Actuators are described that operate as a result of double-layer charge injection in electrodes having very high gravimetric surface areas and gravimetric capacitances. The actuator output of the actuators may be a mechanical displacement that can be used to accomplish mechanical work. As a result of the non-faradaic process and the actuator materials utilized, such as carbon nanotubes, the actuators have improved work capacity, power density, cycle life, and force generation capabilities. Other benefits include low voltage operation and high temperature performance. The actuators also convert a mechanical energy input to an electrical energy output. The actuators may be used to control either thermal, electrical or fluid transport or cause either the switching, phase shift, or attenuation of electromagnetic radiation.