Login
How scientists turned foam structures into white, water-repellent printable films
A single manufacturing step can now do something that normally takes two separate chemicals. It makes a material bright white and water-repellent at the same time, without using either titanium dioxide or PFAS. Researchers at Kyoto University say the technique could remove two of the materials industry’s most persistent chemical dependencies in one move.
Professor Easan Sivaniah, at Kyoto University’s Institute for Integrated Cell-Material Sciences, led the project with collaborators from Tokyo Metropolitan University and Donghua University. The team calls the resulting process Deep Foam Photolithography.
Two chemicals under pressure
Titanium dioxide has long served as the default white pigment across packaging, films, and coatings. The European Union recently banned its use as a food additive, though, over safety concerns. PFAS compounds face a parallel reckoning. These fluorinated chemicals give materials their water- and oil-repellent properties, yet mounting evidence of their environmental persistence has manufacturers worldwide hunting for substitutes.
Sivaniah’s team set out to solve both problems using physics rather than chemistry. Rather than finding safer replacement chemicals, they asked whether a material’s structure alone could deliver the same effects.
A trick borrowed from nature
The underlying phenomenon is called structural whiteness, and it appears throughout nature without any pigment involved at all. Snow, sea spray, and clouds all owe their brightness to how light scatters off foam-like structures made mostly of air. That same principle is at work in plant tissues and the protective nests certain frogs build.
That principle even shows up in centuries-old art. The blinding white of the waves in Hokusai’s The Great Wave off Kanagawa comes entirely from light scattering off bare washi paper fibers. The print itself contains no white ink at all.
Researchers engineered porous structures that replicate this same light-scattering effect, drawing additional inspiration from how light interacts with leaves and flower petals in nature.
A two-step process
Making the material requires just two steps. Light exposure first breaks a polymer down into smaller molecular fragments. A mild solvent treatment then causes those fragments to react and swell, forming an open, porous structure throughout the material.
That single process yields two properties at once. Internally, the porous structure scatters light to produce bright whiteness with no added pigment whatsoever. On the surface, that same structure becomes rough enough to repel water and oil, mimicking the effect seen on a lotus leaf.
Working with textile researchers at Donghua University, the team confirmed the process works on fabrics in addition to printable polymer films. Crucially, it required no newly invented specialty chemicals, succeeding instead with polymers already available commercially.
The resulting platform supports printing resolutions up to 20,000 DPI while delivering structural whiteness and water repellency together, all without titanium dioxide or PFAS. Rather than relying on added pigments or persistent chemical coatings, the approach builds both color and function directly into a material’s physical structure. That points toward a lighter, more sustainable way to manufacture everyday materials.
