Based on an unexpected discovery, a Stanford University research team recently developed a new nanophotonic polymer "metasurface" material that can change its color and surface texture under external stimulation and restore it to its original state when needed. It is considered to be promising for cutting-edge applications such as bionic "artificial skin", environment-aware robots, and advanced camouflage.
The researchers used a polymer previously used in solar panels and printable electronics to create nanostructured metasurfaces using electron-beam lithography, a technique common in semiconductor manufacturing. When observing these nanostructures with a scanning electron microscope, the team unexpectedly discovered a key characteristic of the material: it swells when in contact with water, and the surface microstructure changes accordingly, allowing the material to show different colors and textures; and after contact with certain solvents (such as alcohol-based solvents), the material can return to its original state.
According to the newly published paper, this metasurface is the first polymer material that can simultaneously change color and surface texture driven by demand, and its behavior is highly similar to the skin of cephalopods such as octopuses. These organisms can change the color and roughness of the body surface by adjusting the microstructure in the skin for complex functions such as camouflage and communication, and this new material shows similar "adjustable skin" capabilities in artificial systems.
Siddharth Doshi, a doctoral student in Stanford's Materials Science and Engineering major and the first author of the paper, said that the team realized that they could use electron beams to precisely control the morphology of the material surface on an extremely fine scale to adjust its absorption properties of liquids and the way it scatters light. On this basis, the researchers designed a variety of microscopic textures so that the material can selectively scatter light into a high-gloss or matte-like effect after contact with moisture, making the visual effects presented more realistic than current smartphone and computer displays.
Despite its excellent optical and tactile appearance control capabilities, this material will not replace existing digital display technology in the short term. The research team is currently paying more attention to the directions of robotics, wearable devices, bioengineering and camouflage systems, such as providing flexible robots with shells that can both "feel" the environment and actively change their appearance, or developing more realistic and feedback-capable "electronic skins" for medical treatment and human-computer interaction.
In the next step, the researchers also plan to introduce artificial intelligence methods such as neural networks to equip this polymer "skin" with an automatic adjustment mechanism. The envisaged system can compare the optical characteristics of the material surface with the surrounding environment in real time, and autonomously adjust the color and texture without manual intervention, achieving truly intelligent camouflage or adaptive appearance control.