By Suherman Candra Maholtra 
The pursuit of effective sun protection has long been hindered by a persistent aesthetic barrier: the thick, chalky residue left behind by mineral-based sunscreens. For decades, this "white cast" has served as a significant deterrent for consumers, particularly those with darker skin tones, leading to inconsistent application and increased vulnerability to ultraviolet (UV) radiation. However, a multidisciplinary team of researchers at the University of California, Los Angeles (UCLA) has announced a breakthrough in materials science that could redefine the dermatological landscape. By altering the physical geometry of zinc oxide particles, the team has created a formula that maintains high-level UV protection while appearing nearly invisible on a wide range of skin tones.
The study, led by investigators at the UCLA Health Jonsson Comprehensive Cancer Center and published in the journal ACS Materials Letters, suggests that the key to improving sunscreen compliance does not necessarily lie in discovering new chemical filters, but in re-engineering the structural properties of existing, FDA-approved ingredients. By transforming spherical zinc oxide nanoparticles into microscopic, four-armed structures known as tetrapods, the researchers have addressed the fundamental physics of light scattering that causes the unsightly gray or white film associated with traditional mineral sunscreens.
The Public Health Imperative of Sunscreen Compliance
Skin cancer remains the most prevalent form of malignancy in the United States, with more than five million cases diagnosed annually. According to the Skin Cancer Foundation, one in five Americans will develop skin cancer by the age of 70. While the vast majority of these cases are preventable through the consistent use of broad-spectrum sunscreen, public adherence to dermatological guidelines remains low.
Dermatologists have long advocated for mineral sunscreens—specifically those containing zinc oxide or titanium dioxide—because they provide a physical barrier that reflects and scatters both UVA and UVB rays. Unlike chemical filters, which absorb into the skin and convert UV radiation into heat, mineral filters sit on the surface, making them the preferred choice for individuals with sensitive skin, rosacea, or melasma. Furthermore, the U.S. Food and Drug Administration (FDA) has classified zinc oxide as "generally recognized as safe and effective" (GRASE), a designation not currently shared by several common chemical ingredients due to concerns regarding systemic absorption and environmental impact on coral reefs.
Despite these benefits, the aesthetic limitations of mineral formulas have created a public health gap. "This isn’t just about cosmetics," explained Dr. Paul S. Weiss, a senior author of the study and a distinguished professor of chemistry, biochemistry, and materials science at UCLA. "If improving how sunscreen looks leads to more consistent use, it could have real implications for skin cancer prevention."
Addressing Racial Disparities in Dermatological Outcomes
The "white cast" problem is not merely an inconvenience; it is a factor in health inequity. Research indicates that while melanoma is less common in people with darker skin tones, it is often diagnosed at significantly later stages when the prognosis is more dire. A study published in the Journal of the American Academy of Dermatology found that the five-year survival rate for melanoma is approximately 71% for Black patients, compared to 93% for white patients.
Late-stage diagnoses are frequently attributed to a lack of awareness regarding skin cancer risks in communities of color and a lack of products tailored to their needs. When mineral sunscreens leave a visible, ashy residue on deeper complexions, users are less likely to apply the recommended amount or may forgo sun protection entirely.
For AJ Addae, the study’s first author and a doctoral candidate in chemical biology at UCLA, the research was personal. As a cosmetic science entrepreneur, Addae had experienced the frustration of mineral sunscreens firsthand. "I started thinking about this because I was frustrated by how mineral sunscreen looks on my own skin," Addae said. "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."
The Science of Light Scattering and Particle Geometry
To solve the white cast issue, the UCLA team had to investigate why zinc oxide looks white in the first place. Traditional mineral sunscreens utilize spherical nanoparticles of zinc oxide. Because of their shape and surface chemistry, these spheres tend to clump together—a process known as aggregation. When these particles aggregate into larger clusters, they reach a size that effectively scatters visible light. This scattering is what creates the opaque, white appearance on the skin.
