Controllable and Flexible 4D Fabrication Strategy for Expandable Micro-Sensor Elements on the Fiber

In the realm of high-precision integrated applications involving optical fiber sensor components and materials, conventional macro-processes such as fiber coating and tip dispensing lack precise control and flexibility. In this paper, a two-photon polymerization technique was employed to fabricate a microscopic F-P framework and a peripheral fence on the tip of a single-mode fiber. Subsequently, precision dispensing methods were utilized to introduce hydrogel into the fence. A concept of the "sensitization-fence"is introduced to enhance sensitivity. Finite element simulations revealed that as the height of the fence increased, the displacement of the F-P sensing cavity also increased, indicating heightened sensitivity. In the subsequent experimental exploration, acrylic acid hydrogels, PDMS, and polyvinyl alcohol were successively filled into the fence, and ideal experimental results were obtained. This proof of the sensitizing concept provides a new application idea for improving the function of micro-devices on the fiber.