Fiber Optic Sensor Improves Displacement Measurement in Dielectric Elastomers Actuators

Currently, developments in mechatronics have enabled the creation of compliant actuators and synthetic muscles, surpassing the constraints of inflexible actuators in assistive robotics systems. Dielectric elastomer actuators (DEAs) are comprised of an elastomer layer situated amidst two flexible electrodes, able to change dimensions under the influence of an electric voltage. While DEAs can function as autonomous sensors due to their viscoelastic behavior, accurately measuring actuator displacement continues to be an unresolved challenge. In this study, we introduce the development and assessment of a fiber-constrained dielectric elastomer actuator (FCDEA) with embedded optical fiber sensors for displacement measurement through optical potential difference. The DEAs were fabricated with VHB 4910, conductive carbon grease, and PETG as constrain fiber to restrict its displacement to the vertical direction. Silica optical fiber was integrated in the PETG strips and clamps to measure the actuator deformation upon activation. Different fabrication parameters of DEAs were investigated to obtain greater strain rates. DEAs with 90 mm x 90 mm, stretch (λ) = 3.6, and load (τ) = 120 kPa, and 90 mm x 110 mm, λ=3.6, and τ=120 kPa, presented the highest deformation capacity, with 90% and 80%, respectively. Moreover, results showed great linearity between the DEA deformation and optical potential, indicating the proposed configuration is suitable for displacement measurement.