ABSTRACT
Biological ActuatorsMuscles are biological actuators that contract under stimuli and provide linear actuation. Based on some metrics, muscles may appear to perform worse than artificial actuators. For example, the muscle’s continuous power-to-mass ratio is an order of magnitude lower than that of an internal combustion engine (not considering the mass of the “fuel reservoir”). Several other important characteristics and performance metrics, based on which muscles show clear superiority over artificial actuators, are as follows: (1) Muscles exhibit the property of scale invariance-their
mechanism works equally efficiently at all sizes, which is why fundamentally the same muscle tissue powers both small insects and big animals. (2) Glucose and oxygen are delivered to muscles while heat and waste are removed from muscles via an integrated circulation
system. Due to this excellent cooling system, large powers can be generated for prolonged periods of time. (3) The “combustion” of sugars and fats using freely available oxygen provides a fuel energy density that is two orders of magnitude greater than that of batteries.
