Fluid processes in smart microengineered devices: Hydrodynamics and thermodynamics in microspace

Lead Research Organisation: Imperial College London
Department Name: Department of Chemical Engineering

Abstract

The current microfluidic devices market is $2 Billion and expected to double by 2016. Such microdevices are usually integrated in multifunctional units, which not only offer numerous advantages over traditional large-scale technologies, but also provide a multitude of potential uses in many different research fields that exploit fluids in confined geometries. They have numerous practical applications including drug delivery (e.g. inhalers, microneedles), analytical devices, point of care diagnostics, continuous flow small scale intensified manufacturing, pharmaceutical research, clinical and veterinary diagnostics, etc. In microchannel devices fluids flow in confined geometries and although significant progress has been made, understanding how the different phenomena occurring across a wide range of lengths scales, from molecular-scale processes to macroscopic hydrodynamic ones, and how they are related to each other, is still lacking. More specifically, the proposed research focuses on how microstructures, e.g. membranes, microcontactors, or patterned substrates, affect the hydrodynamics and thermodynamics of multiphase flows in microspace; and more importantly how they are influenced by the presence of the microstructure. Such understanding is critical for furthering the applications of microfluidic devices and their utilisation for heat-mass transport enhancement.

The study of microengineered devices in the presence of microstructure posseses many challenges from both a fundamental and applied research point of view. It is our belief that a complete and systematic study of such devices should involve an interdisciplinary approach that requires the use of tools and the development of new methodologies from different areas. This proposal seeks funding for a comprehensive four-year research programme into a novel synergistic approach that will combine state-of-the-art experimental techniques, sophisticated computational fluid dynamics and molecular modeling as well as advanced theoretical physics elements, never attempted before. We aim at rationally understanding, and quantitatively characterising fluid processes in microstructured confined geometries, on both the molecular/thermodynamic and hydrodynamic level, hence establishing connections between phenomena occurring at widely separated scales. As a main case study we shall consider microscale fluid separation which highlights some of the currently unresolved, yet key issues in microengineering technology, namely vapour-liquid equilibrium in confined geometries and breakthrough process (i.e. one phase invading into another). Our main findings will also be used to explore other applications where microstructures play a central role, such as microdistillation, or slip flows and droplet formation.

The work will be undertaken by a team from the Chemical Engineering Department at Imperial College London with complementary skills and strengths: Kalliadasis (Hydrodynamics/Statistical Mechanics -- Computations, Theory), Galindo (Statistical Mechanics/Molecular Dynamics -- Computations), and Pradas (Statistical/Theoretical Physics -- Computations, Theory); and a team from the Chemical Engineering Department at University College London: Gavriilidis (Experimental Microchemical Engineering and Microfluidics), Kuhn (Microfluidics, Multiphase Flows Modelling and Experiments), and Sorensen (Process Design, Microdistillation).

Planned Impact

The economic and societal impact of the proposed research will be realised through the development of modelling and predictive tools for complex fluid processes in microengineered devices (MED). Such systems are key to several rapidly developing technologies in the UK's smart materials, specialty manufacturing sectors and biomedical industries. Future developments in these sectors will require sophisticated mathematical, computational and experimental techniques, as proposed here, which can contribute to many aspects, from improvements in product and design all the way to production.

The research will also lead to the development of state-of-the-art numerical methodologies for the accurate and reliable multiscale simulations of fluid flow in confined microgeometry. These codes will be of benefit to the control and optimisation of industrial processes and devices that exploit microscale flows.

Finally, the team of Investigators has a strong track record of technology transfer through close collaborations with industry, short courses, workshops and training of high-calibre researchers. The impact plan we have devised is based on a range of routes to maximise the likelihood of success and to reach as wide a community as possible: interactions with industrial partners through other projects, training of the researchers, publication in leading journals, conference presentations, provision of a website and research colloquium.

Publications

10 25 50
 
Description Microengineered devices (MED) have recently seen an
explosive growth in a wide spectrum of areas, from microchemical and biological engineering to materials processing and the rapidly growing field of microfluidics, especially lab-on-a-chip systems. Integrated MED offer
numerous advantages over traditional technologies, such as small operating volume, ease of use point-of-care diagnostics, fast reaction of samples and excellent control of the fluids involved. At the same time, advances in microengineering technology have led to the ability to fabricate microstructures, e.g.~membranes/microcontactors and microscale patterned
surfaces. These microstructures can be smartly designed and fabricated to substantially enhance heat and mass transport, create microdroplets of specific size, modify the wetting properties of substrates at will, or manufacture liquid repellent (superhydrophobic or superoleophobic)
surfaces.

