Chemistry student develops clear polish that turns your fingernail into a touch-screen stylus

A college student has created a prototype polish to turn a fingernail into a touch-screen stylus, after noticing that people with long nails and calloused fingertips struggled to work their smartphones.

Manasi Desai, a student at Centenary College of Louisiana with an interest in cosmetic chemistry, launched the project with her research supervisor, Joshua Lawrence, an associate professor of chemistry at Centenary. Their goal was to create a clear, nontoxic polish that would allow a nail to access a touch screen the way a human fingertip does.

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

Desai and Lawrence presented their research Monday (March 23) at the annual meeting of the American Chemical Society.

Who needs touchscreen polish?

While touch screens are nearly ubiquitous today, some people cannot use them as easily as others. For example, guitar players and carpenters with callouses on their fingers may be unable to get the screen to register their touch because their fingertip skin prevents electrical flow ‪—‬ a problem Consumer Reports called "zombie finger" in 2015. But touch screens are also difficult to use when a person's hand is gloved, is very dry or has long nails.

After the researchers asked a phlebotomist with long nails who was struggling to operate a smartphone whether touch-screen-compatible nail polish would be useful — and got a resounding "Yes" answer — they set out to develop a new product.

"Chemists are here to solve problems and to try to make your world better," Lawrence said in the statement.

The touch screens in modern tablets and smartphones work through a property called capacitance. A small electric field is created on the screen, and when a conductive material, like a finger, touches the surface, the electric field is interrupted. The screen registers the disruption — a change in capacitance — as a touch at a particular location. But tapping the screen with a nonconductive material, like a fingernail, does not register as a touch.

Previous researchers' attempts at creating a capacitive nail polish focused on including carbon nanotubes or metallic particles to make the fingernail electrically conductive. However, these particles are dangerous if inhaled and limit the color range of polishes.

For her project, Desai methodically tested combinations of 13 commercially available clear-coat nail polishes and more than 50 additives to find one that met three criteria: It was clear, it was nontoxic and it created a conductive top coat.

In her experiments, Desai found that the polishes that performed best included the amino acid taurine and the organic molecule ethanolamine, an amino alcohol. When combined, the taurine and ethanolamine additives created a formula that registered as a touch on a smartphone.

The new polish formula was designed to work through acid-base chemistry rather than the inclusion of metal additives. With acid-base chemistry, acids donate protons and bases accept protons.

"We think that the materials we are producing are working via protons hopping from acidic to basic groups," Lawrence told Live Science in an email, because the mixture of taurine and ethanolamine — an ammonium acid and an amine base — works well. "We think we have proton exchange between acidic and basic groups at the surface of the polish, fulfilling the same role as ion mobility in skin," Lawrence said.

It will be a while before their polish hits store shelves, though. The nail polish does not work long enough yet. "All our formulations lose efficacy too quickly," Lawrence said. "They stop working after hours or days, and we want them to work for days or weeks, minimum."

Desai and Lawrence are working on tweaking their formula to find the best-performing combination of ingredients and to make the current formulation nontoxic. Currently, the least-toxic formulation they devised results in a gritty, speckled finish ‪—‬ "not high fashion to be sure," Lawrence said.

The researchers have already submitted a provisional patent for their invention. "Right now, we have a good proof of concept material, but need to do a lot more work!" Lawrence said.

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