World's Lightest Material Metallic microlattice About

Metallic microlattice held by dandelionseed head

Metallic microlattice is a synthetic porous metallic material, an ultralight form of metal foam with a density as low as 0.9 mg/cm³ developed by a team of scientists from HRL Laboratories in collaboration with researchers at University of California, Irvine and Caltech.^[1]

To produce a metallic microlattice, a polymer template is first prepared using a new technique based on self-propagating waveguide formation.^[2] The process passes UV light through a perforated mask into a reservoir of UV-curable resin. Fiber-optic-like “self-trapping” of the light occurs as the resin cures under each hole in the mask, forming a polymer fiber along the path of the light. By using multiple light beams, multiple fibers can then interconnect to form a lattice. The process is similar to photolithography in that it uses a 2D mask to define the starting template structure, but differs in the rate of formation: where stereolithography might take hours to make a full structure, the self-forming waveguide process enables templates to be formed in 10-100 seconds. In this way, the self-propagating waveguide process enables large free-standing 3D lattice materials to be formed quickly and scalably. The template is then coated with a thin layer of metal by electrodeposition, and the template is etched away leaving a free-standing periodic porous metallic structure.^[3][edit]Synthesis

[edit]Properties

Metallic microlattices are composed of a network of interconnecting hollow struts made of a nickel-phosphorus alloy. Each strut is about 100 micrometres in diameter with a wall 100 nanometres thick. The completed structure is about 99.99% air by volume.^[1]

Metallic microlattices are characterized by very low densities, with the current record of 0.9 mg/cm³ being the lowest value for any solid. The previous record of 1.0 mg/cm³ was held by silica aerogels. Mechanically, these microlattices behave similar to elastomers and almost completely recover their shape after significant compression.^[4] This property results in efficient shock absorption. Their Young's modulus E exhibits different scaling with the density ρ, E ~ ρ² compared to E ~ ρ³in aerogels and carbon nanotube foams.^[3]

[edit]Applications

Metallic microlattices may find potential applications as thermal and vibration insulators (shock absorbers, etc.), battery electrodes and catalyst supports.^[3] The microlattices' ability to compress and return to their original state has also led to proposals to use the material for energy storage.^[1]