When a dielectric elastomer is subject to an electric field, positive and negative charges appear on the surface and attract each other, which leads the dielectric elastomer to reduce its thickness and expand in area. Figure 1 illustrates a spherical dielectric elastomer balloon sandwiched by compliant electrodes. An air mass is pumped into the balloon resulting in an initial pressure. Thereafter, the amount of the air is kept constant by sealing the balloon, followed by applying a voltage across the balloon wall. Driven by the high-pressure air inside and the applied voltage, the balloon undergoes homogeneous deformations.
Fig. 1. A dielectric elastomer balloon actuator in the reference state and a current state (left); actuation range of the balloon actuator, denoted by AB (right).
The deformation of a dielectric elastomer is restricted by the material failures, such as loss of tension (LT) and electric breakdown (EB). Therefore, the balloon actuator receives a limited actuation range, as implied by AB in Fig. 1. With reference to Fig. 2, the experimental result agrees well with the theoretical predication. It’s noted that LT dominates among the material failures because the internal pressure that provides prestretch drops quickly with the expansion of the balloon. We have also done dynamics analyses of the balloon actuator, which may provide insight into the dynamics applications of soft actuators. Interested readers are referred to our publications listed below.
Fig. 2. Experimental results of a dielectric elastomer balloon actuator
To further expand the actuation range, we developed the network of dielectric elastomer balloon actuators, as shown in Fig. 3, where two balloon actuators are interconnected and independently controlled by two input voltages. Figure 4 demonstrates how the deformations of the networked balloons vary with the applied voltages, leading to the conclusion that the network can remarkably expand the actuation space. The experimental validation is in process and we expect to further release the actuation space by incorporating more interconnected balloon actuators. In the long term, our goal is to develop distributed and interconnected balloon actuators to interact with soft bodies, capable of generating complex motions.
Fig. 3. Two networked dielectric elastomer balloon actuators in the reference state (left) and a current state (right).
Fig. 4. (a)(b) The applied voltages functions as the deformations of the two balloons; (c) the prestretched state denoted by point S; (d) the phase of deformations of balloon A and balloon B with the realizable actuation space highlighted by the narrow blue area.
1. Chen, F., & Wang, M. Y. (2015). Dynamic performance of a dielectric elastomer balloon actuator. Meccanica, 50(11), 2731-2739.
2. Chen, F., Zhu, J., & Wang, M. Y. (2015). Dynamic electromechanical instability of a dielectric elastomer balloon. EPL (Europhysics Letters), 112(4), 47003.
3. Chen, F., & Wang, M. Y. (2016). Simulation of Networked Dielectric Elastomer Balloon Actuators. IEEE Robotics and Automation Letters, 1(1), 221-226.