Bacteria-repellent cling film

Hate cleaning? Wish things just wouldn’t get dirty? Technology to the rescue...

A treatment for cling film that prevents most things from attaching to it - including bacteria - has been unveiled in Canada.

The team, from McMaster University, plan to use their self-cleaning film in high-risk areas, such as hospitals, and for food packaging, although the new films can potentially be used to wrap almost anything.

A current challenge in medicine is that the bacteria evolve and become resistant to new drugs. "We, as engineers, can approach it in a different way; and that’s to design surfaces to prevent cross-contamination and the spread of these superbugs," explains study author Tohid Didar.

The new polystyrene wraps reduced contamination by touch of two multidrug resistant and World Health Organisation-designated priority pathogens, Staph aureus and Pseudomonas aeruginosa, both of which can cause serious skin and soft tissue infections, by 87 and 84%, respectively; the new materials suppressed E.coli completely.

To make the new coatings, Didar and his team first produced a film using standard polystyrene. This was rendered bacteria-repellent by adding texture on it in three stages: heat-shrinking; adding nanoparticles; and coating with teflon-like chemicals.

The first step, heat shrinking, involves using high temperatures to make the film shrink and wrinkle. "Heat-shrinking is very simple, you can even do it with a hair dryer!" says Didar.

The second step involves dipping the films in a solution of silicon nanoparticles 50 to 100 nanometres wide.

The third step is to coat the surfaces in fluorine-based chemicals similar to the coatings used in teflon cookware.

Didar compared the hierarchy of micro-structures obtained through these three processes, to a landscape with several layers of textures.

Imagine a landscape with hills, which contains trees, which in turn have flowers on them. "Those hills that go up and down, they are like the wrinkled surfaces, the trees that stick out in the land are the nanoparticles. The fluorine could be the flowers that come out of the trees."

These complex microstructures trap air between the nanoparticles, making it very difficult for water droplets, or bacteria, to attach to the surface. Put simply, for agents such as bacteria, dust particles, or even tiny water droplets, the surfaces of the new self-cleaning film, “have minimum anchor points to attach to the surface,” so dirt and bugs just slide off.