A Dual-Adhesion-Enhanced Soft Gripper With Microwedge Adhesives and SMA-Driven Microspines

Soft grippers are highly valued for their adaptability and safety, but their inherent softness often leads to grasping failure under heavy loads. Most adhesion-enhanced grippers rely on single-adhesion strategies tailored for either smooth or rough surfaces. Lizards, however, effectively navigate in unstructured environments by seamlessly transitioning between different adhesion mechanisms based on surface conditions. Inspired by the hybrid adhesion strategies of geckos and chameleons, this study presents a bioinspired soft gripper that integrates microwedge dry adhesives and SMA-driven microspines. The microwedge adhesives provide controllable adhesion for smooth surfaces, while the SMA-driven microspines extend for rough-surface adhesion and retract to avoid interference. An optimization model was developed to determine optimal link dimensions, enhancing grasping performance in terms of force and radius. Experimental results on various surfaces validated its efficacy. Notably, the gripper with non-backed adhesives achieved 34.9 N payload and 260 mm grasping diameter, marking improvements of 209% and 117%, respectively, over the version without adhesives. In microspine mode, the gripper supported a 20.4 N payload and a 280 mm diameter. In tip clamping mode, the maximum payload reached 6.2 N when grasping a 2 cm block.