Flow measurement and thrust estimation of a vibrating ionic polymer metal composite

Abstract

Ionic polymer metal composites (IPMCs) are an emerging class of soft active materials that are finding growing application as underwater propulsors for miniature biomimetic swimmers. Understanding the hydrodynamics generated by an IPMC vibrating under water is central to the design of such biomimetic swimmers. In this paper, we propose the use of time-resolved particle image velocimetry to detail the fluid kinematics and kinetics in the vicinity of an IPMC vibrating along its fundamental structural mode. The reconstructed pressure field is ultimately used to estimate the thrust produced by the IPMC. The vibration frequency is systematically varied to elucidate the role of the Reynolds number on the flow physics and the thrust production. Experimental results indicate the formation and shedding of vortical structures from the IPMC tip during its vibration. Vorticity shedding is sustained by the pressure gradients along each side of the IPMC, which are most severe in the vicinity of the tip. The mean thrust is found to robustly increase with the Reynolds number, closely following a power law that has been derived from direct three-dimensional numerical simulations. A reduced order distributed model is proposed to describe IPMC underwater vibration and estimate thrust production, offering insight into the physics of underwater propulsion and aiding in the design of IPMC-based propulsors.

Design and characterization of a miniature free-swimming robotic fish based on multi-material 3D printing

“…(3), as C T SBT ¼ pd f max =4L t , tends to overestimate the thrust coefficient, in agreement with previous observations (Aureli et al 2010;Chen et al 2010). Our results are in good agreement with similar experimental studies on vibrating thin films (Aureli et al 2010;Cen and Erturk 2013;Chae et al 2015;Eastman et al 2012;Peterson et al 2009;Prince et al 2010), shown in Fig. 7.…”

“…7. These experimental studies include ionic polymer metal composites (Aureli et al 2010;Chae et al 2015;Peterson et al 2009;Prince et al 2010), with a highly comparable Reynolds numbers, and thin piezoelectric (Cen and Erturk 2013;Eastman et al 2012) and mylar films with a larger Reynold number range.…”

An alternative explanation of back-relaxation in ionic polymer metal composites

“…Other important areas of future research should aim at including: i) steric effects associated with the cation pile-up at the ionomer-cathode interface [15,29,25,26]; ii) diffusion phenomena within the composite layers, leading to a Warburg impedance [24,33]; and iii) fluid-structure interactions during actuation, shaping the time response of the IPMC [34]. These phenomena are expected to play a significant role in the quantification of backrelaxation as a function of material composition and experimental conditions, toward feedback design to mitigate back-relaxation [35].…”

A multiple-shape memory polymer-metal composite actuator capable of programmable control, creating complex 3D motion of bending, twisting, and oscillation

“…Many actuators have been developed using electroactive polymers. In particular, robots have been developed with ionic polymer-metal composites (IPMCs) as actuators and sensors 34 35 36 37 38 39 40 . For example, Palmre et al developed a soft bio-inspired fin 41 .…”