Flexible Poly‐ m ‐Phenylene Isophthalamide Paper‐Based Heater Fabricated via Femtosecond Laser‐Induced Graphene: Design and Electrothermal Performance

Conventional thermal therapy devices, such as chemical heat packs and electric heaters, are often inadequate for managing the rising incidence of muscle spasms, joint injuries, and arthritis due to inherent drawbacks like rigidity, slow heating, and lack of portability. To address these challenges, this study develops a novel flexible heater fabricated from laser‐induced graphene (LIG). A one‐step femtosecond laser scribing process directly converts the surface of a poly‐ m ‐phenylene isophthalamide (PMIA) paper substrate into a conductive LIG heating layer, followed by PDMS/VHB encapsulation for skin safety and comfort. By engineering structural patterns, we optimize thermal performance and mechanical flexibility: under low voltages (6–10 V), the heater reaches 40°C in ~3 min at 9 V and stabilizes at ~50°C–60°C; at 10 V the maximum temperature rise approaches ~50°C. A sawtooth trace yields a heating rate of ~0.34°C/s with improved temperature uniformity. The device remains stable over 30 on/off cycles (1 min on/1 min off at 9 V) and > 20,000 s continuous operation, and on‐skin tests reach 44.4°C (wrist) and 52.7°C (elbow) within ~2 min at 9 V. Considering heating rate, uniformity, energy use at low voltage, and wearing comfort, the proposed LIG‐based flexible heater offers a promising route toward personalized, wearable thermal‐therapy devices.