72 research outputs found
Colloidal suspensions under external control
In this thesis, we developed ideas to control the structure and the dynamics\ud
of colloidal suspensions by manipulating the boundary conditions\ud
and applying external elds. The aforementioned manipulations\ud
of colloidal \ud
uids not only provide opportunities to improve\ud
our understanding of fundamental physical phenomena, but also initiate\ud
ideas for developing advanced materials. External control over\ud
colloidal suspensions with hard-sphere like interactions -arguably the\ud
simplest model system for soft matter studies- can be evoked to tune\ud
the interplay between structure and dynamics for both equilibrium\ud
and out-of-equilibrium systems. Interplay between structure and dynamics\ud
is commonly encountered in Soft Matter systems including\ud
but not limited to colloidal suspensions, emulsions, polymers, polyelectrolydes\ud
and proteins
Industrial Separation Processes:Fundamentals
Separation processes on an industrial scale account for well over half of the capital and operating costs in the chemical industry. Knowledge of these processes is key for every student of chemical or process engineering. This book is ideally suited to university teaching, thanks to its wealth of exercises and solutions. The second edition boasts an even greater number of applied examples and case studies as well as references for further reading. - An authoritative introduction to industrial separation technology. - Contains exercises at the end of each subject as well as solutions. - Now with extended and updated examples and case studies
Calculating the motion of highly confined, arbitrary-shaped particles in Hele-Shaw channels
We combine theory, numerical calculations, and experiments to accurately
predict the motion of anisotropic particles in shallow microfluidic channels,
in which the particles are strongly confined in the vertical direction. We
formulate an effective quasi-two-dimensional description of the Stokes flow
around the particle via the Brinkman equation, which can be solved in a time
that is two orders of magnitude faster than the three-dimensional problem. The
computational speedup enables us to calculate the full trajectories of
particles in the channel. To test our scheme, we study the motion of
dumbbell-shaped particles that are produced in a microfluidic channel using
`continuous flow lithography'. Contrary to what was reported in earlier work
(Uspal et al., Nature communications 4 (2013)), we find that the reorientation
time of a dumbbell particle in an external flow exhibits a minimum as a
function of its disk size ratio. This finding is in excellent agreement with
new experiments, thus confirming the predictive power of our scheme.Comment: 18 pages, 5 figures, 4 supplemental movie
Controlling and predicting droplet size of nanoemulsions: scaling relations with experimental validation
Gupta, Ankur et al. “Controlling and Predicting Droplet Size of Nanoemulsions: Scaling Relations with Experimental Validation.” Soft Matter 12.5 (2016): 1452–1458.Eni S.p.A
Nanoemulsions: formation, properties and applications
Nanoemulsions are kinetically stable liquid-in-liquid dispersions with droplet sizes on the order of 100 nm. Their small size leads to useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology. Nanoemulsions are finding application in diverse areas such as drug delivery, food, cosmetics, pharmaceuticals, and material synthesis. Additionally, they serve as model systems to understand nanoscale colloidal dispersions. High and low energy methods are used to prepare nanoemulsions, including high pressure homogenization, ultrasonication, phase inversion temperature and emulsion inversion point, as well as recently developed approaches such as bubble bursting method. In this review article, we summarize the major methods to prepare nanoemulsions, theories to predict droplet size, physical conditions and chemical additives which affect droplet stability, and recent applications.Eni S.p.A
Charge injection from carbon nanofibers into hexane under ambient conditions
The observation of charge injection from carbon nanofibers (CNFs) into liquid hexane under ambient conditions is reported. A CNF-coated electrode and a counter electrode are brought into micrometer proximity in a quasi-parallel geometry using a strain-gauge-based proximity sensor. Controlled charge injection is obtained at interelectrode distances of 4, 6, 9, and 15 μm. The resulting emission current shows an onset of about 3 V/μm , and it follows the Fowler-Nordheim behavior. The work reported here opens new applications for free electron chemistry in liquids and novel liquid field emitter devices
