Publications

@article{,

title = {Nonspherical Particle Stabilized Emulsions Formed through Destabilization and Arrested Coalescence.},

author = {Lobel Benjamin T and Baiocco Daniele and Al-Sharabi Mohammed and Routh Alexander F and Zhang Zhibing and Cayre Olivier J},

doi = {10.1021/acs.langmuir.4c03812},

year  = {2024},

date = {2024-12-01},

journal = {Langmuir},

abstract = {To form nonspherical emulsion droplets, the interfacial tension driving droplet sphericity must be overcome. This can be achieved through interfacial particle jamming; however, careful control of particle coverage is required. In this work, we present a scalable novel batch process to form nonspherical particle-stabilized emulsions. This is achieved by concurrently forming interfacially active particles and drastically accelerating emulsion destabilization through addition of electrolyte. To achieve this, surfactant-stabilized oil-in-water emulsions in the presence of dopamine were first produced. These emulsions were then treated with tris(hydroxymethyl)aminomethane hydrochloride buffer to both simultaneously initiate polymerization of dopamine in the emulsion continuous phase and reduce the Debye length of the system, thus accelerating droplet coalescence while forming surface-active particles. The concentration of buffer and imposed shear was then systematically varied, and the behavior at the interface was studied using pendent drop tensiometry and interfacial shear rheology. It was found that polydopamine nanoparticles formed in the emulsion continuous phase adsorbed to the reducing interface during coalescence, resulting in anisotropic droplets formed via arrested coalescence. Greater shear rates resulted in accelerated coalescence and formation of secondary droplets, whereas lower shear rates resulted in thicker interfacial films. The efficacy of this method was further demonstrated with a second system consisting of sodium dodecyl sulfate as the surfactant and polypyrrole particles, which also resulted in nonspherical droplets for optimized conditions.},

key = {1672145},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Bubbling forth on thin films},

author = {Neufeld JA},

doi = {10.1017/jfm.2024.900},

year  = {2024},

date = {2024-12-01},

journal = {Journal of Fluid Mechanics},

abstract = {The motion of a bubble of negligible viscosity, such as air, forced down a tube filled with a viscous fluid which wets the walls of the tube has become a classic of the fluid dynamical literature. The differential motion of the bubble and the fluid are determined by the thin film which surrounds the bubble, whose shape and thickness are set by the interplay between gradients in surface tension and viscous shear stresses. Bretherton (J. Fluid Mech., vol. 10, issue 2, 1961, p. 166) provided a first, clear mathematical analysis in the lubrication limit coupled with carefully constructed experimental confirmation of the thin films deposited by a bubble moving in the confining geometry of the capillary tube. Its lasting impact has been not only in the migration of bubbles, but in a host of related fluid dynamical, industrial, biological and environmental processes for which thin lubricating films on the sometimes convoluted geometries of complex microstructures, such as porous media, determine the large-scale behaviour.},

key = {1669502},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {A general model for spin coating on a non-axisymmetric curved substrate},

author = {Shepherd RG and Boujo E and Sellier M},

doi = {10.1017/jfm.2024.654},

year  = {2024},

date = {2024-11-01},

journal = {Journal of Fluid Mechanics},

abstract = {We derive a generalised asymptotic model for the flow of a thin fluid film over an arbitrarily parameterised non-axisymmetric curved substrate surface based on the lubrication approximation. In addition to surface tension, gravity and centrifugal force, our model incorporates the effects of the Coriolis force and disjoining pressure, together with a non-uniform initial condition, which have not been widely considered in existing literature. We use this model to investigate the impact of the Coriolis force and fingering instability on the spreading of a non-axisymmetric spin-coated film at a range of substrate angular velocities, first on a flat substrate, and then on parabolic cylinder- and saddle-shaped curved substrates. We show that, on flat substrates, the Coriolis force has a negligible impact at low angular velocities, and at high angular velocities results in a small deflection of fingers formed at the contact line against the direction of substrate rotation. On curved substrates, we demonstrate that, as the angular velocity is increased, spin-coated films transition from being dominated by gravitational drainage with no fingering to spreading and fingering in the direction with the greatest component of centrifugal force tangent to the substrate surface. For both curved substrates and all angular velocities considered, we show that the film thickness and total wetted substrate area remain similar over time to those on a flat substrate, with the key difference being the shape of the spreading droplet.},

