16 research outputs found
Biomass Processing for Biofuels, Bioenergy and Chemicals
Biomass can be used to produce renewable electricity, thermal energy, transportation fuels (biofuels), and high-value functional chemicals. As an energy source, biomass can be used either directly via combustion to produce heat or indirectly after it is converted to one of many forms of bioenergy and biofuel via thermochemical or biochemical pathways. The conversion of biomass can be achieved using various advanced methods, which are broadly classified into thermochemical conversion, biochemical conversion, electrochemical conversion, and so on. Advanced development technologies and processes are able to convert biomass into alternative energy sources in solid (e.g., charcoal, biochar, and RDF), liquid (biodiesel, algae biofuel, bioethanol, and pyrolysis and liquefaction bio-oils), and gaseous (e.g., biogas, syngas, and biohydrogen) forms. Because of the merits of biomass energy for environmental sustainability, biofuel and bioenergy technologies play a crucial role in renewable energy development and the replacement of chemicals by highly functional biomass. This book provides a comprehensive overview and in-depth technical research addressing recent progress in biomass conversion processes. It also covers studies on advanced techniques and methods for bioenergy and biofuel production
On-Chip Fabry-PĂ©rot Microcavity for Refractive Index Cytometry and Deformability Characterization of Single Cells
Une identification correcte et précise du phénotype et des fonctions cellulaires est fondamentale
pour le diagnostic de plusieurs pathologies ainsi quâĂ la comprĂ©hension de phĂ©nomĂšnes
biologiques tels que la croissance, les rĂ©ponses immunitaires et lâĂ©volution de maladies.
Conséquemment, le développement de technologies de pointe offrant une mesure multiparamétrique
Ă haut dĂ©bit est capital. Ă cet Ă©gard, la cytomĂ©trie en flux est lâĂ©talon de
référence due à sa grande spécificité, sa grande sensibilité et ses débits élevés. Ces performances
sont atteintes grĂące Ă lâĂ©valuation prĂ©cise du taux dâĂ©mission de fluorophores,
conjugués à des anticorps, ciblant certains traits cellulaires spécifiques. Néanmoins, sans ce
précieux étiquetage, les propriétés physiques caractérisées par la cytométrie sont limitées à la
taille et la granularité des cellules. Bien que la cytométrie en flux soit fondamentalement un
dĂ©tecteur optique, elle ne tire pas avantage de lâindice de rĂ©fraction, un paramĂštre reflĂ©tant
la composition interne de la cellule. Dans la littĂ©rature, lâindice de rĂ©fraction cellulaire a Ă©tĂ©
utilisé comme paramÚtre phénotypique discriminant pour la détection de nombreux cancers,
dâinfections, de la malaria ou encore de lâanĂ©mie. Ăgalement, les structures fluidiques de la
cytomĂ©trie sont conçues afin dâempĂȘcher une dĂ©formation cellulaire de se produire. Cependant,
les preuves que la dĂ©formabilitĂ© est un indicateur de plusieurs pathologies et dâĂ©tat
de santĂ© cellulaire sont manifestes. Pour ces raisons, lâĂ©tude de lâindice de rĂ©fraction et de
la déformabilité cellulaire en tant que paramÚtres discriminants est une avenue prometteuse
pour lâidentification de phĂ©notypes cellulaires.
En consĂ©quence, de nombreux biodĂ©tecteurs qui exploitent lâune ou lâautre de ces propriĂ©tĂ©s
cellulaires ont Ă©mergĂ© au cours des derniĂšres annĂ©es. Dâune part, les dispositifs microfluidiques
sont des candidats idéaux pour la caractérisation mécanique de cellules individuelles.