Not surprisingly therefore, MED have been an active topic of both fundamental and applied research especially over the last decade. However, despite the several developments and considerable attention they have received, a large
number of key issues and problems remain unresolved and many aspects of fluid processes in MED, especially in the presence of a microstructure, still elude us. In particular, the precise influence of microstructure on the dynamics
and detailed characterisation and quantification of the mechanism for heat or mass transport enhancement. Furthermore, one of the key features of MED is that the interaction between different phases in contact with a solid surface is strongly influenced by the high surface-to-volume ratio achieved as the system is downsized and as a consequence, the microstructure has a big impact on both the molecular (thermodynamic) level and on the macroscopic (hydrodynamic) state of the involved fluids. As far as
molecular-scale phenomena are concerned, they affect strongly the macroscale while the need in macroscopic description is interlinked with the necessity to take into consideration microscopic factors, which come to influence the
fluid motion and transport at incommensurately larger scales. At the same time, the presence of additional complexities in MED, i.e. free-boundaries/interfaces, whose location is not known a priori, makes the corresponding problems inherently nonlinear and hence difficult to analyse. On a practical level, our ability to predict accurately and systematically as well as scale-out rationally complex hydrodynamic processes
in confined geometries, crucial for the design of the corresponding engineering systems, is lacking. The same is true for reference literature and data that design engineers of MED can turn to in order to predict reliably transport coefficients.

The proposed research aims to address these questions through a synergistic approach at the crossroads between applied mathematics, fluid dynamics, microengineering, molecular modelling and theoretical physics, never attempted before in the field.} It will involve a balanced combination
of sophisticated analytical, computational and experimental techniques, a major strength of the research.
Exploitation Route The impact plan we have developed is based on the identification of several roots to societal-economic impact and impact on peers.

The following activities offer a means of dissemination of the results obtained in this proposal to fellow academics as well as industrial researchers: (i) Our national and international network of academic contacts; (ii) National and international conferences. These are leading international forums for the exchange of information on all aspects of applied mathematics, fluid flow and thermodynamics-statistical mechanics of fluids; (iii) We have strong records in publication of articles in the leading international journals of high impact factor (hence read by a wide audience) of our respective fields. It is anticipated that the results from this project will be submitted to high-profile international journals devoted to the publication of authoritative articles at the forefront of the topics of the proposed research; (iv) Research seminars in the UK and overseas; (v) Sabbatical and occasional visits by overseas scientists to the UK and visits to overseas institutions. Each Investigator has active international collaborations and regularly visits overseas institutions and receives visitors from abroad. This will aid to the dissemination of the research and increase its impact; (vi) Web-based dissemination, i.e. via the creation of an interactive website with a Wiki architecture that will provide the latest news, access to results, codes and relevant publications. In particular, the resulting numerical codes will be made available on the web as open source. This would also allow for contributions from our peers to the codes' further development. The project will thus contribute to the wider dissemination of our computational tools; (vii) As noted below there are linkages with industry, through other research.

This is fundamental research, however the applications are far reaching and have potential for commercial exploitation. IC has a dedicated commercial exploitation group, Imperial Innovations Ltd (IIL), and consultancy arm while the engineering faculty has a Knowledge Transfer Fellow and Intellectual Property is protected through IIL. There are also links with industry through other research and, therefore, we are ideally placed to disseminate the relevant parts of this research to those who could ultimately use it in applications. These industrial collaborations are vital resources that will be used to facilitate the wider impact of the research and to ensure that results are channelled towards appropriate applications.
Sectors Chemicals,Digital/Communication/Information Technologies (including Software),Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

URL http://www.imperial.ac.uk/complex-multiscale-systems
 
Description The research aims to provide both physical insight in complex fluid flows in confined geometry and the appropriate modelling/predictive tools for such systems. These should be of great interest to researchers and engineers whose technological processes involve at some stage MED as they will enable them to tackle classes of problems that have hitherto been inaccessible to them. Also to workers in the commercial/private sector with interests and/or stakes in the development of predictive models for systems utilising MED. In terms of applications, these are quite extensive: From small-scale separations, e.g. microdistillation, to lab-on-chip systems, e.g. DNA microarrays. A central problem in microfluidics is also how to control and manipulate fluids at small scales. This is crucial for a variety of applications. For example, an active area of microfluidic applications has recently been the study of fundamental properties of liquid molecules. Here, controlled microfluidics could offer the possibility to stably confine molecules to very small spaces, or to subject them to controlled forces. In this respect, microfluidics can be used as an engineering tool to extract fundamental knowledge for e.g. biological applications, such as nuclear pore complexes and the transport of particles in the circulatory and respiratory systems.
First Year Of Impact 2016
Sector Chemicals,Energy,Manufacturing, including Industrial Biotechology
 
