# Phase transitions in 2D multistable mechanical metamaterials via collisions of soliton-like pulses

## TL;DR

This study demonstrates that collisions of soliton-like pulses can induce phase transitions in 2D multistable mechanical metamaterials, with control over nucleation and growth of new phases through nonlinear pulse interactions.

## Contribution

It reveals a novel mechanism for phase transition initiation via pulse collisions and explores the directional control of nucleation in mechanical metamaterials.

## Key findings

- Phase transitions occur when colliding soliton-like pulses form a critical nucleus.
- The critical nucleus size determines if a phase transition propagates.
- Direction-dependent pulse behavior enables control of nucleation sites.

## Abstract

In this work, we report observations of phase transitions in 2D multistable mechanical metamaterials that are initiated by collisions of soliton-like pulses in the metamaterial. Analogous to first-order phase transitions in crystalline solids, we experimentally and numerically observe that the multistable metamaterials support phase transitions if the new phase meets or exceeds a critical nucleus size. If this criterion is met, the new phase subsequently propagates in the form of transition waves, converting the rest of the metamaterial to the new phase. More interestingly, we observe that the critical nucleus can be formed via collisions of soliton-like pulses. Moreover, the rich direction-dependent behavior of the nonlinear pulses enables control of the location of nucleation and the spatio-temporal shape of the growing phase.