key = {1639592},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Front-Tracking and Gelation in Sessile Droplet Suspensions: What Can They Tell Us about Human Blood?},

author = {Bhatt Sheila and Smethurst Peter A and Garnier Gil and Routh Alexander F},

doi = {10.1021/acs.biomac.4c00753},

year  = {2024},

date = {2024-11-01},

journal = {Biomacromolecules},

abstract = {Recently developed imaging techniques have been used to examine the redistribution of human red blood cells and comparator particles dispersed in carrier fluids within evaporating droplets. We demonstrate that progressive gelation initiates along an annular front, isolating a central pool that briefly remains open to particulate advection before gelation completes across the droplet center. Transition to an elastic solid is evidenced by cracking initiating proximal to front locations. The arrested flow of cellular components, termed a "halted front", has been investigated using a time-lapse analysis "signature". The presence of a deformable biocellular component is seen to be essential for front-halting. We show a dependence of front-halt radius on cell volume-fraction, potentially offering a low-cost means of measuring hematocrit. A simple model yields an estimate of the gel zero-shear yield-stress. This approach to understanding the drying dynamics of blood droplets may lead to a new generation of point-of-care diagnostics.},

key = {1650563},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Scraping of a viscoplastic fluid to model mountain building},

author = {Ribinskas Elvinas and Ball Thomasina V and Penney Camilla E and Neufeld Jerome A},

doi = {10.1017/jfm.2024.908},

year  = {2024},

date = {2024-11-01},

journal = {Journal of Fluid Mechanics},

abstract = {We present a thin-film viscoplastic fluid model of a mountain range, where a uniform fluid layer is deformed by a vertical backstop moving at constant speed. This represents a simplification of the geometry in subduction zones, where an overlying tectonic plate scrapes sediments off the underthrusting plate, thereby forming an accretionary wedge. By using a viscoplastic rheology, we aim to generalise Newtonian models that capture the effective viscous behaviour of rock at large length scales. The model system is characterised by the dimensionless Bingham number, which is the ratio of the yield stress to characteristic shear stress. At low and high Bingham numbers and at early and late times the system is found to be asymptotically self-similar, which we confirm by solving the governing equations numerically. In addition, we test the high-Bingham-number results experimentally using ultrasound gel as the working fluid. The experiments reproduce many features of the theoretically predicted behaviour. The size of the observed wedge grows in the manner predicted, and the fluid surface profile is found to collapse to a universal shape. The viscoplastic fluid wedge exhibits features of both viscous continuum and Coulomb models of accretionary wedges, suggesting that a viscoplastic rheology may provide quantitative insights into the dynamics of real accretionary wedges found in convergent tectonic settings.},

key = {1646279},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Transient Joule–Thomson cooling during CO2 injection in depleted reservoirs},

author = {Tweed LEL and Bickle MJ and Neufeld JA},

doi = {10.1017/jfm.2024.845},

year  = {2024},

date = {2024-10-01},

journal = {Journal of Fluid Mechanics},

abstract = {The injection of 

	      

		

		${rm CO}_2$

	      

	     into depleted reservoirs carries the potential for significant Joule–Thomson cooling, when dense, supercritical 

	      

		

		${rm CO}_2$

	      

	     is injected into a strongly under-pressured reservoir. The resulting low temperatures around the wellbore risk causing thermal fracturing of the well/near-well region or causing freezing of pore waters or formation of gas hydrates which would reduce injectivity and jeopardise well and reservoir integrity. These risks are particularly acute during injection start-up when 

	      

		

		${rm CO}_2$

	      

	     is in the gas stability field. In this paper we present a model of non-isothermal single-phase flow in the near-wellbore region. We show that during radial injection, with fixed mass injection rate, transient Joule–Thomson cooling can be described by similarity solutions at early times. The positions of the 

	      

		

