Highly Sensitive Fiber-Optic Fabry-Perot Microforce Probe

In this paper, we report fabrication of highly sensitive nano- and micro-force probes on the end facet of optical fibers using two-photon-polymerization (TPP) 3D printing technique. These probes are tailored to accurately detect forces at the nano- and micro-Newton scales. The architecture of these sensors incorporates Fabry-Perot (F-P) interferometric elements combined with elastic supporting brackets that compress under minimal forces. Our results indicated a sensitivity of 0.185 nm/μN for the probes, with a measurement capability extending beyond 100 μN. We also performed numerical simulations using the finite element method to verify the deformation of F-P cavities due to applied forces. As a proof-of-principle demonstration, we used the microforce probe to measure the Young's modulus of a copper wire. This novel microforce sensor is designed for the precise measurement of contact forces, aiding in the evaluation of mechanical properties in biological samples and flexible materials. Advantages of the developed sensor include its high sensitivity, compact size, ease of integration with micro-electromechanical systems, considerable deflection capacity for contour analysis, straightforward operational principle, and broad dynamic range. We anticipate that this new sensing approach will prove extremely valuable in precision biomedical and materials science research.