Responsive structural color materials emerge from the physical interaction of light with nanoscale architectures rather than from molecular absorption. Moving beyond phenomenological descriptions of color change, this review points out responsive dynamic materials as functional porous media. Analyte transports through the nanoconfined pore network, and interfacial interactions at pore walls modulate optical properties thermodynamically. This framework reveals key design parameters linking structure to performance. Pore tortuosity governs response time, while analyte adsorption capacity determines sensitivity. These mass transport and interfacial processes collectively alter key structural parameters including effective refractive index and lattice spacing, which are then transduced into visible optical shifts via Bragg diffraction, plasmonic resonance, or other structural coloration mechanisms. We systematically analyze how pore architecture influences analyte transport kinetics, and how interfacial thermodynamics from adsorption isotherms to polymer swelling equilibria to control response sensitivity and selectivity. We also concluded emerging industrial applications of structural color sensors, particularly in intelligent packaging for real-time freshness monitoring, pathogen detection, and gas sensing. We critically discuss practical challenges, including nonspecific adsorption, fouling, limited selectivity, and long-term stability, and present interfacial engineering strategies to overcome these barriers. For the first time, this review establishes a quantitative cascade from analyte concentration to optical readout, thereby providing a rational design pathway for next-generation structural color sensors in food safety, environmental monitoring, and beyond. Quantitative mechanism of responsive structural color sensors: from analyte concentration to wavelength shift. The diagram indicates the complete physicochemical cascade from analyte stimulus to optical response. Gas or liquid molecules (ammonia, water vapor) generated within a package diffuse into the nanostructured porous film. The molecules transport through the confined pore network of a photonic crystal-like material. Key interfacial events occur at the pore walls including non-specific adsorption forming a molecular layer, specific molecular recognition (antibody-antigen binding), and swelling of a functional polymer matrix. These processes thermodynamically modulate the material's key structural parameters: increasing the effective refractive index or expanding the lattice spacing. Incident white light interacts with the modulated nanostructure. The altered optical path conditions governed by Bragg's law led to selective reflection of a specific wavelength, resulting in a visible color shift. The entire process integrates mass transport kinetics and interfacial thermodynamics to transduce a chemical stimulus into a macroscopic optical signal. • A porous media framework for structural color sensing. • Quantitative cascade from mass transport to color change. • Pore architecture determines sensing kinetics and selectivity. • Bio-based structural colors for sustainable smart packaging.
Huang et al. (Fri,) studied this question.