Self-assembled granular walkers

TL;DR

This paper introduces a self-assembling granular system of mixed-size spheres that, under oscillating forces, exhibits locomotion through nonlinear force rectification, offering scalable insights into microscopic movement mechanisms.

Contribution

It presents a novel self-assembling granular walker system driven by oscillating forces, with a model explaining its locomotion and demonstrating broad applicability.

Findings

System exhibits locomotion under oscillating forces

Model accurately predicts observed behavior

Potential for scalable microscopic movement applications

Abstract

Mechanisms of locomotion in microscopic systems are of great interest not only for technological applications, but also for the sake of understanding, and potentially harnessing, processes far from thermal equilibrium. Down-scaling is a particular challenge, and has led to a number of interesting concepts including thermal ratchet systems and asymmetric swimmers. Here we present a system which is particularly intriguing, as it is self-assembling and uses a robust mechanism which can be implemented in various settings. It consists of small spheres of different size which adhere to each other, and are subject to an oscillating (zero average) external force eld. An inherent nonlinearity in the mutual force network leads to force rectication and hence to locomotion. We present a model that accounts for the observed behaviour and demonstrates the wide applicability and potential scalability of the concept.