Universal Toner-Masked Transfer Patterning of Liquid Metal Composite Electrodes for Stretchable, Recyclable, and Epidermal Electronics.

Liquid metals (LMs) are promising candidates for stretchable and wearable electronics due to their unique combination of metallic conductivity and intrinsic deformability. However, existing patterning methods for LMs, whether mask-free or mask-based, suffer from inherent trade-offs among process simplicity, activation-free conductivity, scalability, and substrate universality. To address these limitations, we report a toner-masked transfer patterning strategy that enables the facile fabrication of high-performance LM composite microelectrodes on diverse substrates. This laser-printer-compatible approach integrates activation-free patterning and spontaneous mask removal into a single lamination step, eliminating complex masking procedures while preserving scalability and compatibility with diverse substrates, including plastics, elastomers, paper, and even human skin. By engineering strength gradients via cellulose filters, optimizing LM formulation, and controlling thermal conditions, the resulting electrodes offer tunable sensitivity, excellent stretchability, and long-term cycling stability, achieving a minimum linewidth of 30 μm and ethanol-triggered recyclability. As proof-of-concept wearable devices, these electrodes enable high-sensitivity strain sensing and high-fidelity electrocardiogram monitoring, with lower skin impedance than commercial gel electrodes. This work provides a scalable, eco-friendly, recyclable patterning strategy for high-performance flexible and epidermal electronic devices.