# Quantifying Nature’s Bistability: Simulation of Earwig Fan Folding

## TL;DR

This paper presents a simulation tool to study how earwig wings fold, with potential applications in engineering and space technology.

## Contribution

The novel contribution is a scalable simulation tool for modeling insect wing folding dynamics with potential engineering applications.

## Key findings

- A Python-based simulation tool using MuJoCo models earwig wing folding with elastic tendons.
- Bistability in wing folding is characterized using tendon properties and actuation.
- Upscaled geometry identifies feasible tendon characteristics for biomimetic structures.

## Abstract

In this work, a numerical tool is presented to simulate the dynamics of insect wing folding by example of the fan folding of the dermapteran hindwing. The scalability of the system is demonstrated by generalising the mechanical behaviour from the small geometry of the wing to a suitable scale for engineering applications, such as deployable structures for space applications. The tool is written in Python and based on the MuJoCo physics engine. Sections of the anal fan are modelled as a bar-and-hinge model with elastic tendons, allowing a high number of design parameters and fast computation. In light of these advantages, the wing folding and unfolding behaviour is investigated with respect to the tendon’s elastic properties and the actuation of the deformation. Bistability is characterised using a single tendon and the entire fan section. Given the upscaled geometry of the analysed section, the required tendon characteristics to transition between the stable states are identified within a reasonable range for technological transfer towards biomimetic structures modelled after the dermapteran hindwing.