(Photo by Joshua Earle on Unsplash+)
PERTH, Australia — In a laboratory at Curtin University in Australia, researchers have stumbled upon what might seem like a magical transformation: ordinary glass that repels water like it’s afraid of getting wet. But there’s no magic involved—just sound.
A team led by Associate Professor Nadim Darwish has developed a new technique that uses ultrasonic waves to permanently modify glass surfaces, making them either water-repellent or electrically charged. This innovation, detailed in a recent paper published in Advanced Functional Materials, could transform how we use glass in applications ranging from vehicle windshields to industrial filtration systems.
Unlike traditional methods for modifying glass, which typically rely on toxic chemicals and produce coatings that degrade over time, this new “sonochemical” approach creates a durable bond at the molecular level. Glass surfaces modified with this technique maintain their properties even after exposure to hot solvents—a significant improvement over conventional coatings that often peel off within days.
The science behind this innovation is surprisingly straightforward. When special compounds called diazonium salts are exposed to ultrasound, sound waves create microscopic bubbles in the solution. These bubbles rapidly form and collapse—generating localized spots of extreme temperatures and pressures for microseconds at a time.
This process triggers a chemical reaction that bonds the compounds to the glass surface. By varying the type of diazonium salt used, researchers can control surface properties, making glass either water-repellent or positively charged as needed.
“Unlike conventional coatings, that wear off over time, our method creates a chemical bond at the molecular level, making it far more durable and environmentally friendly,” explains Darwish, an ARC Future Fellow at Curtin’s School of Molecular and Life Science.
Differences in water behavior on treated versus untreated glass are dramatic. Standard glass typically has a water contact angle of about 14 degrees—meaning water spreads out almost flat across its surface. After treatment with the right compound for 90 minutes, that angle increases to nearly 98 degrees, causing water to bead up rather than spread out.
Study co-author Dr. Tiexin Li, a Research Associate at Curtin’s School of Molecular and Life Sciences, said the ability to modify glass surfaces in a simple and sustainable way has far-reaching implications across multiple industries.
“Glass is used everywhere—from cars and buildings to industrial filters—but its natural tendency to attract water limits its performance,” Dr. Li said. “Unlike traditional coatings, this film won’t peel off, dissolve in water or deteriorate, so it’s ideal for real-world applications where reliability and durability are key. This could mean clearer windshields in heavy rain, self-cleaning skyscraper windows, and solar panels that stay dust-free.”
Beyond Water Resistance: The Microorganism Connection
Potential applications extend far beyond keeping surfaces dry. Perhaps the most surprising discovery came when researchers tested how various microorganisms interact with their modified glass surfaces. Co-author Zane Datson, also from Curtin’s School of Molecular and Life Sciences said this unexpected benefit demonstrates the ability of the modified glass to attract bacteria, fungi, and algae.
“This is very exciting as we can tailor glass properties for specific uses, including in advanced filtration systems and biofuel production,” Datson said. “For example, the coated glass can help bind yeast in brewing, capture bacteria in wastewater filtration systems, or act as a chemical barrier to microorganisms in air filters.”
When cultivated on various glass surfaces for seven days, microalgae coverage increased from just 18% on ordinary glass to more than 92% on positively charged modified glass. Positively charged surfaces attract negatively charged exterior coatings of algae, causing them to firmly adhere to the surface.
Similarly, tests with yeast and bacteria revealed that water-repellent glass surfaces achieved remarkable adhesion—82% coverage for yeast and 89% for bacteria, compared to minimal adhesion on untreated glass.
Industrial Applications and Future Possibilities
The ability to selectively capture microorganisms opens up new applications. For breweries and wineries, surfaces that efficiently capture and immobilize yeast could improve fermentation processes. Water treatment facilities might employ filters coated with bacteria-attracting glass to remove harmful microorganisms more effectively. Even biofuel production could benefit, as efficiently capturing algae is a critical step in that process.
