Perforated PVP encapsulated AgNWs for high mass loading in silver nanowire inks for printed RFID integrated wearable smart bands

Abstract

Silver nanowire (AgNW) based conductive inks have gained considerable attention for realizing printed flexible electronics (PFE). The present work discusses a novel approach to producing highly dispersible silver nanowires, easing the formulation of screen-printing inks with high nanowire loading. A perforated encapsulation of polyvinylpyrrolidone (PVP) with an average thickness of 5.03 ± 1.16 nm was produced on the AgNWs’ surface through a controlled washing procedure, which increased the dispersibility of AgNWs at higher mass loadings. A screen-printing ink formulation with nearly 36% AgNW loading was developed, which generated highly conductive traces with a conductivity of (1.16 ± 0.06) × 106 S m−1 at a low annealing temperature of 120 °C. The printed traces exhibited superior adhesion (ASTM Class 5), stability towards bending (10 000 cycles), resistance to accelerated ageing (ΔR/R0 < 2.5% at 60 °C – 95% RH), and stability towards sweat exposure (ΔR/R0 = 0.5%), making them a suitable candidate for PFE. Utilizing this conductive ink, a highly flexible UHF antenna operating at 945 MHz was fabricated, and an RFID tag was developed by integrating the antenna with a chip. The fabricated tag exhibited exceptional communication performance with a handheld reader and had high stability toward bending (at a bending radius of 1.5 cm for 500 cycles). A wearable smart band for Android-based human position sensing was also developed using the tag, which precisely located the wearer's position.