Plant-Based Spray Graphic
Photo (left) of a nanowire forest being sprayed on a miniature tree, with color (purple) arising from embedded gold nanoparticles. Electron microscope image (right) of the nanowire/nanoparticle blend. (Credit: Jonathan P. Singer/Lin Lei)

Engineers have invented a way to spray extremely thin wires made of a plant-based material that could be used to improve N95 mask filters. The spray could also potentially be used in the creation of human organs. The method involves spraying methylcellulose, a renewable plastic material derived from plant cellulose, onto 3D printed objects.

Thin wires (nanowires) made of soft matter have many applications, including the cilia that keep our lungs clean and the setae (bristly structures) that allow geckos to grip walls. With methylcellulose, they have created “forests” and foams of nanowires that can be coated onto 3D objects. They also demonstrated that gold nanoparticles could be embedded in wires for optical sensing and coloration.

In the near term, N95 masks are in demand as personal protective equipment during the COVID-19 pandemic, and the spray method could add another level of capture to make filters more effective. This could be the first step towards 3D manufacturing of organs with the same kinds of properties as those seen in nature, the researchers say.