Spatial Activity Patterning and Topological Defect Transport in Acoustically Energized Active Liquid Crystals.

Patterning activity in space is expected to transform active nematics from chaotic dynamic fluids into reconfigurable materials capable of controlled transport of topological defects. Although some of these capabilities have been investigated in computational models, the experimental realization has been limited by the challenges of reliable generation and modulation of spatiotemporal activity patterns. Here, we report a versatile approach for spatial activity patterning in a quasi 2D acoustically powered active liquid crystal with activity controlled solely by the local confinement height. We demonstrate that linear gradients and step-like variations in the local channel height set the local activity level in the active liquid crystal and govern the behavior of topological defects. Based on our findings, we realized activity patterns that support a sustained antiparallel transport of +1/2 and -1/2 topological defects. A minimal agent-based model confirms that the observed topological defect transport arises from geometry-induced spatial modulation of activity rather than from direct geometric rectification of defect motion. Our findings establish a scalable strategy for programming the dynamics of active nematic materials, and advance the development of active microfluidic architectures that utilize topological defect transport for information processing.