Researchers at the University of Osaka have made significant advancements in the quest for innovative technologies. In a recent publication in Nature Communications, the team outlines their method of utilizing a miniature electrochemical reactor to create pores that approach subnanometer dimensions.
Inspired by Nature's Electrical Channels
Within biological cells, ions navigate through specialized protein channels embedded in the cell membrane, generating electrical signals essential for various physiological processes, including muscle contractions. These channels, composed of proteins, feature extremely narrow regions at the angstrom scale. When subjected to external stimuli, these proteins undergo conformational changes, allowing the channels to either open or close.
Taking cues from this natural mechanism, the researchers engineered a solid-state version capable of forming pores nearly as small as those found in biological ion channels. The process began with the creation of a nanopore in a silicon nitride membrane, which subsequently served as a tiny reaction chamber for the formation of even smaller pores.
By applying a negative voltage across the membrane, the team initiated a chemical reaction within the nanopore, resulting in a solid precipitate that gradually expanded until it completely obstructed the opening. Reversing the voltage caused the precipitate to dissolve, reinstating conductive pathways through the pore.
Lead author Makusu Tsutsui stated, "We were able to repeat this opening and closing process hundreds of times over several hours, demonstrating that the reaction scheme is both robust and controllable."
Understanding Subnanometer Pores Through Electrical Spikes
To gain deeper insights into the processes occurring within the membrane, the researchers monitored the ion current traversing it. They detected sharp spikes in the current, resembling patterns observed in biological ion channels. Further investigation revealed that these signals were indicative of the formation of numerous subnanometer pores within the initial nanopore.
The team also discovered that they could precisely adjust the behavior of the pores. By varying the chemical composition and pH of the reactant solutions, they modified both the size and characteristics of these ultrasmall openings.
Tomoji Kawai, senior author, remarked, "We could vary the behavior and effective size of the ultrasmall pores by changing the composition and pH of the reactant solutions, allowing selective transport of ions of different effective sizes through the membrane."
Potential Applications in DNA Sequencing and Neuromorphic Computing
This chemically driven technique enables the creation of multiple ultrasmall pores within a single nanopore, offering a novel approach to study ion and fluid movement in extremely confined spaces akin to biological systems.
Beyond fundamental research, this technology holds promise for emerging fields such as single-molecule sensing (e.g., utilizing nanopores for DNA sequencing), neuromorphic computing (emulating biological neuron behavior through electrical spikes), and nanoreactors (establishing unique reaction conditions via confinement).
