Field-Programmable Topological Torons in Chiral Nematic Liquid Crystals.

Torons are three-dimensional double-twist solitons in chiral nematic liquid crystals (LCs), bounded by closed defect loops, that behave as particle-like entities while retaining a fully reconfigurable optical response. Here, it is shown that individual torons can be created, translated, and parked on demand in planar antiparallel rubbed cells using a waveform-engineering approach. Torons are found to nucleate across a wide pitch window, set by the ratio of the cell gap to the chiral nematic pitch. Adjusting the voltage waveform parameters, namely, the modulation frequency, the duty-cycle asymmetry, and the addition of small DC offsets superimposed on a kilohertz carrier, results in programmable translation along eight in-plane directions within the LC cell. Transport is governed by two independently tunable channels: reorientation-driven backflow, which is dominant under time-balanced waveforms, and rectified polarity-sensitive coupling, activated by duty-cycle asymmetry. The drift direction can be reversed by changing the modulation conditions, even at zero offset, and a complementary reversal is observed when temperature is varied for fixed drive voltage conditions. Quantitative Landau-de Gennes Q-tensor simulations reproduce the equilibrium toron structure, its formation under the unmodulated carrier, and the relaxation pathway following field removal, while the transport mechanisms are identified from experimental signatures. A dedicated graphical interface enables real-time switching between waveform presets, and three proof-of-concept functions are demonstrated that exploit the resulting multiparameter control space: a software-defined racetrack memory analogue with optical readout, deterministic path writing for reconfigurable patterning, and toron-mediated pick-and-place transport of microparticles.