Manufactured muscles that are stronger than their natural counterparts can be cheaply made by fitting the devices with a folding ‘skeleton’.
Widely used in industrial robots, artificial muscles often work by pumping pressurized fluid into a bladder situated inside an outer mesh. Shuguang Li and Robert Wood at Harvard University in Cambridge, Massachusetts, and their colleagues modified this concept, using a flexible skin to enclose both the fluid and a skeleton folded in a zigzag pattern inspired by origami. As the fluid is sucked out, the skeleton collapses and contracts, applying stresses large enough to pick up a car wheel. The system’s pull is several times stronger than that of human muscles of the same weight. By using increasingly complex folding structures, the muscles can be designed not only to pull in a straight line, but also to bend in multiple directions.
This simple and flexible design could be useful for applications ranging from miniature surgical devices to robotic arms on space stations, the authors write.