Novel coating developed prevents fogging on plastic surfaces and 'self-cleans' – Professor Chen Zhong
We are delighted to share the research achievement of Professor Chen Zhong and team, which has been featured in various media.
Prof Chen Zhong and team have developed a new type of coating that, when applied on a plastic surface, prevents fogging and ‘self-cleans’, overcoming the need for frequent reapplications. The durable coating of a thin double layered silicon dioxide - titanium dioxide film is applied through a two-step technique.
Firstly, the plastic surface is treated with oxygen plasma, which is a common industrial method to clean surfaces to improve adhesion. Then the thin double layered film is deposited on the plastic surface using pulse laser deposition – in which a laser beam is focused to vaporise material from the intended coating targets to achieve the desired level of thickness of the film.
The approach offers better control of the film’s thickness and structure during fabrication, compared to similar industrial methods, and results in a higher quality film. The coating showed excellent adherence to the plastic surface. When subjected to abrasion using a cheese cloth pad – a standard test for optical coating, and an adhesion test using cellophane tapes, the coating maintained good durability.
Fogging is observed when water vapour condenses as water droplets on a surface, and so the anti-fogging performance of coating is measured by the speed at which the condensed water droplets spread into a uniform film that does not block vision. In experiments on the new coating, digital fast frame imaging showed a water droplet spreading within 93 milliseconds, less than the duration of the average human eye blink of 100 milliseconds.
Anti-fogging sprays and wipes are popular products among spectacle or eyeglass wearers, more so since the COVID-19 pandemic as mask wearing becomes the norm and wearers seek to prevent condensation obscuring their view. However, current solutions in the market, such as anti-fogging sprays and wipes are temporary as they cannot withstand washing and must be reapplied regularly. In addition, they are prone to surface contamination by dirt or bacteria, which means replacement or maintenance is necessary.
While researchers elsewhere have developed anti-fogging coatings for plastics, two of the biggest barriers to their widespread adoption are the long processing time for fabrication and poor durability – that is, weak adhesion between the plastic surface and the coating.
Co-principal investigator of the study, Professor Chen Zhong said, “Most anti-fogging solutions today are temporary and have limited efficacy. Our team has demonstrated an approach that is fast to fabricate, taking around an hour, and produces long-lasting results, proving its potential for wide-ranging practical applications.”
As a result of the long-lasting anti-fogging and ‘self-cleaning’ ability of the newly devised coating, the NTU research team believes their innovation offers an attractive, long-term solution to overcome issues of plastic fogging that may also reduce costs and waste.
From left to right: Prof Chen Zhong, Mr Sun Ye and Prof Rajdeep Singh Rawat. Source: NTUsg Youtube
The breakthrough research was published in the peer-reviewed scientific journal Applied Surface Science, with the title "Mechanically robust multifunctional antifogging coating on transparent plastic substrates". The research article can be found via this link: https://www.sciencedirect.com/science/article/abs/pii/S0169433221033304?via%3Dihub
Our heartiest congratulations to Prof Chen and team on the excellent achievement!
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