Abstract
Corrugated paper cardboard provides an everyday example of a lightweight, yet rigid, sandwich structure. Here we present nanocardboard, a monolithic plate mechanical metamaterial composed of nanometer-thickness (25–400 nm) face sheets that are connected by micrometer-height tubular webbing. We fabricate nanocardboard plates of up to 1 centimeter-square size, which exhibit an enhanced bending stiffness at ultralow mass of ~1 g m−2. The nanoscale thickness allows the plates to completely recover their shape after sharp bending even when the radius of curvature is comparable to the plate height. Optimally chosen geometry enhances the bending stiffness and spring constant by more than four orders of magnitude in comparison to solid plates with the same mass, far exceeding the enhancement factors previously demonstrated at both the macroscale and nanoscale. Nanocardboard may find applications as a structural component for wings of microflyers or interstellar lightsails, scanning probe cantilevers, and other microscopic and macroscopic systems.
Highlights
Corrugated paper cardboard provides an everyday example of a lightweight, yet rigid, sandwich structure
Sandwich plates offer significantly higher bending stiffness compared to a solid plate of the same mass because the two face sheets are offset from each other, increasing the effective moment of area, and because the shearing of the two face sheets is restricted by the separating core[1,2]
We present nanocardboard—a plateshaped mechanical metamaterial that is a nanoscale analog of corrugated cardboard or web-core sandwich plates
Summary
Corrugated paper cardboard provides an everyday example of a lightweight, yet rigid, sandwich structure. Using films with nanoscale thickness could lead to much higher enhancement factors and enable large-area structures with nanoscale thickness that do not sag or bend under their weight, feature increased flexural resonance frequencies, or minimize the weight of plate-shaped structural components These characteristics could provide significant advantages to many technologies where weight is extremely important. Films of nanoscale thickness have recently been used as structural elements in novel cellular solids with a truss-like or lattice-like architecture[14,19,20,21,22,23,24,25,26,27] These mechanical metamaterials typically exhibit higher Young’s moduli than their solid or random cellular material counterparts at low densities. We recently introduced the concept of a plate mechanical metamaterial, reporting nanometer-thick single-layer corrugated films that formed continuous plates and measuring their bending stiffness[28]
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