A Dynamic Wall Shear Stress Sensor Based on Ionic Polymers

Abstract

This paper presents the first implementation of a novel class of dynamic time-resolved direct skin friction measurements sensor based on active ionic polymer transducers. These ionic polymer sensors have the advantage that they contain no moving parts, perform a direct measurement of shear, and can be mounted directly to the surface of an existing vessel with no modification. During the present effort we characterize the accuracy of the sensors and validate their dynamic measurement response. Using an oscillating Stokes layer calibration procedure we demonstrate measurement accuracy in fluctuating shear on the order of 4.92% over a range of stresses of +/- 3 Pa and signal-to-noise-ratio on the order of 60 dB. The frequency response of the sensor is over 10 kHz however due to experimental limitations we were not able to calibrate for frequencies higher than 140 Hz. These sensors have been shown to be insensitive to vibration or pressure. Also, an automatic change of impedance compensation approach is proposed that allows in-situ recalibration of the sensors and accounts for environmental effects such as changes of temperature on the sensors performance. The results demonstrate the potential for using ionic polymer sensors to perform accurate, high frequency measurements of shear in turbulent boundary layers.

Ionic Liquids at Electrified Interfaces

“…630,631 As transducers, one can envisage their applications as motion detectors and high performance sensors in artificial organs. [632][633][634][635] Last but not least, engineers think about using such electroactuators for generating electricity from ocean waves, coastal surf, and river white waters. 636,637 The largest e ect on bending is when only ions of one sign can move (can be of several sorts), the other is attached to the side chains of the polymer.…”

Active Sensing Methods of Ionic Polymer Metal Composite (IPMC): Comparative Study in Frequency Domain

“….nl and S.H.HosseinNiaKani@tudelft.nl [17], [18], [19], [20], [21], [22], [23], [24], [25] to describe their sensing dynamics. The reported application studies have investigated exploiting them as translational [11], rotational [26], and omnidirectional [27] position sensors, velocity sensors [28], wall shear stress sensors [29], seismic sensors [30], vibration sensors [31], force sensors [32], flow sensors [33], humidity sensors [34], and wearable pulse and braille sensors [35]. Sensing with IPMCs can be realized by several means i.e.…”

“…Sensing with IPMCs can be realized by several means i.e. measuring voltage [36], [37], [38], [39], [40], current [37], [19], [41], [31], [25], [42], [43], charge [37], [44], [29], [45], [46], and the impedance change [47], [48].…”

Sensing and Self-Sensing Actuation Methods for Ionic Polymer–Metal Composite (IPMC): A Review

“…Nemat-Nasser and Li showed by modelling and experimental data that the amplitude of IPMC sensing voltage is two orders of magnitude smaller than the voltage that is required to produce the same deformation in actuation [68]. The relatively small voltage amplitude has been hypothesized to be due to high capacitance of the material (2–5 mF/cm2) [158]. Several authors also reported offsets in the voltage reading [93,106,127], which are hypothesized to originate from the polyelectrolyte nature of IPMC [93].…”