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Liquid Flow and Control Without Solid Walls

preprint
revised on 19.07.2019 and posted on 19.07.2019 by Peter Dunne, Takuji Adachi, Alessandro Sorrenti, J.M.D. Coey, Bernard Doudin, Thomas Hermans, Arvind Dev, Lucas Giacchetti, Anne Bonnin, Catherine Bourdon, Pierre Mangin
Solid walls become increasingly important when miniaturizing fluidic circuitry. They limit flow-rates achievable for a given pressure drop, and are plagued by fouling. Approaches to reduce the wall interactions include hydrophobic coatings, liquid-infused porous surfaces, nanoparticle surfactant jamming, changing the surface electronic structure, electrowetting, surface tension pinning, and atomically flat channels. A better solution may be to avoid the solid walls altogether. Droplet microfluidics or sheath flow achieves this, but require continuous flow of both the liquid transported and the outer carrier liquid. Here we demonstrate a new approach, where wall-less aqueous liquid channels are surrounded by an immiscible magnetic liquid, both being stabilised by a quadrupolar magnetic field. This creates self-healing, uncloggable, anti-fouling, and near-frictionless liquid-in-liquid fluidic channels with millimetre effective slip lengths. Pumping is achieved by moving permanent magnets that have no physical contact with the liquid channel. We show that this magnetostaltic pumping method can be used to transport whole human blood with very little damage due to shear forces; haemolysis is reduced by an order of magnitude compared to traditional peristaltic pumping. Our liquid-in-liquid approach provides new avenues to transport delicate liquids, particularly when scaling channels down to the micron scale with no need for high pressures, while retaining basic microfluidic circuitry functionalities.

Funding

We acknowledge the support of the University of Strasbourg Institute for Advanced Studies (USIAS) Fellowship, The ‘Chaire Gutenberg’ of the Région Alsace (J.M.D.C.), the Labex NIE 11-LABX-0058_NIE within the Investissement d’Avenir program ANR-10-IDEX-0002-02, and SATT Conectus funding. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 766007. We acknowledge the Paul Scherrer Institut, Villigen, Switzerland for provision of synchrotron radiation beamtime at beamline TOMCAT of the SLS. We are grateful to Dr. Hu Boping, of San Huan Corporation for giving us thin magnetic bilayer sheets. We thank Fabien Chevrier for technical support, and the staff of the STnano nanofabrication facility for help in sample fabrication. We thank Nina Matoussevitch for the synthesis of ferrofluids.

History

Email Address of Submitting Author

hermans@unistra.fr

Institution

University of Strasbourg

Country

France

ORCID For Submitting Author

0000-0003-1121-1754

Declaration of Conflict of Interest

Some of the magnetic fluids featured in this work are available from Qfluidics.com. Thomas M. Hermans holds shares in the company.

Version Notes

Revised version of the manuscript. Main changes: 1) anti-tube sizes one order smaller than previously reported, 2) full model of slip length in 3D, 3) application of magnetostaltic pumping to human blood transport. Five new authors have been added to this version (AAD, LG, AB, CB, PM)

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