Scientists create light-powered microscopic swimmers that could dramatically advance drug delivery

Scientists have created tiny disk-shaped particles that can swim on their own when hit with light, akin to microscopic robots that move through a special liquid without any external motors or propellers.

Published in Advanced Functional Materials, the work shows how these artificial swimmers could one day be used to deliver cargo in a variety of fluidic situations, with potential applications in drug delivery, water pollutant clean up, or the creation of new types of smart materials that change their properties on command.

"The essential new principles we discovered — how to make microscopic objects swim on command using simple materials that undergo phase transitions when exposed to controllable energy sources — pave the way for applications that range from design of responsive fluids, controlled drug delivery, and new classes of sensors, to name a few,” explained lead researcher Juan de Pablo.

Currently the Executive Vice President for Global Science and Technology at NYU and Executive Dean of the NYU Tandon School of Engineering, de Pablo conducted this research in collaboration with postdoctoral researchers and faculty at the Pritzker School of Molecular Engineering at the University of Chicago, the Paulson School of Engineering at Harvard University, and the Universidad Autonoma of San Luis Potosi, in Mexico

The research team designed tiny flat discs about 200 micrometers across, which is roughly twice the width of a human hair. These structures are made from dried food dye and propylene glycol, creating solid discs with bumpy surfaces that are essential for swimming.

When placed in a nematic liquid crystal (the same material used in LCD screens) and hit with green LED light, the discs start swimming on their own. The food dye absorbs the light and converts it to heat, warming up the liquid crystal around the disc. This causes the organized liquid crystal molecules (normally lined up like soldiers in formation) to “melt” and become jumbled and disorganized, creating an imbalance that pushes the disc forward.

Depending on temperature and light brightness, the discs behave differently. Under the right conditions, they achieve sustained swimming at speeds of about half a micrometer per second, notable for something this tiny.

The most spectacular results happen when the discs can move in three dimensions. As they swim, they create beautiful flower-like patterns of light visible under a microscope. These patterns evolve from simple 4-petaled shapes to intricate 12-petaled designs as the light gets brighter.

"The platelet lifts due to an incompatibility between the liquid crystal's preferred molecular orientation at different surfaces," said de Pablo. "This creates an uneven elastic response that literally pushes one side of the platelet upward."

What distinguishes this discovery is how different it is from other swimming methods. Unlike bacteria that use whip-like tails or other artificial swimmers that need expensive chemical reactions, these discs create movement using a simple melting transition, cheap materials and basic LED lights. Plus, they have perfect on/off control: when light is turned off, they stop swimming immediately.

This research taps into the growing field of "active matter", which are materials that can harvest energy from their surroundings and turn it into movement. While these specific discs rely on light and heat to change the extent of order in a liquid crystal , the principles could be adapted to create swimmers in other types of liquid or solid media, powered by light or body heat, for example.

The paper's lead author is Antonio Tavera-Vázquez (Pritzker School of Molecular Engineering at the University of Chicago), who is a postdoctoral researcher in the group of Juan de Pablo. The team also includes Danai Montalvan-Sorrosa (John A. Paulson School of Engineering and Applied Sciences at Harvard University and the Facultad de Ciencias, Departamento de Biología Celular at Universidad Nacional Autónoma de México); Gustavo R. Perez-Lemus (Pritzker School of Molecular Engineering at the University of Chicago and NYU Tandon currently); Otilio E. Rodriguez-Lopez (Facultad de Ciencias and Instituto de Física at Universidad Autónoma de San Luis Potosí in Mexico); Jose A. Martinez-Gonzalez (Facultad de Ciencias at Universidad Autónoma de San Luis Potosí); and Vinothan N. Manoharan (John A. Paulson School of Engineering and Applied Sciences and the Department of Physics at Harvard University).

Funding for this research was primarily provided by the Department of Energy, Office of Science Basic Energy Sciences, with additional support for some aspects of the experiments and equipment provided by the National Science Foundation, the Army Research Office MURI program, and the National Institutes of Health.

Tavera‐Vázquez, Antonio, et al. (2025) Microplate active migration emerging from light‐induced phase transitions in a nematic liquid crystal.” Advanced Functional Materials