We
demonstrated catechol lipid-based bioresin, which is collected
from lacquer trees, to produce conductive pastes that can be processed
at low temperatures, which are highly adhesive and multidurable. Our
conductive paste, which consists of catechol lipid-based urushiol
resin and a multimodal mixture of silver fillers, exhibited stable
dispersion with shear thinning properties. The urushiol lacquer induced
spontaneous reduction of silver salt at the surface of the silver
fillers, thereby contributing to lower the contact resistance between
conductive fillers in the electrical conduction. Furthermore, the
directional volume shrinkage of the urushiol lacquer matrix in a cross-linking
reaction resulted in a highly ordered microstructure of the silver
fillers with layer-by-layer stacking of the silver flakes. This structure
contributed to the improvement of the electrical contact between fillers
as well as excellent mechanical hardness, anti-scratch capability,
and the long-term environmental stability of the conductive films.
Conductive films based on the silver paste with urushiol lacquer exhibited
low electrical resistivity below 4.4 × 10–5 Ω cm, 5B-class strong adhesion strength, and high hardness
exceeding 200 MPa. Finally, we demonstrated the facile room-temperature
processability and screen printability of the UL–Ag paste by
fabricating a printed antenna and three-dimensional (3D) electrode
assembly based on a plastic 3D block.