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SunFly’s invisible ink stamp notifies you when it’s time to put on more sunscreen. (SunFly Photo)

Researchers say we don’t put on enough sunscreen. A Seattle startup has come up with a potential fix: an invisible ink stamp that notifies you when it’s time to re-apply.

Michael Croix, a longtime inventor and Marine Corps veteran, helped come up with the idea for the stamp. He’s the CEO and founder of SunFly, which is in discussions with leading sunscreen manufacturers to affix the UV indicator stamp onto sunscreen bottle caps.

Michael Croix.

The ink is made of chromophores, or color-changing molecules. SunFly developed specific chromophores that change color when hit with enough UV radiation — this is what causes the ink stamp to become visible on the skin.

The idea is that a person would stamp themselves with the invisible ink mark and then apply sunscreen. After enough sun exposure, the stamp becomes visible. That’s when you know too many UVB rays — the kind that causes sunburn and plays a key role in development of skin cancer — are penetrating the skin.

Croix said studies show that people under-apply sunscreen, which results in more sunburn. Getting sunburn just once every two years can triple your risk of melanoma skin cancer, according to CancerResearchUK. Skin cancer is the most commonly diagnosed cancer in the U.S., according to the American Cancer Society.

“The rates of skin cancer in our nation are increasing, creating a serious public health concern we cannot ignore,” wrote Boris D. Lushniak, acting general surgeon for the U.S. Department of Health and Human Services, in The Surgeon General’s Call to Action to Prevent Skin Cancer.

Paul Nghiem, head of the dermatology department at the University of Washington, told GeekWire that under-application is a decades-old problem that doesn’t get talked about enough.

“On average, people apply much less sunscreen than they think, and they don’t apply evenly,” he said.

The American Academy of Dermatology noted that most people only apply 25-to-50 percent of the recommended amount of sunscreen.

Nghiem said SunFly’s stamp would be an “important development” — if it works.

“I have my serious doubts that it would work nearly as well as what is shown,” Nghiem said. “But if it does, you’ve developed something that is unique, easy, and can be a good reminder.”

Croix said SunFly has conducted thorough technical due diligence for its stamp, which has a unique design that prevents the chromophores from leaking onto skin. It also isn’t affected by sweat, water, pool chemicals, and other potential disruptions.

“It was a huge breakthrough to create an accurate and safe stamp that can be applied directly to the skin,” Croix said.

Croix added that similar notification products have been developed, but in a different form factor such as wristbands or stickers.

“This stamp is the preferred format,” he said.

SunFly recently raised more than $1 million to fuel development of the stamp. The company participated in the WeWork Veterans in Residence program, powered by Bunker Labs, designed to help U.S. military vets build their startups.

Other SunFly leaders include Bob Wallach, a consumer product goods veteran and the company’s COO. Its advisory board consists of former executives at Johnson & Johnson and L’Oreal.

The global sun care market is expected to grow to $25 billion by 2025, according to Statista.

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