Scientists Create Brilliant White Material Without a Drop of White Pigment

Some of the brightest whites in nature and art contain no white pigment. In Hokusai's print The Great Wave off Kanagawa, the sea foam, the snow on Mount Fuji and the clouds look brilliant white because light scatters off fibers of the traditional washi paper, an effect scientists call "structural whiteness": structure, not a colored substance, produces the brightness. Sea spray, clouds, snow, plant tissues and some frogs' foamy nests look intensely white too, though made largely of air.

That strategy inspired an international team led by Professor Easan Sivaniah at Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS), with researchers from Tokyo Metropolitan University and Donghua University in China. They aimed to replace two materials widely used for whiteness and water-repellency: titanium dioxide (TiO2), which brightens packaging, films and coatings but was recently banned by the European Union as a food additive over safety concerns, and PFAS, fluorinated chemicals that repel water and oil but face scrutiny for persisting in the environment and possibly harming health.

The researchers engineered porous materials mimicking natural foams and water-repellent leaf and petal surfaces, in a method they call Deep Foam Photolithography (DFP). A polymer is first exposed to light, breaking it into smaller fragments; a mild solvent then swells the polymer, opening a network of microscopic pores. This single step gives the material two properties: the pores scatter light so effectively that it looks intensely white with no pigment, while its rough surface repels water like a lotus leaf.

Working with Donghua University's textile researchers, the team showed DFP also works on fabrics, not just polymer films, using existing commercial polymers with no new specialty chemicals. Assoc. Prof. Taiki Yanagishima of Tokyo Metropolitan University said biomimetic science's key challenge is matching nature-inspired, eco-friendly designs to the scale and cost of existing materials. The resulting printable materials reach 20,000 DPI resolution, combining structural whiteness with water-repelling function, without titanium dioxide or PFAS.