This critical review discusses the current understanding of formation, transport, and merging drops in microfluidics. We focus on physical ingredients which determine flow microchannels recall classical results fluid dynamics help explain observed behaviour. begin by introducing main that differentiate droplet microfluidics from single-phase microfluidics, namely modifications to pressure fields are introduced presence interfacial tension. Then three practical aspects studied detail: (i) The...

The interaction between elasticity and capillarity is used to produce three dimensional structures, through the wrapping of a liquid droplet by planar sheet. final encapsulated 3D shape controlled tayloring initial geometry flat membrane. A 2D model shows evolution open sheets closed structures predicts critical length scale below which encapsulation cannot occur, verified experimentally. This {\it elastocapillary length} found depend on thickness as $h^{3/2}$, scaling favorable...

The miniaturization of droplet manipulation methods has led to drops being proposed as microreactors in many applications biology and chemistry. In parallel, microfluidic have been applied generate monodisperse emulsions for the pharmaceuticals, cosmetics, food industries. To date, production dominated by a few designs that use hydrodynamic forces, resulting from flowing fluids, break at junction. Here we present platform generation does not depend on fluid flows. Instead, devices...

The use of microfluidic drops as microreactors hinges on the active control certain fundamental operations such droplet formation, transport, division and fusion. Recent work has demonstrated that local heating from a focused laser can apply thermocapillary force liquid interface sufficient to block advance in microchannel (C. N. Baroud, J.-P. Delville, F. Gallaire R. Wunenburger, Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2007, 75(4), 046302). Here, we demonstrate generality this...

Droplets are natural candidates for use as microfluidic reactors, if active control of their formation and transport can be achieved. We show here that localized heating from a laser block the motion water-oil interface, acting valve two-phase flows. A theoretical model is developed to explain forces on drop due thermocapillary flow, predicting scaling law favors miniaturization. Finally, we how forcing applied sorting drops, thus demonstrating it may integrated in complex droplet systems.

This paper presents a method to control the motion of nanolitre drops in wide and thin microchannel, by etching fine patterns into channel's top surface. Such is possible for that are squeezed channel roof, allowing them reduce their surface energy as they enter local depression. The resulting gain pulls drop groove such localized holes can be used anchors holding drops, while linear rails guide along complex trajectories. An anchored remain stationary indefinitely, long driving flow rate...

The compatibility of polydimethylsiloxane (PDMS) channels with certain solvents is a well known problem soft lithography techniques, in particular when it leads to the swelling PDMS blocks. However, little about modification microchannel geometries they are subjected solvents. Here, we experimentally measure deformations roof microchannels due such dynamics impregnation and its relation volume dilation first addressed model experiment, allowing precise measurement diffusion coefficients oils...

Three-dimensional cell culture is emerging as a more relevant alternative to the traditional two-dimensional format. Yet ability perform cytometry at single level on intact three-dimensional spheroids or together with temporal regulation of microenvironment remains limited. Here we describe microfluidic platform high-density culture, controlled stimulation, and observation in chip. The method extends capabilities droplet microfluidics for performing long-term adherent cells. Using arrays 500...

As three-dimensional cell culture formats gain in popularity, there emerges a need for tools that produce vast amounts of data on individual cells within the spheroids or organoids. Here, we present microfluidic platform provides access to such by parallelizing manipulation anchored droplets. Different conditions can be applied single device triggering merging new droplets with spheroid-containing drops. This allows cell-cell interactions initiated building microtissues, studying stem cells'...

A strategy to halt dissolution of particle-coated air bubbles in water based on interfacial rheology design is presented. Whereas previously a dense monolayer was believed be required for such an "armored bubble" resist dissolution, fact engineering 2D yield stress interface suffices achieve performance at submonolayer particle coverages. We use suite techniques characterize spherical and ellipsoidal particles air-water as function surface coverage. Bubbles with varying coverages are made...

Abstract Cytotoxic T cells are important components of natural anti-tumor immunity and harnessed in tumor immunotherapies. Immune responses to tumors immune therapy outcomes largely vary among individuals, but very few studies examine the contribution intrinsic behavior this heterogeneity. Here we show development a microfluidic-based vitro method track outcome antigen-specific cell activity on many individual cancer spheroids simultaneously at high spatiotemporal resolution, which call...

We demonstrate the combination of a rails and anchors microfluidic system with laser forcing to enable creation highly controllable 2D droplet arrays. Water droplets residing in an oil phase can be pinned anchor holes made base channel, enabling arrays by appropriate patterning such holes. The introduction forcing, via induced thermocapillary forces anchored droplets, enables selective extraction particular from array. also that filled multiple, our case two, each if have different chemical...

