A bio-inspired multi-directional HASEL actuator-driven soft robotic tail: design and characterization

As a recently invented soft actuator, hydraulically amplified self-healing electrostatic (HASEL) actuators have exhibited strong potential for employment in soft and biomimetic robots. HASEL actuators rely on the principle of hydraulics and electrostatic forces to generate motion. Many existing HASEL actuator-driven robots only exhibit one degree-of-freedom (DoF) motion. The few existing designs that generate multi-DoF motion are often bulky and use multiple stacks of HASEL pouches. In this paper, a bio-inspired robotic tail powered by HASEL actuators is presented. The tail is a popular structure considered for bioinspiration, due to its ability to exhibit fluidic multi-DOF motion while being compliant. While HASEL actuators-driven tails have been developed in the past, very few of them exhibit multi-DOF complex motion, which is a critical aspect of a tail. The proposed robotic tail utilized compact multi-directional HASEL actuators that used two inputs to achieve motion in three-dimensional space. The transient and steady state voltage–deflection angle correlations of the rightward, leftward, and upward curls of the robotic tail under different loading conditions were experimentally characterized. Furthermore, a lifecycle test was conducted at multiple inputs. Satisfactory performance was obtained. For example, the robotic tail could generate 169.8◦ side-ward deflection and 262.7◦ upward deflection when no loads were applied.