Towards shape-adaptive attachment design for wearable devices using granular jamming

Attaching a wearable device to the user's body for comfort and function while accommodating the differences and changes in body shapes often represents a challenge. In this paper, we propose an approach that addresses this problem through granular jamming, where a granule-filled membrane stiffens by rapidly decreasing the internal air pressure (e.g., vacuum), causing the granule material to be jammed together due to friction. This structure was used to conform to complex shapes of the human body when it is in the soft state while switching to the rigid state for proper robot functions by jamming the granules via vacuum. We performed an experiment to systematically investigate the effect of multiple design parameters on the ability of such jamming-based interfaces to hold against a lateral force. Specifically, we developed a bench prototype where modular granular-jamming structures are attached to objects of different sizes and shapes via a downward suspension force. Our data showed that the use of jamming is necessary to increase the overall structure stability by 1.73 to 2.16 N. Furthermore, using three modules, high suspension force, and a low membrane infill (~25%) also contribute to high resistance to lateral force. Our results lay a foundation for future implementation of wearable attachments using granular-jamming structures.