En effet, la taille des structures microfluidiques permet un contrĂŽle rigoureux de lâĂ©coulement
ainsi que de ses attributs. Dâautre part, les dispositifs microphotoniques excellent dans la
dĂ©tection de faibles variations dâindice de rĂ©fraction, ce qui est critique pour un phĂ©notypage
cellulaire correcte. Par consĂ©quent, lâintĂ©gration de composants microfluidiques et
microphotoniques Ă lâintĂ©rieur dâun dispositif unique permet dâexploiter ces propriĂ©tĂ©s cellulaires
dâintĂ©rĂȘt. NĂ©anmoins, les dispositifs capables dâatteindre une faible limite de dĂ©tection
de lâindice de rĂ©fraction tels que les dĂ©tecteurs Ă champ Ă©vanescent souffrent de faibles profondeurs
de pénétration. Ces dispositifs sont donc plus adéquats pour la détection de fluides
ou de molécules. De maniÚre opposée, les détecteurs interférométriques tels que les Fabry-
PĂ©rots sont sensibles aux Ă©lĂ©ments prĂ©sents Ă lâintĂ©rieur de leurs cavitĂ©s, lesquelles peuvent
mesurer jusquâĂ plusieurs dizaines de micromĂštres.----------Abstract Accurate identification of cellular phenotype and function is fundamental to the diagnostic
of many pathologies as well as to the comprehension of biological phenomena such as growth,
immune responses and diseases development. Consequently, development of state-of-theart
technologies offering high-throughput and multiparametric single cell measurement is
crucial. Therein, flow cytometry has become the gold standard due to its high specificity and
sensitivity while reaching a high-throughput. Its marked performance is a result of its ability
to precisely evaluate expression levels of antibody-fluorophore complexes targeting specific
cellular features. However, without this precious fluorescence labelling, characterized physical
properties are limited to the size and granularity. Despite flow cytometry fundamentally being
an optical sensor, it does not take full advantage of the refractive index (RI), a valuable labelfree
measurand which reflects the internal composition of a cell. Notably, the cellular RI has
proven to be a discriminant phenotypic parameter for various cancer, infections, malaria and
anemia. Moreover, flow cytometry is designed to prevent cellular deformation but there is
growing evidence that deformability is an indicator of many pathologies, cell health and state.
Therefore, cellular RI and deformability are promising avenues to discriminate and identify
cellular phenotypes.
Novel biosensors exploiting these cellular properties have emerged in the last few years. On
one hand, microfluidic devices are ideal candidates to characterize single cells mechanical
properties at large rates due to their small structures and controllable flow characteristics.
On the other hand, microphotonic devices can detect very small RI variations, critical for an
accurate cellular phenotyping. Hence, the integration of microfluidic and microphotonic components
on a single device can harness these promising cellular physical properties. However,
devices achieving very small RI limit of detection (LOD) such as evanescent field sensors suffer
from very short penetration depths and thus are better suited for fluid or single molecule detection.
In opposition, interference sensors such as Fabry-PĂ©rots are sensitive to the medium
inside their cavity, which can be several tens of micrometers in length, and thus are ideally
suited for whole-cell measurement. Still, most of these volume sensors suffer from large LOD
or require out-of-plane setups not appropriate for an integrated solution. Such a complex
integration of high-throughput, sensitivity and large penetration depth on-chip is an ongoing
challenge. Besides, simultaneous characterization of whole-cell RI and deformability has never been reported in the literature
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Understanding the Dynamics of Complex Fluids Using Microfluidics: Suspensions and Wormlike Micellar Solutions
Microfluidics are often used to inform the design of applications such as blood additives, high-throughput DNA sequencing, and point-of-care/lab-on-chip diagnostics. The small characteristic length scales in microfluidic systems can be leveraged to maintain low Reynolds numbers Re (ratio of inertial to viscous forces); with a viscoelastic fluid, the length scales can also lead to high elasticity numbers El (ratio of elastic to inertial forces). As a result, flow in microfluidic devices is not turbulent and can be highly elastic, providing a wealth of experimental capabilities. These include multiphase flow manipulation (which can be used to generate monodisperse bubbles and drops), trapping and analysis of single cells, and the development of secondary flows driven by elasticity. This dissertation focuses on three microfluidic studies: 1) microparticle generation and characterization, 2) examination of suspension flow dynamics, and 3) development of elastic instabilities in viscoelastic fluids flowing around a sharp bend.Microfluidic devices are capable of monodisperse, deformable particle generation, which is advantageous for tuning the specific properties of suspension components. This facilitates the systematic study of individual component properties on suspension flow behavior such as lateral migration and enables the study of suspension flow dynamics. Microfluidics is an ideal platform for studying suspension flow phenomena due to the long entry lengths needed to observe lateral migration. Although these length scales are large in macroscale, potentially on the order of meters, in microscale the entry length can be on the order of centimeters. This work additionally concerns the development of elastic instabilities in wormlike micellar solutions, a class of surfactant-based viscoelastic fluids. Due to the coupling of the elastic nature of wormlike micellar strands and the curvature of the flow streamlines, wormlike micellar solutions in flow can develop secondary flows (vortices). Despite the prevalent use of wormlike micellar