  Electrohydrodynamic (EHD) generation, a commonly used method in BioMEMS,
plays a significant role in the pulsed-release drug delivery system for a
decade. In this paper, an EHD based drug delivery system is well designed,
which can be used to generate a single drug droplet as small as 2.83 nL in 8.5
ms with a total device of 2x2x3 mm^3, and an external supplied voltage of 1500
V. Theoretically, we derive the expressions for the size and the formation time
of a droplet generated by EHD method, while taking into account the drug supply
rate, properties of liquid, gap between electrodes, nozzle size, and charged
droplet neutralization. This work proves a repeatable, stable and controllable
droplet generation and delivery system based on EHD method.
