Although the multi-jointed underactuated manipulator is highly dexterous, its grasping capacity does not match that of the parallel jaw gripper. This work introduces a fractal gripper to enhance the grasping capacity of multi-joint underactuated manipulators, preserving their passive clamping features. We describe in detail the working principle and manufacturing process of the fractal gripper. This work, inspired by the 'Fractal Vise' structure, resulted in the invention of a fractal gripper with mode switching capabilities. The fractal gripper inherits the inherent adaptive properties of the fractal structure and realizes the self-resetting function by integrating spring into the original design, thereby enhancing the efficiency of object grasping tasks. The fractal gripper prevents object damage by distributing pressure evenly and applying it at multiple points through its fractal structure during closure. Objects of various shapes are effectively grasped by the fractal gripper, which ensures a safe and secure grasp. The superior performance was provided by the force distribution characteristics of the fractal gripper. By applying the flexible polymer PDMS, which possesses superior elasticity, to the fractal structure's wrapping surface, potential scratching during grasping is effectively prevented, thus protecting the object's geometric surface. Grab experiments with objects of diverse shapes and sizes confirm fractal gripper multi-scale adaptability and superior grasping stability.

翻译：尽管多关节欠驱动机器手具有高度灵活性，但其抓取能力并不匹配平行夹爪。本文提出一种分形夹爪，以增强多关节欠驱动机器手的抓取能力，同时保留其被动夹持特性。我们详细阐述了分形夹爪的工作原理与制造工艺。受“分形台钳”结构启发，本研究发明了具备模式切换功能的分形夹爪。该夹爪继承了分形结构固有的自适应特性，并通过将弹簧集成至原始设计中实现自复位功能，从而提升了物体抓取任务的效率。在闭合过程中，分形夹爪通过分形结构均匀分布压力并在多点施加压力，从而避免物体损伤。分形夹爪可有效抓取多种形状的物体，确保安全可靠的抓取。分形夹爪的力分布特性提供了卓越性能。通过将具有优异弹性的柔性聚合物PDMS应用于分形结构的包裹表面，可有效防止抓取过程中的潜在划伤，从而保护物体的几何表面。对不同形状和尺寸物体的抓取实验证实了分形夹爪的多尺度适应性与优越的抓取稳定性。