Soft Pneumatic Actuator with Adjustable Stiffness Layers for Multi-DoF Actuation

The soft pneumatic actuators (SPAs) are a solution toward the highly customizable and light actuators with the versatility of actuation modes, and an inherent compliance. Such flexibility allows SPAs to be considered as alternative actuators for wearable rehabilitative devices and search and rescue robots. In applications that require a high compliance for safety and a fluid interactivity, the SPAs’ material-based softness returns an inherent back-drivability. One of the main challenges that limits the wide application of SPAs is in the complexity of miniaturizing the actuators and embedding additional degree of freedoms (DoFs) in a single actuator. We present a novel design and fabrication method of a SPA with different modes of actuation using adjustable stiffness layers (ASLs). Unlike conventional SPA designs where one independent chamber is needed for each mode of actuation, here we have a single chamber that drives three different modes of actuation by activating different combinations of ASLs. By using customized micro heaters and thermistors for controlling the temperature and stiffness of ASLs in increments, we considerably broaden the work space of the SPA actuator. Here, a thorough characterization of the materials and the modeling of the actuator are presented. In the conclusion, we propose a design methodology for developing application specific actuators with multi-DoFs that are light and compact.