Additive Manufacturing of Sandwich-Structured Conductors for Applications in Flexible and Stretchable Electronics

Additive manufacturing methods have shown great potentials to substitute the costly and time-consuming conventional subtractive methods in the processing of electronically conductive materials for applications in flexible and stretchable electronics. Herein, additive manufacturing of highly conductive, sandwich-structured conductors with high-temperature processibility and versatility in applicable substrates is reported. The sandwich-structured conductors with silver nanoparticles (Ag NPs) as electronic conductors and polyimide (PI) as encapsulation are layer-by-layer deposited by aerosol printing into PI/Ag/PI composites. A high annealing temperature of 250 degrees C contributes to the high electronic conductivity of the Ag layer at 1.14 x 10(7) S m(-1), which is in the same order of magnitude to the conductivity of bulk Ag at 6.3 x 10(7) S m(-1). The high annealing temperature also significantly improves the interfacial bonding between the Ag and PI layers. For applications in flexible and stretchable electronics, the sandwich-structured conductors are transferrable to various substrates through a thiol-epoxy bonding process, including polystyrene (PS), polyethylene terephthalate (PET), Kapton, and polydimethylsiloxane (PDMS) thin films. The sandwich-structured conductors transferred to flexible and stretchable substrates exhibit highly retained electronic conductivity under deformations such as bending and stretching.