Despite decades of academic and industry effort, achieving efficient and dynamic movement of robots remains a significant challenge. Many robots, particularly humaniod robots and wearable robots such as exoskeletons and prostheses, are quite limited in their versatility and usefulness because of the force and speed limitations of actuators. Weight and power consumption are particularly important factors in determining the operating range and effectiveness of these devices. Geared electric motors are most commonly used in these applications, but often result in slow, stiff, and halting operation. Other options include hydraulic actuators, pneumatic actuators, electroactive polymer actuators, and shape memory materials, but none of these are able to achieve the combination of high power output, high efficiency, and low weight that would enable dynamic movement of untethered robots. Many proposed solutions to this problem involve using clutches to improve the efficiency and capability of actuation systems. However, conventional clutches such as electromagnetic and magnetorheological clutches are themselves too heavy and power-hungry to be practical. This thesis presents an electroadhesive clutch that has 10£ lower weight and 1000£ lower power consumption than conventional clutches. To inform a variety of possible implementations, I extensively characterized the effects of design choices on the holding force, responsiveness, and power consumption of the electroadhesive clutch. Next, I investigated the use of the clutch in a walking assistance exoskeleton, demonstrating the reliability and advantages of the electroadhesive clutch in a challenging robotics application. Finally, I studied the use of electroadhesive clutches to harvest, store, and return mechanical energy with rubber springs, and used multiple of these units in parallel to create a force controllable energy recycling actuator. My aspiration is that the work in this dissertation will lead to improved robotic hardware that enables exciting new capabilities in next generation robotics.