Fabrication of flexible copper-based electronics with high-resolution and high-conductivity on paper via inkjet printing

Flexible and printable electronics are attractive techniques which have potential for broad applications not only in flexible but also in large area electronics. An effective and convenient method of fabricating high-resolution copper patterns with high conductivity and strong adhesion on flexible photopaper is demonstrated in this paper. Functional photopaper was prepared with inkjet printing of a palladium salt solution onto its surface, followed by electroless deposition of copper. Parameters of the printing process, such as voltage control waveform, temperature of printhead and substrate, meniscus vacuum level, printing height, etc. were optimized to obtain a robust and high resolution printing with feature dimensions down to 50 mm. Through a unique thermal sintering process, printed copper lines showed excellent conductivity of up to 3.9 x 10(7) S m (1) (>65% of bulk copper). The developed technique was successfully applied for fabricating paper based functional flexible circuits such as RFID antennae, micro-inductive coils and complex circuit boards.