Snapping beams enable rapid geometric transitions through nonlinear instability, offering an efficient means of generating motion in soft robotic systems. In this study, a tendon-driven mechanism consisting of spiral-based metabeams was developed to exploit this principle for producing both reciprocating and non-reciprocating motion. The snapping structures were fabricated using fused deposition modeling with polylactic acid (PLA) and experimentally tested under different boundary conditions to analyze their nonlinear behavior. The results show that the mechanical characteristics, including critical forces and stability, can be tuned solely by adjusting the boundary constraints. The spiral geometry allows large reversible deformation even when made from a relatively stiff material such as PLA, providing a straightforward design concept for controllable snapping behavior. The developed mechanism was further integrated into a swimming robot, where tendon-driven fins exhibited two distinct actuation modes: reciprocating and non-reciprocating motion. The latter enabled efficient propulsion, producing a forward displacement of about 32 mm per 0.4 s cycle ($\approx$ 81 mm/s, equivalent to 0.4 body lengths per second). This study highlights the potential of geometry-driven snapping structures for efficient and programmable actuation in soft robotic systems.

翻译：弹跳梁通过非线性失稳实现快速几何构型转变，为软体机器人系统提供了一种高效的运动生成方式。本研究开发了一种基于螺旋结构超梁的肌腱驱动机构，利用该原理同时产生往复与非往复运动。采用聚乳酸（PLA）材料通过熔融沉积成型技术制备弹跳结构，并在不同边界条件下进行实验测试以分析其非线性行为。结果表明，仅通过调整边界约束即可调控临界力与稳定性等力学特性。螺旋几何设计使得即使采用PLA这类相对刚性的材料仍能实现大范围可逆变形，为可控弹跳行为提供了简洁的设计方案。该机构进一步集成于游泳机器人中，其肌腱驱动鳍展现出两种截然不同的驱动模式：往复运动与非往复运动。后者实现了高效推进，每0.4秒周期产生约32毫米的前向位移（$\approx$ 81毫米/秒，相当于每秒0.4倍体长）。本研究凸显了几何驱动弹跳结构在软体机器人系统中实现高效可编程驱动的潜力。