Improved fatigue resistance in transfer-printed flexible circuits embedded in polymer substrates with low melting temperatures

Flexible electronics are of great interest and importance due to their applications in a range of fields, from wearable electronics to solar cells. While resolutions of printed flexible electronics have been improving in recent years, there remain problems with mechanical fatigue and substrate cost, curtailing the use of such devices due to performance-related issues, and resulting in increased cost and waste products. Here we present a novel method for improving the fatigue resistance of printed flexible electronics by a factor of ~ 40 by sintering the electronic circuits prior to transferring them into low-cost polymer substrates with low melting temperatures, such that the circuits remain embedded in the substrates. This method is demonstrated using circuits printed using silver nanoparticulate ink with an aerosol jet printer, and could be applicable to multiple different metallic inks and polymer substrates. Importantly, this method can be used to transfer-print circuits into polymer substrates with low melting temperatures, without subjecting the polymers to the otherwise detrimentally high sintering temperatures required for ink curing.