Recyclable Thin-Film Soft Electronics for Smart Packaging and E-Skins

Despite advances in soft, sticker-like electronics, few efforts have dealt with the challenge of electronic waste. Here, this is addressed by introducing an eco-friendly conductive ink for thin-film circuitry composed of silver flakes and a water-based polyurethane dispersion. This ink uniquely combines high electrical conductivity (1.6 × 10⁵ S m^-1 ), high resolution digital printability, robust adhesion for microchip integration, mechanical resilience, and recyclability.  Recycling is achieved with an ecologically-friendly processing method to decompose the circuits into constituent elements and recover the conductive ink with a decrease of only 2.4% in conductivity. Moreover, adding liquid metal enables stretchability of up to 200% strain, although this introduces the need for more complex recycling steps. Finally, on-skin electrophysiological monitoring biostickers along with a recyclable smart package with integrated sensors for monitoring safe storage of perishable foods are demonstrated.