An Edible Humidity Indicator That Responds to Changes in Humidity Mechanically
Elevated humidity levels in medical, food, and pharmaceutical products may reduce the products' shelf life, trigger bacterial growth, and even lead to complete spoilage. In this study, we report a humidity indicator that mechanically bends and rolls itself irreversibly upon exposure to high humidity conditions. The indicator is made of two food-grade polymer films with distinct ratios of a milk protein, casein, and a plasticizer, glycerol, that are physically attached to each other. Based on the thermogravimetric analysis and microstructural characterization, we hypothesize that the bending mechanism is a result of hygroscopic swelling and consequent counter diffusion of water and glycerol. Guided by this mechanism, we demonstrate that the rolling behavior, including response time and final curvature, can be tuned by the geometric dimensions of the indicator. As the proposed indicator is made of food-grade ingredients, it can be placed directly in contact with perishable products to report exposure to undesirable humidity inside the package, without the risk of contaminating the product or causing oral toxicity in case of accidental digestion, features that commercial inedible electronic and chemo-chromatic sensors cannot provide presently.</p
A review on laser-induced crystallization from solution
Crystallization is abound in nature and industrial practice. A plethora of
indispensable products ranging from agrochemicals and pharmaceuticals to
battery materials, are produced in crystalline form in industrial practice.
Yet, our control over the crystallization process across scales, from molecular
to macroscopic, is far from complete. This bottleneck not only hinders our
ability to engineer the properties of crystalline products essential for
maintaining our quality of life but also hampers progress toward a sustainable
circular economy in resource recovery. In recent years, approaches leveraging
light fields have emerged as promising alternatives to manipulate
crystallization. In this review article, we classify laser-induced
crystallization approaches where light-material interactions are utilized to
influence crystallization phenomena according to proposed underlying mechanisms
and experimental setups. We discuss non-photochemical laser-induced nucleation,
high-intensity laser-induced nucleation, laser trapping-induced
crystallization, and indirect methods in detail. Throughout the review, we
highlight connections amongst these separately evolving sub-fields to encourage
interdisciplinary exchange of ideas.Comment: V. Korede and N. Nagalingam contributed equally to this wor
Laser-Induced Cavitation for Controlling Crystallization from Solution
We demonstrate that a cavitation bubble initiated by a Nd:YAG laser pulse
below breakdown threshold induces crystallization from supersaturated aqueous
solutions with supersaturation and laser-energy dependent nucleation kinetics.
Combining high-speed video microscopy and simulations, we argue that a
competition between the dissipation of absorbed laser energy as latent and
sensible heat dictates the solvent evaporation rate and creates a momentary
supersaturation peak at the vapor-liquid interface. The number and morphology
of crystals correlate to the characteristics of the simulated supersaturation
peak
Universal motion of mirror-symmetric microparticles in confined Stokes flow
Comprehensive understanding of particle motion in microfluidic devices is
essential to unlock novel technologies for shape-based separation and sorting
of microparticles like microplastics, cells and crystal polymorphs. Such
particles interact hydrodynamically with confining surfaces, thus altering
their trajectories. These hydrodynamic interactions are shape-dependent and can
be tuned to guide a particle along a specific path. We produce strongly
confined particles with various shapes in a shallow microfluidic channel via
stop flow lithography. Regardless of their exact shape, particles with a single
mirror plane have identical modes of motion: in-plane rotation and cross-stream
translation along a bell-shaped path. Each mode has a characteristic time,
determined by particle geometry. Furthermore, each particle trajectory can be
scaled by its respective characteristic times onto two master curves. We
propose minimalistic relations linking these timescales to particle shape.
Together these master curves yield a trajectory universal to particles with a
single mirror plane.Comment: 10 pages, 4 figures, 1 table, 1 PDF file containing Supplementary
Text, Figures and Tabl
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