Tuning Stiffness with Granular Chain Structures for Versatile Soft Robots.

Area of Science:

• Robotics
• Materials Science
• Mechanical Engineering

Background:

• Variable stiffness is crucial for enhancing soft robot load capacity and compliance.
• Current jamming methods for stiffness variation face challenges in being lightweight, adaptive, and avoiding deformation-induced softening.
• Existing mechanisms limit applications requiring both large deformation and high stiffness.

Purpose of the Study:

• To propose a novel multifunctional granular chain assemblage for variable stiffness in soft robots.
• To address limitations of existing jamming mechanisms, particularly deformation-induced softening.
• To demonstrate the versatility of the proposed mechanisms in various soft robot applications.

Main Methods:

• Development of a granular chain assemblage where particles are threaded into chains.
• Classification and investigation of two chain jamming types: Granular Chain Jamming (GCJ) with spherical particles and Stretch-Enhanced Particle Jamming (SPJ) with cubic particles.
• Demonstration of GCJ and SPJ mechanisms in soft grippers, crawlers, and bending actuators.

Main Results:

• GCJ achieves high stiffness and adaptability with lightweight components.
• SPJ exhibits a unique deformation-induced stiffening mechanism.
• Demonstrated applications include passive adaptability, high load capacity, joint-like bending, friction enhancement, and buckling postponement.

Conclusions:

• The granular chain assemblage provides a facile and low-cost strategy for fabricating versatile soft robots.
• The proposed GCJ and SPJ mechanisms offer significant improvements over existing variable stiffness methods.
• This work enables enhanced performance and broader applicability of soft robotic systems.