Strain-Relief Patterns for Flexible SubstrateSupported Optimized Serpentine Configurations

Serpentine printed conductors have been explored in flexible and stretchable electronics as a way to reduce strains in the conductors and thus, the overall normalized resistance increase under stretching and other mechanical loading conditions. In this study, it is shown that the substrate stiffness to conductor stiffness ratio plays an important role in the effectiveness of the serpentine geometry to reduce strains under axial stretching. The benefit of serpentine structure is evident when the substrate stiffness is significantly reduced. Also, it is shown through experimental resistance measurements that the normalized resistance increases less for a serpentine conductor compared to a straight-line conductor under axial stretching. When serpentine conductors are printed on stiffer flexible substrates, the benefits of the serpentine structure can be leveraged through introducing cut-out regions that can reduce localized strains.