Photosensitive polyimide enabled simple, reversible and environmentally friendly selective metallization on diverse substrates

Abstract

For breaking through the limitation of metal patterning in constructing conductive pathways of electronic devices, which is proposed to be an upgrade of traditional etching technique, a photo-reversible, transparent and soluble polyimide carrying spiropyran side chains is synthesized. The merocyanine isomers produced from the spiropyran moieties under digitalized ultraviolet irradiation bind the silver−histidine complexes in water, while the absorbed silver ions are in-situ reduced into metal silver seeds by the photo-generated radicals from histidine molecules, catalyzing copper deposition and yielding the desired copper patterns. Accordingly, the conventional time-consuming steps (like surface modification, immobilization of catalytic ions and (photo)chemical reduction) are simplified to a single one, and the environmentally unfriendly solvent and costly/toxic palladium reagent are excluded. The Cu patterns deposited on the polyimide show high resolution, electrical conductivity (1.785 × 10−6 Ω‧cm), adhesion strength (18.14 MPa) and fatigue resistance (> 2.6 million cycles of bending). Due to the absence of invasive surface treatments (e.g., surface hydrolysis and laser direct structuring), extremely low surface roughness of 7.83 nm is achieved. Besides, the developed strategy can be easily expanded to stretchable elastomer and other organic/inorganic substrates with irregular surfaces, showing promising application prospects. The solubility of the polyimide and ultraviolet/visible light triggered reversibility of the included spiropyran groups further enable repeated recycling, erasing and re-patterning.