Mechanically robust and highly conductive laser-induced graphene-metal heterojunction for high-performance flexible sensors

Three-dimensional (3D) graphene has attracted considerable attention as a functional material due to its high electrical conductivity, mechanical compliance, and large surface area. However, the integration of 3D graphene with conventional electronic components remains challenging because reliable and miniaturizable interconnection strategies are still limited. In particular, the mismatch between porous graphene structures and planar metal electrodes often leads to poor electrical contact and mechanical instability, restricting the practical use of graphene-based devices in integrated systems. In this work, we introduce a localized interconnection strategy that enables robust electrical coupling between 3D graphene and metal electrodes. The approach utilizes a reservoir-structured electrode geometry that confines a small amount of silver nanoparticle (Ag-NP) ink within a defined region. Under a controlled thermal environment, solvent evaporation is selectively accelerated, allowing conductive Ag networks to form while minimizing lateral spreading. As a result, micrometer-scale interconnections can be achieved with improved electrical contact and structural stability. Electrical characterization shows low contact resistance and stable impedance behavior, while mechanical tests confirm reliable operation under repeated bending conditions. The proposed interconnection scheme was further demonstrated in integrated wearable devices, including multimodal motion sensors and electrochemical biosensors, highlighting its potential for practical implementations in applications such as human-robot interaction and point-of-care diagnostics.