Dial-in Topological Metamaterials Based on Bistable Stewart Platform

Ying Wu,Rajesh Chaunsali,Kaiping Yu,Hiromi Yasuda,Jinkyu Yang

doi:10.1038/s41598-017-18410-x

Abstract

Recently, there have been significant efforts to guide mechanical energy in structures by relying on a novel topological framework popularized by the discovery of topological insulators. Here, we propose a topological metamaterial system based on the design of the Stewart Platform, which can not only guide mechanical waves robustly in a desired path, but also can be tuned in situ to change this wave path at will. Without resorting to any active materials, the current system harnesses bistablilty in its unit cells, such that tuning can be performed simply by a dial-in action. Consequently, a topological transition mechanism inspired by the quantum valley Hall effect can be achieved. We show the possibility of tuning in a variety of topological and traditional waveguides in the same system, and numerically investigate key qualitative and quantitative differences between them. We observe that even though both types of waveguides can lead to significant wave transmission for a certain frequency range, topological waveguides are distinctive as they support robust, back scattering immune, one-way wave propagation.

Highlights

There have been significant efforts to guide mechanical energy in structures by relying on a novel topological framework popularized by the discovery of topological insulators
We propose a dial-in topological metamaterial system based on the bistable Stewart Platform (SP) and report robust one-way propagation of mechanical waves in it along tailorable wave paths
By arranging the bistable SP cells hexagonally in an alternating fashion, we can create two types of topologically distinctive lattices, which can be transformed to each other by a dial-in action. We prove that this transformation changes the topology of the system—quantified by the valley Chern numbers

Summary

Introduction

There have been significant efforts to guide mechanical energy in structures by relying on a novel topological framework popularized by the discovery of topological insulators. It is recent that these fundamental concepts have been extended to the fields of photonics[7], acoustics[8,9,10,11,12,13,14], and mechanics[15,16,17,18,19,20,21,22,23,24,25,26] Such extension is of the fundamental interest to the research community as it has potential to set new design principles for topological metamaterials that aim to strategically tailor energy transport for waveguiding, isolating, switching, filtering, and related applications. In situ tunability requires complex components or mechanisms to be present in the system, so that the wave path in the lattice structure can be reconfigured in a controllable and versatile manner Such complexity in design could again make the system cumbersome for practical use, and it would defeat the purpose of building a simple QVHE-based system to some extent. Such a comparison plays a key role in extending our knowledge and appreciation towards the uniqueness of topological waveguides in the proposed system

Methods

Results

Conclusion