Nanotextured walls sacrifice themselves for clean surfaces

Engineers at Rice University have created containers that can keep volatile organic compounds (VOCs) from accumulating on the surfaces of stored nanomaterials. This portable and inexpensive storage technology, reported in a paper in Nano Letters, addresses a ubiquitous problem in nanomanufacturing and materials science laboratories.

“VOCs are in the air that surrounds us every day,” said Daniel Preston, an assistant professor in Rice’s Department of Mechanical Engineering and corresponding author of the paper. “They cling to surfaces and form a coating, primarily of carbon. You can’t see these layers with the naked eye, but they form, often within minutes, on virtually any surface exposed to air.”

VOCs are carbon-based molecules that are emitted from many common products, including cleaning fluids, paints, and office and crafting supplies. They accumulate indoors in particularly high concentrations, and the thin layers of carbon gunk they deposit on surfaces can hinder industrial nanofabrication processes, limit the accuracy of microfluidic testing kits and produce confusion for scientists who conduct fundamental research on surfaces.

To address this problem, PhD student and lead author Zhen Liu, together with Preston and others from his lab, developed a new type of storage container that keeps nanomaterials clean. Experiments showed that her approach effectively prevented surface contamination for at least six weeks and could even clean VOC-deposited layers from previously contaminated surfaces.

The technology relies on an ultraclean wall inside the container. The surface of this interior wall is enhanced with tiny bumps and divots ranging in size from a few millionths to a few billionths of a meter. These microscopic and nanoscopic imperfections increase the wall’s surface area, making more of its metal atoms available to VOCs that are in the air inside the containers when they are sealed.

“The texturing allows the internal container wall to act as a ‘sacrificial’ material,” Liu said. “VOCs are pulled onto the surface of the container wall, which allows other objects stored inside to remain clean.”

She said that the idea of using a large precleaned surface to accumulate pollutants was proposed 50 years ago but went largely unnoticed. She and her colleagues improved on the idea with modern methods of cleaning and nanotexturing surfaces. They showed, through a series of experiments, that their approach did a better job of preventing VOCs from coating the surfaces of stored materials than other approaches, including sealed petri dishes and state-of-the-art vacuum desiccators.

Preston’s group also built on these experiments, by developing a theoretical model that accurately characterized what was happening inside the containers. Preston said this model will allow them to refine their designs and optimize system performance in the future.

This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.