This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers from Skoltech and their colleagues from Harbin Institute of Technology in China and ITMO University in Russia have devised a way to deposit elaborate geometric patterns of carbon nanotubes without wasting material. Such patterns are used in advanced optical devices and mechanical strain sensors for structural integrity monitoring.
The new technique will make nanotube patterning cheaper, faster and more resource-efficient, lowering the barrier to integrating the high-tech material into optical and electronic devices. The study is published in Light: Advanced Manufacturing. "Single-walled carbon nanotube films are a material with outstanding properties useful in optical and electronic devices," explained one of the study's authors, Dmitry Krasnikov, an associate professor at Skoltech Photonics.
"The challenge is that, in fabricating a device, nanotube films have to be structured as conductive nanopatterns. The way this is usually done is by depositing a continuous film and then etching away the 'excess' material where it is not needed." "This, however, is fairly wasteful because as much as 90% of the nanotubes can be lost, and they are pretty expensive. Also, etching deteriorates the quality of the remaining nanotubes.
We came up with a better solution." The team demonstrated a way to deposit nanotube patterns in a single-stage process that does not waste material or introduce additional reactants. The new technique involves the use of a conventional pressing tool and a nitrocellulose membrane—a type of filter commonly used in molecular biology experiments. Before nanotube deposition, the membrane is pressed with a laser-cut hot metal stencil that carries the inverse of the desired pattern.
At about 200 megapascals, the stencil press clogs the pores in the filter, effectively preventing nanotube deposition in the clogged regions. Prepared in this way, the membrane becomes a sturdy, reusable template that serves as a substrate for aerosol chemical vapor deposition—a standard technique for producing single-walled carbon nanotube films. The nanotube aerosol is filtered through the membrane, but because only the unclogged areas are permeable, the flow passes through them and the nanotubes are collected, ready for transfer to another substrate.
Importantly, the method does not introduce foreign materials into the membrane (for example, organic solvents), which eliminates postprocessing, avoids contamination, preserves nanotube quality and facilitates subsequent transfer of the patterned film. "The key insight comes from aerosol science: Single-walled carbon nanotubes are so light that their inertia is negligible, so they follow the carrier gas wherever it flows. By pairing that principle with a structured membrane—where we simply close off the pores we do not need—we let the gas flow itself draw the pattern, depositing nanotubes only where they belong and nowhere else.
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