New polish helps people with long nails use touchscreens

By Stephen Beech

People with long fingernails may not have to struggle much longer to use touchscreens thanks to a new innovation.

A prototype nail polish could turn long nails into styluses for smartphones or tablets, say scientists.

They explained that most smartphones use capacitive touchscreen technology, the operation of which relies on skin conductivity.

But that is challenging for users with long manicures or "zombie fingers".

Researchers at Centenary College of Louisiana are formulating a clear nail polish that could turn long fingernails into touchscreen-compatible styluses.

Manasi Desai, an undergraduate at Centenary, had an interest in cosmetic chemistry and went to her research supervisor, Professor Joshua Lawrence, looking for a suitable project.

Lawrence, an organometallic chemist, said: "Chemists are here to solve problems and to try to make your world better.”

When the researchers noticed the difficulty many people had when operating smartphones with long nails, they asked if a touchscreen-compatible nail would be useful.

When the answer was positive, the project came to be.

Most modern touchscreens work by creating a small electric field across the screen.

When a conductive material - something that allows electricity to flow through itself - disrupts that field, such as a fingertip or a droplet of water, the surface changes its capacitance.

Then, the device interprets that capacitance change as a touch.

But tapping a screen with a non-conductive material, such as a long fingernail or pencil eraser, does not change the capacitance and, as a result, the device doesn’t register the touch.

To make long fingernails touchscreen compatible, the researchers explained that they need to carry a small electric charge.

Other scientists have previously attempted the process by incorporating electrically conductive carbon nanotubes or metallic particles into nail polish.

But those substances can introduce hazards to the manufacturers, as they’re dangerous if inhaled.

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The additives also result in a deep black or metallic shimmer, limiting the shade range of the polishes.

The Centenary team wanted to instead create a polish that was, ideally, both clear and non-toxic to both the wearer and the manufacturer.

To find the perfect combination of clarity and conductivity, Desai turned to trial and error.

Using 13 commercially available clear-coat polishes and more than 50 different additives, she worked her way through the combinations to find which ones resulted in a conductive topcoat for nails.

Desai said: "The molecules that performed the best were forms of taurine, an organic compound commonly sold as a dietary supplement, and ethanolamine, another simple, organic molecule.

"Ethanolamine provided the conductivity and polish compatibility they were looking for but has some toxicity.

"And while modified taurine formula is nontoxic, it took on a slightly opaque hue.

"But when combined, these additives created a formula that was able to register as a touch on a smartphone, so it’s a promising first step.

“Our final, clear polish could be put over any manicure or even bare nails, which could help people with calluses on their fingertips, too. So, it has both a cosmetic and lifestyle benefit."

Unlike the previous attempts, Lawrence and Desai believe that their polish works through a slightly different pathway: acid-base chemistry instead of inherently conductive metal or carbon nanotubes.

They arrived at that hypothesis because the best initial results came from ethanolamine-based formulas, which can release protons to move charge around.

They believe that when the nail polish contacts a touchscreen’s electric field, it causes the protons to jump between the molecules, slightly changing the polish’s capacitance - but just enough for the smartphone to recognise it as a touch.

Desai said the initial results were "promising" - but there is still a long way to go before the polish will be available in shops.

She added: "Even the best-performing ethanolamine-taurine formula is finicky and doesn’t yet work consistently when painted on a nail.

"Plus, ethanolamine evaporates quickly, so the polish only works on a touchscreen for a few hours once outside of the bottle."

But the researchers say they now have an idea of how the successful formula works, and they are continuing to screen compounds and test new formulas to find the best-performing combination.

Lawrence added: “We’re doing the hard work of finding things that don’t work, and eventually, if you do that long enough, you find something that does."

The researchers are due to present their findings at the spring meeting of the American Chemical Society (ACS) in Atlanta, Georgia.