RMIT University researchers have developed a sound wave-based manufacturing technique capable of creating and applying protective coatings on delicate surfaces, including living plant leaves, according to a new study published in Science Advances.
The university said the approach uses high-frequency sound waves to generate a fine mist that rapidly forms into a UV-blocking coating at room temperature, potentially opening new manufacturing applications for sensitive materials that cannot withstand heat or harsh processing methods.
The study demonstrated the process on living plant leaves, where the coating acted as a “plant sunscreen” by absorbing harmful ultraviolet light while still allowing visible light needed for photosynthesis to pass through.
Lead author Javad Khosravi Farsani said the coating protected the leaves without affecting plant growth.
“The coating absorbs harmful UV light while allowing visible light through,” Farsani said.
“That means the plant can continue photosynthesis while being protected from damage.”
According to the researchers, treated leaves continued growing normally for months after the coating was removed, which the team said demonstrated the gentleness of the process.
The coating material was produced from a covalent organic framework (COF) liquid, which assembled into a solid layer as it was sprayed. COFs are part of a broader class of porous materials valued for applications including light absorption, molecule separation and surface protection.
Leslie Yeo, a senior author on the study from RMIT’s School of Engineering, said existing manufacturing and coating methods for such materials often involve trade-offs between preserving material quality and protecting sensitive surfaces.
“These materials have extraordinary properties, but you’ve typically had to choose between preserving their structure and protecting the surface you’re applying them to,” Yeo said.
“What this work shows is a way to avoid that trade-off by forming and coating the material under very gentle conditions.”
The researchers said conventional coating techniques commonly rely on ovens, aggressive solvents or specialised equipment that can damage fragile materials.
Amgad Rezk said the new manufacturing process instead used sound waves to both form and deposit the coating in a single step.
“By using sound waves, we’re able to form and deposit the coating within minutes without heating or damaging the surface,” Rezk said.
“That’s a major shift from conventional coating methods and it allows us to work with fragile materials, including living plant tissue.”
The process works by using high-frequency vibrations to break a liquid formulation into microscopic droplets. As the droplets move through the air, the COF material assembles into an organised solid layer before settling onto the target surface.
Co-corresponding author Joseph Richardson said the process could simplify coating production for a range of industries handling sensitive materials.
“Our method effectively combines manufacturing and coating into a single step,” Richardson said.
“That simplicity is what makes it adaptable across different surfaces and applications.”
The researchers said the technology could have potential applications in electronics, sensors and membranes that require protective coatings but are sensitive to heat or chemicals.
RMIT said it filed a provisional patent related to the work earlier this year. The research was conducted with collaborators in Australia and Europe, including the Catalan Institute of Nanoscience and Nanotechnology.