Paramecium and other protists are able to swim at velocities reaching several times their body size per second by beating cilia in an organized fashion. The beat asymmetric stroke, which breaks the time reversal symmetry of small scale flows. Here we show that uses three different swimming gaits escape from aggression, applied form a focused laser heating. For weak normal is sufficient produces steady velocity. As heating amplitude increased, higher acceleration faster achieved through...

A small hole etched in the top of a wide microchannel creates well surface energy for confined drop. This produces an attractive force ${F}_{\ensuremath{\gamma}}$ equal to gradient, which is estimated from geometric arguments. We use drag ${F}_{d}$ outer flow probe trapping mechanism. When ${F}_{d}<{F}_{\ensuremath{\gamma}}$, drop deforms but remains anchored hole. Its shape provides information about pressure field. At higher velocities, detaches, defining critical capillary number...

We revisit the physical balance that takes place when an interface between two immiscible fluids reaches a step change in height of microchannel. This situation leads to production droplets process known as 'step emulsification'. However, mechanism is responsible for drop breakup and determines its size has not been explained simple terms. propose geometric model based on quasi-static curvature thread inside inlet channel "bulb" downstream step. find confinement limits lowest values can be...

Culturing and screening cells in microfluidics, particularly three-dimensional formats, has the potential to impact diverse areas from fundamental biology cancer precision medicine. Here, we use a platform based on anchored droplets for drug screening. The response of spheroids Ewing sarcoma (EwS) A673 simultaneous or sequential combinations etoposide cisplatin was evaluated. This done by culturing EwS inside 500 nL then merging them with secondary containing fluorescent-barcoded drugs at...

Evaluating the ability of cytotoxic T lymphocytes (CTLs) to eliminate tumor cells is crucial, for instance, predict efficiency cell therapy in personalized medicine. However, destruction a by CTLs involves CTL migration extra-tumoral environment, accumulation on tumor, antigen recognition, and cooperation killing cancer cells. Therefore, identifying limiting steps this complex process requires spatio-temporal measurements different cellular events over long periods. Here, we use...

Our velocity measurements on quasi-two-dimensional turbulent flow in a rapidly rotating annulus yield self-similar (scale-independent) probability distribution functions for longitudinal differences, deltav(l) = v(x+l)-v(x). These are strongly non-Gaussian, suggesting that the coherent vortices play significant role. The structure <[deltav(l)](p)> approximately l(zeta)p exhibit anomalous scaling: zeta(p) p / 2 rather than expected 3. Correspondingly, energy spectrum is described by E(k)...

We demonstrate that holographically generated optical patterns offer greater flexibility for the thermocapillary control of water droplets than Gaussian spots; can be stopped in faster flows while using less intensity when surface tension variations are created by line instead single spots. Further, experiments performed making use variable light to achieve controlled droplet routing a four-way cross microfluidic channel. Finally, multiple storage is demonstrated as well changing drop order.

The localized heating produced by a tightly focused infrared laser leads to surface tension gradients at the interface of microfluidic drops covered with surfactants, resulting in net force on drop whose origin and magnitude are focus this paper. First, colocalization surfactant micelles fluorescent dye, we demonstrate that alters their spatial distribution, driving out equilibrium. This soluto-capillary effect opposes overcomes purely thermal dependence tension, leading reversed interfacial...

Doublet and triplet microtubules are essential highly stable core structures of centrioles, basal bodies, cilia, flagella. In contrast to dynamic cytoplasmic micro­tubules, their luminal surface is coated with regularly arranged microtubule inner proteins (MIPs). However, the protein composition biological function(s) MIPs remain poorly understood. Using genetic, biochemical, imaging techniques, we identified Tetrahymena RIB72A RIB72B as ciliary MIPs. Fluorescence tagged showed that both...

We describe a universal, user-friendly and robust microfluidic platform for bacterial culture that provides the parallel, time-resolved monitoring abilities of multiwell plates selection phenotypes interest.

Bubbles are dynamic objects that grow and rise or shrink disappear, often on the scale of seconds. This conflicts with their uses in foams where they serve to modify properties material which embedded. Coating bubble surface solid particles has been demonstrated strongly enhance foam stability, although mechanisms for such stabilization remain mysterious. In this paper, we reduce problem stability study behavior a single spherical coated monolayer particles. The armored is monitored while...