Hierarchical Interlayer Design for Wheat Straw-Based Straws: Exceptional Mechanical Robustness and In-Situ Capture of Micro/Nano Plastics

Abstract Biodegradable drinking straws derived from agricultural residues are limited by poor wet durability, weak interfacial bonding, and insufficient functionality. Herein, wheat straw was converted into a biodegradable straw for potential food-contact applications through hierarchical interface engineering comprising stearic acid hydrophobization, a poly(lactic acid)/cellulose nanocrystal-thioctic acid (PLA/CNC-TA) reinforcing interlayer, and a polydopamine (PDA) outer layer. Stearic acid reduced water uptake, whereas CNC-TA enhanced interfacial compatibility and stress transfer through hydrogen bonding and thioctic-acid-associated interactions. The optimized PP4/WS-SA straw achieved a tensile strength of 64.8 MPa and retained approximately 46 MPa after water exposure. PDA introduced catechol and amine groups, enabling partial capture of negatively charged micro-/nano plastics (MNP), with a maximum turbidity-based removal efficiency of approximately 36%. The straw also exhibited improved thermal stability, food-simulant migration values below the tested limits, and progressive soil degradation, demonstrating a promising value-added application for agricultural-residue tableware.