Researchers Steer Tiny Waves of Energy Through Liquid Crystals
Controlling energy movement could eventually help researchers design active or autonomous materials that act without mechanical manipulation.
Waves called solitons were first observed in Union Canal in Edinburgh, Scotland. Now researchers are guiding them through liquid crystals to unlock the potential of autonomous materials.
In physics, some waves behave in a surprising way: instead of spreading out and fading, they hold their shape as they travel at constant speeds. These unusual waves, called solitons, have interested scientists since they were first observed in canals in the 19th century. Today, researchers study solitons in everything from optical fibers to biological systems.
A new study published in Proceedings of the National Academy of Sciences, shows that these stubborn waves can be guided and steered through materials by carefully designing internal strain, offering new ways to move energy or information at microscopic scales.
The research focuses on liquid crystals, the same class of materials used in LCD screens. But beyond displays, liquid crystals are prized by physicists because their internal structure can be manipulated with remarkable precision. Molecules inside them tend to align in a common direction, but that alignment can be twisted, bent, or reoriented with electric fields or surface chemistry.
In the new work, a research team from NYU and Cornell created special liquid-crystal cells where the molecules were forced to align differently at two opposite surfaces. One surface caused molecules to lie flat, while the other made them stand upright. The result was a continuously bent molecular orientation across the film — a built-in strain field inside the material.
When the researchers applied a high-frequency alternating electric field, something interesting happened. Tiny, localized pulses called “soliton bullets” began shooting through the liquid crystal. These bullets are not physical particles. Instead, they are traveling distortions of molecular alignment, moving through the material while maintaining a stable shape.
Earlier experiments showed that in uniformly aligned liquid crystals, these bullets typically move in just one direction. Under the new conditions, instead of following a single straight path, the soliton bullets traveled along two slanted trajectories, forming diagonal routes through the material. Even more intriguing, the direction of these paths could be tuned simply by adjusting the frequency of the electric field.
To understand why, the team combined experiments with theoretical models and computer simulations. The key turned out to be a phenomenon called flexoelectricity, a coupling between electric fields and mechanical distortions in liquid crystals.
Because the background molecular alignment in the strained cells was already bent, the electric field produced uneven torques on different parts of the soliton structure. Each soliton has two “wings,” regions where the molecular orientation tilts in opposite ways. In the strained environment, one wing becomes stronger than the other, generating a sideways push that sends the soliton along an angled path.
“In these systems, the material itself becomes a way to steer nonlinear signals,” said Juan de Pablo, Executive Dean at NYU Tandon and a coauthor of the study. “By engineering strain into the liquid crystal, we can control how these localized waves move.”
The finding illustrates a broader principle in materials science: the geometry and internal stresses of a material can shape how energy moves through it. In this case, carefully designed strain fields turn a simple liquid-crystal film into a kind of microscopic racetrack for solitons.
Such control could eventually help researchers design active or autonomous materials: systems that move energy, particles, or signals without mechanical components. Previous work has already shown that soliton waves in liquid crystals can transport tiny particles or even trigger droplet formation at fluid interfaces.
While practical devices may still be years away, the study highlights how liquid crystals serve as powerful model systems for exploring nonlinear physics.
“Controlled propagation of soliton bullets in an engineered strain field,” Alexis de la Cotte, Xingzhou Tang, Chuqiao Chen, S. J. Kole, Noe Atzin, Juan J. de Pablo, and Nicholas L. Abbott PNAS, #2025-18064R.
