The research team created what they called "photonic skin ," a thin artificial coating with patterns smaller than a human hair. In its dry state, the structures are invisible, but when it comes into contact with liquid, the surface swells, forming raised letters and colored spots.
This skin is based on the conductive polymer PEDOT:PSS , where water molecules penetrate between the polymer chains, creating localized bulges. Areas exposed to less electron irradiation bulge, forming a stable, raised texture. This effect was replicated using electron lithography . Upon wetting, the liquid penetrates the less irradiated areas, transforming the flat surface into one with a raised texture. This change in texture affects the optical properties: the fine bumps scatter light, while the smooth areas reflect it mirror-like.
Engineers can also adjust the gloss without using pigments, as the color is formed by the interplay of light between the metallic layers. After 250 wetting and drying cycles, the material maintains its contrast and flexibility. The supply of water and alcohol is controlled via microchannels, allowing for precise doses of swelling. The adaptive texture also affects friction, opening new possibilities in robotics and
The developers point to the ongoing need for safer working fluids and automated control systems, potentially using neural networks. This development demonstrates how inflated polymers and nanolithography allow for control of color, texture, and tactile properties, bringing it closer to artificial animal skin .
