Periodic Reporting for period 4 - PaDyFlow (Particle dynamics in the flow of complex suspensions)
Período documentado: 2021-03-01 hasta 2022-02-28
Particle laden flows are ubiquitous in nature and industrial applications. Particle trajectories determine transport in porous media or biomedical conducts and effective suspension properties dictate flow behavior in food processing or biofluid flow. For better control it is necessary to know how to predict these processes from the involved particle and flow properties.
The objective of PaDyFlow is to provide a systematic experimental approach filling the gap in current understanding. This is achieved using novel microfabrication and characterization methods providing a set of complex anisotropic microscopic particles with tunable properties, covering size, shape, deformability and activity. Microfluidic flow geometries are designed to investigate particle transport in various well controlled flow conditions. By systematically combining relevant particle and flow properties PaDyFlow addresses many degrees of freedom simultaneously, a situation too complex for current modeling. PaDyFlow establishes a direct link between the microscopic particle flow interaction and the macroscopic properties of dilute suspensions of complex particles using original microfluidic rheometers of outstanding resolution.
The comprehensive understanding of fluid structure interactions at low Reynolds number gained during PaDyFlow constitutes the basis for novel numerical approaches that can now be developed based on experimentally validated hypotheses. Our knowledge permits the development of local flow sensors, targeted delivery and novel microfluidic filtration or separation devices. In the future suspension can be designed to demonstrate unprecedented properties by carefully choosing particle and flow properties following our results.
The objective of PaDyFlow is to provide a systematic experimental approach filling the gap in current understanding. This is achieved using novel microfabrication and characterization methods providing a set of complex anisotropic microscopic particles with tunable properties, covering size, shape, deformability and activity. Microfluidic flow geometries are designed to investigate particle transport in various well controlled flow conditions. By systematically combining relevant particle and flow properties PaDyFlow addresses many degrees of freedom simultaneously, a situation too complex for current modeling. PaDyFlow establishes a direct link between the microscopic particle flow interaction and the macroscopic properties of dilute suspensions of complex particles using original microfluidic rheometers of outstanding resolution.
The comprehensive understanding of fluid structure interactions at low Reynolds number gained during PaDyFlow constitutes the basis for novel numerical approaches that can now be developed based on experimentally validated hypotheses. Our knowledge permits the development of local flow sensors, targeted delivery and novel microfluidic filtration or separation devices. In the future suspension can be designed to demonstrate unprecedented properties by carefully choosing particle and flow properties following our results.
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
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
Several novel experimental methods have been developed during PaDyFlow. Novel passive and active particle tracking methods follow microparticles transported in viscous flows. Our 3D Lagrangian tracking method permits to follow swimming bacteria with or without flow over large distances and a new two-color tracking method permits for the first-time full observation of flagella dynamics during bacteria swimming. New original particle fabrication methods have been developed, concerning mainly flexible microhelices of tunable geometry and 3D micro-impression of helicoidal particles. A very precise liquid-based pressure sensor has been developed using a photonic hydrogel that changes color under applied pressure and has been successfully implemented into a microfluidic device.
Unexpected particle morphologies have been uncovered. We discovered for example the formation of helicoidal structures under viscous compression of flexible filaments. This discovery was surprising as normally the application of an external torque is necessary to form such chiral structures (no torque is applied in our system). Following the gained understanding these structures were identified in many other systems, as fiber spinning or biological applications.
Novel numerical approaches have been developed by our collaborators, based on our experimental results obtained in our well controlled model systems. They constitute validated hypotheses that theory can be based on and allowed for the first time for the emergence of modeling able to capture at least partially the complexity of the applications and experiments.
Unexpected particle morphologies have been uncovered. We discovered for example the formation of helicoidal structures under viscous compression of flexible filaments. This discovery was surprising as normally the application of an external torque is necessary to form such chiral structures (no torque is applied in our system). Following the gained understanding these structures were identified in many other systems, as fiber spinning or biological applications.
Novel numerical approaches have been developed by our collaborators, based on our experimental results obtained in our well controlled model systems. They constitute validated hypotheses that theory can be based on and allowed for the first time for the emergence of modeling able to capture at least partially the complexity of the applications and experiments.