Researchers at The University of Osaka have developed ultra-small pores in silicon nitride membranes that approach the scale of natural ion channels. These structures enable repeatable opening and closing through voltage-controlled chemical reactions. The advance could aid DNA sequencing and neuromorphic computing.
Ion channels in living organisms are narrow protein structures that regulate the flow of charged particles, essential for functions like nerve impulses. Their tightest sections span just a few angstroms, comparable to atomic widths. Replicating such precision has challenged nanotechnology experts.
A team led by Makusu Tsutsui and Tomoji Kawai at The University of Osaka addressed this by fabricating nanopores in silicon nitride membranes. These served as miniature electrochemical reactors. Applying a negative voltage initiated a reaction that formed a solid precipitate, blocking the pore. Reversing the voltage dissolved the precipitate, reopening the pathway.
"We were able to repeat this opening and closing process hundreds of times over several hours," Tsutsui said. "This demonstrates that the reaction scheme is robust and controllable."
Monitoring ion currents revealed sharp spikes akin to those in biological channels, pointing to the creation of multiple subnanometer pores within the initial structure. Adjustments to the reactant solutions' composition and pH allowed control over pore size and ion selectivity.
"We were able to vary the behavior and effective size of the ultrasmall pores by changing the composition and pH of the reactant solutions," Kawai noted. "This enabled selective transport of ions of different effective sizes through the membrane by tuning the ultrasmall pore sizes."
The method supports studies of matter in confined atomic-scale spaces and holds potential for single-molecule sensing, such as nanopore-based DNA sequencing, as well as neuromorphic computing that emulates neuronal electrical patterns. The findings appear in Nature Communications.
