Engineers have discovered an innovative approach to avoid the laborious task of tunneling individual sub-nanometer pores for nanoporous membranes, opting instead to create multiple pores simultaneously. This team has developed a new technique that involves designing materials with specific weak spots and using a remote electric field to efficiently generate numerous nano-scale pores at once.
Nanoporous membranes, featuring atomic-scale openings smaller than one-billionth of a meter, hold great promise for purifying contaminated water, extracting valuable metal ions, and fueling osmotic power generators.
Despite their potential, these applications have faced challenges primarily due to the painstaking process of drilling out individual sub-nanometer pores one at a time.
“For us to scale 2D material membranes for practical use beyond the lab, the current ‘one pore at a time’ approach simply won’t work,” said Eli Hoenig, a PhD graduate from the UChicago Pritzker School of Molecular Engineering (PME). “Even in laboratory settings, a nanoporous membrane produces significantly stronger signals than a single pore, enhancing sensitivity.”
Hoenig, as the first author of a recent Nature Communications paper, identified a creative solution to this long-standing challenge. Collaborating with PME Assistant Professor Chong Liu, the team developed a pore generation technique that involves creating materials with predetermined weak points and applying a remote electric field to generate multiple nanoscale pores simultaneously.
“Our concept is to pre-design the material’s structure and indicate where the weak spots are. When we initiate pore generation, the field will target these weaker areas, creating holes first,” Liu explained.
The power of weakness
By layering polycrystalline molybdenum disulfide, the team can direct the locations where the crystals intersect.
“Imagine two flawless crystals. When they come together, they don’t simply bond seamlessly; there’s a boundary at their connection point, known as the grain boundary,” Liu noted.
This allows them to “pre-pattern” these grain boundaries—and the resultant pores—with impressive precision.
Moreover, it’s not just the location that can be adjusted through this method; the density and even the size of the pores can also be predetermined. The researchers were able to modify pore sizes from 4 nanometers down to less than 1 nanometer.
This capability provides versatility for designing systems for water treatment, fuel cells, and various other applications.
“There’s a demand to create and confine pores accurately, but traditional methods limit you to making one pore at a time,” Liu emphasized. “That’s why we established a method that enables high-density pores while still allowing exact control over each pore’s size and precision.”
Although this technique has various potential applications, Hoenig is particularly enthusiastic about its environmental benefits. These include water treatment and the recovery of valuable materials like lithium, essential for the grid-scale batteries needed for the shift to renewable energy.
“Focused water purification and resource recovery are fundamentally connected, and both are crucial at this foundational scientific level,” Hoenig remarked.
Liu added that this new research is a product of interdisciplinary collaboration with the battery-focused lab of PME Professor Shirley Meng and PME Assistant Professor Shuolong Yang’s quantum group. The three labs previously worked together to overcome a significant challenge in growing quantum qubits on crystals.
“Our teams aim to develop precise synthesis techniques across diverse materials and properties,” Liu said. “Together, we are exploring ways to manipulate a material’s composition, structure, and defects to craft specific pores and defects accurately.”
