Acinus-on-a-chip: a microfluidic platform for pulmonary acinar flows.

Area of Science:

• Pulmonary fluid dynamics
• Microfluidics
• Respiratory system research

Background:

• Current methods like computational fluid dynamics (CFD) and scaled-up models have limitations in replicating acinar tree complexity and cyclic wall motion.
• Existing experimental setups struggle to simultaneously capture both airflow and inhaled particle dynamics.
• Understanding convective respiratory flows is crucial for predicting inhaled particle fate.

Purpose of the Study:

• To introduce a novel microfluidic device that mimics pulmonary acinar flow characteristics at the alveolar scale.
• To experimentally validate predicted alveolar flow patterns and characterize the flow environment.
• To establish a platform for future investigations into inhaled particle dynamics within the lung.

Main Methods:

• Development of a microfluidic device with anatomically inspired geometry, featuring five generations of branching airways and periodic wall motion.
• Utilized micro-particle image velocimetry (micro-PIV) with a glycerol solution to quantify detailed flow patterns.
• Measured key flow parameters including Reynolds and Womersley numbers, and cyclic wall displacements.

Main Results:

• Experimentally demonstrated a gradual transition of alveolar flow patterns from recirculating to radial streamlines along the acinar tree.
• Confirmed that the microfluidic system accurately replicates realistic acinar flow characteristics at the alveolar scale.
• Successfully matched key dimensionless numbers (Reynolds, Womersley) and captured cyclic wall motion.

Conclusions:

• The novel microfluidic device successfully mimics key aspects of the pulmonary acinar flow environment.
• This platform provides the first experimental validation of predicted alveolar flow pattern transitions.
• The device holds promise as an in vitro tool for studying inhaled particle deposition in the deep lung.