Patterning microporous paper with highly conductive silver nanoparticles via PVP-modified silver–organic complex ink for development of electric valves

Abstract

The reactive ink composed of a silver-organic complex has shown potential for developing conductive patterns on various substrates such as glass and PET. However, the incompatibility with Whatman No. 1 and conventional office paper, on which it transduces to silver oxides, has limited its application in developing flexible paper-based electronic devices such as electrofluidics and microfluidics electroanalytical devices. Herein, the stabilization of silver cations generated from silver-reactive ink by polyvinylpyrrolidone (PVP) on hydroxyethyl cellulose (HEC)-premodified Whatman No. 1 paper to induce the formation of silver metal nanoparticles is reported. FTIR studies confirmed the stabilization of silver cations by PVP through nitrogen and oxygen atoms. The modification of paper with HEC prevents the formation of silver oxide and silver acetate salts, thus lowering the curing temperature to 60 °C and achieving high conductivity, calculated to be 6.246 × 10⁶ S m⁻¹. FE-SEM images confirmed the uniform formation of silver nanoparticles on the surface of the cellulose fibers simultaneously preserving the porosity of paper. The microporous silver patterned paper was further coated with a ferroelectric fluoropolymer: PVDF-HFP to enhance its electrowetting properties and was applied in the development of a paper-based microfluidic device equipped with an electrical valve.