A Review of Soft Robots for Entangling-style Grasping: Structural Classification, Grasping Mechanisms and Key Challenges

This review synthesizes recent advances in soft robots that utilize entangling-style grasping, categorizing them into two principal domains: soft grippers designed for target entangling, and continuum robots that leverage their entire body for both entangling and manipulation. Within the first category, we examine various end-effector structures, including pneumatic network structures, high aspect ratio slender elements and arrays, stimulus responsive materials with preset configuration programming, fabric constraints and textile forming, and tendon driven structures with configuration design. The second category focuses on systems where the continuum robot body directly engages in grasping, following a conceptual development overview, these systems are classified into basic bending and enveloping, variable cross section, elongating and coiling, specialized, and functionally augmented robots. This framework elucidates that entangling-style grasping is fundamentally governed by continuous contact, geometric enveloping, entanglement-induced interlocking, and stiffness modulation. Furthermore, the review explores the modeling and control strategies integral to these continuum systems. Finally, we identify persistent challenges regarding the modeling and regulation of wrapping deformation, the quantification of wrapping, the maintenance of stiffness, and the implementation of model and sensor closed-loop control. Collectively, this synthesis provides a structured foundation for advancing the engineering applicability of soft robots for entangling-style grasping.