solutions in consumer products, in drug delivery, and in drag-reducing agents, their structure and the mechanics of their flow behavior are not well understood. Planar microdevices can be used to investigate purely elastic instabilities that develop from a combination of shear or extensional flows. In contrast to flow in the more commonly studied microfluidic cross slot and contraction geometries, which is predominantly extensional, the flow in a sharp 90-degree bend is shear-dominated.This dissertation first investigates controlled microparticle generation and characterization. Monodisperse particles of varying size, shape, and deformability were produced using two microfluidic strategies. First, monodisperse emulsion droplets of a crosslinkable polymer solution were generated via a flow-focusing design, in which drops are formed from a central emulsified phase that is focused by adjacent continuous phases, generating well-controlled drop sizes from 45 to 183 ”m. Subsequently, droplets were crosslinked either 1) on chip, resulting in spherical particles, or 2) in an external gelation bath, resulting in an assortment of non-spherical, axisymmetric particles. Particle deformability was then quantified using micromechanics in a tapered capillary, where a particle is trapped at the tip of the taper. The shear and compressive moduli were obtained simultaneously by applying a range of hydrostatic pressures on the particle and analyzing the resulting particle deformation. This method allowed for differentiation between shear and compressive moduli and determined an effective modulus for an entire particle rather than a localized modulus. Changing the polymer system, crosslinker concentration, or polymer concentration produced particles with shear moduli (G) ranging over three orders of magnitude, from 0.013 kPa to 26 kPa.This library of particles was then used for lateral migration studies in long channels. The lower moduli microparticles (G < 0.10 kPa) are sufficiently soft to deform in channel flow, undergoing similar shape transitions as those seen in literature for capsules and vesicles. With increasing viscous shear, initially circular solid elastic particles in confined channel flow form egg-like, triangular, arrowhead, and finally parachute-like shapes. These shapes are distinct from previously reported capsule and vesicle deformation shapes and can be quantified by dimensionless quantities such as circularity, elongation, depth of the dimple at the trailing edge, and radius of curvature at the leading edge of the particle. Correlations were observed between capillary number Ca (ratio of viscous forces to restoring forces, in this case shear modulus) and the deformation as characterized by two parameters: circularity and radius of curvature at the tip. At low Ca, particle deformation is small and circularity is very close to 1; as Ca increases, circularity changes become more significant. Using circularity and radius of curvature at the tip, it is possible to obtain Ca and the corresponding shear modulus for individual particles from their deformation in channel flow.The final focus of this work is to examine the behavior of wormlike micellar solutions in a shear-dominated flow, particularly considering the flow and instabilities of shear thinning polymeric and wormlike micellar solutions through a microfluidic 90-degree bend. Two wormlike micellar solutions of cetylpyridinium chloride (CPCl) and sodium salicylate (NaSal) in water were investigated. At low NaSal to CPCl ratios, the wormlike micelles were linear; however, at high ratios the wormlike micelles became branched and showed shear banding within a range of shear rates. Microfluidic experiments on all solutions studied revealed unique regimes as secondary flows developed. At a critical Weissenburg number Wi (the ratio of elastic forces to viscous forces in shear), the flow of the polymeric solution transitioned from a steady base flow to a secondary flow that is characterized by the formation of a stationary lip vortex. The wormlike micellar solutions developed intermediate secondary flow behavior as Wi increased before transitioning to a third regime characterized by a time-dependent lip vortex. The linear wormlike micellar solution revealed a second regime similar to the one observed in the polymeric solution, but the branched, shear-banding wormlike micelle solution developed an intermittent outer corner vortex in addition to a time-dependent lip vortex. In contrast, no third regime was apparent in the polymeric solution over the same range of Wi. These differences in flow behavior demonstrate that the stability of elastic flows is a strong differentiator of rheological differences
Performance Enhancement of Building-Integrated Concentrator Photovoltaic System Using Phase Change Materials
Building-integrated Concentrator Photovoltaic (BICPV) technology produces noiseless and pollution free electricity at the point of use. With a potential to contribute immensely to the increasing global need for a sustainable and low carbon energy, the primary challenges such as thermal management of the panels are overwhelming. Although significant progress has been made in the solar cell efficiency increase, the concentrator photovoltaic industry has still to go a long way before it becomes competitive and economically viable. Experiencing great losses in their electrical efficiencies at high temperatures that may eventually lead to permanent degradation over time, affects the market potential severely. With a global PV installed capacity of 303 GW, a nominal 10 °C decrease in their average temperatures could theoretically lead to a 5 % electricity efficiency improvement resulting in 15 GW increase in electricity production worldwide. However, due to a gap in the research knowledge concerning the effectiveness of the available passive thermal regulation techniques both individually and working in tandem, this lucrative potential is yet to be realised.
