As computing has become ubiquitous, transitioning from desktops to mobile devices to wearables, our environments have been augmented with a myriad of sensors (e.g., your home may have dozens of sensors). However, the proliferation of actuators - devices capable of creating physical motion or haptic effects - has lagged behind (how many does your home have?). This is due to a key challenge facing haptic devices: high power consumption. Unlike sensors, which can often operate on just microwatts, actuators require orders of magnitude more power, making it impractical to densely instrument entire environments with them due to battery maintenance. This power constraint has hindered the realization of ubiquitous actuation: the seamless integration of actuated and haptic devices at scale. To overcome this challenge, we propose engineering actuator architectures and working principles with scale in mind from the start. Notably, we do not add batteries to the environment; instead, we place them on the user to power wearable actuators. These actuators enable scale since they are one-to-many: one wearable actuator can add actuation to many otherwise passive objects and surfaces, transforming them into interactive devices. We apply these principles to present a series of actuators to achieve vibration, friction, and thermal feedback at scale. Along the way, we interrogate and circumvent the limitations of traditional actuators through new materials (e.g., soft and stretchable magnets) and working principles (e.g., microfluidics). Finally, we demonstrate a generalizable approach to actuation at scale through a wearable wireless power transmitter that powers battery-free devices during interaction. Our approach offers a lens into the future in which even any seemingly passive object or surface can respond through actuation, without the constraints that have typically limited actuation at scale.