# Topological defects produce exotic mechanics in complex metamaterials

## TL;DR

This paper introduces a systematic method to embed topological defects into mechanical metamaterials, revealing their unique mechanical signatures and enabling control over deformation and stress distribution.

## Contribution

It provides a novel approach to design and analyze topological defects in mechanical metamaterials, combining experiments and simulations to explore their effects.

## Key findings

- Topological defects produce distinct mechanical signatures.
- Metamaterials can be engineered to steer deformations and stresses.
- Systematic inclusion of topology enhances metamaterial design.

## Abstract

Defects, and in particular topological defects, are architectural motifs that play a crucial role in natural materials. Here we provide a systematic strategy to introduce such defects in mechanical metamaterials. We first present metamaterials that are a mechanical analogue of spin systems with tunable ferromagnetic and antiferromagnetic interactions, then design an exponential number of frustration-free metamaterials, and finally introduce topological defects by rotating a string of building blocks in these metamaterials. We uncover the distinct mechanical signature of topological defects by experiments and simulations, and leverage this to design complex metamaterials in which we can steer deformations and stresses towards parts of the system. Our work presents a new avenue to systematically include spatial complexity, frustration, and topology in mechanical metamaterials.