title: Ultralight shape-recovering plate mechanical metamaterials.
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°.
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Keivan
authors.initials: K
authors.lastname: Davami
authors.affiliation: Nanotechology Master's Program, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Lin
authors.identifier: http://orcid.org/0000-0002-8865-859X
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Vagelos Integrated Program in Energy Research, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Lu
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: John
authors.initials: J
authors.lastname: Cortes
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Chen
authors.initials: C
authors.lastname: Lin
authors.affiliation: Vagelos Integrated Program in Energy Research, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Drew E
authors.initials: DE
authors.lastname: Lilley
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Purohit
authors.affiliation: Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Igor
authors.identifier: http://orcid.org/0000-0003-0305-9932
authors.initials: I
authors.lastname: Bargatin