Revolutionary Water-in-Water Sunscreen: How Cosmecca Korea is Redefining UV Protection

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Cosmecca Korea, a cosmetics R&D and manufacturing company, has become the first in the world to develop a sunscreen based on a water-in-water (W/W) emulsion.

Today’s sunscreens are typically made as oil-and-water emulsions. Those formulations rely on oils and surfactants, which have raised environmental concerns and left users complaining about greasiness, stickiness, and eye irritation.

Cosmecca partnered with a research team from Seoul National University of Science and Technology to apply a W/W (water-in-water) emulsion structure to a sunscreen formula. They used an aqueous two-phase system in which, under specific conditions, two different water-soluble polymers separate into distinct phases within water.

Together, the teams clarified the scientific principles behind a fully aqueous sunscreen formulation. The findings were published in the Chemical Engineering Journal, an international journal in chemical engineering (impact factor: 13.2).

Cosmecca says the oil-free formula delivers both formulation stability and strong UV protection. After application, as water evaporates, a dense, mesh-like film forms, and the researchers confirmed that the UV-filtering ingredients distribute evenly across the skin’s surface.

The study shows that UV-blocking performance depends not only on ingredient type or concentration but also on the structural characteristics created by how ingredients arrange and lock into place within the formula. Experts call it a potential game-changer for next-generation sun-care products. The Biological Research Information Center (BRIC) also recognized the study, naming it among its “People Who Brighten Korea (Hanbit-sa).”