BOULDER, Colo. — Researchers at the University of Colorado Boulder have uncovered a groundbreaking way to guide tiny nanoparticles through complex, liquid-filled environments using electric fields, a discovery that could revolutionize drug delivery systems and industrial purification processes.
The study, led by engineers Ankur Gupta and Daniel K. Schwartz, reveals how varying the strength of electric fields can control the movement of these nanoparticles in porous materials, potentially enabling them to act like miniature robots for targeted tasks in medicine and environmental cleanup.
Published on Nov. 10, 2025, in the Proceedings of the National Academy of Sciences, the research demonstrates that weak electric fields speed up nanoparticles' random searching, while strong fields direct them precisely, according to the findings detailed in the paper.
Ankur Gupta, an assistant professor of chemical and biological engineering at the university, explained the concept in an article for The Conversation. "In the home, the lab and the factory, electric fields control technologies such as Kindle displays, medical diagnostic tests and devices that purify cancer drugs," Gupta wrote, co-authoring with Daniel K. Schwartz, a professor in the same department.
The process, known as electrophoresis, involves applying an electric field to push charged particles through a fluid. The team's work focuses on nanoparticles navigating porous, spongy materials, which are common in technologies like DNA analysis and medical diagnostics.
According to the researchers, mastering this control could lead to nanoparticles functioning as nanorobots that perform intricate tasks, such as seeking out tumors for drug delivery or neutralizing toxic chemicals in soil.
In their experiments, the team observed nanoparticles behaving differently based on field strength. "A weak electric field acts only as an accelerator, boosting the particle’s speed and dramatically improving its chance of finding any exit from a cavity, but offering no directional guidance – it’s fast, but random," the researchers noted in their Conversation article.
Conversely, a strong field provides clear direction. "In contrast, a strong electric field provides the necessary ‘GPS coordinates,’ forcing the particle to move rapidly in a specific, predictable direction across the network," they added.
To uncover these behaviors, the team combined laboratory observations with computational modeling. They used an advanced microscope to track individual nanoparticles in a structured porous material called silica inverse opal, which mimics a liquid-filled maze.
Computer simulations helped model the physics, including the particles' random jiggling, electrical forces, and fluid flows. This approach allowed them to quantify each factor's impact, from natural Brownian motion to the directed push of the electric field.
One key insight was the role of fluid dynamics in weak fields. "A weak field causes the stagnant liquid to flow in random swirling motions within the material’s tiny cavities," the researchers explained. "This random flow enhances a particle’s natural jiggling and pushes it toward the cavity walls."
By hugging the walls, particles increase their odds of escaping cavities quickly, compared to wandering aimlessly. In strong fields, however, the directional force overrides these random elements, ensuring predictable movement.
"This discovery was puzzling but exciting, because it suggested that we could control the nanoparticles’ motion. We could choose to have them move fast and randomly with a weak field or directionally with a strong field," the team wrote. "The former allows them to search the environment efficiently while the latter is ideal for delivering cargo."
The implications extend to real-world applications. In drug delivery, for instance, nanoparticles could be guided to specific tissues, improving efficiency and reducing side effects. Industrial uses might include faster purification of chemicals or contaminant filtration.
Daniel K. Schwartz, who receives funding from the U.S. Department of Energy, the National Science Foundation, and the National Institutes of Health, emphasized the potential for "new, efficient strategies to move, sort and separate particles." Gupta, funded by the National Science Foundation and the Air Force Office of Scientific Research, echoed this, noting the method as a "two-lever control tool" for speed and direction.
The University of Colorado, a member of The Conversation US, provided additional funding for the dissemination of the research. The study's DOI is https://doi.org/10.64628/AAI.v53yxf3ka, offering a permanent reference for the work.
While the primary findings come from this team, a summary from The Conversation reinforces the core idea: "Moving tiny particles through materials quickly can improve the efficiency of a variety of technologies." No conflicting reports were available, but the consistency across the provided sources underscores the reliability of the observations.
Background on electrophoresis dates back to the 19th century, but its application to nanoparticles in porous media is a modern frontier. Porous materials, like those in silica inverse opals, feature interconnected cavities that challenge particle navigation, much like a submarine in a maze, as the researchers analogized.
The team's lead researchers, Anni Shi and Siamak Mirfendereski, contributed to the experimental design, focusing on how confinement affects nanoscale motion. This fits into a broader scientific effort to understand boundaries' influence on tiny objects, crucial as technologies miniaturize.
For context, similar research has explored electrophoresis in diagnostics, such as rapid COVID-19 tests, where electric fields separate biomolecules. The Boulder team's work builds on this by addressing navigation in complex 3D structures, potentially speeding up processes that currently rely on diffusion alone.
Experts in the field have not yet publicly commented on this specific study, but the publication in PNAS, a prestigious journal, suggests peer-reviewed validation. The researchers themselves acknowledge limitations, noting that key questions remain unanswered.
"What are the upper and lower sizes of particles that can be controlled in this way? Can this method be reliably applied in complex, dynamic biological environments?" they questioned in their article, highlighting the need for further investigation.
Most critically, the mechanism behind the speedup in weak fields requires deeper exploration. "Most fundamentally, we’ll need to investigate the exact mechanism behind the dramatic speedup of these particles under a weak electric field," the team stated.
Looking ahead, this research could accelerate developments in personalized medicine, where nanoparticles deliver therapies directly to cancer cells, or in environmental remediation, targeting pollutants at the molecular level. Engineers might design devices that switch between weak and strong fields to optimize particle behavior for different tasks.
As part of a larger push, the work aims to turn nanoparticle control from trial-and-error into a predictable science. With funding from major institutions, the University of Colorado team plans to expand their models to biological settings, potentially collaborating with medical researchers.
The discovery opens doors for faster diagnostic tools and more efficient purification systems, promising advancements that could touch everyday life, from healthcare to manufacturing. As Gupta and Schwartz conclude, understanding these interactions will be key to harnessing the full potential of nanoscale technologies.