At home, in the laboratory and in the factory, electric fields monitoring technologies such as Kindle displays, medical diagnostic tests, and devices that clear cancer drugs. In an electric field, anything that has an electrical charge—from a single atom to a large particle—experiences a force that can be used to nudge it in a desired direction.
When an electric field pushes charged particles in a liquid, the process is called electrophoresis. Our research team is studying how tourniquet electrophoresis move tiny particles called nanoparticles – V porous, spongy materials. Many new technologies, including those used in DNA analysis and medical diagnostics, use these porous materials.
Figuring out how to control the tiny charged particles as they travel through this medium could make them faster and more efficient with existing technologies. It can also provide completely new smart features.
Ultimately, scientists aim to make particles like these serve tiny nanorobots. They can perform complex tasks in our body or in our environment. They could be looking tumors and treatment or look for sources toxic chemicals in soil and turn them into harmless compounds.
To achieve these advances, we need to understand how charged nanoparticles pass through porous sponge materials when exposed to an electric field. In a new studypublished November 10, 2025 in Proceedings of the National Academy of Sciences, our team from research engineers under the leadership of Annie Shea and Siamak, Mirfendereski sought to do just that.
Weak and strong electric fields.
Think of a nanoparticle as a tiny submarine sailing through complex, interconnected, fluid-filled labyrinth while experiencing random swaying motion. By observing the movement of nanoparticles through a porous material, we noticed some surprising behavior related to the strength of the applied electric field.
A weak electric field acts only as an accelerator, increasing the speed of the particle and significantly increasing its chances of finding a way out of the cavity, but does not give direction – it is fast, but random.
Instead, a strong electric field provides the necessary “GPS coordinates,” causing the particle to move quickly in a specific, predictable direction through the network.
This discovery was mysterious but exciting because it suggested that we could control the movement of nanoparticles. We could choose to have them move quickly and randomly in a weak field, or directionally in a strong field.
The former allows them to efficiently explore the environment, while the latter is ideal for delivering cargo. This mysterious behavior prompted us to take a closer look at what the low field does to the surrounding fluid.
This diagram shows how a particle moves through a porous material over time in a weak or strong electric field. The darkest color indicates the particle's starting point, and lighter colors indicate the particle's position after some time has passed. A particle in a weak field moves chaotically, while in a strong field the particle gradually moves in the direction determined by the electric field. Annie Shi
Having studied this phenomenon more closely, we discovered the reasons for this behavior. The weak field causes the stagnant fluid to flow in random vortex movements in the tiny cavities of the material. This random flow enhances the natural wobble of the particle and pushes it towards the walls of the cavity. Moving along the walls, the particle sharply increases the probability of finding a random escape route compared to searching throughout the entire space of the cavity.
However, a strong field provides a powerful directed push to the particle. This push overcomes the natural rocking of the particle, as well as the random flow of the surrounding fluid. This ensures that the particle will migrate predictably along electric field direction. This discovery opens the door to new, efficient strategies for moving, sorting and separating particles.
Nanoparticle tracking
To conduct this research, we integrated laboratory observation with computer simulation. In the experiment, we used a state-of-the-art microscope to carefully monitor how individual nanoparticles move within a perfectly structured porous material called quartz inverse opal.
Scanning electron micrograph of a quartz inverse opal showing a cross section of an artificial porous material with 500 nanometer diameter cavities located within small 90 nanometer diameter holes. Annie Shi
We then used computer simulations to simulate the underlying physics. We simulated the random rocking motion of the particle, the electrical driving force, and the fluid flow near the walls.
By combining this precise imaging with theoretical modeling, we deconstructed the overall behavior of the nanoparticles. We could quantify the effect of every single physical process, from rocking to electric shock.
This high-resolution fluorescence microscope, located at the University of Colorado Boulder's Advanced Light Microscopy Facility, captured 3D tracks of nanoparticles moving inside porous materials. Joseph Dragavon
Devices that move particles
This research could have major implications for technologies that require precise microscopic transport. In them, the goal is fast, precise and differential movement of particles. Examples include medication delivery that requires guidance.nanocargo” for specific tissue purposesor industrial division, which entails cleaning chemicals and filtration of contaminants.
Our discovery – the ability to separately control the speed of a particle using weak fields and its direction using strong fields – acts as a two-lever control tool.
This control could allow engineers to design devices that apply weak or strong fields to individually move different types of particles. Ultimately, this tool could improve faster and more efficient diagnostic tools and cleaning systems.
What's next
We have established independent control over the search for particles by speed and their migration by direction. But we still don't know the full extent of this phenomenon.
Key questions remain: what are the upper and lower particle sizes that can be controlled in this way? Can this method be reliably applied in complex, dynamic biological environments?
Most importantly, we will need to investigate the exact mechanism for the sudden acceleration of these particles under the influence of a weak electric field. Answers to these questions are necessary to unlock the full accuracy of this particle control method.
Our work is part of a larger scientific project aimed at understanding how constraints and boundaries affect the movement of nanoscale objects. As technology shrinks, understanding how these particles interact with nearby surfaces will help develop efficient tiny devices. And when moving through spongy, porous materials, nanoparticles constantly collide with surfaces and boundaries.
The collective goal of ours and others related studies is to transform the control of tiny particles from a process of trial and error into a reliable and predictable science.
This article has been republished from Talka nonprofit, independent news organization bringing you facts and trusted analysis to help you make sense of our complex world. He was written by: Daniel K. Schwartz, University of Colorado Boulder And Ankur Gupta, University of Colorado Boulder
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Daniel K. Schwartz receives funding from the U.S. Department of Energy, the National Science Foundation, and the National Institutes of Health.
Ankur Gupta receives funding from the National Science Foundation and the Air Force Office of Scientific Research.
