Ionic polymer-metal composites (IPMCs) have inherent sensing properties, one application of which is flow sensing. However, the transduction physics and mechanics of IPMC pose challenges in deciphering the sensor output for DC flows. In this work we propose a novel IPMC flow sensor that exploits self-generated von Kármán vortices to produce vibration of the sensor, the frequency and amplitude of which are correlated with the stream flow. The sensor consists of a 3D-printed soft cylindrical sheath housing an IPMC beam, and one end of the sheath takes the shape of a sphere. In the sensing configuration, the sheath is placed parallel to the stream flow direction, with the sphere end fixed. Experiments are conducted in a flow channel to measure the IPMC sensor output and free-end displacement of the sheath under different flow speeds. The results indicate that the proposed sensor structure can produce significant oscillatory signals for effectively decoding the flow speed.
The lateral line system is the flow-sensing organ of fishes, which consists of arrays of flow sensors, known as neuromasts, with hair cells embedded inside a gel-like structure called cupula. There are two types of neuromasts: the superficial ones, which extend from the skin and respond directly to the local velocity, and the canal ones, which are located in recessed canals under the skin and tend to respond to the flow pressure gradient. Inspired by the canal system of fish lateral lines, we propose a pressure gradient sensor integrating an ionic-polymer metal composite (IPMC) sensor with a 3D-printed canal filled with a viscous fluid. Unlike the biological counterpart that has open ends on the surface of the body, the proposed canal has two pores that are covered with a latex membrane, which prevents the canal fluid from mixing with the ambient fluid. Experimental results involving a dipole source show that the proposed sensor is able to capture the pressure difference across the two pores, and the viscosity of the canal fluid has a pronounced effect on the sensitivity of the device. Preliminary finite-element simulation results are also presented to provide insight into the experimental observations.
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.