A hyperelastic torque-reversal mechanism for soft joints with compression-responsive transient bistability

Snap-through, a rapid transition of a system from an equilibrium state to a non-adjacent equilibrium state, is a valuable design element of soft devices for converting a monolithic stimulus into systematic responses with impulsive motions. A common way to benefit from snap-through is to embody it within structures and materials (e.g., bistable structures). Meanwhile, torque reversal mechanisms discovered in nature, which harness snap-through instability through muscular forces, may have comparative advantages. However, the current intricacy of artificial torque reversal mechanisms, which require sophisticated kinematics/kinetics, constrains design possibilities for soft joints and devices. In this paper, we harnessed hyperelasticity to implement a torque reversal mechanism in a soft joint, generating repetitive cilia-like beating motion through an embedded tendon. The developed hyperelastic torque reversal mechanism (HeTRM) exhibits transient bistability under a specific compressive dis..., , , # A Hyperelastic Torque Reversal Mechanism for Soft Joints with Compression-Responsive Transient Bistability

This project simulates the behavior of a HeTRM joint model using a hyperelastic material model. To characterize the hyperelastic behavior of soft joints, the mechanical properties of **Ecoflex 00-30 (Smooth-On, Inc.)** were fitted using the [Yeoh model]([https://doi.org/10.5254/1.3538343]\(https://doi.org/10.5254/1.3538343\)). The mechanical modeling of reaction forces and bending moments was derived using an approach similar to the **Winkler foundation model**. Detailed derivations and equations related to the methodology can be found in the Supplementary Methods section of the manuscript.

The associated data files include a Python script for calculating the model and an example dataset generated from the simulation.

## Background Concepts and Terminology

This section provides brief definitions of key terms used in the associated publication and throughout the dataset to sup...,