<p>Reed membrane, a natural cellulosic material traditionally used in musical instruments, holds promise in flexible electronics due to its abundance, low cost, and excellent biocompatibility. However, its native form contains water-soluble ions and lipid-soluble waxes that hinder performance in acoustic and electronics by compromising electrical insulation and mechanical stability. Here, supercritical fluid superposition purification (SCSP-WA) is introduced, which utilizes supercritical CO₂ with water and acetone as bipolar co-solvents to selectively remove these impurities. Post-SCSP-WA treatment, the reed membrane exhibits significant enhancements in mechanical strength and electrical insulation, achieving a 4-fold increase in elongation at break, improved tensile strength and Young’s modulus, and a 98.5% reduction in leakage current, all while maintaining low and stable capacitance. These improvements stem from the restructuring of the fibrous network into a porous, interconnected microstructure. Material characterization (X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM)) confirmed the effective removal of magnesium and waxy functional groups, along with enhanced fiber cross-linking. Cytotoxicity tests further validated the biocompatibility of the SCSP-WA-treated membranes. This environmentally sustainable approach expands the potential of reed membranes in flexible bioelectronics and bio-integrated acoustic systems.</p>