Elastic metallic conductors enabling stretchable electronic circuits for on-skin motion recognition

• Solution-processed high-performance elastic conductors based on hybrid indium-tin alloys. • High conductivity of 2.98 × 10 6 S/m with minimal resistance alteration over 1000 % strain. • Enabling stretchable multilayer printable circuit board for various soft electronic applications. • Integration with machine-learning for on-skin motion recognition in 3D free space. Soft sensing applications typically incorporate stretchable sensors tied to rigid processing circuits, leading to challenges including compromised conformability and large noise induced during coupling with external circuits. Here, we developed an innovative strategy to synthesize high-performance elastic metallic conductors, which serve to enable stretchable multilayer printable circuit boards (SMPCBs). The SMPCBs can seamlessly incorporates soft sensors, electronic components, and processing circuits, facilitating the applications of stretchable integrated electronic systems, including a soft RFID temperature sensing device, a soft wireless-powered pressure sensing circuit, and an on-skin motion-recognition device in this study. Furthermore, we developed a Dual-Tower Transformer Network model to accurately identify hand motions in 3D free space, which can recognize over 30 distinct motions with an accuracy exceeding 90%.