Poly(vinyl alcohol)/Chitosan/Glycine Composite-Based Eco-Friendly Biodegradable Triboelectric Nanogenerators

Triboelectric nanogenerators (TENGs) offer a low-cost approach for harvesting ambient mechanical energy; however, most devices rely on synthetic, nonbiodegradable polymers. This study presents an eco-friendly biodegradable TENG constructed using a ternary composite of poly-(vinyl alcohol) (PVA), chitosan (CS), and glycine (GL). Moderately transparent PVA/CS/GL composite films were fabricated via a simple in situ solvent-casting process using physical mixing and ambient drying, avoiding toxic solvents and complex thermal processing. The composite film served as the tribo-positive layer, while a polydimethylsiloxane film served as the tribo-negative layer in a vertical contact-separation configuration. The GL content (0-25 wt %) was varied to evaluate its effect on the film structure, mechanical properties, and triboelectric performance. SEM showed GL-dependent surface texturing, and FTIR confirmed the presence of polar functional groups (-OH, -NH₂/-NH₃ ⁺, and -COO^-) and interaction changes consistent with hydrogen bonding within the composite network. GL incorporation also improved flexibility and mechanical stability compared with the pristine PVA/CS film. The GL20 film exhibited the best electrical performance, delivering an open-circuit voltage of ∼70 V at 10 Hz and a short-circuit current of ∼9-10 μA at a low external resistance, with a peak current of ∼4 μA near the matched load. A maximum power density of 12-13 μW cm^-2 was achieved at an external load resistance of 5.1 MΩ. The rectified output powered LEDs and charged capacitors (0.22-10 μF), with a 0.22 μF capacitor reaching ∼2.3 V within 40 s. The EB-TENG maintained a stable output over 7500 operating cycles and showed rapid hydrolytic mass loss in phosphate-buffered saline within 1 week. Overall, these results demonstrate the potential of PVA/CS/GL-based EB-TENGs as sustainable and biodegradable power sources for eco-friendly self-powered electronics.