Toward 4R Electronics: Liquid‐Metal‐Enabled Thin Film, and Field‐Effect Transistors for Sustainability and E‐Waste Reduction

ABSTRACT The rapid generation of electronic waste (e‐waste) underscores the urgent need for device technologies that are designed with circularity and sustainability in mind. Conventional field‐effect transistors (FETs), dominated by rigid silicon and oxide semiconductors, have fueled decades of technological progress but remain inherently brittle, inflexible, and difficult to recycle. These limitations hinder their integration into emerging fields such as soft robotics, wearable systems, and bioelectronics, while contributing substantially to the global e‐waste burden. Gallium‐based liquid metals (LMs) have recently emerged as transformative building blocks for next‐generation FETs, combining metallic conductivity, fluidic deformability, room‐temperature processability, and recyclability. Their multifunctional nature enables their deployment as electrodes, interconnects, dielectrics, and even semiconducting components, while their fluidity imparts self‐healing, reconfigurable, and repairable features. This review examines the transition from solid‐state to LM‐enabled FETs, emphasizing strategies in structural engineering, intrinsically stretchable materials, and LM‐based composites that merge electronic performance with mechanical adaptability. Special focus is placed on the 4R framework—resilient operation, repairability, recyclability, and renewable design principles—as pathways to advance sustainable transistor technologies and mitigate e‐waste. By uniting high performance with adaptability and closed‐loop reusability, LM‐enabled transistors represent a paradigm shift toward 4R electronics for a sustainable future.