Actuators enable movement across the expanse of human invention; their role in technological advancement cannot be overstated. Revolutionary technological developments have accelerated the need for new actuators for aerospace, automotive, consumer, and medical applications: actuators that perform fast, large-strain actuation in a compact, conformable package while doing external work. Despite tremendous advances in materials, architecture, fabrication, characterization, and modeling of dielectric elastomer (DE) actuators, challenges remain: no architecture possesses all the desired actuation properties, and design process methodological issues persist. Because material and actuator properties vary with strain state and exhibit hysteric and viscoelastic behaviors, only complex viscoelastic analytical models have effectively predicted performance over a wide range of operating conditions, limiting actuator design to researchers with specialized expertise. This dissertation addresses technological and methodological issues in DE actuators. The primary technical contribution is a new DE tape actuator architecture that utilizes a novel flexible release frame, silicone elastomer, single-wall carbon nanotube (SWNT) electrodes, and innovative multifunctional tape connectors. The architecture performs fast, lightweight, conformable, large-strain actuation while doing external work; it is compact and modular to facilitate scaling; over time, it is repeatable and robust; and it supports a simplified design process, enabling predictable and controllable design with variable performance. The research established a new categorization rubric for frame configurations, created a new flexible release frame, and developed pioneering multifunctional tape connectors. The dissertation delineates a design approach – characterization, modeling, and system design – based on the actuator’s application context, encompassing the application situation, actuation requirements, and actuator architecture. Given the material and actuation property complexities, hysteric behavior, and viscoelasticity associated with DE actuators, application context dictates characterization requirements and provides a simple process for full actuator characterization. Viscoelastic performance can be simplified into the quasi-static force-deflection realm without losing critical information, while data simplification facilitates analytical modeling of actuators’ viscoelastic behavior without requiring complex time-dependent models. The resulting model enables a simple quasi-static design process that accurately predicts the performance of the actuator/device. This dissertation establishes a process for characterizing cyclical steady-state actuation – defined as the repeated actuation performance level reached after some number of cycles when the long-term transient viscoelastic properties, Mullins effect, or actuator shakedown, have settled out – that captures key mechanical and electrical actuation properties which drive performance. The dissertation also presents a new variable shear Gent strain energy model for terminated primary creep steady-state cycling actuation, created from first principles. The elegance of this model is that the new variable shear term is only dependent on the driving voltage, yet it effectively encompasses all the relevant viscoelastic effects over the whole actuation range for steady-state cyclical actuation. The model calibration requires data from only two actuation performance curves operating at different voltages yet provides virtually the same accuracy as if the model was calibrated at each desired operating voltage level. The new model enables simple quasi-static model-based design for DE actuators while promoting an intuitive understanding of how the parameters impact the performance of the actuation system. Three case studies are used to validate the technological and methodological advances. The outcomes of this research – a new DE actuator architecture, characterization paradigm, predictive design model, and design methodology – provide a foundation for future progress to enable wider adoption and advancement of DE actuators.