Ultralight shape-recovering plate mechanical metamaterials

Keivan Davami,Igor Bargatin,Lin Zhao,Eric Lu,John Cortes,Prashant K Purohit,Chen Lin,Drew E Lilley

doi:10.1038/ncomms10019

Abstract

Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale. We introduce a class of nanoscale mechanical metamaterials created by forming continuous corrugated plates out of ultrathin films. Using a periodic three-dimensional architecture characteristic of mechanical metamaterials, we fabricate free-standing plates up to 2 cm in size out of aluminium oxide films as thin as 25 nm. The plates are formed by atomic layer deposition of ultrathin alumina films on a lithographically patterned silicon wafer, followed by complete removal of the silicon substrate. Unlike unpatterned ultrathin films, which tend to warp or even roll up because of residual stress gradients, our plate metamaterials can be engineered to be extremely flat. They weigh as little as 0.1 g cm−2 and have the ability to ‘pop-back' to their original shape without damage even after undergoing multiple sharp bends of more than 90°.

Highlights

Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale
Advances in micro/nanofabrication techniques recently resulted in demonstrations of macroscopic solids made solely out of free-standing films with nanoscale thickness[1]. These mechanical metamaterials have a carefully engineered structure at the micro- and nanoscales, with periodic geometries that lead to unusual mechanical properties
Alumina material was chosen as the cell wall material for its high stiffness, chemical and high-temperature resistance, as well as the highly conformal and pinhole-free nature of its atomic layer deposition (ALD) films

Summary

Introduction

Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale. Advances in micro/nanofabrication techniques recently resulted in demonstrations of macroscopic solids made solely out of free-standing films with nanoscale thickness[1] These mechanical metamaterials have a carefully engineered structure at the micro- and nanoscales, with periodic geometries that lead to unusual mechanical properties. A number of low-density carbon-based materials composed of sheets as thin as a single atomic layer[16,17,18,19] have been demonstrated These often have unique mechanical properties; as with aerogels, the micro/nanoscale geometry of these cellular materials can only be partly controlled and is largely random

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Conclusion