Direct-write printing of reactive oligomeric alkoxysilanes as an affordable and highly efficient route for promoting local adhesion of silver inks on polymer substrates

A novel approach for improving the printability and adhesion of silver inks on flexible and stretchable polymeric substrates is reported. The method is based on polymer surface functionalisation with an organosilicon interlayer by solution processing and, more specifically, the deposition of a self-assembled layer (SAL) from thiol-containing oligomeric alkoxysilanes prepared under active medium conditions. We demonstrate the potential of SAL formation on polymer substrates by large-area uniform coating or by small feature printing. The direct-writing method, which is also referred to as reactive inkjet printing, enables the selective modification of polymer surfaces with functional thiol-containing interlayers, resulting in local adhesion enhancement of screen-printed silver nanoparticle inks. This study establishes that SALs printed from oligo(3-mercaptopropyl)(methoxy)siloxane (OMPMS) lead to significant adhesion improvements of both aqueous- and organic-based silver inks approaching approximately 100% for polyethylene naphthalate (PEN) and even polydimethylsiloxane (PDMS) substrates. Exceptional electrical and mechanical stabilities of the printed silver conductors under bending and stretching are demonstrated.