Scientists at Osaka University have designed a nanogate that opens and closes using electrical signals, offering precise control over ions and molecules.
This tiny innovation has the potential to transform sensing technology, chemical reactions, and even computing. By adjusting voltage, researchers can manipulate the gate’s behavior, making it a versatile tool for cutting-edge applications.
Nanogates: Control at the Macro and Nanoscale
Gates are used to control movement, whether it’s livestock passing through a farm gate or molecules moving at the nanoscale. Just as a physical gate can open or close to regulate larger entities, nanogates can control the passage of single molecules.
Researchers at Osaka University have developed a nanogate that opens and closes in response to electrical signals. Its behavior depends on both the voltage applied and the materials present in the surrounding solutions. This makes it a promising tool for applications such as molecular sensing and precisely controlled chemical reactions.
How the Nanogate Works: A Tiny Pore with Big Potential
The nanogate is a tiny pore embedded in a silicon nitride membrane. This membrane is housed in a flow cell on a chip, with solutions introduced on both sides. By applying voltage through electrodes on the chip, researchers measured the resulting ionic current, which indicates ion movement through the pore. Since this current is highly sensitive to the composition of the surrounding solutions, researchers can precisely control the flow of ions and trigger the formation or dissolution of metal compounds within the pore.
The change of pore diameter resulting from precipitation (which closed the nanogate) or dissolution (which opened the nanogate) led to distinct types of ion transport. “Precipitates grew and closed the pore under negative voltage, decreasing ionic current,” says lead author of the study, Makusu Tsutsui. “Inverting the voltage polarity caused the precipitates to dissolve, reopening the pore.”
Memristive Behavior and One-Way Ion Transport
Under certain conditions, the formation of a precipitate that blocked the pore resulted in the highest rectification ratio, which is a measure of the propensity of ions to travel only in one direction, achieved to date for a nanofluidic device. As well as acting as a rectifier, the system could also behave as a memristor; that is, a memory effect was observed in its relationship between current and voltage. The sequential precipitation and dissolution of materials in the pore led to this memristive behavior.
Biomolecule Detection: DNA Sensing in Action
Additionally, in-pore reactions could be regulated to allow biomolecule detection. This was demonstrated using DNA. The system exhibited distinct output signals as individual DNA molecules moved through the pore.
“The ability to finely control pore size using applied voltage should allow pores to be tailored for specific analytes immediately before conducting measurements,” explains senior author Tomoji Kawai. “We also anticipate that our approach can be used to develop reaction systems to access new chemical compounds.”
Future Applications: Sensing, Chemistry, and Computing
Using a membrane with a single controlled pore in nanofluidic electrochemical devices is a versatile approach that can be tailored for specific applications including sensing, chemical reactions, and neuromorphic computing.
Reference: “Transmembrane voltage-gated nanopores controlled by electrically tunable in-pore chemistry” by Makusu Tsutsui, Wei-Lun Hsu, Chien Hsu, Denis Garoli, Shukun Weng, Hirofumi Daiguji and Tomoji Kawai, 5 February 2025, Nature Communications.
DOI: 10.1038/s41467-025-56052-0
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