Andrea Spanou: Graphene-enhanced polymers for additive manufacturing in biomedical applications

Abstract

The integration of functional composite materials into additive manufacturing (AM) processes offers promising avenues for advancing healthcare, electronics, and sustainable production. This thesis explores the development and application of graphene-enhanced polymer composites across multiple AM techniques—fused filament fabrication (FFF), laser powder bed fusion (PBF-LB/P), and direct ink writing (DIW)—to address critical challenges in antibacterial surfaces, industrial scalability, and energy harvesting.

To combat bacterial infections and antibiotic resistance, polyvinylidene fluoride (PVDF) -graphene nanoplatelet composites were fabricated via thermal compounding and FFF. These materials were evaluated for bacterial adhesion and proliferation. Bacterial attachment was reduced by 21% for Escherichia coli and 81% for Staphylococcus aureus within the first hour, attributed to exposed graphene flakes. However, no significant inhibition of biofilm formation was observed, likely due to limited graphene exposure on the surface. Importantly, different printing configurations resulted in distinct surface topographies, which significantly influenced bacterial response, highlighting the role of process parameters in biological performance.

For scalable and sustainable AM, bio-based polyamide 11 powders coated with partially reduced graphene oxide (prGO) were developed for PBF-LB/P. Electrostatic dissipative properties were achieved at ultra-low prGO concentrations (0.07 wt%), and key printing parameters were identified that influence coating and part performance. Reused prGO-coated powders demonstrated a 10% and 27% increase in the tensile strength of printed parts compared to those produced with fresh and reused uncoated powders, respectively. Furthermore, a 3.8-fold improvement in elongation at break was observed in parts fabricated using the coated powder reused three times, relative to those made with freshly coated powder. These results indicate that the prGO coating not only enhances powder recyclability but also improve part functionality.

Additive manufacturing is also becoming a valuable tool for microsystems technology and decentralized device fabrication. DIW was used to print PVDF-TrFE and PVDF-TrFE–rGO composite inks. Electrical conductivity of 2.8 S/cm was achieved at 7 wt% rGO, and fully 3D-printed piezoelectric devices retained their functional response, confirming fabrication compatibility. The conductive ink also served effectively as an electrode material.

Building on these results, the same ink systems were used to fabricate piezoelectric devices aimed at addressing the growing energy demands of wearables and lightweight electronics. Printed polymer–graphene electrodes matched gold electrode performance, generating open-circuit voltages up to 65 V and useful capacitor charging at 2 Hz. Strain sensitivity of 0.03% (detecting deformations below 10 µm) was demonstrated, highlighting their potential for physiological monitoring and sustainable energy solutions.

This work expands the functional scope of graphene composites in AM, contributing to the next-generation biomedical devices through sustainable, decentralized production pathways.