Schematic model depicting in-pore precipitation reaction in a solid-state nanopore.
Researchers at The University of Osaka use a nanoreactor to produce pores that mimic biological ion channels
Osaka, Japan – Ion channels are narrow passageways that play a pivotal role in many biological processes. To model how ions move through these tight spaces, pores need to be fabricated at very small length scales. The narrowest regions of ion channels can be just a few angstroms wide, about the size of individual atoms, making reproducible and precise fabrication a major challenge in modern nanotechnology.
In a study published in Nature Communications, researchers at The University of Osaka have addressed this challenge by using a miniature electrochemical reactor to create ultra-small pores approaching subnanometer dimensions.
In biological cells, ions flow in and out through channels in cell membranes. This ion flow is the basis for generating electrical signals, such as nerve impulses that trigger muscle contraction. The channels themselves are made of proteins and can have angstrom-wide narrow regions. Conformational changes of these proteins in response to external stimuli open and close the channels.
Inspired by these biological systems, the research team developed a solid-state analogue that enables the formation of subnanometer pores approaching biological ion-channel dimensions. A nanoscale pore was used as a reactor to form the subnanometer pores. First, the nanopore was created in a silicon nitride membrane. Applying a negative voltage across the membrane induced a reaction in the pore that produced a precipitate. The precipitate grew until the pore was completely blocked. Applying a positive voltage to the membrane caused the precipitate to dissolve and reopened conductive pathways within the pore.
“We were able to repeat this opening and closing process hundreds of times over several hours,” explains lead author Makusu Tsutsui. “This demonstrates that the reaction scheme is robust and controllable.”
The team measured the ion current through the membrane. There were spikes in the current, which have also been observed in biological channels. Analysis of these spikes suggests that precipitate formation is most consistent with the formation of many subnanometer pores within the nanopore.
“We were able to vary the behavior and effective size of the ultrasmall pores by changing the composition and pH of the reactant solutions,” reports Tomoji Kawai, senior author. “This enabled selective transport of ions of different effective sizes through the membrane by tuning the ultrasmall pore sizes.”
The novel reaction scheme enables the formation of many ultrasmall pores within a single nanopore. This route provides a powerful tool for performing fundamental studies on the transport of ions and fluids in highly confined spaces at biological scales. The chemically driven membrane system holds promise for applications in emerging technologies such as single-molecule sensing (e.g., using nanopores to sequence DNA), neuromorphic computing (using electrical spikes to mimic the behavior of biological neurons), and nanoreactors (creating unique reaction conditions through confinement).
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The article, “Chemistry-driven autonomous nanopore membranes,” will be published in Nature Communications at DOI: https://doi.org/10.1038/s41467-026-68800-x
About The University of Osaka
The University of Osaka was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world. Now, The University of Osaka is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.
Website: https://resou.osaka-u.ac.jp/en
