Influence of manufacturing parameters on the quality of electrodes of a multi-layer capacitive strain sensor based on dielectric elastomers

Since the significant growth of interest in soft robotics, artificial muscles and biomimetics, soft, capacitive dielectric elastomer sensors (DES) have been in the focus of development. However, when including a sensor into any device, tool or, for example, a machine element, there are several factors which have to be considered, e.g., the ease of embedding the sensor, the maintenance of the functionality of the machine element, as well as the quality of the embedded sensors and their reproducibility. In this work, we will focus on the quality of the sensor and present a procedure for manufacturing multi-layer capacitive strain sensors. In order to assess the influence of different manufacturing processes on the quality of capacitive DES, a variety of thin multi-layer sensors were fabricated. Furthermore, using an LCR meter, the equivalent electrical capacitances (C) at the two sensor contacts were measured. It is shown that C varies depending on the quality of the electrodes. By testing multi-layer DES (ML-DES) with an electrode diameter of delectrode = 3 mm, with three and four electrode layers, a maximum capacitance of C0 = 6.7 pF and C0 = 10.5 pF was achieved for the undeformed sensor, respectively. The obtained capacitance values show that following the presented recommendations for creation the electrodes enables to improve the reproducibility and quality of the manufactured ML-DES. The fabricated sensor is soft and deformable due to the compliance of the elastomeric film used. Such a capacitive ML-DES can be used, for example, as a soft strain sensor implemented into the elastic element of a jaw coupling.