Scientists 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.

Story Source: Materials provided by Nanyang Technological University. Note: Content may be edited for style and length.