Integrated All-Graphene Flexible Strain Sensors via Programmable Laser-Induced Conductivity Optimization for Wearable Motion Monitoring

Abstract

Flexible strain sensors are essential components in wearable electronics and soft robotic systems, yet their reliability is often compromised by the mechanical mismatch and interfacial instability inherent in heterogeneous material integration. Herein, we present an integrated all-laser-induced graphene (all-LIG) flexible strain sensor fabricated via a processing-induced electrical contrast strategy. By spatially selective tuning of laser power and focal position, we achieved orders-of-magnitude differences in electrical resistance within a single LIG material system, creating both a high-resistance sensing line and low-resistance integrated electrodes without incorporating foreign conductive materials. Through systematic optimization of the laser processing and transfer parameters, the sensor exhibits a low detection limit of 0.2%, a fast response time of ∼89.7 ms, a wide working range up to 40.0% strain, and a maximum gauge factor of ∼5.3. Furthermore, the device demonstrates excellent frequency-independent stability, robust durability over 1900 loading–unloading cycles, and remarkable resistance to mechanical damage and water exposure. Owing to the integrated all-graphene architecture and customizable structural design, the sensors enable reliable and conformal motion monitoring across various human joints and deformable surfaces while minimizing redundant interconnects and material interfaces. This work establishes a material-unified and digitally tunable platform for high-reliability flexible strain sensing, offering a scalable and generalizable strategy for next-generation wearable motion monitoring, health-care devices, and human-machine interfaces.