All-optical Mie void sensor for complex nanoplastic mixtures.

The fragmentation and direct release of plastic debris have emerged as a pressing ecological concern. Once dispersed, these particles infiltrate food webs, accumulate within organisms, and bind toxic co-contaminants, posing long-term risks to ecosystems and human health. Despite growing awareness, the characterization of nanoplastics remains highly challenging. Moreover, obtaining additional information, such as particle shape or material composition, further exacerbates these detection hurdles. Here, we introduce a photonic sensing platform based on nanoscale voids that enables the simultaneous material- and morphology-sensitive detection of particles below 500 nm. Void arrays embedded in a high-refractive-index material act in parallel as both sorting elements and color reporters. Spherical and elongated particles are selectively trapped in circular and elliptical voids, while different polymer types are distinguished simultaneously. This approach offers a scalable route toward optical identification of nanoplastics in environmental settings. Its compatibility with high-throughput analysis positions it as a promising tool for real-time studies.