This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at the National Graphene Institute have shown that naturally occurring channels within a common clay mineral can respond to pressure, voltage and pH, offering possibilities for controlling the movement of ions through extremely small, confined spaces. The study, published in Advanced Materials, focuses on vermiculite, a naturally abundant layered clay whose structure contains channels only a few angstroms high, providing naturally confined pathways through which ions can move.
Biological ion channels, which have angstrom-scale constrictions, can respond to multiple signals from their surroundings and regulate the movement of ions across cell membranes. Inspired by this principle, researchers investigated whether naturally occurring angstrom-scale channels in vermiculite could also exhibit responsive ion transport when exposed to different external stimuli, such as mechanical, electrical and chemical signals. Depending on the conditions applied, the channels altered both the amount and direction of ion flow, showing behavior similar to ion-gating behavior in biological channels.
"Biological ion channels are remarkably sophisticated systems that can respond to multiple signals from their environment and regulate molecular transport accordingly. Our work shows that naturally occurring channels in vermiculite can emulate this behavior, responding to pressure, voltage and pH while controlling how ions move through the material," said Professor Radha Boya. The clay channels naturally favor positively charged ions.
The team found that by changing the acidity of the surrounding solution, they were able to influence this selectivity. Pressure and electrical voltage also altered how ions traveled through the channels, revealing a complex interplay between the different stimuli. Raj Kumar Gogoi, first author of the study, added, "We observed that applying pressure and voltage together could change the behavior of the flowing ions in ways not seen when either stimulus was applied alone.
Under certain conditions, the direction of the pressure-driven current could even reverse, highlighting the sensitivity of the system to multiple environmental inputs." Professor Narayana R. Aluru, from the University of Texas at Austin, said, "The experimental observations could not be fully explained using conventional models. We introduce a modified surface-charge regulation model, where pressure, voltage and ion concentration influence the distribution of ions inside the channels and modify the charge at the channel surface, which in turn affects ion transport." Unlike conventional models, which typically consider surface charge as a function of ion concentration alone, the new approach incorporates the combined effects of voltage, pressure and concentration to describe how these coupled factors influence ion transport in highly confined channels.
The findings suggest that naturally layered materials could offer a versatile platform for studying and controlling ionic transport at extremely small scales. The authors say future applications could include adaptive nanofluidic systems, energy conversion devices and bioelectronic platforms, though these applications were not explored in the present study. The research was conducted by scientists from the Department of Physics and Astronomy, National Graphene Institute and Photon Science Institute at The University of Manchester; the Department of Mechanical Science and Engineering and Beckman Institute for Advanced Science and Technology at the University of Illinois Urbana-Champaign; and the Walker Department of Mechanical Engineering at The University of Texas at Austin.
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