Microplastic Transport in Buckwheat Root-Inspired Microfluidic Structures: Microfluidic and Numerical Analysis

Microplastics released from synthetic textiles are increasingly recognized as an important source of environmental contamination and a potential pathway of their entry into soil-plant systems. This study quantified microfibre release from warp-knitted polyester fabric during domestic washing and investigated the migration behaviour of microplastics within root epidermis-like structures using a combined experimental and numerical approach. Microfibre emission was determined gravimetrically according to ISO 4484-1:2023. The average release per washing cycle was 0.6 ± 0.5 g of microfibres per kilogram of polyester textile. Raman spectroscopy and differential scanning calorimetry analysis confirmed that the released particles consisted of polyethylene terephthalate. Scanning electron microscopy of buckwheat (Fagopyrum esculentum) roots revealed a well-defined epidermal and cortical tissue organization, which served as a basis for designing simplified epidermis-inspired microchannel geometries. Numerical simulations and microfluidic experiments showed that microplastics predominantly follow streamline-oriented pathways under laminar flow conditions. However, particle accumulation can induce localized clogging within pore-like structures, modifying flow pathways and redirecting particle transport. These results indicate that root epidermal tissues may function as a partial filtration barrier that restricts the transport of larger microplastics while allowing smaller particles to migrate through outer root layers.