		${rm CO}_2$

	      

	     and thermal fronts are described by self-similar scaling relations. We show that, in contrast to steady-state flow, transient flow causes slight heating of 

	      

		

		${rm CO}_2$

	      

	     and reservoir gas either side of the thermal front, as pressure diffuses into the reservoir. The scaling analysis here identifies the parametric dependence of Joule–Thomson cooling. We present a sensitivity analysis which demonstrates that the primary controls on the degree of cooling are reservoir permeability, reservoir thickness, injection rate and Joule–Thomson coefficient. The analysis presented provides a computationally efficient approach for assessing the degree of Joule–Thomson cooling expected during injection start-up, providing a complement to complex, fully resolved numerical simulations.},

key = {1646312},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Environmentally friendly calcium carbonate-polydopamine microcapsules with superior mechanical, barrier, and adhesive properties},

author = {Baiocco D and Lobel BT and Al-Sharabi M and Cayre OJ and Routh AF and Zhang Z},

doi = {10.1016/j.susmat.2024.e01001},

year  = {2024},

date = {2024-09-01},

journal = {Sustainable Materials and Technologies},

abstract = {There is a rising need to deliver perfume molecules to fabric surfaces during washing cycles to enhance consumers' perception. With upcoming regulations phasing out intentionally produced microplastics by 2027, the focus is on sustainable alternatives to conventional non-biodegradable synthetic microcapsules (e.g. melamine-formaldehyde). Calcium carbonate (CaCO3) has shown promise to form the microcapsule shells due to its environmental benignity, inexpensiveness, and potential for liquid formulations, particularly detergents. Notwithstanding, its inherent porosity undermines the performance of the ensuing microcapsules. Bio-inspired by the adhesive properties of mussel proteins, dopamine is proposed for forming a protective organic coating on CaCO3-based microcapsules. This research aims towards developing primary microcapsules with CaCO3 shells encapsulating hexylsalicylate (HS) as a perfume oil, applying a polydopamine (PDA) coating via oxidative auto-polymerisation of dopamine-hydrochloride (pH 8.5), and conducting a comprehensive analysis of morphological, mechanical, barrier, and adhesive properties through advanced techniques, namely fluorescent-sensing/scanning electron microscopy (SEM), micromanipulation, UV–Vis spectrometry, and a microfluidic chamber fitted with polyethylene-terephthalate (PET) fabrics. The obtained microcapsules (D[2, 3]=31.2 ± 0.4 μm) exhibited a spherical core-shell structure with a smooth PDA-coated surface. Mechanical assessments reveal remarkable rupture stress (2.2 ± 0.3 MPa) comparable to that of commercial microcapsules. After one month in water, ∼40% of HS was released from PDA-coated microcapsules, while the primary ones released the entire amount within 4 h. When mimicking washing conditions (pH 9), the PDA-coated microcapsules demonstrated improved retention (∼60%) on the PET substrate at hydrodynamic shear stress of ∼1 Pa, whereas that of the primary microcapsules was below 10%. Overall, this study suggests the successful fabrication of eco-friendly microcapsules featuring a hybrid inorganic-organic shell, with enhanced mechanical strength, reduced leakage, and improved adhesion, showcasing their potential in applications within the fast-moving consumer goods industry.},

key = {1620138},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Current Challenges in Microcapsule Designs and Microencapsulation Processes: A Review.},

author = {Lobel Benjamin T and Baiocco Daniele and Al-Sharabi Mohammed and Routh Alexander F and Zhang Zhibing and Cayre Olivier J},