Processing techniques developed by the team are relatively simple and potentially scalable. While researchers primarily used a specialized sound device to achieve optimal results in just one hour, they also demonstrated that conventional ultrasonic baths—the kind found in laboratories for cleaning jewelry—can produce similar modifications with slightly longer processing times.
The accessibility of this technology also makes it appealing for practical applications. Research shows the process works not only on flat glass surfaces but potentially on any silica-based material, including those used in filtration systems.
As water scarcity becomes an increasingly pressing global issue, more efficient filtration systems that can selectively capture microorganisms could play a vital role in water reclamation and purification. Similarly, as the world seeks more sustainable energy sources, improved methods for algae cultivation and harvesting could accelerate biofuel development.
The research team is now seeking industry partners to test and scale up the technology, particularly in the automotive, construction, and environmental sectors. With its combination of simplicity, durability, and versatility, this sound-based method for glass transformation may soon bring clearer windshields in heavy rain, self-cleaning skyscraper windows, and advanced microbial filtration systems from the laboratory to our everyday lives.
Paper Summary
Methodology
Scientists used a straightforward process to modify ordinary glass. First, they cleaned glass pieces to remove any contaminants. Then, they prepared solutions containing special compounds called diazonium salts dissolved in a common laboratory solvent. Clean glass was placed in these solutions and subjected to ultrasonic treatment—essentially high-frequency sound waves beyond human hearing range.
Sound waves created tiny bubbles in the liquid that rapidly collapsed, generating microscopic hotspots of extreme temperature and pressure. These conditions triggered chemical reactions that bonded the compounds to the glass surface, creating a thin organic film. After treatment, they simply washed the modified glass and dried it before testing its properties.
Results
Glass became much more water-repellent after treatment with specific compounds. While normal glass causes water to spread out flat, treated glass made water form beads that easily roll off. Chemical analysis confirmed that the organic film formed strong chemical bonds with the glass surface that weren’t easily broken, even when exposed to hot solvents.
Microorganisms showed dramatic increases in adhesion to modified surfaces. Microalgae coverage increased from just 18% on ordinary glass to over 92% on positively charged modified glass. Similarly, bacteria coverage jumped from 16.8% to 89.0% and yeast from 5.2% to 82.0% on water-repellent modified glass. Modified surfaces maintained their properties over time and resisted degradation when exposed to various solvents.
Limitations
While research presents promising results, several limitations should be acknowledged. Study primarily focused on initial stages of microorganism adhesion and didn’t explore how these organisms function after attachment—important considerations for applications like biofuel production or water filtration. Researchers tested only a few types of microorganisms, not the wide variety relevant to specific applications.
Additionally, durability testing involved exposure to hot solvents but didn’t include long-term performance through extended weathering or repeated cleaning cycles that would occur in real-world scenarios.
Funding and Disclosures
This research was supported by the Australian Research Council through several grants (DP190100735, IC210100056, FT200100301, and DP220100553). The researchers also acknowledged support from Hydrobe for providing the Chlorella vulgaris microalgae used in their experiments. The paper was published as an open access article, made possible through Curtin University as part of the Wiley-Curtin University agreement via the Council of Australian University Librarians. The authors declared no conflicts of interest in connection with this work.
Publication Details
This research was published in Advanced Functional Materials in 2025 under the title “Sonochemical Functionalization of Glass.” The authors include Tiexin Li, Zane Datson, Sufia Hena, Steven Chang, Shane Werry, Leqi Zhao, Nasim Amiralian, Tejas Bhatelia, Francisco J. Lopez-Ruiz, Melanie MacGregor, K. Swaminathan Iyer, Simone Ciampi, Muhammad J. A. Shiddiky, and Nadim Darwish, with Nadim Darwish serving as the corresponding author. The paper is available online under DOI: 10.1002/adfm.202420485 as an open access article under the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited.
