Dissertation

Colloidal mechanical metamaterials

This thesis describes how to scale down concepts of macroscopic mechanical metamaterials to the thermal scale using a system of flexibly-linked colloids.

Author: J. Melio
Date: 05 June 2025
Links: Thesis in Leiden Repository

Using this system, square lattices were made and an analysis method was developed to quantitatively extract the normal modes. The resulting mode spectra exhibited the expected number of soft modes, nonlinear effects onto stiffer modes, and harmonic stiff modes. The experimental findings were complemented by Brownian particle simulations, a linear response model, and Monte-Carlo based stochastic conformation sampling. Next, colloids assembled in rigid anisotropic units made it possible to create the archetypical auxetic metamaterials, the rotating diamond lattice and rotating triangle, or Kagome, lattice. Adding magnetic interactions in the system provided control over the conformation and the possibility for actuation. Ring-like structures of four particles are stable in their diamond conformation in presence of magnetic interactions, and this symmetry can be broken by using particles of different sizes. Finally, a method was developed to use anisotropic building blocks such as cubic particles in flexible colloidal structures.