Pneumatically Actuated Morphing Manipulator Employing Shape Memory Polymer-based External Auxetic Structure

Soft manipulators feature compliant components, allowing them to conform to external objects during interaction. However, lifting external objects with these manipulators is challenging, as maintaining high load capacity using inherently soft components is difficult. To address this issue, we introduce a pneumatically actuated morphing manipulator that incorporates a shape memory polymer-based external auxetic structure with a silicone insert that elongates when inflated. This design enables adaptive modulation of structural stiffness based on system temperature, allowing for increased load-carrying capacity on demand. Additionally, the auxetic structure, with its negative Poisson's ratio, ensures the manipulator can conform to complex target shapes. We introduce three distinct sets of auxetic unit cell designs. By aggregating these unit cells differently, we produce four variations of the external structure, each modifying the elongation of the inflatable insert to facilitate morphing behavior. The effects of different unit cell arrangements on the manipulator’s structural stiffness, load-carrying performance, and attainable morphing motions were experimentally characterized through preliminary tensile, compression, and conformability tests. The initial results demonstrate that the novel integration of auxetic design and SMP material offers a promising approach to addressing the tradeoff between conformability and load-carrying performance in existing soft manipulators, enabling the development of the next generation of adaptive and resilient morphing manipulator designs.