Latch-mediated spring actuation (LaMSA): the power of integrated biomechanical systems.

Abstract

Across the tree of life - from fungi to frogs - organisms wield small amounts of energy to generate fast and potent movements. These movements are propelled with elastic structures, and their loading and release are mediated by latch-like opposing forces. They comprise a class of elastic mechanisms termed latch-mediated spring actuation (LaMSA). Energy flow through LaMSA begins when an energy source loads elastic element(s) in the form of elastic potential energy. Opposing forces, often termed latches, prevent movement during loading of elastic potential energy. As the opposing forces are shifted, reduced or removed, elastic potential energy is transformed into kinetic energy of the spring and propelled mass. Removal of the opposing forces can occur instantaneously or throughout the movement, resulting in dramatically different outcomes for consistency and control of the movement. Structures used for storing elastic potential energy are often distinct from mechanisms that propel the mass: elastic potential energy is often distributed across surfaces and then transformed into localized mechanisms for propulsion. Organisms have evolved cascading springs and opposing forces not only to serially reduce the duration of energy release, but often to localize the most energy-dense events outside of the body to sustain use without self-destruction. Principles of energy flow and control in LaMSA biomechanical systems are emerging at a rapid pace. New discoveries are catalyzing remarkable growth of the historic field of elastic mechanisms through experimental biomechanics, synthesis of novel materials and structures, and high-performance robotics systems.