Highly deformable bodies are essential for numerous types of applications in all sorts of environments. Joint-like structures comprising a ball and socket joint have many degrees of freedom that allow mobility of many biomimetic structures. Recently, soft robots are favored over rigid structures for their highly compliant material, high-deformation properties at low forces, and ability to operate in difficult environments. However, it is still challenging to fabricate complex designs that satisfy application constraints due to the combined effects of material properties, actuation method, and structural geometry on the performance of the soft robot. Therefore, a combination of a rigid joint and a soft body can help achieve modular robots with fully functional body morphology. Yet, the fabrication of soft parts requires extensive molding for complex shapes, which comprises several processes and can be time-consuming. In addition, molded connections between extremely soft materials and hard materials can be critical failing points. In this paper, we present a functionally graded 3D-printed joint-like structure actuated by novel contractile actuators. Functionally graded materials (FGMs) via 3D printing allow for extensive material property enhancement and control which warrant tunable functionalities of the system. The 3D-printed structure is made of 3 rigid ball and socket joints connected in series and actuated by integrating twisted and coiled polymer fishing line (TCP_FL) actuators, which are confined in the FGM accordion-shaped channels. The implementation of the untethered TCP_FL actuation system can be highly beneficial for deployment in environments that require low vibrations and silent actuation. The fishing line TCP actuators produce an actuation strain up to 40% and bend the joint up to 40° in any direction. The TCP_FL can be actuated individually or as a group to control the bending trajectory of the modular joint, which is beneficial when deployed in areas that contain small crevices. Obtaining complex modes of bending, the FGM multidirectional joint demonstrated a great potential to achieve different functionalities such as crawling, rolling, swimming, or underwater exploration.

中文翻译：

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由TCP FL肌肉驱动的多方向3D打印功能梯度模块化关节，适用于软机器人

高度可变形的主体对于在各种环境中的多种类型的应用都是必不可少的。包括球窝关节的关节状结构具有许多自由度，允许许多仿生结构的活动性。近来，软机器人因其高柔顺性的材料，在低力下的高变形特性以及在恶劣环境下工作的能力而受到刚性结构的青睐。但是，由于材料属性，驱动方法和结构几何形状对软机器人性能的综合影响，制造满足应用约束的复杂设计仍然具有挑战性。因此，刚性关节和软体的结合可以帮助实现具有完整功能形态的模块化机器人。然而，软零件的制造要求复杂形状的大量模制，这包括多个过程并且可能很耗时。另外，极软的材料和硬质材料之间的模制连接可能是关键的失效点。在本文中，我们介绍了一种由新型可收缩执行器驱动的功能渐变3D打印关节状结构。通过3D打印的功能分级材料（FGM）可实现广泛的材料性能增强和控制，从而保证了系统的可调功能。3D打印结构由3个刚性球窝关节串联而成，并通过集成扭曲和盘绕的聚合物钓鱼线（TCP）进行驱动 极软的材料和硬质材料之间的模制连接可能是关键的失效点。在本文中，我们介绍了一种由新型可收缩执行器驱动的功能渐变3D打印关节状结构。通过3D打印的功能分级材料（FGM）可实现广泛的材料性能增强和控制，从而保证了系统的可调功能。3D打印结构由3个刚性球窝关节串联而成，并通过集成扭曲和盘绕的聚合物钓鱼线（TCP）进行驱动 极端柔软的材料和坚硬的材料之间的模制连接可能是关键的失效点。在本文中，我们介绍了一种由新型可收缩执行器驱动的功能渐变3D打印关节状结构。通过3D打印的功能分级材料（FGM）可实现广泛的材料性能增强和控制，从而保证了系统的可调功能。3D打印结构由3个刚性球窝关节串联而成，并通过集成扭曲和盘绕的聚合物钓鱼线（TCP）进行驱动 通过3D打印的功能分级材料（FGM）可实现广泛的材料性能增强和控制，从而保证了系统的可调功能。3D打印结构由3个刚性球窝关节串联而成，并通过集成扭曲和盘绕的聚合物钓鱼线（TCP）进行驱动 通过3D打印的功能分级材料（FGM）可实现广泛的材料性能增强和控制，从而保证了系统的可调功能。3D打印结构由3个刚性球窝关节串联而成，并通过集成扭曲和盘绕的聚合物钓鱼线（TCP）进行驱动_FL）执行器，它们限制在FGM手风琴形通道中。不受束缚的TCP _FL致动系统的实施对于在要求低振动和静音致动的环境中的部署非常有利。钓线TCP执行器产生高达40％的驱动应变，并在任何方向上将关节弯曲高达40°。TCP _FL可以单独或成组启动，以控制模块化接头的弯曲轨迹，这在将其部署在缝隙较小的区域时非常有用。FGM多向接头具有复杂的弯曲模式，在实现各种功能（例如爬行，滚动，游泳或水下勘探）方面具有巨大的潜力。