The work presented in this thesis has been focussed on incremental performance improvement of BICPV by developing innovative solutions for passive cooling of the low concentrator based BICPV. Passive cooling approaches are selected as they are generally simpler, more cost-effective and considered more reliable than active cooling. Phase Change Materials (PCM) have been considered as the primary means to achieve this. The design, fabrication and the characterisation of four different types of BIPCV-PCM assemblies are described. The experimental investigations were conducted indoors under the standard test conditions. In general, for all the fabricated and assembled BICPV-PCM systems, the electrical power output showed an increase of 2 %-17 % with the use of PCM depending on the PCM type and irradiance. The occurrence of hot spots due to thermal disequilibrium in the PV has been a cause of high degradation rates for the modules. With the use of PCM, a more uniform temperature within the module could be realised, which has the potential to extend the lifetime of the BICPV in the long-term. Consequentially, this may minimise the intensive energy required for the production of the PV cells and mitigate the associated environmental impacts.
Following a parallel secondary approach to the challenge, the design of a micro-finned back plate integrated with a PCM containment has been proposed. This containment was 3D printed to save manufacturing costs and time and for reducing the PCM leakage. An organic PCM dispersed with high thermal conductivity nanomaterial was successfully tested. The cost-benefit analysis indicated that the cost per degree temperature reduction (£/°C) with the sole use of micro-fins was the highest at 1.54, followed by micro-fins + PCM at 0.23 and micro-fins + n-PCM at 0.19.
The proposed use of PCM and application of micro-finned surfaces for BICPV heat dissipation in combination with PCM and n-PCM is one the novelties reported in this thesis. In addition, an analytical model for the design of BICPV-PCM system has been presented which is the only existing model to date. The results from the assessment of thermal regulation benefits achieved by introducing micro-finning, PCM and n-PCM into BICPV will provide vital information about their applicability in the future. It may also influence the prospects for how low concentration BICPV systems will be manufactured in the future.The financial support provided jointly by Engineering and Physical Science Research Council, UK (EP/J000345/1 and EP/K03619X/1) and Department of Science and Technology (DST), India is greatly acknowledged
COMPUTATIONAL STUDY OF DROPLET AND CAPSULE FLOW IN CHANNELS WITH INERTIAL EFFECTS
The flow of droplets and capsules in channels is important for a variety of industrial and biological applications. Droplet flow is common in microfluidic devices and emulsion processing as well as oil recovery from porous materials. Capsules are used to encapsulate sensitive materials and can be used to study the mechanical properties of biological cells. A computational method was developed to study the two-phase flow of drops with and without surfactants, and capsules surrounded by a thin elastic membrane. This new computational method allowed for the inclusion of inertial effects on droplet and capsule flow which has not received much attention in the past. Results are presented for both the steady flow in straight cylindrical channels, and the transient flow in response to sudden expansions or contractions in the channel diameter. Increasing the Reynolds number was seen to cause non-monotonic trends in the capsule deformation and velocity. Parameters such as the drop viscosity and presence of surfactants were seen to have smaller effects when the Reynolds number became large. Capsules flowing in channels were seen to have limiting elastic capillary numbers above which no stable shape could be found. The transient deformation of drops and capsules moving through expansions depended strongly on the shape of the drop upstream of the expansion. The transient deformation increased with the capillary number up to a limiting value. The flow of droplets through channels was seen to produce large deformations that could break the drop apart at low viscosity ratios. The inclusion of inertial effects caused increases in the transient deformation as well as oscillations as the drops relaxed back into their steady shape
