NYU Scientists Use Light to Build and Melt Crystals

Imagine using a flashlight to build tiny crystals, then melting them and reshaping them with just another beam of light. Scientists at New York University just made that possible.

The research team developed a technique that uses light to control microscopic particles floating in liquid, making them snap together into perfectly ordered crystal structures or break apart on command. Published in the journal Chem, this discovery gives scientists unprecedented control over materials that could transform everything from smartphone screens to medical sensors.

Crystals are everywhere in nature and technology, from diamonds to the silicon in computer chips. Colloidal crystals, made of microscopic particles suspended in liquid, have been difficult to control because they typically form spontaneously and stay fixed once created.

The NYU team solved this challenge by adding special molecules called photoacids to the liquid suspension. When light hits these molecules, they temporarily change the electric charge on the particle surfaces, making them either stick together or push apart.

"Our approach effectively uses light as a remote control for matter organization at the microscopic scale," explained Stefano Sacanna, professor of chemistry at NYU and lead author of the study. By adjusting the brightness, timing, and pattern of light, researchers can sculpt crystals with remarkable precision.

Postdoctoral researcher Steven van Kesteren discovered that tiny changes in light intensity created dramatically different results, shifting particles from completely sticky to fully free. This means scientists can run multiple experiments in one container just by changing the light, instead of preparing dozens of separate solutions.

The practical applications are exciting. Future displays could change color or reflectivity instantly when exposed to specific light patterns. Sensors could adjust their sensitivity on the fly, and information storage devices could be rewritten without physical contact.

The Ripple Effect

This breakthrough extends far beyond the lab. Materials engineered through light-programmed crystallization could revolutionize photonics, the science of using light in technology. Adaptive coatings could shift from transparent to opaque, or change color to match their surroundings.

The technique also provides a powerful new tool for fundamental science research. Glen Hocky, associate professor at NYU, noted that this light-matter interplay opens new opportunities to test theories about how particles self-organize under changing conditions.

Funded by the US Army Research Office, the Swiss National Science Foundation, and the Simons Foundation, this work represents a creative fusion of chemistry, physics, and materials engineering. Light becomes more than just a tool to observe matter—it becomes an active sculptor of the microscopic world.

The future of materials science just got brighter, more flexible, and infinitely more programmable.