Capillary micromechanics for core–shell particles

Kong, Tiantian; Wang, Liqiu; Wyss, Hans M.; Shum, Ho Cheung

doi:10.1039/c3sm53066c

Cited by 31 publications

(19 citation statements)

References 53 publications

(115 reference statements)

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“…These droplets can function as micro-reactors for chemical reactions 10 11 and biological assays 12 13 14 such as single-molecule polymerase chain reaction (PCR) 15 , or as carriers for active ingredients such as drugs 16 17 , proteins 18 and cells 19 . Typically, as micro-reactors or carriers, droplets are merged in diverging channels to initiate chemical reactions 20 21 , or squeezed through narrow channels to probe the mechanical property of encapsulated protein networks 18 22 and microcapsules 23 24 , or split into several daughter droplets 25 26 for different biological assays 12 13 . Thus, channels with complex geometry are normally designed to facilitate manipulation of droplets, including mixing, splitting, diluting and fission 20 21 25 26 27 .…”

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Droplet Breakup in Expansion-contraction Microchannels

Zhu

Kong

Lei

et al. 2016

Sci Rep

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We investigate the influences of expansion-contraction microchannels on droplet breakup in capillary microfluidic devices. With variations in channel dimension, local shear stresses at the injection nozzle and focusing orifice vary, significantly impacting flow behavior including droplet breakup locations and breakup modes. We observe transition of droplet breakup location from focusing orifice to injection nozzle, and three distinct types of recently-reported tip-multi-breaking modes. By balancing local shear stresses and interfacial tension effects, we determine the critical condition for breakup location transition, and characterize the tip-multi-breaking mode quantitatively. In addition, we identify the mechanism responsible for the periodic oscillation of inner fluid tip in tip-multi-breaking mode. Our results offer fundamental understanding of two-phase flow behaviors in expansion-contraction microstructures, and would benefit droplet generation, manipulation and design of microfluidic devices.

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confidence: 99%

Droplet Breakup in Expansion-contraction Microchannels

Zhu

Kong

Lei

et al. 2016

Sci Rep

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“…in splenic sinuses. 36 More generally, it shows how pressure-driven flow of soft objects couples to confinement 37 and sets the stage for adhesion with the wall 38 to ultimately arrest motion and eventually cascade to larger scales to form a jam or clot.…”

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confidence: 99%

Pressure-driven occlusive flow of a confined red blood cell

2016

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When red blood cells (RBCs) move through narrow capillaries in the microcirculation, they deform as they flow. In pathophysiological processes such as sickle cell disease and malaria, RBC motion and flow are severely restricted. To understand this threshold of occlusion, we use a combination of experiment and theory to study the motion of a single swollen RBC through a narrow glass capillary of varying inner diameter. By tracking the movement of the squeezed cell as it is driven by a controlled pressure drop, we measure the RBC velocity as a function of the pressure gradient as well as the local capillary diameter, and find that the effective blood viscosity in this regime increases with both decreasing RBC velocity and tube radius by following a power-law that depends upon the length of the confined cell. Our observations are consistent with a simple elasto-hydrodynamic model and highlight the role of lateral confinement in the occluded pressure-driven slow flow of soft confined objects.

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“…This causes the microcapsule to be drawn into the capillary, where it blocks further flow of fluid at the point at which the pressure difference falls off across the length of the particle, applying external stresses to the capsule, causing deformation. This is observed directly with an optical microscope to determine the compressive and shear moduli of microcapsules (Kaufman et al, 2014;Kong, Wang, Wyss, & Shum, 2014;Wyss, Franke, Mele, & Weitz, 2010). This method can be easily incorporated into existing microfluidic devices, although it is primarily used on biological and soft cells where inhomogeneities make the determination of elastic properties difficult using other techniques of comparable sensitivity.…”

Section: Individual Particle Measurementsmentioning

confidence: 99%

Determination of microcapsule physicochemical, structural, and mechanical properties

et al. 2016

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a b s t r a c tResearch into the fundamental properties of microcapsules and use of the results to develop a wide variety of products in industries such as printing, fast-moving consumer goods, construction, pharmaceuticals, and agrochemicals is a dynamic and ever-progressing field of study. For microcapsules to be effective in providing protection from harsh environments or delivering large payloads, it is essential to have a good understanding of their properties to enable quality control during formulation, storage, and applications. This review aims to outline the commonly used techniques for determining the physicochemical, structural, and mechanical properties of microcapsules, and highlights the interlinked nature of these three areas with respect to the end-use industrial application. This review provides information on techniques that are well supported in the literature, and also examines microcapsule analytical techniques that will become more prevalent as a result of new technological developments or extensions from other areas of study.

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Capillary micromechanics for core–shell particles

Cited by 31 publications

References 53 publications

Droplet Breakup in Expansion-contraction Microchannels

Droplet Breakup in Expansion-contraction Microchannels

Pressure-driven occlusive flow of a confined red blood cell

Determination of microcapsule physicochemical, structural, and mechanical properties

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