doi = {10.1021/acsami.4c02462},

year  = {2024},

date = {2024-08-01},

journal = {ACS Applied Materials & Interfaces},

abstract = {Microencapsulation is an advanced methodology for the protection, preservation, and/or delivery of active materials in a wide range of industrial sectors, such as pharmaceuticals, cosmetics, fragrances, paints, coatings, detergents, food products, and agrochemicals. Polymeric materials have been extensively used as microcapsule shells to provide appropriate barrier properties to achieve controlled release of the encapsulated active ingredient. However, significant limitations are associated with such capsules, including undesired leaching and the nonbiodegradable nature of the typically used polymers. In addition, the energy cost of manufacturing microcapsules is an important factor to be considered when designing microcapsule systems and the corresponding production processes. Recent factors linked to UN sustainability goals are modifying how such microencapsulation systems should be designed in pursuit of "ideal" microcapsules that are efficient, safe, cost-effective and environmentally friendly. This review provides an overview of advances in microencapsulation, with emphasis on sustainable microcapsule designs. The key evaluation techniques to assess the biodegradability of microcapsules, in compliance with recently evolving European Union requirements, are also described. Moreover, the most common methodologies for the fabrication of microcapsules are presented within the framework of their energy demand. Recent promising microcapsule designs are also highlighted for their suitability toward meeting current design requirements and stringent regulations, tackling the ongoing challenges, limitations, and opportunities.},

key = {1627194},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Stratification in drying films: diffusiophoresis driven by nanoparticles and their counterions},

author = {Rees-Zimmerman CR and Routh AF},

doi = {10.1093/imamat/hxae015},

year  = {2024},

date = {2024-08-01},

journal = {IMA Journal of Applied Mathematics},

abstract = {Abstract

               Recent experimental work has highlighted that electrolyte-driven diffusiophoresis is likely to be the most significant phoretic motion in a mixture of silica nanoparticles and relatively large latex particles, which are commonly used in coatings. In this work, this diffusiophoretic effect, powered by gradients in the nanoparticles and their stabilizing cations, is modelled in drying films. A continuum hydrodynamic model is derived, and the resulting partial differential equations solved numerically. An asymptotic solution is found for high evaporation rate. It is found that the final film structure is governed by the relative magnitudes of the diffusive and diffusiophoretic terms. Two methods are discovered to control the resulting stratification: (i) setting the surface charge on the particles, and (ii) setting the background salt concentration. Either of these can be used to select either small- or large-on-top stratification or a homogenous film. The diffusiophoretic term promotes small-on-top stratification, and so may account for experimental observations of accumulated small particles at the top surface of dried films.},

key = {1621576},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Magnetic zinc oxide/silica microbeads for the photocatalytic degradation of azo dyes},

author = {Al-Sharabi M and Baiocco D and Lobel BT and Cayre OJ and Zhang Z and Routh AF},

doi = {10.1016/j.colsurfa.2024.134169},

year  = {2024},

date = {2024-08-01},

journal = {Colloids and Surfaces A: Physicochemical and Engineering Aspects},

abstract = {Photocatalysis is a promising technique for the complete degradation of azo dyes that are present in wastewater. In this work, a new photocatalyst in the form of ZnO/Fe3O4/SiO2 hybrid microbeads was fabricated for the photocatalytic degradation of methylene blue. The microbeads were synthesised through self-assembly and subsequent agglomeration of nanoparticles within an aqueous phase of a water-in-oil emulsion template. Photocatalytic degradation experiments were conducted through exposure of a methylene blue solution to UV light. The hybrid microbeads performed better than ZnO powder at the same initial dye and ZnO concentration because of higher adsorption and degradation. The initial concentration of dye solution and catalyst dosage have a significant impact on the degradation. Higher degradation is seen with lower initial dye concentration and higher catalyst dosage. The presence of magnetic nanoparticles within the beads allows for their full recovery and reuse for degradation experiments. Complete degradation of dye was achieved using the new ZnO/Fe3O4/SiO2 microbeads.},

key = {1610402},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Eco-Friendly Fungal Chitosan-Silica Dual-Shell Microcapsules with Tailored Mechanical and Barrier Properties for Potential Consumer Product Applications.},

author = {Baiocco Daniele and Al-Sharabi Mohammed and Lobel Benjamin T and Cayre Olivier J and Routh Alexander F and Zhang Zhibing},

