Electrical control of droplet direction with phase-varied fresnel lens on acoustic wave liquid ejector

This paper describes a novel design of a multi-directional acoustic ejector with capability of electrical control on the droplet ejection angle by changing the operating frequency. The newly developed ejector consistently ejects uniform droplets in diameter of 70 μm, with electrical control of the directional angle from -30° to 35° (with respect to normal direction of liquid surface plane) as the operating frequency is varied from 16.78 MHz to 19.08 MHz. To produce the electrically adjustable oblique ejections of nano-liter droplets, destructive wave interference is intentionally introduced through a phase-varied lens. With the novel lens, the direction of the droplet ejection depends monotonically on the operating frequency of the driving signal. This paper presents the experimental results, as well as the theoretical analysis and simulation verification of the phase-varied lens design that gives the electrical control on the direction of ejected droplets.