A monocrystalline whisker is a filament of material that is structured as a single, defect-free crystal.
Some typical whisker materials are graphite, alumina, iron, silicon carbide and silicon.
Single-crystal whiskers of these (and some other) materials are known for having very high tensile strength (on the order of 10–20 GPa).
Prior to the discovery of carbon nanotubes, single-crystal whiskers had the highest tensile strength of any materials known, and were featured regularly in science fiction as materials for fabrication of space elevators, arcologies, and other large structures.
Despite showing great promise for a range of applications, their usage has been hindered by concerns over their effects on health when inhaled.