Low-Temperature Single-Step Inkjet-Printed Metallic Patterns With Self-Regulated Vertical Compositional Gradient

For the rapidly growing demands and expanding range of applications of printed electronics in medicine lower processing temperatures and simpler steps are preferred to minimize the fabrication processes onto a range of substrates. Various hybrid inks are formulated for fabricating multi-compositional functional patterns with fewer manufacturing processes. However, most hybrid inks can only form patterns with fully-mixed compositional distribution. This study proposes a novel hybrid metal-based ink formulation pathway and develops a particle-free Ag-Cu hybrid metal-organic decomposition (MOD) ink. When sintering under N₂ the in situ formed Ag and Cu nano-particulates during the sintering process self-regulate into a unique vertical compositional gradient with Cu dominant on top and the majority of Ag existing beneath. Highly conductive (1.88 ± 0.7 × 10⁶ S m^-1) metallic patterns are fabricated by single-step inkjet printing at low temperature (<150 °C) on both rigid and cellulose fiber substrates. When sintered under air a porous CuO layer is generated on the surface with high electrocatalytic activity with glucose (stable for over 2 h of continuous measurement). This work shows the feasibility of fabricating a glucose sensor including electrode layer and functional layer by single-step printing.