Electric Fields Guide Nanoparticles Through Liquid Mazes — Weak Fields Speed Searching, Strong Fields Enable Precise Delivery

Electric fields steer nanoparticles through a liquid-filled maze

Summary: Researchers found that the strength of an applied electric field can switch nanoparticle transport between two distinct modes inside porous, liquid-filled materials: weak fields enhance random, fast searching; strong fields produce predictable, directional migration. The discovery could enable better drug-delivery systems, diagnostics and purification technologies.

What the study examined

Electric fields are already used across many technologies — from e-readers and diagnostic strips to devices that purify chemotherapy drugs. Anything that carries a charge, from an ion to a micron-scale particle, feels a force in an electric field. When charged particles move through a fluid under an electric field, the process is called electrophoresis.

In a new study published Nov. 10, 2025 in Proceedings of the National Academy of Sciences, a team led by Anni Shi and Siamak Mirfendereski investigated how electrophoresis can be harnessed to steer nanoparticles through porous, sponge-like materials. These porous media play central roles in DNA analysis, medical diagnostics and other emerging technologies.

Key finding: two transport modes

By tracking individual nanoparticles with high-resolution microscopy inside a carefully structured porous material (a silica inverse opal) and by building complementary computer simulations, the team uncovered a surprising dichotomy:

• Weak electric fields increase particle speed and induce small, random fluid circulations inside the cavities. Those flows amplify Brownian ‘‘jitter’’ and tend to push particles toward the cavity walls. Particles traveling near walls have a dramatically higher chance of finding an escape route, so weak fields greatly improve search efficiency without providing directional guidance.
• Strong electric fields overwhelm both the particle’s Brownian motion and the induced fluid eddies, providing a robust, directional push that drives particles predictably along the field lines through the network.

How the researchers reached their conclusions

The study combined direct laboratory observation with physics-based computational modeling. Experiments used advanced microscopy to follow single nanoparticles moving in the structured porous medium. Simulations modeled Brownian motion, the electrical driving force and the fluid flows that form near solid walls. By matching visualization and theory, the authors decomposed the particle dynamics and quantified the contributions of each mechanism.

Implications and applications

This two‑lever control — using weak fields to enhance searching (speed) and strong fields to impose direction (migration) — suggests practical strategies for moving, sorting and separating microscopic particles inside porous materials. Potential applications include:

• Targeted drug delivery, where ‘‘nanocargo’’ must explore tissue and then be steered to a specific site.
• Faster and more selective diagnostic assays that rely on transport through porous matrices.
• Industrial separations and purification processes, including removing contaminants or refining chemical feeds.

Open questions

Important limits and mechanisms remain to be explored: What are the smallest and largest particle sizes that can be controlled this way? How robust is the method in complex, dynamic biological environments? What precisely causes the dramatic speedup under weak fields? Answering these questions is essential to convert the observed effects into a precise engineering tool.

Big picture: As devices shrink and porous, confined geometries become more common, understanding how boundaries and surfaces influence nanoscale motion will be critical for designing efficient microscopic systems. This work moves control of tiny particles toward a more predictable, designable science.

Authors, funding and source

This article was written by Daniel K. Schwartz and Ankur Gupta, both at the University of Colorado Boulder, and is adapted from a Conversation piece republished with permission. The original research was led by Anni Shi and Siamak Mirfendereski. Funding disclosures: Daniel K. Schwartz receives support 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.

Source: Proceedings of the National Academy of Sciences, published Nov. 10, 2025. Republished from The Conversation.