An international research team led by Professor Easan Sivaniah of Kyoto University has developed a new material platform that produces vivid white coloring and water-repellent properties through physical structure rather than chemical additives. The innovation addresses growing environmental and health concerns surrounding two widely used substances: titanium dioxide, which the European Union recently banned as a food additive, and PFAS chemicals, which persist in the environment and raise potential health risks.
The researchers drew inspiration from natural phenomena where structural whiteness occurs without pigmentation. Examples include the white foam in Hokusai’s famous artwork, which relies on light scattering through washi paper fibers, as well as naturally occurring white materials like sea spray, clouds, snow, and certain plant tissues. The research team, collaborating with institutions including Tokyo Metropolitan University and Donghua University, engineered porous materials that mimic these natural light-scattering mechanisms while also incorporating water-repellent properties inspired by lotus leaves and similar botanical surfaces.
The manufacturing process, termed Deep Foam Photolithography (DFP), is straightforward and uses readily available materials. A polymer is first exposed to light, which fragments the molecular structure. Mild solvent treatment then causes the polymer to expand, creating an open network of microscopic pores. This single transformation produces both structural whiteness through effective light scattering and extreme water repellency from a rough surface texture. The technique achieves ultrahigh resolution printing capability at 20,000 DPI.
A significant advantage of the approach is its applicability to multiple material types. Researchers demonstrated the process works not only on polymer films suitable for printing but also on fabrics, in collaboration with textile science researchers. The method relies on commercially available polymers rather than requiring specialized new chemicals, potentially facilitating broader adoption.
The technology represents a shift toward building functional properties directly into material structure rather than relying on chemical additives. By using microscopic architecture to control light behavior and water interaction, this approach offers potential benefits including lighter materials, reduced dependence on mined mineral pigments, and decreased use of persistent fluorinated chemicals.
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