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Researchers at IMDEA Materials Institute have developed a pioneering method to assemble silicon nanowires into ordered, macroscopic networks: a key step toward expanding their industrial applications.

Silicon nanowires offer exceptional energy storage capacity, electrical conductivity, and mechanical strength, making them ideal for next-generation batteries, electronics, and advanced functional materials.

However, individual silicon nanowires are just 10–50 nanometers in diameter, roughly 1,000 times thinner than a strand of human hair. As such, many of their most promising current and potential applications require the ability to process and assemble them into larger bundles.

Scaling this assembly process to an industrial level has typically proven difficult as it requires precise control over the alignment and density of the bundled nanowires, crucial for their performance in applications like batteries and sensors.

"One-dimensional nanomaterials typically exit the reactor as randomly aggregated powders," explains researcher Dr. David Tilve. "In this disordered state, their properties and potential applications are severely limited. A key challenge is to self-assemble these nanowires into ordered, nanostructured materials to unlock their full potential."

"By successfully processing these nanowires into highly aligned bundles, we can significantly increase the contact surface between individual nanowires, a feature not observed in randomly oriented networks."

"This level of structural order is not straightforward to achieve and marks a notable advancement in nanowire assembly techniques," he adds.

The method is outlined in the recent publication "Ordered silicon nanowire bundle networks from aqueous dispersions" by IMDEA Materials researchers Dr. Tilve, Felipe Lozano-Steinmetz, Dr. Isabel Gómez and Dr. Juan José Vilatela. The research is in the journal Nanotechnology.

They found that suspending the nanowires in water—a process known as aqueous suspension—and then slowly filtering the liquid via vacuum filtration, caused the wires to line up into tightly packed bundles, which then link together to form paper-like networks.

"The finding of spontaneous alignment in solution, in particular, will lead to advances in liquid crystal devices, photonic fibers and semiconducting textiles, among other possibilities," says Dr. Tilve.

Specifically, each bundle analyzed by researchers featured around 15 individual self-assembled nanowires with a separation between them of just 0.4 nm, only slightly larger than the width of a single atom.

This tight bonding process resulted in macroscopic sheets with ordered arrays and a controlled density, which were found to be highly ordered and robust. This opens the door to better batteries, faster electronics, and advanced materials with new optical or mechanical properties.

This research is of particular relevance given recent advances in large-scale silicon nanowire production.

This work is part of IMDEA's project to bridge the nano and macro-scales through the fabrication of paper-like network materials made of nanowires and to study the properties of these materials for possible optical applications or as electrodes for energy storage.