Hydrophobic/Hydrophilic Microfluidics

Capillary-based microfluidics Hydrophobic/ hydrophilic microfluidics Surface tension-confined microfluidics Wetting on stmemred substrates... 

Surface tension-confined confined microfluidics Wetting on structured substrates Capillary-based microfluidics Hydrophobic/hydrophilic microfluidics... 

Hydrophilic and Hydrophobic Patterning Microfluidics for Stem Cell Therapy... 

Surface forces tend to be inherently important for capillary-driven microfluidic devices as surface area-to-volume ratios are rather high and surface tension-induced interfacial curvature is significant enough to promote capillary wicking. For chemically patterned devices depending on hydrophobic/hydrophilic confinement in particular, the capillary number must be sufficiently low (i.e., Ca 1) in order to maintain fluid confinement within intricate geometry implying AF < ylw [1],... 

Organic core-shell droplets in an aqueous phase, which can be described as an O1/O2/W emulsion, can be produced in hydrophilic microfluidic channels [90-93]. In this case, localized surface modification is not needed when the organic phase to be encased (Oi) is more hydrophobic than the middle organic phase (O2). For example, Kumacheva and coworkers [90] produced photopolymerizable droplets that encapsulate smaller droplets of silicone oil through the flow focusing of a coaxial stream of the two organic phases. Encapsulation of fluorinated oil droplets in other organic phases has also been reported [91-93]. 

Hydrophobic/hydrophilic patterning is a useful technique for preparing microfluidic channels. The technique is... 

Conformal hydrophobic/hydrophilic and supethydrophobic/ hydrophilic thermal switchable surfaces were reported to be composed of LbL assemblies of PAH and silica nanopartides postfunctionalized by a thermosensitive polymer poly (N-isopropylacrylamide) and perfluorosilane for microfluidic valves. A tunable sigmoidal wetting transition from superfiy-drophobidty to superhydrophilidty via gradient UV ozone was demonstrated on a continuous nanostmctured hybrid film of silica nanopartides and PAH. ... 

Fairweather et al. [204] developed a microfluidic device and method to measure the capillary pressure as a function of fhe liquid water saturation for porous media wifh heferogeneous wetting properties during liquid and gas intrusions. In addition to being able to produce plots of capillary pressure as a function of liquid wafer safuration, their technique also allowed them to investigate both hydrophilic and hydrophobic pore volumes. This method is still in its early stages because the compression pressure and the temperatures were not controlled however, it can become a potential characterization technique that would permit further understanding of mass transport within the DL. 

In microfluidic devices, multiphase flows are created when two (or more) immiscible fluids come into contact. Depending on the interaction between the mterfacial and viscous forces, the resulting multiphase flow can take different forms, such as suspended droplets, slugs (droplets occupying the whole channel) or stratified flow (parallel) [141, 142]. In addition to the forces exerted between the two liquids, the channel geometry and physical characteristics also play an important role in the process [143]. In this respect, the use of hydrophobic channels is suitable for the formation of water-m-oil emulsions, whereas hydrophilic channels favor the creation of oil-m-water emulsions [144]. 

Microfluidic devices can be used for either premix emulsification (a method in which a coarse emulsion is broken up by passing it through a geometry) or direct emulsification (a method in which oil and water are introduced separately in the device and the emulsion is formed at their point of contact). Depending on the surface properties of the microfluidic device or other microstructured devices (e.g., membrane) either oil in water (hydrophilic device) or water in oil (hydrophobic device), emulsions are formed. Also related products, such as double emulsions, particles, and capsules, are reported in literature. Eor an extensive description of the construction of various microfluidic devices for emulsion preparation, and the various products that have... 

The concept of chemical patterning generally involves the deposition of hydrophobic curbs upon an otherwise hydrophilic substrate. Consequently, capillarity can be exploited to promote autonomous fluid transport eliminating the requirement to integrate pumping equipment into the microfluidic platform. 

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