Structural Assessment of Silver Conductive Ink using Nanoindentation

Abstract

Stretchable conductive inks have emerged as a key enabling technology for the development of flexible and wearable electronic devices. Silver nanoparticles are commonly incorporated into these inks to impart electrical conductivity while maintaining stretchability. However, the amount of silver in the ink formulation can significantly influence the structural integrity and mechanical performance of printed conductive inks. This study investigates the impact of different silver contents on the structural assessment of stretchable conductive ink. Three samples of conductive inks, each with a different silver concentration (40%, 60%, and 80%) were produced by combining a PDMS-OH binder, organic solvent, cross-linking agent, catalyst, viscosity controller, additives, and silver nanoparticles. The ink samples with varying silver concentrations are characterized using nanoindentation and field-emission scanning electron microscopy (FESEM). The electrical conductivity of the silver conductive ink was measured with a digital multimeter. Among the three samples, the optimal silver concentration for conductive ink formulation is 60%, which exhibits a hardness of 2.04 MPa and an elastic modulus of 32.9 MPa to balance mechanical elasticity with an electrical conductivity of 1.389x104 S/m. Increasing silver content reduces the ink's flexibility, making it more brittle and less stretchable, but it also boosts its conductivity. The findings provide valuable insights into optimizing the silver content in stretchable conductive inks for achieving robust structural integrity and reliable performance in flexible and stretchable electronics.