Development of stretchable conductive inks based on cellulosic materials

Stretchable printed electronics represent a promising and expanding field for flexible and wearable devices in areas such as healthcare, energy, and smart textiles.

To meet mechanical requirements beyond simple flexibility, conductive inks must maintain their electrical performance under mechanical deformation—ensuring both strong adhesion to substrates and the integrity of the percolated conductive network when stretched. In this work, we report the development of bio-based stretchable conductive inks formulated with oxidized cellulose nanofibrils (CNFt) and hydroxypropyl methylcellulose (HPMC) as sustainable binders, combined with silver particles to provide electrical conductivity. These inks are designed to be screen-printable and were evaluated using innovative, multi-scale characterization methods to assess their electromechanical behavior under strain. This includes in-situ monitoring of electrical resistance during uniaxial or cyclic stretching, as well as tensile testing under Scanning Electron Microscopy to gain insight into the evolution of the silver percolation network during deformation. Various formulations have been proposed to optimize final stretchability and conductivity. 

The inks demonstrate excellent performance, maintaining electrical conductivity under 100% elongation and withstanding over 100 deformation cycles at 25% strain, with a silver content limited to 50 wt%. This novel approach provides a sustainable alternative to petroleum-based elastomeric inks and contributes to the advancement of eco-designed, stretchable electronic systems.