  Highly articulated organisms serve as blueprints for incredibly dexterous
mechanisms, but building similarly capable robotic counterparts has been
hindered by the difficulties of developing electromechanical actuators with
both the high strength and compactness of biological muscle. We develop a
stackable electrostatic brake that has comparable specific tension and weight
to that of muscles and integrate it into a robotic joint. Compared to
electromechanical motors, our brake-equipped joint is four times lighter and
one thousand times more power efficient while exerting similar holding torques.
Our joint design enables a ten degree-of-freedom robot equipped with only one
motor to manipulate multiple objects simultaneously. We also show that the use
of brakes allows a two-fingered robot to perform in-hand re-positioning of an
object 45% more quickly and with 53% lower positioning error than without
brakes. Relative to fully actuated robots, our findings suggest that robots
equipped with such electrostatic brakes will have lower weight, volume, and
power consumption yet retain the ability to reach arbitrary joint
configurations.
