Materials Engineering

Inventions whose primary historical significance is a material or a material-dependent product rather than a mechanism or circuit. Belongs here: the pencil as a graphite-based writing material, the vacuum flask as a thermal-insulation product, Velcro as a fastening material system, and the lithium-ion battery as an energy-storage device defined by its electrode materials. Does not belong here: devices whose significance is their mechanism or circuit rather than the material itself, grouped under Mechanical Engineering or Electrical Engineering.