Harnessing Neem Gum (Azadirachta indica) as a Binder for Conducting Ink: Rheological and Electrical Properties

This study presents the development of sustainable conductive inks using neem gum (NG) as a natural binder. Three conductive fillers, cupric oxide nanopowder, copper particles, and polypyrrole, were incorporated and optimized for screen‐printing performance. FTIR analysis confirmed the presence of hydroxyl and carboxyl groups in the NG binder. The addition of fillers increased the viscosity of the NG solution from 276.15 to 1101.03 mPa s at a strain rate of 0.1 s −1 . Amplitude sweep tests showed that NG/CuO, NG/copper particles, and NG/polypyrrole inks exhibited higher storage modulus than loss modulus in the strain range 0.001 to 1 s −1 , while the NG/copper particle and NG/polypyrrole inks displayed a crossover at 0.1 s −1 , indicating a viscoelastic transition. Frequency sweep tests revealed that NG/CuO and NG/polypyrrole inks had predominantly viscous behavior, whereas NG/copper particle‐based inks were more elastic. The electrical conductivity ranged from 43.7 × 10 −3  S/m to 4.93 × 10 −3  S/m for 20 wt% conductive fillers and from 23.6 × 10 −3  S/m to 3.97 × 10 −3  S/m for 30 wt% conductive fillers. These findings demonstrate the potential of NG as a sustainable binder for developing conductive inks with tunable rheological and electrical properties.