Smaller is better: reducing silver nanoparticle size without excess ligands enhances conductivity and flexibility in printed thin films

Achieving simultaneous high conductivity and mechanical durability in printed flexible electronics remains a central challenge. Here we report a systematic investigation of silver nanoparticle (AgNP) size effects on film performance using a pH-mediated synthesis that decouples particle size from organic content. This strategy enables direct assessment of size-dependent sintering and mechanical behaviors, previously obscured by varied polymer concentrations of traditional size control methods. With consistent organic content, AgNPs of smaller size demonstrated more effective sintering, forming denser and more cohesive microstructures, contrary to prior reports with varied organic concentration. This yielded highly conductive films with resistivities as low as 2.34 μΩ cm, approaching bulk silver. Additionally, electrohydrodynamic (EHD) printing of these inks produced flexible circuits with significantly improved mechanical resilience. The resistance of a printed pattern remained stable over 1,000 bending cycles at a 2.9 mm radius and increased by only 56.7% after 50,000 cycles, with no visible microstructural cracking.