Title Development of new theoretical, computational and experimental methodologies for complex multiphase flows in microengineered devices (MED) 
Description --The design and assembly of new experimental setups for complex multiphase flows in MED. --The computational characterization of such flows using diffuse-interface/phase-field models. --The characterisation of the hydrodynamic critical transitions in MED, in terms of critical phenomena, thus connecting the communities of critical phenomena theory (modern theoretical physics) with microfluidics (modern engineering). --The scrutiny of fluid-solid interaction using molecular dynamics (MD) (for fluids in flat substrates) and density-functional theory (for fluids in confinement). --The application of the experimental-theoretical findings to study specific applications-driven problems. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact Characterising of the hydrodynamic critical transitions in MED, in terms of critical phenomena, thus connecting the communities of critical phenomena theory (modern theoretical physics) with microfluidics (modern engineering) is particularly novel. Also the general approach and philosophy of the project, in that it is synergistic on the crossroads between applied mathematics, fluid dynamics, microengineering, molecular modelling and theoretical physics, are particularly novel and have never been attempted before in the field. The rational and systematic use of advanced theoretical, computational and experimental methods and techniques, currently being developed by the project, already generates valuable insight into many aspects of MED from optimal product design all the way to production. This in turn should substantially contribute to the UK's capability to develop integrated multiscale models describing MED with obvious economic benefits, when considering that the current microfluidic device market is $2 Billion. 
URL http://www.imperial.ac.uk/complex-multiscale-systems
 
Title Deevlopment of novel theoretical and computational methodologies for complex multiphase flows in confinement 
Description We have developed a number of novel theoretical and computational methodologies for fluids in confinement ranging from the microscale (using molecular dynamics and density-functional theory) all the way to the macroscopic-continuum scale (using diffuse interface/Cahn-Hilliard models). 
Type Of Material Computer model/algorithm 
Provided To Others? No  
Impact Integrated multiscale models for complex fluid flows in confinement do not exist at present. The research aims to provide both physical insight in complex fluid flows in confined geometry and the appropriate modelling/predictive tools for such systems. These should be of great interest to researchers and engineers whose technological processes involve at some stage MED as they will enable them to tackle classes of problems that have hitherto been inaccessible to them. Also to workers in the commercial/private sector with interests and/or stakes in the development of predictive models for systems utilising MED. In terms of applications, these are quite extensive: From small-scale separations, e.g. microdistillation, to lab-on-chip systems, e.g. DNA microarrays. A central problem in microfluidics is also how to control and manipulate fluids at small scales. This is crucial for a variety of applications. For example, an active area of microfluidic applications has recently been the study of fundamental properties of liquid molecules. Here, controlled microfluidics could offer the possibility to stably confine molecules to very small spaces, or to subject them to controlled forces. In this respect, microfluidics can be used as an engineering tool to extract fundamental knowledge for e.g. biological applications, such as nuclear pore complexes and the transport of particles in the circulatory and respiratory systems. 
URL http://www.imperial.ac.uk/complex-multiscale-systems
 
Description Collaboration with Prof. A. Galindo 
Organisation Imperial College London
Department Department of Life Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution A central theme of this project is the computation of phase transitions of fluids in structured geometries. Although the sizes of the microengineered devices are at the micron level, they are still prohibitive for molecular dynamics (MD). Density-functional theory (DFT) on the other hand retains the microscopic elements of macroscopic systems but at a cost much smaller compared to MD. My group has made many contribution in the DFT of classical fluids over the last few years. However, the fluid-fluid and fluid-solid intermolecular interaction parameters in DFT are not known a priori. Our idea was then to use MD, but for simpler systems, e.g. a fluid on a flat substrate, as the fluid-fluid and solid-fluid intermolecular parameters are geometry independent, and thus benchmark these DFT parameters.
Collaborator Contribution Prof. Galindo's group on the other had has extensive expertise on MD and its use in different fluid settings.
Impact So far we have looked at MD of fluid droplets on planar substrates with the aim of obtaining equilibrium contact angles. Despite the considerable attention this problem has received, there are still several issues that elude us, in particular obtaining contact angles without necessarily using large system sizes which hamper the MD computations. We have made substantial progress on this problem and we are now ready for the next step, benchmarking the DFT parameters with MD. The equilibrium contact angles obtained from MD so far will play a crucial role in this direction.
Start Year 2015
 
Description Collaboration with Prof. A. Gavriilidis 
Organisation University College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Our team is focusing on the development of novel theoretical and computational tools, covering both the molecular and the continuum scale, for complex multiphase flows in smart microengineered devices (MED).
Collaborator Contribution The UCL team designs and assembles new experimental setups which will make the investigation of new phenomena in MED more efficient with particular emphasis on micro fluid scale separation processes. The experiments guide our theoretical-computational investigations. And vice versa, by appropriately narrowing down the parameter spaces, our theoretical-computational studies suggest intelligent experiments.
Impact The main outcomes so far have been: --The design and assembly of new experimental setups for complex multiphase flows in MED. --The computational characterization of such flows using diffuse-interface/phase-field models. --To characterise the hydrodynamic critical transitions in MED, in terms of critical phenomena, thus connecting the communities of critical phenomena theory (modern theoretical physics) with microfluidics (modern engineering). --Scrutinise fluid-solid interaction using molecular dynamics (MD) (for fluids in flat substrates) and density-functional theory (for fluids in confinement). --The application of the experimental-theoretical findings to study specific applications-driven problems. The work is interdisciplinary in that it involves a collaboration between two Chemical Engineering Departments (IC and UCL) and a Mathematics & Statistics Department (Open Univ.) but also from the point of view that it is synergistic approach on the interface between applied mathematics, fluid dynamics, MD and theoretical physics, never attempted before in the field.
Start Year 2015