Development and characterization of carbon-based conductive pastes with high mechanical integrity under bending stress for room-temperature printable electronics

Room temperature processing of flexible electronics has become of great interest, as it allows for simpler and cheaper methodologies for high throughput manufacturing of printed electronics. This study focuses on the development and characterization of carbon-based conductive pastes made from a combination of graphite (G) and carbon black (CB), in a polymethyl methacrylate (PMMA) polymer matrix. Raw materials were characterized by Raman Spectroscopy, FTIR, SEM and TEM, showing the structural properties, morphologies and particles size which influenced the characteristics of the pastes. By varying the ratios of G/CB (1 to 4), carbon filler content (11.6-20%), and polymer content (1.5-7%), 48 different formulations were fabricated and further analyzed to determine their electrical conductivity as films. This process identified the optimal formulation for each G/CB ratio. Pastes with higher relative graphite content (G/CB ratios of 3 and 4) yielded the lowest resistivities (as low as 0.078 Ω cm) attributed to the effective formation of conductive networks between G and CB. Best-performing pastes were further characterized by sheet resistance, viscosity, adhesion, and scanning electron microscopy (SEM) analysis to understand the microstructure of the films. Flexible electrodes fabricated on PET substrates withstood 6000 bending cycles, thermal stress at 70 °C, and immersion in water, maintaining electrical conductivity. These results have significant implications for the future development of carbon-based conductive materials for room-temperature applications in flexible and printed electronics.