Dielectric elastomer strain sensors with enhanced measuring sensitivity

With the known dielectric elastomer strain sensors, large elongations over long distances with strains up to more than 100 % can be measured with high accuracy, but the sensitivity is limited, when extremely small strains below 1 % have to be monitored. To enhance the accuracy of the strain sensor, an advanced sensor design for low strain measurements was developed. The new sensor consists of two zones, which are connected in series along the sensor length. The active short zone is a stretchable dielectric elastomer strain sensor strip, whereas the passive long zone exhibits non-stretchable, but flexible polymer films. When the whole sensor is stretched, the strain is concentrated only in the stretchable shorter zone. Such sensors with enhanced measuring sensitivity were manufactured with silicone elastomer and investigated with a self-constructed electro-mechanical stretch testing device. The results of the measurements of capacitance, electrode resistance and stretch force vs. elongation were compared with those of corresponding conventional dielectric elastomer strain sensors. Furthermore, the dependence of the capacitance on the strain was calculated with finite element method (FEM) simulations for both sensor types. The advanced sensor design, the results of the experimental characterization and the comparison with the simulation are described in the paper.