Multifunctional shape memory polymer composites reinforced with bio-based nanofillers for energy harvesting applications

This study reports the fabrication of multifunctional, fully bio-based shape memory polymer (SMP) composites reinforced with cellulose nanocrystals (CNCs) and lignin nanofibers for sustainable energy harvesting applications. Polycaprolactone (PCL) and polylactic acid (PLA) matrices were reinforced with 1–10 wt.% bio-based nanofillers using solution casting, melt mixing, and in-situ polymerization. Dynamic mechanical analysis revealed a significant increase in storage modulus (up to ~ 25%) and a shift in viscoelastic transition behaviour, confirming effective filler–matrix interactions. The composites exhibited excellent shape memory performance, with shape fixity ratios (Rf) of ~ 97% and recovery ratios (Rr) of ~ 95% at 5 wt.% CNC loading, maintained over multiple thermomechanical cycles. Triboelectric nanogenerator (TENG) measurements demonstrated a substantial increase in output voltage from ~ 25 V to ~ 80 V under 25% strain, attributed to enhanced surface roughness, dielectric properties, and effective contact area induced by CNC incorporation. Notably, the intrinsic shape recovery process of the SMP served as an internal mechanical driving force for electrical energy generation, eliminating the need for external actuation. This work presents the first demonstration of a biodegradable SMP system where thermally triggered shape recovery is directly coupled with triboelectric energy harvesting, offering a sustainable, flexible, and self-powered platform for wearable electronics, soft robotics, and autonomous sensing systems.