The integration of magnetic sources in a fluidic circuit enclosure, and the stabilization of ferrofluid surrounding the cylindrical flow of the liquid of interest has been successfully achieved. A stabilized water cylinder embedded in a ferrofluid enclosure was imaged in 3D by X-ray tomography at the PSI synchrotron light source facility (CH). The team is now capable of stabilizing and imaging tubes down 6 microns diameter. This finding shows how this approach is relevant for the field of microfluidics, in particular for flowing viscous liquids or delicate biological compounds. A resulting milestone publication involving three beneficiaries of the ITN appeared in Nature. Under dynamic flow conditions, particle velocimetry was performed in a fourth partner laboratory, and showed a nearly ideal plug flow of the inside viscous liquid.
Liquid-in-liquid flow is the archetype of non-stable fluid dynamics conditions. However, the addition of magnetic forces makes it remarkably stable, within a wide range of Reynolds numbers. Furthermore, the absence of solid walls strongly diminishes the friction forces. Reduction factors reaching 99,8 % were measured, while usual reports in the literature do not exceed a few tens of percent. Such impressive improvement opens new perspectives for flowing viscous materials in microfluidic channels under small pressure.
Progress in the study of fluids dynamics of ferrofluids small entities under magnetic field have also been obtained. Numerical algorithms for the simulation of three dimensional dynamics of magnetic fluid free interface did not existed so far. Synthesis and investigation of flexible ferromagnetic filaments gives new possibilities for the field of microrobotics and microfluidics, fields developing nowadays very fast.
Design and set up of an actuation system with permanent magnets and electromagnets, with on-chip microscopy and image analysis was achieved. Studies showed how it was possible to transport droplets surrounded by a ferrofluid through an external magnetic field, and magnetic actuation of cilia has been shown. Cell integration and cell culturing in microfluidic devices under the passage of fluid through circulatory system has been performed in frames of Biological Test Platforms and Integration stream. The team evaluated cell adhesion, cytotoxicity, viability and specific functions.
The combination of fundamental understanding of the fluid dynamic of systems sensitive to magnetic forces, the successful realization of magnetic confinement in microfluidic circuits, and the integration of bio-inspired magnetic components in microfluidics devices make this emerging new field promising and mature enough for the book publication in Springer ‘Topics in Applied Physics Series’
