Mechanics, modeling, and shape optimization of electrostatic zipper actuators

Generating actuation for haptic feedback is a major challenge for wearable devices and soft robotics. Current methods such as piezoelectric, pneumatic, or responsive material actuators are limited by the response time, power consumption, and their reliance on external mechanisms such as pumps or large voltage amplifiers. The emerging technology of electrostatic zipper actuators, where a dielectric-filled pouch is sandwiched between flexible conducting electrodes, is a promising alternative. However, the voltage required to actuate such systems remains in the relatively large kilovolt range. Additionally, there do not currently exist efficient modeling methods to explore more effective designs. Our work looks to address both of these issues. We start by discussing the mechanics of the zipping phenomenon which leads to actuation. Then, we formulate a novel mechanics model for these systems. By considering an elastic plate coupled with the electrostatic interactions, we develop an efficient and robust numerical method to simulate the actuation process. We then verify the model by demonstrating excellent agreement to analytical predictions for simplified cases. As the complex physics of such systems create challenges for intuitive design, we turn to optimal design methods. We formulate the shape optimization problem through the method of mappings to design actuators for maximum actuation pressure and work of actuation. Our method navigates the trade-offs between zipping susceptibility and volume displacement, and we explore optimal designs for various geometric and loading scenarios. Finally, we discuss further directions and open problems relevant to the industrial deployment of zipper actuators moving forward.