UCLA-led researchers reshaped zinc oxide into microscopic tetrapods to create a mineral sunscreen that offers strong UV protection with far less white cast. The advance could help more people, especially those with darker skin tones, use sunscreen every day.
For many people, especially those with darker skin tones, mineral sunscreen comes with a trade-off: protection from the sun at the cost of a chalky white film that can be hard to ignore.
Now researchers say a simple tweak to the shape of zinc oxide particles could change that — and potentially help more people protect themselves from skin cancer.
In a new study, a team led by researchers at the UCLA Health’s Jonsson Comprehensive Cancer Center engineered zinc oxide into microscopic four-armed structures called tetrapods. When used in test mineral sunscreen lotions, these tetrapod-shaped particles provided strong ultraviolet protection while greatly reducing the stark white or gray cast that conventional zinc oxide often leaves on skin.
The work, published in ACS Materials Letters, points to a new way to make mineral sunscreens more wearable without inventing new chemical ingredients.
The stakes are high. Excessive exposure to ultraviolet radiation is the leading preventable cause of skin cancer, the most common cancer in the United States. Dermatologists have long urged people to apply sunscreen every day, but many still skip it, in part because they dislike how mineral formulas look and feel.
Senior author Paul S. Weiss, a distinguished professor of chemistry & biochemistry, bioengineering, and materials science & engineering at UCLA and an investigator in the UCLA Health Jonsson Comprehensive Cancer Center, framed the research as about more than appearances.
“This isn’t just about cosmetics,” Weiss, who is also a UC Presidential Chair, said in a news release. “If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention.”
For first author AJ Addae, a UCLA chemical biology doctoral candidate and cosmetic science entrepreneur, the problem was personal long before it became a research project.
“I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin,” Addae said in the news release. “A lot of my motivation came from my own experience trying to use mineral sunscreen and dealing with the white cast and other unsightly aesthetic issues. This led me to simply avoid sunscreen altogether. That frustration really became the starting point for this work.”
Mineral sunscreens rely on physical filters like zinc oxide to block ultraviolet A (UVA) rays, which contribute to skin aging, and ultraviolet B (UVB) rays, which cause sunburn and increase skin cancer risk. Zinc oxide is widely used, classified by the U.S. Food and Drug Administration as safe and effective, and often recommended for people with sensitive or acne-prone skin, rosacea, or those who prefer non-chemical options.
But conventional zinc oxide particles are typically tiny and roughly round. They tend to clump together in sunscreen formulas, which destabilizes the lotion and scatters visible light in a way that produces a noticeable white or gray residue — particularly on darker skin.
The UCLA-led team asked a simple question: What if they changed the physical shape of the zinc oxide instead of its chemistry?
Most zinc oxide for sunscreen is made through chemical processes that produce very small nanoparticles. In the new study, the researchers instead used a patented high-temperature flame process that creates much larger particles shaped like tiny tetrapods, each with four arms extending from a central point.
“Because of their structure, these tetrapod-shaped particles have standoffs and form porous networks instead of collapsing into clumps,” Addae added. “They can’t pack tightly and aggregate, so they stay evenly distributed in the sunscreen.”
The team formulated test sunscreens using the tetrapod-shaped zinc oxide and compared them with lotions made using conventional zinc oxide nanoparticles at the same concentration.
The tetrapod-based formulas reached a sun protection factor, or SPF, of about 30, which is comparable to standard mineral sunscreens. They also stayed more stable over time, showing fewer signs of separation or thickening.
But the most striking difference was visible. In lab tests and controlled skin applications, the tetrapod sunscreens reflected light differently. Instead of a harsh white or gray cast, they appeared warmer and closer to natural skin tones — and they did so without relying on special coatings or added pigments to hide the whiteness.
“When I spread it on my own skin, I didn’t get that white cast I usually see with zinc oxide,” added Addae. “That was the moment I realized this could really work.”
Weiss notes the team did not expect to see such a clear change so quickly.
“What surprised us was how quickly it worked,” Weiss added. “The very first formulations already showed a visible difference.”
The findings suggest that particle engineering — changing the size and shape of mineral filters — could be a powerful tool for improving sunscreen aesthetics while preserving, or even enhancing, performance.
The research is still in early stages. More testing will be needed to understand how tetrapod-shaped zinc oxide behaves on different skin types, how it interacts with living skin over time, and how it might be scaled up for commercial products.
To move closer to real-world use, the team is now working with the UCLA Health department of dermatology, including UCLA Health’s Skin of Color Clinic. One focus is studying how these particles interact with the skin microbiome, the community of microorganisms that live on the skin and can influence health.
If future studies confirm the benefits and safety of tetrapod zinc oxide, the approach could help sunscreen makers design mineral products that work better for a wider range of users — including people who have historically been underserved by the cosmetics and skin care industries.
Addae sees that as central to the project’s impact.
“The best sunscreen is the one people will actually use,” she added. “If zinc oxide can be made to look better on more skin tones without sacrificing protection, it could help more people protect themselves from the sun’s most dangerous effects.”
For now, the work offers a hopeful glimpse of a future where choosing daily sun protection does not mean compromising on how your skin looks — and where a small change in particle shape could support a big shift in public health.
Source: UCLA Health