doi = {10.1021/acsomega.4c02287},

year  = {2024},

date = {2024-07-01},

journal = {ACS Omega},

abstract = {Commercial perfume microcapsules are becoming popular across the globe to fulfill consumers' demands. However, most of microcapsules rely on synthetic polymers and/or animal-sourced ingredients to form the shells. Therefore, replacement of the shell materials is imperative to minimize environmental microplastic pollution, as well as to meeting peoples' needs, religious beliefs, and lifestyles. Herein, we report a methodology to fabricate environmentally benign dual-shell (fungal chitosan-SiO2) microcapsules laden with fragrance oil (hexyl salicylate). Anionically stabilized oil droplets were coated with fungal chitosan via interfacial electrostatic interactions at pH 2, which were then covered by an inorganic coating of SiO2 produced via external alkaline mineralization of sodium silicate. Core-shell microcapsules with a spherical morphology were achieved. Under compression, dual-shell chitosan-SiO2 microcapsules yielded a mean nominal rupture stress of 3.0 ± 0.2 MPa, which was significantly higher than that of single-shell microcapsules (1.7 ± 0.2 MPa). After 20 days in neutral pH water, only ∼2.5% of the oil was released from dual-shell microcapsules, while single-shell microcapsules cumulatively released more than 10%. These findings showed that the additional SiO2 coating significantly enhanced both mechanical and barrier properties of microcapsules, which may be appealing for multiple commercial applications, including cosmetics and detergents.},

key = {1624877},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Video-based measurements of the entrainment, speed and mass flux in a wind-blown eruption column},

author = {Mingotti N and Woods AW},

doi = {10.1038/s43247-024-01402-x},

year  = {2024},

date = {2024-05-01},

journal = {Communications Earth and Environment},

abstract = {On May 4 2010 a wind-blown ash plume issued from Eyjafjallajökull volcano in Iceland. Analysis of a 17-minute long video recording of the eruption suggests that  within $2-2.5$ km of the vent, the flow was moving with the wind and rising under buoyancy, following a trajectory directly analogous with laboratory experiments of turbulent buoyant plumes in a cross-flow. The visible radius of the time-averaged ash cloud grew with height $z$ at a rate $r=0.48 z$, corresponding to an entrainment coefficient of $0.4$, again consistent with laboratory experiments. By analysing the frames in the video and comparing the shape of the plume to that predicted by the  model, we estimate that during the 17 minutes recorded, the eruption rate gradually decreased by about 43$%$ from an initial eruption rate of $1.11times 10^4$ kg/s to $0.63times 10^4$ kg/s. The analysis reported herein opens the way to assess eruption rates and eruption column processes from video recordings during explosive volcanic eruptions.},

key = {1593918},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Experimental and Numerical Investigation of Stratification Regimes in Drying Polystyrene and Silica Nanoparticle Films: Implications for Evaporative Self-Assembly of Colloidal Particles},

author = {Carr AJ and Rees-Zimmerman CR and Zheng B and Routh AF and Bhatia SR},

doi = {10.1021/acsanm.4c00702},

year  = {2024},

date = {2024-04-01},

journal = {ACS Applied Nano Materials},

abstract = {Controlled evaporative self-assembly of colloidal particles based on particle size is desirable when designing efficient, single-step deposition coating processes such as those encountered in specialized antireflective silica coatings. Particle movement during the drying process is complex. We experimentally and numerically investigate particle concentration profiles in binary colloidal films as a function of the small particle volume fraction and particle size ratio. Using a chemical potential expression that incorporates dilute interactions and also accounts for different particle size ratios, initial concentrations, and Peclet values, we calculate small and big particle concentration profiles. By characterizing the full film profile, we observe complex sandwich structures that were previously not predicted by theoretical models of film stratification and are relevant to specific coating applications. We employ microbeam X-ray scattering to characterize dried film profiles as a function of the film depth. These concentration data also show complex sandwich structures and highlight the necessity of full film characterization as opposed to only examining the surface. The presented numerical model does not correctly predict the measured film configurations, implying that additional particle interactions may need to be considered.},

key = {1602513},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {A dynamic model of CO2 storage in layered anticlines},

author = {Mortimer PK and Mingotti N and Woods AW},

doi = {10.1017/jfm.2023.900},

year  = {2024},

date = {2024-01-01},

journal = {Journal of Fluid Mechanics},

abstract = {We explore 

	      

		

