A newly formulated nail polish could one day let people activate touchscreens with their fingernails.
When pressed to a screen, the polish disrupts the screen’s electric field, which the device registers as touch. While the formula isn’t commercially viable yet, it could allow people with long nails to use them like styluses.
“This is huge, because it shows that functional behavior can be embedded invisibly into everyday cosmetic materials,” says Shuyi Sun, a computer scientist who has studied cosmetic biosensors and now works at the Association of California Nurse Leaders in Sacramento.
Touchscreens, such as on smartphones and tablets, are typically made of glass coated with a thin, transparent layer of electrically conductive material. That layer creates a small electric field across the screen. When another conductive object, such as a fingertip, contacts the screen, it disturbs the electric field. The device registers that disturbance as a touch and can detect the point on the screen where it occurred.
But nonconductive materials — like a fingernail or the fabric of a glove — don’t distort the field, so they don’t register on the screen. People with long nails must use the pads of their fingers to type because they can’t use their nails.
“It’s really hard to use your phone,” says Manasi Desai, an undergraduate student studying chemistry and biology at Centenary College of Louisiana in Shreveport. Changing which part of the finger people type with can cause typing errors, at least until users adjust to the new angle.
To remedy this common inconvenience, Desai and her research adviser, organometallic chemist Joshua Lawrence, mixed several different additives into commercially available clear nail polish. Two of those additives, ethanolamine and taurine, each resulted in a clear polish formulation that, in a blob held with tweezers, could activate the touchscreen. While ethanolamine has some toxicity, taurine is a common dietary supplement that occurs naturally in the human body.
“One of our major goals was to make it clear and colorless, so that you could apply it over any manicure or even on your bare nails,” Desai says. Desai shared the findings on March 23 at the American Chemical Society’s spring meeting in Atlanta.
The modified nail polish uses acid-base chemistry to activate the touchscreen, the team suspects, though more research is needed to confirm. When in contact with the screen’s electric field, the added molecules probably shuffle protons between themselves, moving just enough charge to affect the field and register as touch.
The lacquer isn’t ready to hit the shelves just yet, Lawrence says. Right now, painting the polish on a fingernail doesn’t leave enough additive behind to activate the screen. In future work, the duo plans to focus on improving the formula’s performance in thin coats on fingernails, possibly by getting more taurine into the polish.
