A fluidic-based approach is proposed as a means to reconfigure the reflected phase of a microstrip reflectarray element. Reactive loading for reconfiguration is provided by altering the volume fraction of a fluidic colloidal dispersion within a device. Aspects of design, modeling, and measurement are discussed for a unit-cell prototype design. The impact of losses within the fluidic and colloidal material systems are also investigated. Measurements from waveguide experiments demonstrate up to 220\ of phase change and a return loss of less than 2 dB at the operating frequency of 3 GHz. \ 2011 IEEE.