		${rm CO}_2$

	      

	     injection into a layered permeable rock consisting of high permeability reservoir layers, separated by low permeability mudstone, and taking the shape of an anticline within a laterally extensive aquifer. We first show how the storage capacity of the formation depends on the capillary entry pressure of the inter-layer mudstone, so that 

	      

		

		${rm CO}_2$

	      

	     cannot flow from one layer into the next. We then consider a formation composed of two layers, overlain by a cap rock. For injection into the lowest layer, we show that the injection rate, capillary entry pressure and buoyancy driven flux through the mudstone determine whether the lower or upper layer fills to the spill point first. We also show that at the end of the injection phase, 

	      

		

		${rm CO}_2$

	      

	     may continue to flow from the lower to the upper layer. This implies that injection should be stopped once the injected volume matches the static capacity of the formation in order to prevent spilling after injection. We present a series of analogue experiments of a two layered system that illustrate some of the principles described by the model, and assess the implications of the results for field scale systems.},

key = {1581004},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Optical absorbance profilometry for tracking time-resolved particle redistribution in high volume fraction colloidal droplets},

author = {Bhatt Sheila J and Routh Alexander F},

doi = {10.1038/s41598-024-51250-0},

year  = {2024},

date = {2024-01-01},

journal = {Scientific Reports},

abstract = {AbstractThe distribution of components within colloidal suspensions is important in many complex biological and industrial fluids. A convenient method of measuring such distributions in low-volume-fraction suspensions is that of optical absorbance. Here we introduce a time-dependent validity criterion allowing extended use of optical absorbance to track colloidal distribution in high volume fraction suspensions. We define our validity criterion and show its use on a range of volume fractions from 15 to 55%, and also on larger micron sized particles, common for biological cells. Within the validity criterion, we establish the evaporative time duration in which the material’s intrinsic coefficient of extinction can be treated as constant. This method enables rapid, low-cost, time-based study of the advective flow of suspended particulates, enabling advection to be straightforwardly measured from digital imaging. The residue profile predicted using our method in two test systems is compared with conventional laser profilometry measurements of the final evaporated residue, with good agreement at most radial positions.},

key = {1578806},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide.},

author = {Armstrong Alexander J and Apóstolo Rui FG and McCoy Thomas M and Allen Finian J and Doutch James and Cattoz Beatrice N and Dowding Peter J and Welbourn Rebecca JL and Routh Alexander F and Camp Philip J},

doi = {10.1039/d3nr05080g},

year  = {2024},

date = {2024-01-01},

journal = {Nanoscale},

abstract = {The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.},

key = {1577663},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Optical absorbance profilometry for tracking time-resolved particle redistribution in high volume fraction colloidal droplets.},

author = {Bhatt Sheila J and Routh Alexander F},

doi = {10.1038/s41598-024-51250-0},

year  = {2024},

date = {2024-01-01},

journal = {Scientific Reports},

abstract = {The distribution of components within colloidal suspensions is important in many complex biological and industrial fluids. A convenient method of measuring such distributions in low-volume-fraction suspensions is that of optical absorbance. Here we introduce a time-dependent validity criterion allowing extended use of optical absorbance to track colloidal distribution in high volume fraction suspensions. We define our validity criterion and show its use on a range of volume fractions from 15 to 55%, and also on larger micron sized particles, common for biological cells. Within the validity criterion, we establish the evaporative time duration in which the material's intrinsic coefficient of extinction can be treated as constant. This method enables rapid, low-cost, time-based study of the advective flow of suspended particulates, enabling advection to be straightforwardly measured from digital imaging. The residue profile predicted using our method in two test systems is compared with conventional laser profilometry measurements of the final evaporated residue, with good agreement at most radial positions.},

key = {1577491},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Scalloped pattern deposition during the spreading and drying of polymer droplets.},

author = {Othman Ahmed M and Poulos Andreas S and Torres Ophelie and Routh Alexander F},

