A Computational Study of Aerosol Droplet Formation Mechanism for Personalised Airway and Lung Management (PALM)

Abanoub Shenoda, Jason Brenker, Jackson Gum & Tuncay Alan

Monash University, Department of Mechanical and Aerospace Engineering, Melbourne VIC, 3800 Australia


Personalised Airway and Lung Management (PALM) is an acoustically actuated hand-held inhaler that can produce aerosols with tuneable diameters. The device employs an array of microfabricated hydrophilic channels, which bound the liquid to be aerosolised in a well-defined region. When the microfluidic chip is vibrated at high frequencies, capillary waves form within the liquid/ air interface and after a threshold amplitude is reached, those waves start to break up and eject droplets. Our experiments show that the formation of the droplets, as well as their size, can be accurately controlled on-demand by dialling the actuation parameters. This has unique applications for personalised, effective pulmonary drug delivery to address specific patients’ needs. This paper presents a mathematical model and numerical simulations to explain the on-demand control mechanism. A two-dimensional (2D) computational fluid dynamics (CFD) model is used to simulate the microfluidic component of the inhaler. Our results illustrate that the actuation frequency and amplitude strongly influence the onset of the droplet break-up mechanism as well as the droplet size. The simulations agree well with a mathematical model relying on the damped Mathieu equation and the predicted amplitude for the onset of aerosolisation lies within the expected range.

Key Message

CFD simulations of the PALM device demonstrate its capability to tune the diameter of aerosol droplets for personalised pulmonary drug delivery.