Fabrication of multilayer superhydrophobic and biodegradable filters through electrospinning and electrospraying of PHA-SiO2 biopolymer composites

The COVID-19 pandemic has dramatically increased the global demand for personal protective equipment (PPE), which is predominantly composed of non-biodegradable materials. Improper disposal of PPE leads to long-term environmental persistence and substantial ecological risks. This urgent situation highlights the need to study sustainable alternatives such as biodegradable materials with enhanced water resistance. In this study, polyhydroxyalkanoates (PHAs), specifically poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), were subjected to electrospinning and electrospraying and incorporated with silica nanoparticles (NPs) to develop multi-layer filtration membranes with enhanced hydrophobic properties for PPE applications. The solubility of PHAs in different solvents was analysed, revealing that PHBV in formic acid produced defect-free nanofibers with a diameter of 106 nm, suitable for filtration membranes, while PHBHHx in dimethylformamide formed beaded nanofibers appropriate for hydrophobic membranes. The incorporation of polydimethylsiloxane (PDMS) or organosilane fumed silica NPs increased surface roughness and promoted the formation of a secondary hierarchical structure, achieving a water contact angle of 153° and roll-off angle under 3°. A dual-layer filter design integrating both filtration and hydrophobic membranes was optimised for PPE applications, achieving a high filtration efficiency of 95 %, differential pressure of 4.98 mm H₂O cm⁻², and water contact angle of 149.7°. Biodegradation studies demonstrated that the PHA bilayer filters degraded by up to 73 % in a marine environment within 600 h, highlighting their potential for environmentally friendly applications. © 2025 Elsevier B.V.