Micro Triaxial Force Plate Supported by Tilted UV-Curable PDMS Pillars with Isotropic Spring Constants via Liquid-Immersion Inclined Exposure

This paper reports on a micro triaxial force plate designed to measure ground reaction force (GRF) of small insects. The force plate is supported by a 45° tilted UV-PDMS spring structure fabricated using a liquid-immersion inclined exposure (LIE) method. By reducing the in-plane to out-of-plane spring constant ratio from 8.6 to 1.6, compared to a simple vertical pillar array, the tilted spring structure (diameter: 0.5 mm, height: 1mm) achieves near-isotropic spring constants. To measure the applied forces from the plate displacements, a measurement system incorporating tilted springs and a prism was developed using the sampling moiré (SM) method. As a demonstration, the developed force plate was used to measure GRF during ant walking.