Metallosupramolecular assemblies : development of novel cyclometalated Pt(II) and Ir(III)-based capsules
Inspired by natureâs use of self-assembled systems to carry out virtually all biological processes, chemists have taken to building simplified synthetic systems that mimic the biotic world. Although transition metal-ligand interactions are rarely used for the purpose of biological self-assembly, they have several advantages over other weak noncovalent interactions, such as pronounced directionality and significant strength. These particular attributes have allowed chemists to construct a comprehensive library of self-assembled polygons and polyhedra, using different transition metal-ligand motifs. Many of these supramolecular assemblies possess cavities of defined shape and size, which are able to accommodate guest molecules. It has further been realised that isolation of guest species from the bulk phase can lead to many interesting functions, such as containment, sensing and catalysis. Herein, a new self-assembly strategy has been used to construct novel cyclometalated Pt cages and assembly of the first known [Ir(ppy)2]-based capsule has also been achieved. Chapter 1 includes an introduction to metallosupramolecular assemblies, followed by a comprehensive review of three-dimensional architectures with accessible cavities, their synthetic strategies and applications. Chapter 2 reports on the construction of novel Pt(II)-based trigonal prisms using an unusual, kinetically controlled protocol. By exploiting asymmetric cyclometalated 2-phenylatopyridine based platinum corner units that possess both labile and non-labile cis-coordination sites, trigonal prismatic stereoisomeric architectures have been selectively prepared by altering the sequence of addition of ditopic 4,4âČ-bipy (4,4âČ-bipyridine) and tritopic tpt (2,4,6-tris(4-pyridyl)-1,3,5-triazine) molecular structural components using a template free method. Collision-induced-dissociation mass spectrometry experiments were used to differentiate between the structural isomers due to their significantly different fragmentation profiles. Chapter 3 describes the synthesis and characterisation of the first molecular capsule based on an [Ir(ppy)2]+ 90° metallosupramolecular acceptor unit. Initial work focused on pyridine-based donor ligands from which an Ir2L2 metallamacrocycle was assembled. However, when the highly conjugated tpt âpanelsâ were used, due to postulated constraints in the dihedral angle, self-assembly of the Ir6tpt4 octahedral was unsuccessful. The constraints in the dihedral angle were eliminated by swapping pyridine for nitrile-based ligands and following the development of a method to resolve rac-[(Ir(ppy)2Cl)2] into its enantiopure forms, homochiral Ir6tcb4 (tcb = 1,3,5-tricyanobenzene) octahedral capsules where realised. Photophysical studies on the Ircapsules have shown that the ensemble of cooperative, weakly coordinating ligands can lead to luminescence not present in the comparative mononuclear analogues. X-ray crystallographic analysis revealed that the Ir capsules possess cavities large enough to accommodate 4 triflate counterions. Through a series of titration experiments the ability of the capsules to act as anion sensors was also exposed. Further exploration into the host-guest chemistry of the Ir6tcb4 capsule is reported in Chapter 4. Subsequent experiments have shown that self-assembly is highly dependent on the counterions associated with the system. While a number of different anions (OTf-, BF4 -, ClO4 -, PF6 -) facilitate the formation of the same octahedral scaffold, when triflimide was employed as a bulkier counterion, no capsule was observed. On subsequent addition of smaller counterions, such as triflate, the same Ir6tcb4 cage assembles, demonstrating that the anions also act as templates. Kinetic stability experiments, undertook by monitoring the rate of scrambling of the Î and Î-[Ir(ppy)2]+ components within the preformed ensembles, show that the Ir capsules are up to 1.4Ă104 times more stable than their mononuclear analogues. The counter anions were also observed to play a crucial role in the capsuleâs stability with measured scrambling half-lives ranging from 4.7 mins with tetrafluoroborate to as long as 4.5 days with triflate. In contrast, the rate of ligand exchange in simple mononuclear complexes, as ascertained using EXSY NMR experiments, was found to be approximately independent of the associated anion
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