Influencing factors in PVDF-HFP - graphene nanocomposite manufacturing via solvent casting for sensing units in future wearable devices

This study investigates the fabrication of flexible conductive sensors made from PVDF-HFP doped with GNPs, focusing on how ultrasonication dispersion time and solvent evaporation temperature influence their electrical and electromechanical properties. Using Triton X-100 as a surfactant and tip sonication to disperse the GNPs, the research shows that longer sonication improves nanoparticle dispersion but can also introduce structural defects that reduce electrical conductivity. Similarly, higher solvent evaporation temperatures affect nanoparticle re-agglomeration, which further impacts conductivity. Microstructural, electrical (DC and AC), and electromechanical analyses reveal that an optimal balance between dispersion, defect formation, and re-agglomeration is key to maximizing performance. The best results in terms of sensitivity were achieved with 15 min of sonication and an evaporation temperature of 60 °C, yielding sensors with high sensitivity (148 at 15 % of strain) to mechanical strain. The sensors were also evaluated under transient loads, demonstrating excellent robustness and low response times (0.2 s). Proof-of-concept tests demonstrated potential for their use in medical and biomechanical applications, such as touch sensing, respiratory monitoring, and foot pressure mapping. These findings offer valuable insights into optimizing sensor fabrication processes for flexible and wearable electronics. • PVDF-HFP/GNP nanocomposites made via controlled sonication and solvent casting. • Optimal sensor performance at 15 min sonication and 60 °C solvent evaporation. • High sensitivity at low strain (GF = 148 at 15% strain) was achieved. • Conductivity depended on a balance between dispersion and structural integrity. • Tests in breathing and gait proved the composites' use in wearable health systems.