC electric fields of different amplitude, carrier, and modulation frequencies. We also demonstrate the capability of an external fixed magnetic field to steer driven skyrmions, which can be inserted and controlled within microfluidic channels. Experimental suggest an acceleration when skyrmions are introduced in micro-channels due to distortions in the LC molecular alignment generated by the presence of homeotropic walls. We also show that skyrmions can act as micro-cargo transporters.
[1] Shon, et. al., Nat. Commun, 10:14744 (2019), 1-11.
[2] Ackerman, et. al., Nat. Commun, 6:673 (2017), 1-13.
[3] Shon, et. al., Opt. Express, 28:5 (2020), 6306-6319.
