Highly selective yet durable membranes for salinity gradient power generating systems have yet to be perfected, but researchers from McGill University, Canada, report a major improvement to this key blue, or osmotic, energy building block.

Mechanical strength meets exceptional selectivity in a thin 2D nanomaterial fabricated with hexagonal boron nitride monolayers supported by silicon nitride membranes. The hybrid membrane was synthesized with a new technology, tip-controlled local breakdown, developed at the university. The method uses an atomic force microscopic tip to form a nanopore in a synthetic membrane and allows multiple pore-sensors to be combined, or combined with additional detectors, electronic circuitry or tiny micro/nanochannels. The process yields very small pores at precise positions, allowing for fabrication of multiple pores exactly where needed.

The hybrid membrane is synthesized with hexagonal boron nitride monolayers supported by silicon nitride membranes. Source: Khadija Yazda/McGill UniversityThe hybrid membrane is synthesized with hexagonal boron nitride monolayers supported by silicon nitride membranes. Source: Khadija Yazda/McGill University

A pore-to-pore spacing of 500 nm was observed to deliver optimum membrane selectivity and overall power density. The tip-controlled local breakdown technique successfully produced an array of 20 by 20 pores on a membrane surface 40 µm² in size. The researchers say that the technology described in Nano Letters could be used to produce much larger arrays.

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