Droplet Ejection by Pulsatile Airflow

Droplet ejection is a promising technology for a variety of biological and chemical processes. In its applications, an important and challenging issue is the precise control on the droplet size, frequency and velocity. Herein, a pulsatile perturbation strategy is proposed to improve the control of droplet parameters. Using this active method, the ejection frequency is synchronized with applied pulsation disturbance. Both the droplet volume and ejection velocity are independently and linearly tunable. Moreover, it expands the regulation range of droplet size, and the generated droplets are highly monodisperse. The relative standard deviation (RSD) of the droplet volume and ejection velocity is 3.5 and 3.9%, respectively. The applicable fluid viscosity is up to 100 mPa·s. The influences of the pulsation amplitude, frequency, duty cycle, and the liquid viscosity are also investigated. The improved control flexibility will greatly facilitate potential applications of the droplet ejection technology.