A Wearable Colorimetric Sensor for Ultraviolet Monitoring via Radical‐Triggered Gold Nanoparticle Clustering

ABSTRACT

Reliable monitoring of ultraviolet (UV) radiation is critical for protecting human health, yet existing sensors often rely on costly or rigid components that hinder portability. Here we report a wearable, low‐cost colorimetric sensor for quantitative UV dosimetry, enabled by radical‐triggered aggregation of gold nanoparticles (AuNPs). Using 2‐hydroxy‐2‐methyl‐1‐phenyl‐1‐propanone (HMPP) as a photosensitizer, UV irradiation generates radicals that induce AuNP clustering, producing a distinct and dose‐dependent color change. The sensor provides accurate quantification across UVA, UVB, and UVC bands, with multivariate fitting enabling spectral differentiation. Its biological relevance was validated using keratinocyte models, directly correlating colorimetric responses with cell viability and oxidative stress. We further fabricated a skin‐conformal smartphone‐readable device for real‐time outdoor monitoring through integration into a flexible, transparent polydimethylsiloxane (PDMS) matrix. This low‐cost, disposable sensor unites quantitative precision and practical usability, offering a promising platform for personal healthcare, occupational safety, and consumer‐level UV protection.