The UCLA researchers moved away from the standard chemical precipitation methods used to create spherical particles. Instead, they utilized a patented high-temperature flame process to synthesize zinc oxide in the shape of tetrapods—structures with four "arms" protruding from a central point.
The geometric properties of tetrapods prevent them from packing tightly together. "Because of their structure, these tetrapod-shaped particles have standoffs and form porous networks instead of collapsing into clumps," Addae explained. "They can’t pack tightly and aggregate, so they stay evenly distributed in the sunscreen."
By maintaining a more uniform and porous distribution, the tetrapod particles interact with light differently than their spherical counterparts. They continue to absorb and reflect harmful UV radiation, but they do not scatter visible light to the same degree, allowing the natural pigment of the skin to show through.
Experimental Results: Protection and Stability
The research team conducted rigorous comparative testing between the new tetrapod-based formula and conventional zinc oxide nanoparticles. The results demonstrated that the structural change did not compromise the efficacy of the sunscreen.
- Sun Protection Factor (SPF): When tested at equal concentrations, the tetrapod formula achieved an SPF of approximately 30. This is the baseline recommended by the American Academy of Dermatology for daily use, providing protection against 97% of UVB rays.
- Broad-Spectrum Efficacy: The tetrapod structures remained highly effective at blocking UVA rays, which penetrate deeper into the dermis and are primarily responsible for premature skin aging and long-term DNA damage.
- Formula Stability: One of the challenges in sunscreen formulation is preventing the active ingredients from settling or the emulsion from breaking. The tetrapod lotions showed superior stability over time, resisting the separation and thickening that often plague mineral sunscreens during storage.
- Visual Analysis: In controlled laboratory applications and skin trials, the tetrapod formula produced a "warmer" appearance. Unlike the stark white or gray cast of traditional formulas, the tetrapod-based lotion integrated with various skin tones without the need for added tints, pigments, or chemical coatings.
"What surprised us was how quickly it worked," said Weiss, who also holds a UC Presidential Chair. "The very first formulations already showed a visible difference."
Implications for the Future of Materials Science in Medicine
The success of the tetrapod zinc oxide formula highlights a growing trend in "functional morphology"—the idea that the shape of a material is just as important as its chemical composition. This approach could have applications beyond sunscreens, potentially influencing how topical medications, antimicrobial coatings, and even drug-delivery systems are designed.
However, the path from the laboratory to the pharmacy shelf involves several more steps. While the ingredients are already FDA-approved, the specific tetrapod formulation will require additional clinical testing to ensure long-term safety and efficacy in real-world conditions. The researchers are also interested in how these unique structures interact with the skin’s microbiome—the community of beneficial bacteria that live on the skin’s surface.
To facilitate this next phase, the team is collaborating with the UCLA Health Department of Dermatology and the UCLA Health Skin of Color Clinic. These partnerships will allow the researchers to test the formula on a diverse range of participants and gather qualitative data on user experience and cosmetic elegance.
Conclusion: Bridging the Gap Between Protection and Aesthetics
The development of tetrapod zinc oxide represents a significant milestone in the evolution of sun protection. By solving a decades-old aesthetic problem through innovative materials science, the UCLA team has removed a major hurdle to skin cancer prevention.
As the climate continues to change and UV exposure remains a constant health risk, the need for inclusive, effective, and "wearable" sun protection has never been greater. If this technology reaches the commercial market, it could lead to a shift in consumer behavior, encouraging more people to adopt daily sun protection habits regardless of their skin tone.
As AJ Addae noted, "The best sunscreen is the one people will actually use. 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."
The research was supported by the National Science Foundation, the Challenge Initiative at UCLA, and a Sigma Xi IFoRE Grant-in-Aid. Additional contributors to the study included researchers from the University of Southern Denmark, further emphasizing the international and interdisciplinary nature of this breakthrough. As the team moves toward commercialization, the focus remains clear: leveraging the power of science to make health-saving products accessible and appealing to everyone.
