Fiber-tip magnetic field probe with spring-type microcantilever

An optical fiber probe based on micro-nanoscale structured film has been verified theoretically and experimentally, enriching the variety of optical fiber magnetic field sensors through a “Lab on Fiber” technology. The micro-nanoscale structure of single-spring-type microcantilever (SSC) is designed and fabricated by femtosecond laser direct writing (FLDW), which solves the hysteresis effect and saturation effect of traditional fiber magnetic field sensor. By modifying graphene oxide (GO) with Fe₃O₄ nanoparticles, Fe₃O₄/GO films as magnetic response units are obtained. Through the design and optimization of micro-nano film structure, the magnetic field sensitivity of the prepared SSC is increased by 10.24 times to 189.39 pm/mT, with a fast response time of 217 ms. Compared with the magnetic field sensors reported so far, the proposed probe has broad application prospects due to its advantages of miniaturization (30 μm × 62.5 μm, length × radius), high stability (σ=±0.02732 nm), and low temperature crosstalk (0.13 mT/°C). Furthermore, the proposed scheme is universal and not limited to magnetic field measurement. With the rapid development of advanced smart materials, the scheme will be suitable for the preparation of fiber tip microsensors and micro-actuators with various stimulus response characteristics (light, heat, electric, magnetic, gas, liquid).