Light-Guided Crystals: New Method for Building Responsive Materials

New York University researchers have demonstrated a novel method for controlling the formation of crystals using light, effectively turning illumination into a tool for shaping matter at a microscopic level. Published March 2, 2026, in the journal Chem, the study details a reversible technique that could pave the way for a new generation of adaptable materials with programmable properties. This breakthrough addresses a longstanding challenge in materials science: the difficulty of precisely controlling crystal growth in real-time.

Harnessing Photoacids for Dynamic Control

Crystals, from the familiar structure of snowflakes to the silicon wafers powering our electronics, are defined by the highly ordered arrangement of their constituent particles. Researchers have long studied colloidal crystals – arrangements of tiny particles suspended in liquid – as models for understanding these structures and as building blocks for advanced materials used in optics, photonics, sensors, and lasers. However, initiating and directing crystal formation has historically been a complex process. “The challenge in the field has been control: crystals usually form where and when they want, and once conditions are set, you have limited ability to adjust the process in real time,” explains study author Stefano Sacanna, a professor of chemistry at NYU.

The NYU team’s approach centers on the use of light-sensitive molecules called photoacids. When introduced into a liquid containing colloidal particles, these photoacids undergo a change in acidity when exposed to light. This alteration, in turn, modifies the electrical charge of the particles. By carefully controlling the light’s intensity and pattern, the researchers can manipulate the attractive or repulsive forces between particles, dictating whether they coalesce to form crystals or disperse. Essentially, light acts as a “remote control” for particle interactions.

Real-Time Manipulation and ‘One-Pot’ Simplicity

Through a combination of experimentation and computer simulations, the researchers demonstrated remarkable precision in directing crystal behavior. They were able to initiate crystal growth, dissolve existing crystals, reshape structures, and enhance uniformity – all in real-time by adjusting the light. “Using our photoacid gave us a surprising level of control over the attraction between particles. Just turning the light up or down a little made the difference between the particle fully sticking or being fully free,” said study author Steven van Kesteren, formerly of NYU and now at ETH Zürich. The team could even selectively dissolve portions of a crystal structure simply by “unsticking” particles at specific locations.

A significant advantage of this method is its simplicity. The process operates as a “one-pot” experiment, meaning the researchers didn’t need to repeatedly redesign particles or adjust solution conditions. Changing the illumination level was sufficient to trigger assembly or disassembly, streamlining the experimental process. This contrasts with many existing crystal growth techniques that require meticulous control of multiple parameters.

Implications for Programmable Materials

This research opens up exciting possibilities for creating materials with dynamically tunable properties. Imagine photonic materials whose color or optical response can be written, erased, and rewritten on demand using light. Potential applications include reconfigurable optical coatings, adaptive sensors that respond to changing light conditions, and advanced display and data storage technologies where patterns and functions are defined by illumination rather than fixed during manufacturing. The Lee Research Lab at NYU, for example, focuses on crystal engineering for sustainable energy applications, exploring how controlling nanocrystal structures can improve the efficiency of solar energy harvesting and photodetection. More information about their work can be found on their website.

Glen Hocky, an associate professor of chemistry at NYU and a faculty member at the Simons Center for Computational Physical Chemistry, highlights the potential for testing fundamental theories of self-assembly. “This system also allows us to test a number of predictions on how self-assembly should behave when interactions between particles or molecules are changing across space or time.”

Beyond the Lab: Next Steps and Potential Challenges

The research team’s findings represent a significant step forward, but several avenues for further investigation remain. The current study focused on colloidal crystals in a controlled laboratory setting. Scaling up the process to create larger, more complex structures and integrating it into practical devices will require addressing challenges related to light penetration and maintaining uniform illumination across larger volumes.

Further research will likely focus on exploring different photoacid molecules to optimize their sensitivity and responsiveness to light. The team also plans to investigate the use of more complex light patterns to create increasingly intricate crystal structures. The Department of Chemistry at NYU provides a robust environment for this continued exploration, offering cutting-edge research opportunities and advanced facilities.

The initial findings, published in Chem, will undergo the standard process of peer review and replication by other research groups. Successful replication and further development could lead to the emergence of light-programmable materials with a wide range of applications, transforming fields from optics and photonics to sensing and data storage. A related breakthrough, also reported recently, details how scientists have turned light into a remote control for crystals, as detailed by ScienceDaily, further demonstrating the growing potential of light-based material manipulation.