Researchers at The University of Osaka have developed a novel “breathing” membrane capable of forming and closing nanoscale pores on demand, mimicking the function of biological ion channels. Published in in Nature Communications, the technology utilizes a chemically controllable process to create subnanometer pores within a solid-state nanopore, offering a new tool for studying ion transport and potentially enabling advancements in areas like single-molecule sensing and neuromorphic computing.
Mimicking Nature’s Tiny Channels
Biological ion channels are fundamental to life, regulating the flow of ions across cell membranes and driving essential processes like nerve impulses. These channels are remarkably precise, featuring constrictions measured in ångströms – the size of individual atoms. Replicating this level of control in synthetic systems has been a significant challenge in nanotechnology. The University of Osaka team’s breakthrough addresses this by creating a solid-state analogue that allows for the reproducible formation of pores approaching these biological dimensions.
The core innovation lies in using a nanoscale pore as a miniature electrochemical reactor. By applying a transmembrane voltage, the researchers induce a reaction within the pore that leads to the precipitation of a material, effectively blocking the pore. Crucially, this process is reversible; altering the voltage dissolves the precipitate, reopening the pore. This dynamic control over pore size and permeability is what gives the membrane its “breathing” characteristic.
How the ‘Breathing’ Membrane Works
The membrane itself is constructed from silicon nitride (SiNx). A nanopore is first created within this material. The key to the process is the in-pore electrochemical reaction. Applying a negative voltage initiates a precipitation reaction, causing a material to build up within the pore. This growth continues until the pore is completely blocked. Reversing the voltage dissolves the precipitate, restoring the pore’s openness. The researchers demonstrated the ability to repeatedly form and close these pores, showcasing the system’s stability and controllability.
Ionic current measurements revealed distinct conductance features consistent with ion dehydration and transport through highly confined channels. This suggests that the pores are indeed shrinking to sub-nanometer dimensions, forcing ions to squeeze through extremely narrow spaces. The ability to control the pore size allows researchers to study how ions behave under extreme confinement, providing insights into fundamental aspects of ion transport and fluid dynamics.
Scalability and Potential Applications
One of the significant advantages of this approach is its scalability. The platform allows for the simultaneous actuation of multiple pores, opening up possibilities for high-throughput experiments and applications. Here’s a departure from many existing nanopore fabrication techniques, which often struggle to create large arrays of consistently sized pores.
The potential applications of this technology are diverse. Beyond advancing our understanding of ion transport, the researchers highlight several promising areas. Single-molecule sensing is one possibility, where the nanopores could be used to detect and analyze individual molecules as they pass through the channel. Neuromorphic computing, which aims to mimic the structure and function of the human brain, could also benefit from this technology, potentially leading to the development of new types of artificial synapses. The membrane system could serve as a nanoreactor, providing a confined space for chemical reactions to occur.
Building on Previous Research
The development builds upon earlier work exploring the creation of responsive pore membranes. Researchers at the University of California, Berkeley, for example, developed a thermo-responsive pore membrane in that utilized temperature changes to control pore opening and closing, drawing inspiration from the micro-respirational pores found in plants. While that research focused on thermal actuation, the University of Osaka team’s approach utilizes electrochemical control, offering a different mechanism for achieving dynamic pore regulation.
Other approaches to nanopore fabrication, as noted in supplementary research, often struggle with achieving the precise control and reproducibility offered by this new method. The ability to create subnanometer pores through voltage-driven precipitation and dissolution represents a significant step forward in the field of nanotechnology, bringing synthetic nanopores closer to the functionality of their biological counterparts.
The researchers emphasize that this chemically driven membrane system provides a powerful tool for probing ion transport and fluid dynamics in extreme confinement. Further research will likely focus on optimizing the membrane’s performance, exploring its potential in various applications, and investigating the fundamental physics governing ion transport at the nanoscale.
