27 March 2018 Capacitive coupling as a new form of signal transmission in underwater dielectric elastomer sensing
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Abstract
Accurately capturing human motion underwater has potential applications in diver health monitoring, human- machine interaction and performance sport coaching. Unfortunately the human body has approximately 200 bones and 600 skeletal muscles giving rise to a broad range of degrees of freedom. To effectively capture this movement with dielectric elastomer sensors a substantial network is required. One often overlooked challenge is the connection between the dielectric elastomer sensor and central electronics. On land this is as simple as wires connecting the two. Underwater however, especially when considering a network of sensors, this becomes a more complicated task.

In the proposed method parallel plate capacitors are used to transfer power across the encapsulation layer to the sensor, removing any need for protruding wires or cable glands. With one electrode placed within the encapsulation and the second connected to the sensor, sensors are replaceable even underwater. To maintain sensor performance however, a relatively high capacitance is required. For example if the coupling capacitance is 20x greater than sensor capacitance, sensitivity is reduce by approximately 20%. Whereas if the coupling capacitance is only 10x greater, sensitivity is reduced by 40%. Due to these high capacitance requirements combined with the area and weight restrictions of wearable applications, we have investigated the practicality of implementing capacitive coupling. A capacitive coupling interface has been developed and tested with dielectric elastomer sensors underwater. Analysis of the interface's impact on sensor sensitivity, measurement electronics and overall coupling capacitor size is presented.
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Christopher R. Walker, Samuel Rosset, Iain A. Anderson, "Capacitive coupling as a new form of signal transmission in underwater dielectric elastomer sensing", Proc. SPIE 10594, Electroactive Polymer Actuators and Devices (EAPAD) XX, 105941N (27 March 2018); doi: 10.1117/12.2293808; https://doi.org/10.1117/12.2293808
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