Abstract
The objective of this design project was to develop a working on demand droplet generator for use in ambient conditions as well as in a vacuum environment. The primary design parameters set by this project include the droplet size, speed, consistency as well as the overall generator size and cost. Several different concept designs for a generator were considered. For the purposes of this project the use of a piezoelectric design was used and modified to fit the design specifications that were given. This design features an actuating piezoelectric disk that deflects with voltage potential. This deflection drives the droplet generator system. By adjusting the size of the sapphire nozzle diameter and regulating the voltage and pulse width it is possible to vary the initial velocity and size of the droplets produced. Initial testing in atmospheric condition proved successful. The generator produced an average droplet size of 1.57 mm with a percent standard deviation of 4.15% (through 15 drops). However, testing in vacuum down to 10-6 torr gave way to a problem of air out-gassing in vacuum. Small, trapped air pockets from the priming process began to rapidly expand in the generator, explosively forcing the fluid out of the generator. It was found that the primary issue was in the priming process of the generator. Several different approaches were taken to solve this problem. The out-gassing problem has proven to be a substantial technical challenge in this project and due to time constraints no current solution exists. However, there is no fundamental reason the design proposed in this project cannot work and future work will be done to alleviate these out-gassing issues.