Why can't your smartphone destroy microbes? - Wired.co.uk

You’re constantly touching your smartphone and, if you don’t use a headset, mouthing it, too. You get it out all over the place and you almost certainly don't wash your hands each time before you do so.

Unfortunately, we’re living in the age of the Covid-19 pandemic, and this particular coronavirus has been found by US National Institute of Allergy and Infectious Diseases researchers to survive for up to three days on plastic and stainless steel, which doesn’t bode well for your phone or the kind of germs you could transfer to it from your hands.

In 2011, the London School of Hygiene and Tropical Medicine found that 16 per cent of smartphones harboured E. coli bacteria. If we can’t stop faecal bacteria from getting on our phones, what are the odds that we’ll manage to avoid transferring microbes that are happy to hang out for days on hard surfaces?

Between fiddling with screen protectors and wondering whether alcohol wipes will take off the oil-repelling and smudge-resistant oleophobic coating on your phone’s display (they might, but you can easily re-apply it), you may wish for a self-cleaning, anti-microbial smartphone screen.

The good news is that the technology exists. So why doesn't you iPhone or Galaxy or Pixel 4 have it?

There are various antimicrobial doping and coating systems for screen cover glass, notably medical industry grade ionic silver – microbes are killed by the release of silver ions at a sufficiently high concentration – and cutting-edge titanium dioxide nanomaterials.

Titanium dioxide is catalysed by ultraviolet light – normal sunlight or even indoor light can be sufficient – to release single atoms with unpaired electrons (free radicals) that break down organic materials – microbes in this instance.

It’s specifically titanium dioxide photocatalytic coatings, in which the outer layer of the coating actually comes off in this way, destroying and breaking down microbes as it goes, that are most commonly referred to as ‘self-cleaning’.

But the most widely used anti-microbial surfaces right now, from chopping boards to computer keyboards intended for hospitals, are still based on silver ions, and that includes screen cover glass technology intended for use on hospital instruments.

Corning makes an ionic silver based antimicrobial version of its toughened Gorilla Glass. Launched in 2014, it’s designed for use as cover glass for displays, as well as on wall panels, windows and doors. The company says that the glass showed a greater than 99.9 per cent reduction of bacteria in a JIS Z 2801 compliant antimicrobial activity test.

Currently, it’s largely used by medical equipment and public payment terminal providers, but as far as consumer smartphones go, it appeared in the ZTE Axon in 2015 and hasn’t been much seen beyond that.

That’s perhaps surprising given the results of an informal Infection Control Today poll, which found that 83 per cent of the medical publication's surveyed readers used their personal mobile phones at their hospitals but only 68 per cent regularly cleaned or decontaminated them.

Samsung Display also holds, with optical chemicals firm Don Co, an active patent involving the use of silver ions in antimicrobial optical coating.

However, although antimicrobial screen cover elements have been shown successful in reducing bacterial loads on phone screens under lab conditions, a 2019 study of the impact of silver-coated antimicrobial screen covers on resident physicians’ phones at Duke University Medical Center found that “no major shifts were observed in the overall microbial community structure of personal phones.”

The results of research into the effectiveness of photocatalytic titanium dioxide coatings to limit microbe growth in intensive care units was disappointing, finding that the coating had had no effect. Although we’ve yet to find it built into a commercial smartphone screen, industry bodies are promoting the idea of a smartphone screen that can “decompose pollutants and inactivate microorganisms, bacteria, fungi and viruses, before dissipating.”

You can already get titanium dioxide-based liquid screen protectors that claim to kill 99.9 per cent of bacteria, along with repelling water and resisting scratches. The Titanium Dioxide Manufacturer’s Association plugs Nanofixit’s TiO2 based Gadget Sanitizer, which has to be re-applied every 30 days as the titanium dioxide sloughs off over time as a result of photocatalysation. Both Nanofixit and rival producer Wowfixit claim their screen protectors are “anti-cellphone radiation” or “reduce harmful radiation”, which is a disconcerting to find associated with an otherwise promising product.

Unfortunately, while some manufacturers correctly describe the antimicrobial photocatalytic effect of ultraviolet light on titanium dioxide, none have published detailed research on the effectiveness of their specific formulations when it comes to controlling the microbial load on smartphone screens.

Wowfixit is an exception in that it at least publishes certification from the independent TÜV testing body stating that "the starting total bacterial count 104 of Staphylococcus aureus was reduced with 97.5 per cent and in the case of the starting total bacterial count 104 of Escherichia coli was reduced with 79.3 per cent on the treated surface."

However, there’s no information there about how this test was carried out or on how many devices. We have contacted Wowfixit for further information.

If those figures don’t impress you, then German firm Bedifol advertises its “active metal-oxide agent” based Upscreen Bacteria Shield stick-on screen protector as eliminating 99.9 per cent of phone-screen bacteria in ISO 22196 compliant tests of antibacterial activity.

Ultimately, although self-cleaning or antimicrobial glass would be nice to have – if you have a classic ZTE Axon, this is a good time to get it out of retirement – the real fix for our bacteria-laden smartphones is actually cleaning them regularly. Apple recommends using a 70 per cent isopropyl alcohol based disinfecting wipes to clean down your phone’s hard surfaces, whilst carefully avoiding getting any liquid into your phone’s internals.

Sticking a couple of isopropyl alcohol swabs (available from chemists) into your wallet and regularly wiping down your phone is a sensible move towards a less microbe-laden smartphone screen that you can take right now.

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