In this work, microwave dielectric heaters are designed and their design procedures are explained, for given set of specifications that require fast, uniform and spatially selective microwave dielectric heating of the nL-µL scale water droplets. The targeted application for microwave heaters is the digital microfluidic platform, and the goal is to achieve the specified PCR motivated temperature increase of 80 . After discussion of the theory framework that includes theory of microwave dielectric heating, heat transfer and digital microfluidics, and introducing the design environment used for microwave heater design, the following heater designs are reported. The ''4-parallel continuous CPW transmission lines'' heater is designed at 5 GHz. It provides uniform, but also low efficient microwave dielectric heating of the 80 nL droplet volume. The ''Unfolded shape increasing gap width based CPW topology'' heater design represents the heating of the 115 nL droplet volume, that provided uniform microwave dielectric heating at 15 GHz. The last presented heater in this work, the ''Alpha'' heater is designed at 25 GHz, for heating the 115 nL droplet volume. It is based on the variable central conductor and gap widths along the length of the heater. This heater design presents the best microwave dielectric heating performance in this work, for which the multiphysics simulation showed satisfying temperature distribution results.