In Situ Copper Electroplating Turns Material Extrusion 3D Printers Into Metal–Polymer Hybrid Fabricators

ABSTRACT Material Extrusion (MEX) has emerged as a promising method for fabricating electrically conductive polymers (ECPs), enabling the integration of sensors, actuators, and conductive tracks directly into polymeric structures. However, the limited electrical performance of ECPs restricts their functionality in real‐world applications. This study presents an innovative in situ electroplating technique that allows copper deposition directly inside the 3D printer during the additive manufacturing process. This approach contrasts with state‐of‐the‐art techniques, where electroplating is performed externally and thus cannot achieve full integration. The proposed framework combines three core elements: i) a compact electroplating head integrated into a modified printer, ii) g‐code modification powered by Machine Learning (ML) algorithms to achieve plating selectivity and synchronization, and iii) a stop‐and‐go strategy that pauses printing for copper plating before encapsulation This process yields a 4 order of magnitude increase in conductivity, approaching behaviors typical of bulk copper. Functional prototypes, including an inductive proximity sensor, a strain gauge with an integrated Wheatstone bridge, an underwater circuit, and a multifunctional electronic die, demonstrate the method's effectiveness, flexibility, and robustness. This in situ electroplating process enables unprecedented metal–polymer integration, offering a new pathway for manufacturing fully embedded, copper‐integrated components and advancing MEX toward the fabrication of assembly‐free electronic architectures.