3D-printed polylactic acid/carbon dot nanocomposites: mechanical, interfacial, and dielectric performances toward multifunctional additive manufacturing applications

Abstract

The development of multifunctional polymer nanocomposites with integrated sensing capabilities has attracted considerable research interest for advanced engineering applications. In this study, carbon dot (CD)-reinforced polylactic acid (PLA) nanocomposite filaments were fabricated via melt extrusion and subsequently processed through fused deposition modeling (FDM) to develop multifunctional 3D-printed structures with potential sensing applications. The CDs were synthesized and incorporated into the PLA matrix at varying concentrations, and the effects of CD content, extrusion temperature, and screw speed on the mechanical, interfacial, and dielectric properties of the resulting composites were investigated systematically. Tensile testing revealed that the nanocomposite containing 3.5 wt.% CDs processed at 170 °C and 4 rpm exhibited the most favorable mechanical performance, achieving a peak stress of 3.10 MPa, Young’s modulus of 49.92 MPa, and modulus of toughness of 0.096 MJ/m 3 . Fourier-transform infrared (FT-IR) spectroscopy confirmed successful incorporation of the CDs into the PLA matrix and demonstrated strong interfacial interactions between the filler and PLA matrix, as reflected by the characteristic shifts in the carbonyl and hydroxyl absorption bands. Dielectric characterization demonstrated that the PLA/CD nanocomposites exhibited reduced dielectric losses, suppressed polarization effects, and improved frequency-dependent dielectric behaviors relative to pure PLA, consistent with enhanced charge transport behavior and greater electrical reliability. The synergistic enhancement of mechanical integrity and dielectric performance highlights the potential of CD-reinforced PLA nanocomposites for application to multifunctional sensing, flexible electronics, smart structural systems, and sustainable additive manufacturing.