Ultralight material

Ultralight materials are solids with a density of less than 10 mg/cm³, including silica aerogels, carbon nanotube aerogels, metallic foams, polymeric foams, and metallic microlattices. The density of air is about 1.275 mg/cm³, which means that the air in the pores contributes significantly to the density of the material.

References

TA Schaedler, AJ Jacobsen, A Torrents, AE Sorensen, J Lian, JR Greer, L Valdevit, WB Carter (18 November 2011). "Ultralight Metallic Microlattices". Science 334 (6058). pp. 962–965. doi:10.1126/science.1211649.