Implementation of an experimental flow and particle fabrication platform
A unique experimental platform has been built, combining control over particle properties (using microfabrication methods) and flow geometries (using optimized microfluidic devices). Novel particle fabrication methods have been developed, including in situ polymerization of hydrogel particles, 3D printing at the micron-scale and fabrication of flexible helical structures from nano-ribbons using a stop flow method. Biological objects as actin filaments or E-coli bacteria have been included. Well controlled flow geometries ranging from simple to more complex geometries have been implemented and rely on optimization algorithms and various fabrication methods, from classical soft lithography devices to 3D glass microchips. Stationary as well as periodic flow conditions can be imposed. The platform is complemented with a Lagrangian 3D particle tracking technique as well as original microfluidic rheometers. A novel pressure sensor has been developed.
This platform constitutes the experimental basis permitting the systematic exploration of the role of particle and flow properties on microparticle dynamics as well as the investigation of suspensions properties performed during PaDyFlow.
Microscopic particle dynamics – a systematic study
To respond to objective (I) “Understand how fluid-structure interactions determine microscopic particle dynamics” many relevant particle and flow properties have been investigated. Systematic results on particle dynamics, including morphologies and transport properties have been obtained and have been made available to numerical simulation and theory, in direct collaboration with international groups, one of the goals of PaDyFlow.
The combined results obtained elucidate the role of different particles properties as elongation, shape, activity or Brownian noise on particle dynamics. These observations pave the way to novel control of particle transport as well as being the microscopic origin of macroscopic suspension properties. These observations thus constitute a crucial ingredient for the design of complex suspensions. The comprehensive results also pave the way for the development of novel simulations approaches based on experimentally validated hypothesis.
Suspension properties
To respond to objective (II) of PaDyFlow “Understand how fluid-structure interactions determine macroscopic suspension properties” experimental measurements have been performed for fiber suspensions as well as active suspensions and suspensions of flexible discs. The fabrication of reasonable amounts of suspensions of specifically designed micro-particles has been achieved, but despite the novel microfluidic rheological methods developed, quantitative experimental results remain scarce. The objective (III) to directly link the microscopic structure of complex particles under flow and the macroscopic properties of their dilute suspensions, has thus been addressed from a numerical point of view.
The outcome of PaDyFlow has been published in high impact journals as Phys. Rev. Lett., Nature Communications, Nature Physics, PNAS, Science Advances and a European patent has been accepted
