Flexible Antimicrobial Polyurethane Foam Composites with Chitosan-Montmorillonite for Enhanced Triboelectric Nanogenerator Performance

Flexible polyurethane (FPU) foam is a promising tribopositive layer for triboelectric nanogenerators (TENGs) owing to its high electron-donating capability. However, its limited mechanical robustness and the susceptibility of its porous structure to bacterial growth hinder device performance and durability. In this investigation, montmorillonite (MMT) clay was modified with chitosan (CT) via a cation-exchange mechanism to form a CT/MMT biofiller, which was incorporated for the first time into PU foam during synthesis at varying loadings (0–0.4 wt %). The resulting PU-CT/MMT nanocomposite foams were systematically characterized using XRD, XPS, FTIR, SEM, and TEM, while the antimicrobial efficacy of the biofiller was assessed via the agar well diffusion and broth microdilution methods. The results confirmed successful exfoliation of MMT platelets within the CT matrix. Furthermore, the CT/MMT biofiller exhibited strong antimicrobial activity against E. coli, S. typhi, S. aureus, E. faecalis, and C. albicans, significantly outperforming pristine MMT. Incorporation of 0.2 wt % CT/MMT into PU foam improved compressive strength by 16.7% relative to virgin PU. Triboelectric testing of PU-CT/MMT0.2-based devices yielded an output voltage of 188 V and a maximum power density of 0.036 mW/cm2 at 6.5 Hz under a 10 MΩ load. Furthermore, the device successfully charged a 10 μF capacitor to 14.7 V within 20 s, corresponding to 1080 μJ of stored energy. These results highlight CT/MMT as a multifunctional biofiller that simultaneously enhances the mechanical, antimicrobial, and triboelectric performance of PU foams, advancing their applicability in durable and antimicrobial energy-harvesting devices.