Mucus pumping from artificial magnetic cilia in an open to air microfluidic channel
The pulmonary bronchi are lined with a thin mucus layer that protects the airways by trapping and removing foreign particles. This mucus is cleared from the lungs by coordinated beating of motile cilia on the epithelial surface, which transport mucus upward toward the throat. Impairment of this mucociliary clearance mechanism can lead to respiratory infection, reduced lung function, and increased mortality [1].
To better understand this process, artificial cilia systems have been developed, particularly those based on microfabricated magnetic cilia [2]. Here, we present artificial cilia composed of micrometer-scale elastomeric pillars embedded with iron microparticles, rendering them superparamagnetic [3]. We characterize their magnetoelastic behavior and model their motion under external magnetic actuation. Under a rotating magnetic field, the cilia perform periodic rowing motions that pump fluid through microchannels.
We introduce a novel analysis of unstable pillar dynamics, expanding conventional magnetoelastic models to capture the irregular, non-periodic motion observed experimentally and its impact on pumping performance. Following this, we demonstrate a new open-to-air microchannel platform that more closely replicates the physiological conditions of mucociliary clearance. This configuration enables direct investigation of mucus–air interfaces and their influence on flow behavior. Finally, we assess the effect of mucus rheology by comparing fluid pumping in Maxwellian and Newtonian systems.
Left: Scanning electron microscopy images of microfabricated magnetic cilia Right: Time lapse of a magnetic cilia actuation.
[1] Bustamante-Marin, and Ostrowski, (2017), Cold Spring Harb Perspect Biol, 9:a028241.
[2] ul Islam, et al. (2022), Lab Chip, 22.9:1650-1679.
[3] Moore et al. (2025), Lab Chip, 25.12:2949-2960.