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This paper presents a low-power Ultra Low Frequency (ULF) transmitter design that uses a static, permanent magnet to bring the surrounding magnetic shield near saturation. A low-power control coil modulates this static magnetic field by toggling sections of the shield between saturated and unsaturated states. The transmitter, operating at 400 Hz and tested using a 3D magnetometer, demonstrated an increase of 22.3 dB along the pole at 800 Hz and a 17.7 dB increase at 400 Hz perpendicular to the pole, with a further 33 dB enhancement than the control coil’s leakage at 800 Hz. These results highlight a novel method for efficient magnetic field modulation with significantly lower power requirements than traditional approaches. This novel approach reduces power consumption and opens new possibilities for designing scalable, energy-efficient ULF communication systems, with potential applications in underwater communication, remote sensing, and long-range wireless networks. 

Abstract With the recent development of wearable electronics and smart textiles, flexible sensor technology is gaining increasing attention. Compared to flexible film‐based sensors, multimaterial fiber‐based technology offers unique advantages due to the breathability, durability, wear resistance, and stretchability in fabric structures. Despite the significant progress made in the fabrication and application of fiber‐based sensors, none of the existing fiber technologies allow for fully distributed pressure or temperature sensing. Herein, the design and fabrication of thermally drawn multi‐material fibers that offer distributed temperature and pressure measurement capability is reported. Thermoplastic materials, thermoplastic elastomers, and metal electrodes are successfully co‐drawn in one fiber. The embedded electrodes inside the fibers form a parallel wire transmission line, and the local characteristic impedance is designed to change with the temperature or pressure. The electrical frequency domain reflectometry is used to interrogate the impedance change along the fiber and provides information with high spatial resolution. The two types of fibers reported in this manuscript have a pressure sensitivity of 4 kPa and a temperature sensitivity of 2 °C, respectively. This work can pave the road for development of functional fibers and textiles for pressure and temperature mapping.