Abstract: A variety of embodiments of an at least partially flexible actuator are provided. The actuator includes a phase change material contained within an at least partially flexible enclosure of the actuator. Application of heat, using a heater of the actuator, to the phase change material causes the phase change material to boil, increasing the volume of the actuator and/or increasing a pressure within the actuator. As a result, the actuator can be used to apply a force to objects in an environment of interest. The actuator could be incorporated into a wearable blood pressure cuff and used to apply pressure to a body part of a wearer in order to detect a blood pressure of the wearer. In other examples, the actuator could be incorporated into a wearable device and used to secure a sensor or other elements of the device against skin of a wearer.