Synthetic active liquid crystals powered by acoustic waves

TL;DR

This paper introduces a fully synthetic active nematic liquid crystal system powered by ultrasonic waves, enabling stable, tunable activity and novel defect dynamics, advancing the design of reconfigurable microfluidic devices.

Contribution

It presents a non-biological, ultrasonic-powered active nematic system with controllable activity and unique defect behaviors, expanding the scope of active matter research.

Findings

Conversion of acoustic energy into microscopic stresses causes active turbulence.

Emergence of persistent vortices at high activity levels.

Stable material properties over extended activity ranges.

Abstract

Active nematics are materials composed of mobile, elongated particles that can transform energy from the environment into a mechanical motion. Current experimental realizations of the active nematics are of biological origin and include cell layers, suspensions of elongated bacteria in liquid crystal, and combinations of bio-filaments with molecular motors. Here, we report the realization of a fully synthetic active nematic system comprised of a lyotropic chromonic liquid crystal energized by ultrasonic waves. This artificial active liquid crystal is free from biological degradation and variability, exhibits stable material properties, and enables precise and rapid activity control over a significantly extended range. We demonstrate that the energy of the acoustic field is converted into microscopic extensile stresses disrupting long-range nematic order and giving rise to an undulation instability, development of active turbulence, and proliferation of topological defects. We reveal the emergence of unconventional free-standing persistent vortices in the nematic director field at high activity levels. The results provide a foundation for the design of externally energized active nematic fluids with stable material properties and tunable topological defects dynamics crucial for the realization of reconfigurable microfluidic systems.