Model studies on motion of respiratory droplets driven through a face mask

TL;DR

This study models how respiratory droplets move through face masks using Langevin dynamics, revealing factors affecting droplet permeation and informing better mask design for disease prevention.

Contribution

It introduces a microscopic model of droplet interception in masks, analyzing the effects of various parameters on permeation and efficiency.

Findings

Permeation follows an Arrhenius temperature dependence.

Energy barriers increase with droplet size and network rigidity.

Driving force and confinement length decrease energy barriers.

Abstract

Face masks are used to intercept respiratory droplets to prevent spreading of air-borne diseases. Designing face masks with better efficiency needs microscopic understanding on how respiratory droplets move through a mask. Here we study a simple model on the interception of droplets by a face mask. The mask is treated as a polymeric network in an asymmetric confinement, while the droplet is taken as a micrometer sized tracer colloidal particle, subject to driving force that mimics the breathing. We study numerically, using the Langevin dynamics, the tracer particle permeation through the polymeric network. We show that the permeation is an activated process following an Arrhenius dependence on temperature. The potential energy profile responsible for the activation process increases with tracer size, tracer bead interaction, network rigidity and decreases with the driving force and confinement length. A deeper energy barrier led to better efficiency to intercept the tracer particles of a given size in the presence of driving force at room temperature. Our studies may help to design mask with better efficiency.