| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | February 10, 2015 |
| Latest Amendment Date: | February 10, 2015 |
| Award Number: | 1532652 |
| Award Instrument: | Standard Grant |
| Program Manager: |
William Olbricht
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | May 16, 2014 |
| End Date: | February 28, 2017 (Estimated) |
| Total Intended Award Amount: | $206,257.00 |
| Total Awarded Amount to Date: | $206,257.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
9500 GILMAN DR LA JOLLA CA US 92093-0021 (858)534-4896 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
CA US 92093-0934 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | PMP-Particul&MultiphaseProcess |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
1150590
PI: Saintillan
Recent advances in microfabrication techniques have enabled the development of the field of microfluidics. As these techniques become more sophisticated, devices are now being scaled down to the nanoscale, bringing about a new wealth of physical phenomena to be exploited in lab-on-chip devices for instance. The use of electrokinetics in these devices has proven particularly useful in a wide range of applications, and specifically to manipulate fluid, particles and macromolecules. Yet, the modeling of these flows at the nanoscale still suffers from limitations, owing to the inability of classical models to capture certain non-continuum effects, and to the high-cost of direct molecular simulations, which are only able to resolve very short time scales. These observations emphasize the need for renewed modeling efforts in the field of electrokinetics in highly confined environments. In this project, we propose to study electrochemical and macromolecular transport in confined devices using a new simulation approach for diffuse charge dynamics based on a Langevin model and Brownian dynamics for the electrolyte species. This new method will incorporate features from classical continuum models, but will also allow one to capture non-continuum effects without the high cost of atomistic methods. It can be applied to study both electroosmosis and electrophoresis with electrical double layers of arbitrary sizes, and can easily account for complex geometries. A new polymer model based on slender-body theory for a fluctuating elastic filament will also be developed to study the dynamics of polyelectrolytes with arbitrary Debye lengths. These new models and tools will be applied to study a number of technological applications, including: (i) the electrophoretic separation of oligonucleotides in nanochannels, (ii) electrochemical transport through nanocapillary array membranes, and (iii) the electrically driven translocation of biological polymers through nanopores.
The proposed research activities will serve to enhance the fundamental understanding and modeling of electrokinetic flows and macromolecular transport in highly confined geometries, where non-continuum effects may become important. The new models and simulation tools implemented as part of the research will be applicable to a wide range of problems in the fields of physics, engineering, and medicine, among which: biochemical assays on lab-on-chip devices, electrohydrodynamic stretching of DNA for genomic analysis, electrochemical transport through polymer electrolyte membranes in PEM fuel cells, and many others. Educational and outreach activities will also be integrated in this program. A new graduate-level course on fundamentals and applications of micro- and nanofluidics, including electrokinetic flows, will be introduced at the University of Illinois. A tutorial website on electrokinetics and its applications will be designed for use by students and non-specialists, and a visualization software for diffuse charge dynamics and electrochemical transport will be developed and made available online to students and researchers in the field under a public license.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
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This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Recent advances in microfabrication techniques have enabled the development of the field of microfluidics. As these techniques become more sophisticated, devices are now being scaled down to the nanoscale, bringing about a new wealth of physical phenomena to be exploited in lab-on-chip devices for instance. This project has focused on the development of efficient theoretical and numerical models and tools for the study of transport phenomena in small-scale devices, with focus on semi-flexible polymers, passive as well as active particles, and liquid droplets, under both applied flows and external electric fields.
Our study of semi-flexible polymers focused on the nonlinear coupling between polymer elasticity and flow, which can result in a number of instabilities and complex dynamics such as buckling in compressional flows and under sedimentation, tumbling in shear flows, with a variety of mode shapes that depend on the relative importance of shear stresses, elastic bending forces, and thermal fluctuations. This project laid the groundwork for understanding these complex dynamics by developing realistic simulations of such flows using as novel polymer model. Predictions from our simulations were able to explain many outstanding experimental observations with great fidelity, and provide a path towards the modeling of macromolecular transport in more complex flow fields and geometries.
Another aspect of the research considered transport of self-propelled particles in strongly confined environments, such as swimming bacteria or synthetic self-propelled colloids. The ability of such particles to swim leads to intriguing effects in confinement, such as accumulation at walls, upstream swimming, centerline depletion in strong flows, decreased apparent viscosities, and transition to spontaneous flows in the absence of any external forcing. These effects, which are all observed experimentally, had not previously been explained in detail. Theoretical models based on transport equations for both the fluid and particle phases were able to explain these observations and also showed excellent agreement with existing experimental data.
Other aspects of the research involved the formulation and implementation of efficient high-fidelity algorithms for the simulation of viscous particulate flows in microscale geometries, and also considered the dynamics of both rigid and deformable particles such as liquid droplets in the presence of electric fields.
These research activities have served to enhance the fundamental understanding and modeling of particulate and macromolecular transport in confined geometries. The new models and simulation tools implemented as part of the research should also be applicable to a wide range of problems in the fields of physics, engineering, and medicine, among which: biochemical assays on lab-on-chip devices, electrohydrodynamic stretching of macromolecules for genomic analysis, transport of motile cells for instance for fertility tests, and many others. This project also supported educational and outreach activities through the training and mentoring of graduate and undergraduate student researchers, and through the development of a new graduate-level course on Complex and Biological Fluids at the University of California San Diego and of a month-long summer course on Introduction to Fluids Engineering for local high-school students.
Last Modified: 05/31/2017
Modified by: David Saintillan
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