Scientists at New York University have pioneered a groundbreaking technique that harnesses the power of light to manipulate the assembly of microscopic particles into highly ordered crystalline structures. This innovative method, recently published in the prestigious journal Chem, introduces a reversible and precise approach to controlling the formation and disassembly of colloidal crystals—microscopic analogs of traditional crystals such as diamonds or silicon but formed in liquid suspensions. The ability to program such crystallization on demand represents a significant advance toward the development of dynamic, adaptable materials with tunable optical properties.
Crystals are everywhere in nature and technology, fundamentally characterized by their repeating, symmetrical particle arrangements at the atomic or molecular scale. Colloidal crystals, formed by colloidal particles suspended in a liquid medium, serve as versatile models to study crystallization and are critical in fabricating materials used in photonics, sensing, and laser technologies. However, controlling when and where these crystals form has historically been a challenge. Crystals tend to emerge spontaneously under specific conditions, but once formed, their structure is typically fixed, offering limited capability for real-time tuning or reconfiguration.
Addressing this long-standing issue, the NYU team employed a clever approach that involves integrating photoacid compounds into a colloidal suspension. These photoacids are molecules that, upon exposure to light, temporarily alter their acidity. This light-triggered acidification modifies the surface charge of colloidal particles, directly influencing the electrostatic forces that determine whether particles attract or repel one another. By finely controlling the intensity, duration, and spatial pattern of illumination, researchers achieved unprecedented command over the assembly and dissolution of colloidal crystals.
“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 tuning the external light stimulus, the colloidal particles can be induced to either cluster tightly into ordered crystals or disperse back into a disordered state. This reversible process transcends previous methods that required chemical modification or environmental adjustments that are difficult to finely regulate in practice.
Extensive experimentation combined with computer simulations revealed that varying light patterns enable the team to shapeshift the crystals—forming, melting, and even sculpting them with high resolution. This capacity not only controls crystallization in both time and space but also enhances the size and structural order of the resulting colloidal arrangements. Steven van Kesteren, a postdoctoral researcher instrumental in the project, detailed how minute changes in light intensity led to strikingly different outcomes, shifting particles from completely sticky to fully free states.
This technique simplifies experimental design as it eschews the need for multiple separate trials with different particle formulations or solution conditions. Instead, all transformations occur within a unified chemical system, controlled solely by light input. Such a “one pot” flexibility provides a robust platform to explore complex crystallization dynamics and test theoretical predictions regarding self-assembly and spatially varying interaction potentials.
The implications of this technology extend well beyond basic research. Materials engineered through light-programmed colloidal crystallization could revolutionize the field of photonics, enabling devices with dynamically rewritable optical characteristics. Imagine coatings whose color or reflective properties can be instantly tuned simply by projecting a light pattern, or sensors that alter sensitivity and response on command. This could lead to adaptive displays, reconfigurable information storage technologies, and beyond, where structural and functional patterns are defined not during manufacturing but post-fabrication by targeted illumination.
The research also offers a valuable testbed for fundamental science in condensed matter physics and materials chemistry. Glen Hocky, associate professor at NYU and contributor to the work, highlighted how this light-matter interplay opens new vistas to validate models of nonequilibrium self-assembly and spatially heterogeneous particle interactions—a frontier that conventional static systems cannot address.
This work, supported by funding from the US Army Research Office, the Swiss National Science Foundation, and the Simons Foundation, showcases the creative merger of chemistry, physics, and materials engineering. The convergence of precision photochemistry with colloidal science ushers in a new paradigm where light is more than just a probe or passive tool—it becomes an active means to sculpt the microscopic world.
As research progresses, the hope is that this versatile platform will stimulate innovations across nanotechnology, optical engineering, and dynamic materials design. The ability to control and reconfigure crystalline structures on demand with nothing more than a light source promises a versatile toolkit for next-generation devices that blend functionality with elegance and simplicity.
This remarkable advance not only illuminates the path to materials that respond dynamically to their environment but also fundamentally shifts our understanding of how light can be used to govern matter at the microscale. It is a vivid demonstration that the future of materials science is not fixed but fluid, programmable, and profoundly influenced by the interplay of energy and matter.
Subject of Research: Colloidal crystallization controlled by light-induced charge modulation in particle suspensions
Article Title: Light-controlled colloidal crystallization
News Publication Date: 24-Feb-2026
Web References: DOI: 10.1016/j.chempr.2025.102917
Image Credits: Steven van Kesteren / Sacanna Lab, NYU
Keywords
Crystallization, Crystal structure, Crystallography, Crystals, Colloidal crystals, Light, Photonics, Optical materials
