Ionic polymer-metal composites (IPMCs) have inherent underwater sensing and actuation properties. They can be used as sensors to collect ﬂow information. Inspired by the hair-cell mediated receptor in the lateral line system of ﬁsh, the impact of a ﬂexible, cupula-like structure on the performance of IPMC ﬂow sensors is experimentally explored. The fabrication method to create a silicone-capped IPMC sensor is reported. Experiments are conducted to compare the sensing performance of the IPMC ﬂow sensor before and after the PDMS coating under the periodic ﬂow stimulus generated by a dipole source in still water and the laminar ﬂow stimulus generated in a ﬂow tank. Experimental results show that the performance of IPMC ﬂow sensors is signiﬁcantly improved under the stimulus of both periodic ﬂow and laminar ﬂow by the proposed silicone-capping.
Ionic polymer-metal composites (IPMCs) have intrinsic sensing and actuation properties. An IPMC sensor typically has the beam shape and responds to bending deﬂections only. Recently tubular IPMCs have been proposed for omnidirectional sensing of bending stimuli. In this paper we report, to our best knowledge, the ﬁrst study on torsion sensing with tubular IPMCs. In particular, a dynamic, physics-based model is presented for a tubular IPMC sensor under pure torsional stimulus. With the symmetric tubular structure and the pure torsion condition, the stress distribution inside the polymer only varies along the radial direction, resulting in a one-dimensional model. The dynamic model is derived by analytically solving the governing partial diﬀerential equation, accommodating the assumed boundary condition that the charge density is proportional to the mechanically induced stress. Experiments are further conducted to estimate the physical parameters of the proposed model.