Sound waves both form and deposit the coating in a single step
At RMIT University, researchers have found in sound itself an answer to one of manufacturing's quieter dilemmas: how to protect fragile things without harming them in the act of protection. By harnessing high-frequency acoustic waves to assemble a UV-blocking coating at room temperature, the team demonstrated that even living plant leaves could be shielded for months without interrupting their growth or photosynthesis. It is a reminder that the gentlest solutions are sometimes the most powerful — and that the boundary between the biological and the industrial may be more permeable than we assumed.
- Manufacturers have long faced an impossible choice: the heat and chemicals needed to apply advanced coatings routinely destroy the very surfaces they are meant to protect.
- RMIT researchers broke that deadlock by turning to sound — high-frequency vibrations that atomise a liquid formulation into microscopic droplets, which self-assemble into a solid protective layer mid-air before ever touching the target.
- The coating was tested on living plant leaves, where it blocked harmful UV radiation while allowing photosynthesis to continue uninterrupted — and the leaves kept growing normally for months after the coating was removed.
- The material at the heart of the process, a covalent organic framework, is prized across industries for its light-absorbing and molecular-separating properties but was previously too fragile to deploy without damaging what lay beneath.
- With a provisional patent filed and collaborators across Australia and Europe, the technology is now being positioned for broader use in electronics, sensors, and membranes where heat-sensitive surfaces demand a gentler hand.
At RMIT University, researchers have answered a question that has long troubled manufacturers: how do you coat something delicate without destroying it in the process? Their solution came not from chemistry or engineering convention, but from sound itself.
The technique uses high-frequency vibrations to break a liquid formulation into an ultra-fine mist. As those microscopic droplets travel through the air, the coating material — a covalent organic framework, or COF — self-assembles into an organised solid layer before landing on the target surface. The entire process unfolds at room temperature, in minutes, with no heat and no solvents.
To demonstrate just how gentle the method is, the team applied it to living plant leaves. The coating acted as a biological sunscreen, blocking ultraviolet radiation while allowing visible light through so photosynthesis could continue uninterrupted. Months after the coating was removed, the leaves were still growing normally — a quiet but striking proof of concept.
COFs are prized across industries for their ability to absorb light, separate molecules, and shield surfaces, but applying them has always meant choosing between two damaging options: preserve the substrate and risk a poorly formed coating, or use the conditions needed to properly build the material and accept that the surface beneath will suffer. The acoustic approach dissolves that dilemma by forming and depositing the coating in a single step, under conditions mild enough for living tissue.
The research team, which included collaborators from across Australia and Europe, has filed a provisional patent on the work. Published in Science Advances, the findings point toward future applications in electronics, sensors, and membranes — anywhere a protective coating is needed but heat or chemical exposure is not an option.
At RMIT University, researchers have cracked a problem that has long plagued manufacturers: how to coat delicate materials without destroying them in the process. Their solution arrived not from chemistry or engineering tradition, but from sound itself.
The team developed a technique that uses high-frequency sound waves to create an ultra-fine mist, which then assembles into a protective layer at room temperature. They tested it on living plant leaves, where the coating functioned as a biological sunscreen—blocking harmful ultraviolet radiation while letting visible light pass through so photosynthesis could continue uninterrupted. The leaves treated this way kept growing normally for months after the coating was removed, a testament to how gently the process works.
The coating material comes from something called a covalent organic framework, or COF, a porous material prized across industries for its ability to absorb light, separate molecules, and shield surfaces. Normally, applying such materials means choosing between two bad options: preserve the delicate substrate and risk damaging the coating, or use the heat and chemicals needed to properly form the material and accept that the surface underneath will suffer. Javad Khosravi Farsani, the study's lead author, explained the breakthrough simply: the coating absorbs the ultraviolet wavelengths that damage living tissue while allowing the visible spectrum through. The plant continues its work unharmed.
Conventional coating methods rely on ovens, aggressive solvents, or specialized equipment—all of which can wreck fragile materials. The RMIT approach sidesteps this entirely. High-frequency vibrations break a liquid formulation into microscopic droplets. As these droplets travel through air, the COF material self-assembles into an organized solid layer before landing on the target surface. The whole process takes minutes and requires no heat. Amgad Rezk, part of the research team, described it as a fundamental departure from how coating has traditionally worked: sound waves both form and deposit the material in a single step, making it possible to work with living tissue without damage.
Leslie Yeo, a senior author from RMIT's School of Engineering, framed the significance in terms of industrial choice. These materials possess extraordinary properties, he noted, but manufacturers have always faced a bind—preserve the material's structure or protect the surface being coated. This work demonstrates a path around that dilemma by forming and applying the coating under conditions so mild they pose no threat to what lies beneath.
The simplicity of the method is itself valuable. Joseph Richardson, a co-corresponding author, pointed out that combining manufacturing and coating into a single step opens the door to adaptation across different surfaces and industries. The technology could find use in electronics, sensors, and membranes that require protective coatings but cannot tolerate heat or chemical exposure. RMIT filed a provisional patent on the work earlier this year. The research involved collaborators across Australia and Europe, including the Catalan Institute of Nanoscience and Nanotechnology. The findings appear in Science Advances, positioning this acoustic coating technique as a potential inflection point for how sensitive materials get protected in manufacturing.
Notable Quotes
The coating absorbs harmful UV light while allowing visible light through, so the plant can continue photosynthesis while being protected from damage.— Javad Khosravi Farsani, lead author
By using sound waves, we're able to form and deposit the coating within minutes without heating or damaging the surface. That's a major shift from conventional coating methods.— Amgad Rezk, researcher
The Hearth Conversation Another angle on the story
Why does it matter that you can coat something without heat? Doesn't most manufacturing already handle that?
Most does, but not the things that are alive or extremely fragile. Electronics, certain polymers, biological tissues—they break down under conventional heat or solvents. You're forced to choose between protecting the material and protecting what you're coating.
And the sound waves solve that how, exactly?
They create a mist so fine that the coating material assembles as it floats through air, before it ever touches the surface. No oven, no chemicals, no shock to the system. It's almost passive.
The plant leaf test—was that just a proof of concept, or does this actually have agricultural use?
It was proof of concept, but the fact that leaves kept growing normally for months after suggests the process is genuinely benign. Whether farmers will use it is a different question. The real applications are probably in electronics and sensors where heat sensitivity is a hard constraint.
What's a covalent organic framework, and why should anyone care?
It's a porous crystalline material that's excellent at absorbing specific wavelengths of light or filtering molecules. The problem has always been getting it onto something delicate without ruining the thing underneath. This technique solves that.
So what happens next?
They've filed a patent. Now it's about whether industries with heat-sensitive materials—semiconductors, medical devices, advanced membranes—see value in adopting it. That's where the real test begins.