The Observation of Interface Effects Presented on Micrometer-Scale Sphere Tips of Fiber Bragg Grating-Based Probes

The interface effects between microstructural bodies become more and more important as micromechanical and microfluidic devices enter sub-micrometer scale. Scanning probe microscopes like atomic force microscopy are the most significant tools for detecting the interface forces, where the dimension of the cantilever tips is on nanometer scale. In this work, we present a fiber-Bragg-grating-based interface force measurement method for micrometer-sized probe tips and detailed measurements conducted with various sample surfaces, tip radius, and medium environments. The experimental and numerical results unambiguously reveal that probes with micrometer-sized tips are more easily influenced by interface interaction, and forces show varying magnitudes, action ranges, and prioritized contributions, compared with nano-sized probe tips. In addition, the interface force measurement approach could help find the contact zero point when the probe approaches and contacts the measured surface and understand surface characteristics of materials as well. This work could lead to many potential applications of the interface interaction in micro- and nanotechnology using micrometer-scale probe tips.