An unrecognized inertial force induced by flow curvature in microfluidics

Siddhansh Agarwal, Fan Kiat Chan, Bhargav Rallabandi, Mattia Gazzola, Sascha Hilgenfeldt

Research output: Contribution to journalArticlepeer-review


Modern inertial microfluidics routinely employs oscillatory flows around localized solid features or microbubbles for controlled, specific manipulation of particles, droplets, and cells. It is shown that theories of inertial effects that have been state of the art for decades miss major contributions and strongly underestimate forces on small suspended objects in a range of practically relevant conditions. An analytical approach is presented that derives a complete set of inertial forces and quantifies them in closed form as easy-to-use equations of motion, spanning the entire range from viscous to inviscid flows. The theory predicts additional attractive contributions toward oscillating boundaries, even for density-matched particles, a previously unexplained experimental observation. The accuracy of the theory is demonstrated against full-scale, three-dimensional direct numerical simulations throughout its range.

Original languageEnglish (US)
Article numbere2103822118
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number29
StatePublished - Jul 20 2021


  • Inertial microfluidics | oscillatory flows | particle manipulation

ASJC Scopus subject areas

  • General


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