doi = {10.1039/d3sm00968h},

year  = {2023},

date = {2023-11-01},

journal = {Soft Matter},

abstract = {Droplets containing polyvinylpyrrolidone (PVP) dissolved in ethanol display a distinctive scalloped pattern at the rim while spreading and drying on a high-energy surface. Two distinct spreading regimes are observed, leading to the formation of a thin film with a uniform height that extends from the original droplet. An experimental study indicates polymer accumulation at the edge containing trace water, resulting in a surface tension gradient across the droplet, enhancing the droplet's spreading. This fast-spreading film develops a ridge at the contact line and becomes unstable. The influence of evaporation within the droplet shows no significant effect on the wavelength of the instability. Instead, the magnitude of the surface tension gradient and the surface energy of the substrate emerge as the dominant factors influencing the instability. This observation is validated by saturating the environment surrounding the droplet with ethanol vapour to reduce evaporation or employing solvents with low vapour pressure. Additionally, PVP in ethanol droplets deposited on hydrophobic substrates demonstrate a stable and pinned contact line, contrasting the behaviour observed on high-energy surfaces. By identifying the critical overlap concentration of the polymer, the transitional threshold between the scalloped instability and ringlike morphology is determined. The scalloped instability can be suppressed by removing residual water from the solution, eliminating the surface tension gradient, indicating that Marangoni forces are the underlying cause of the observed instability. The long-wave evolution equation, assuming a constant Marangoni shear flow, accurately predicts the most unstable wavelength, demonstrating good agreement with experimental observations.},

key = {1543801},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Online data condensation for digitalised biopharmaceutical processes},

author = {Gangadharan N and Cankorur-Cetinkaya A and Cheeks M and Routh AF and Dikicioglu D},

doi = {10.1016/j.compchemeng.2023.108402},

year  = {2023},

date = {2023-11-01},

journal = {Computers and Chemical Engineering},

abstract = {Efficient control of a bioprocess relies on the ability to systematically capture and represent the process dynamics of critical process parameters. Multivariate monitoring techniques in biopharmaceuticals has resulted in the generation of large amounts of data comprising real-time measurements of critical quality and performance attributes. If exploited efficiently, these can provide an opportunity for developing better control action. For this, it is important to have a comprehensive view of the critical process parameter landscape, which can only be achieved by integrating both online and offline data into a single data matrix that can then be subjected to standard data analysis protocols. However, owing to the difference in the number of readings available for variables recorded online and offline, there is a need for new methods to achieve condensation capability. This paper introduces a novel methodology for condensing online data into an offline data matrix, which performed better when compared to traditionally employed averaging and helped increase the number of variables available for representing the design space of the process. The method was also used to understand how error propagates through online data, so as to identify an interval of tolerance in online monitoring of bioprocesses.},

key = {1533688},

keywords = {},

pubstate = {},

tppubtype = {article}

}

@article{,

title = {Diffusiophoresis of latex driven by anionic nanoparticles and their counterions.},

author = {Rees-Zimmerman Clare R and Chan Derek HH and Armes Steven P and Routh Alexander F},

doi = {10.1016/j.jcis.2023.06.115},

year  = {2023},

date = {2023-11-01},

journal = {Journal of Colloid and Interface Science},

abstract = {HYPOTHESIS: Diffusiophoresis of colloidal latex particles has been reported for molecular anions and cations of comparable size. In the present study, this phenomenon is observed for two types of charged colloids acting as multivalent electrolyte: (i) anionic charge-stabilised silica nanoparticles or (ii) minimally-charged sterically-stabilised diblock copolymer nanoparticles. EXPERIMENTS: Using a Hele-Shaw cell, a thin layer of relatively large latex particles is established within a sharp concentration gradient of nanoparticles by sequential filling with water, latex particles and nanoparticles. Asymmetric diffusion is observed, which provides strong evidence for diffusiophoresis. Quantification involves turbidity measurements from backlit images. FINDINGS: The latex particles diffuse across a concentration gradient of charged nanoparticles and the latex concentration front scales approximately with time1/2. Moreover, the latex particle flux is inversely proportional to the concentration of background salt, confirming electrostatically-driven motion. These observations are consistent with theory recently developed to account for diffusiophoretic motion driven by multivalent ions.},

key = {1518521},

keywords = {},

pubstate = {},

tppubtype = {article}

}