A new type of coating for plastic surfaces prevents fogging and ‘self-cleaning’, claim the developers of Nanyang Technological University, Singapore (NTU Singapore).
The coating of a thin bilayer silicon dioxide-titanium dioxide film is applied by a two-step technique: the plastic surface is first treated with oxygen plasma, then the thin bilayer film is deposited on the plastic surface using pulse laser deposition.
The NTU researchers said their approach, compared to similar industrial methods, provides better control over the thickness and structure of the film during fabrication and results in a higher quality film.
When subjected to abrasion with cheesecloth, standard optical coating test, and adhesion test with cellophane tapes, the coating maintained good durability.
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Fogging occurs when water vapor condenses as water droplets on a surface, so the anti-fog performance of coating is measured by the rate at which the condensed water droplets spread into a uniform film that does not obscure visibility. In experiments with the new coating, digital rapid imaging showed a water droplet spreading within 93 milliseconds.
The findings of the NTU team have been published in: Applied Surface Science†
Anti-fog sprays and wipes are popular products among glasses wearers, especially during the COVID-19 pandemic, when mask wearers tried to prevent condensation from clouding their vision.
Anti-fog coatings are also used in solar panels, windshields and displays or lenses used in humid environments.
Researchers elsewhere have developed anti-fog coatings for plastics, but the NTU Singapore team said two of the biggest barriers to their widespread adoption are long manufacturing processing times and poor durability.
In a statement, co-principal investigator, Professor Chen Zhong of the NTU School of Materials Science and Engineering (MSE), said: “Our team has demonstrated an approach that is quick to fabricate, takes about an hour and produces long-lasting results, showing its potential. for broad practical applications.”
Exposure to sunlight
Titanium dioxide has a photocatalytic ability that allows it to clean itself by reacting with and removing organic residues under exposure to ultraviolet light.
In lab tests of its self-cleaning ability, the newly developed coating was able to break down contaminants on the plastic surface after a full day of exposure to ultraviolet light.
Co-Principal Investigator† Professor Rajdeep Singh Rawat, Head of the Natural Sciences and Science Education Academic Group of the National Institute of Education, NTU, said: “Our innovation holds great promise for use in industrial applications of various optical components, for example on protective covers for surveillance cameras.
“The coating’s ability to be self-cleaning makes it a low-maintenance and hassle-free solution, as the cover is less covered by surface grime and grime, providing a clearer view for surveillance.”
The research team has applied for a patent in Singapore for the innovation and the team is looking for industry collaborations to bring the innovation to market.