In a Los Angeles laboratory, researchers have let loose scores of what amount to living micromachines. Dwarfed by a comma, each tiny device consists of an arch of gold coated along its inner surface with a sheath of cardiac muscle grown from rat cells. With each of the muscle bundles' automatic cycles of contraction and relaxation, the device takes a step.
Viewed under a microscope, "they move very fast," says bioengineer Jianzhong Xi of the University of California, Los Angeles (UCLA). "The first time I saw that, it was kind of scary."
Xi and his UCLA colleagues Jacob J. Schmidt and Carlo D. Montemagno describe their musclebots in the February Nature Materials.