Sustainable Liquid Metal Composites for Soft Electronics and E-Waste Reduction.

There has been tremendous progress in soft printable electronics with liquid metal (LM) for creating elastic, stretchable, and thin-film circuitry. However, such innovation risks outpacing sustainability. As the world moves toward softer, thinner, and more integrated electronics, these advancements may accelerate the exponential rise of electronic waste-projected to surpass 74 million tons by 2030 and reach ≈120 million tons by 2050. Therefore, in developing LM-based electronics, it is critical to address the urgent need for eco-friendly recycling strategies. This review proposes a paradigm shift toward recyclable, repairable, renewable, and resilient ("4R") soft electronics enabled by LM composites. Gallium-based alloys and their eutectics, such as Galinstan and EGaIn, offer a rare convergence of high conductivity, fluidic deformability, and recyclability-ideally suited for stretchable circuits, soft robotics, and wearables. Yet, their promise remains incomplete without scalable, eco-friendly recovery methods. Advanced extraction and recycling approaches are examined, including mechanical-chemical and physicochemical methods using deep eutectic solvents (DESs) and ionic liquids for selective recovery with minimal environmental impact. Emphasis is placed on materials selection, substrate compatibility, and integration strategies that enable circular lifecycles. LM composites offer a path to redefine electronics-not only for performance but also for durability, self-healing, and sustainability.