Tunable, Cost‐Effective, and Scalable Structural Colors for Sensing and Consumer Products

Abstract The cost‐effective colorimetric detection of chemicals can be a potential substitute for expensive spectrometers. Here, a structural color sensor is presented that can distinguish seven different organic solvents through a timed sharp color change. The color sensor is based on interference effects in a metal–insulator–metal Fabry–Perot (FP) cavity with polydimethylsiloxane (PDMS) serving as the dielectric layer. By tuning the cross‐linker to monomer ratio of PDMS and employing a porous nickel (Ni) top layer, the PDMS films experience shrinkage that results in substantial color changes. The time‐dependent color change can be used to indicate the type of solvent that the sensor was exposed to. When the sensor is immersed in a solvent, the PDMS diffuses through the porous Ni film at different rates depending on the solvent, resulting in a shrinkage of the PDMS and resonance shift of the FP cavity. Materials used in this single‐use sensor are cost effective (≈0.28 USD m⁻²), and the fabrication process requires no lithography and is scalable. Moreover, the FP configuration produces vibrant colors that cover ≈50% of the standard Red Green Blue (sRGB) color space and is suited for decorative purposes and consumer products as well.