One area of intensive research at the nanoscale is the creation of electrically conductive meshes made of metal nanowires. Promising exceptional electrical throughput, low cost and easy processing, engineers foresee a day when such meshes are common in new generations of touch-screens, video displays, light-emitting diodes and thin-film solar cells.
Standing in the way, however, is a major engineering hurdle: In processing, these delicate meshes must be heated or pressed to unite the crisscross pattern of nanowires that form the mesh, damaging them in the process.
In a paper just published in the journal Nature Materials, a team of engineers at Stanford has demonstrated a promising new nanowire welding technique that harnesses plasmonics to fuse the wires with a simple blast of light.
At the heart of the technique is the physics of plasmonics, the interaction of light and metal in which the light flows across the surface of the metal in waves, like water on the beach.
"When two nanowires lay crisscrossed, we know that light will generate plasmon waves at the place where the two nanowires meet, creating a hot spot. The beauty is that the hot spots exist only when the nanowires touch, not after they have fused. The welding stops itself. It's self-limiting," explained Mark Brongersma, an associate professor of materials science engineering at Stanford and an expert in plasmonics. Brongersma is one of the study's senior authors.
"The rest of the wires and, just as importantly, the underlying material are unaffected," noted Michael McGehee, a materials engineer and senior author of the paper. "This ability to heat with precision greatly increases the control, speed and energy efficiency of nanoscale welding."
In before-and-after electron-microscope images, individual nanowires are visually distinct prior to illumination. They lay atop one another, like two fallen trees in
|Contact: Andrew Myers|
Stanford School of Engineering