Experimental measurement of base tilting effects in magnetically actuated FeC-PDMS micropillar structures

Abstract

Polymer micropillar structures have been used as microsensors and microactuators in scientific studies. In these studies, the deformation of the micropillar is used to estimate the forces applied on the micropillars from the external environment, or the forces generated by the micropillars. The accuracy of such force calculations depends on the accurate estimation of the structure’s spring constant which requires a correct understanding of micropillar deformation under loading. For a micropillar sitting on top of a flexible polymer base, base deformation, or tilting, is a major contributor to the total pillar deformation and the total spring stiffness of the structure. In this work, we visualize and quantify the base tilting effects for magnetic FeC-PDMS micropillar structures. We compare and verify our experimental observations against those predicted by an analytical model developed accounting for the base tilting effects. In our experiments, for pillars with smaller aspect ratios of L/D ≈ 3, pillar bending and base tilting account for 87% and 13% of the total angular deformation, whereas for pillars with larger aspect ratios of L/D ≈ 7, pillar bending and base tilting account for 94% and 6% of the total angular deformation, respectively. As predicted by analytical models, the contribution of the base tilting effect, largely ignored in many studies, becomes more significant for micropillars with smaller aspect ratios.