Passive mixing enhancement of microliter droplets in a thermocapillary environment

Davanlou, Ashkan; Kumar, Ranganathan

doi:10.1007/s10404-015-1656-3

Cited by 13 publications

(9 citation statements)

References 27 publications

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“…Open-surface micromixers may be of active or passive type, depending on whether external energy input is required or not, respectively. Active micromixer designs for surface microfluidics have recently been adopted by several groups in the community: for example, mixing using electrowetting on dielectric (EWOD) 17 , magnetic 18, 19 , dielectrophoretic 20 , surface acoustic wave (SAW) 21 , or thermocapillary actuation 11 has been found to be effective in controlled manipulation of discrete liquid volumes on solid substrates. However, these devices are complex, since they also include off-chip components ( i .…”

Section: Introductionmentioning

confidence: 99%

“…Droplet-based microfluidics is advantageous over flow-through microfluidics, since the liquid sample handling in the former is relatively free from the common problems of the latter, such as axial dispersion, sample dilution, and cross-contamination 8 , 9 . In droplet-based microfluidics, individual (or sequences of) droplets of the sample liquid may be handled either within an immiscible liquid in a closed microchannel 10 or on open surfaces 11 . The dispensed liquid volumes range from 1 μL to 1 mL; the lower range is common to many microfluidic applications 12 , while the larger volumes are relevant to on-chip liquid storage 13 , or some specialized microfluidic applications that require larger samples ( e .…”

Section: Introductionmentioning

confidence: 99%

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Rapid, Self-driven Liquid Mixing on Open-Surface Microfluidic Platforms

Morrissette

Mahapatra

Ghosh

et al. 2017

Sci Rep

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Self-driven surface micromixers (SDSM) relying on patterned-wettability technology provide an elegant solution for low-cost, point-of-care (POC) devices and lab-on-a-chip (LOC) applications. We present a SDSM fabricated by strategically patterning three wettable wedge-shaped tracks onto a nonwettable, flat surface. This SDSM operates by harnessing the wettability contrast and the geometry of the patterns to promote mixing of small liquid volumes (µL droplets) through a combination of coalescence and Laplace pressure-driven flow. Liquid droplets dispensed on two juxtaposed branches are transported to a coalescence station, where they merge after the accumulated volumes exceed a threshold. Further mixing occurs during capillary-driven, advective transport of the combined liquid over the third wettable track. Planar, non-wettable "islands" of different shapes are also laid on this third track to alter the flow in such a way that mixing is augmented. Several SDSM designs, each with a unique combination of island shapes and positions, are tested, providing a greater understanding of the different mixing regimes on these surfaces. The study offers design insights for developing low-cost surface microfluidic mixing devices on open substrates.Microfluidic devices capable of achieving complex liquid-handling tasks, such as transport, metering, separation and mixing, have found niche applications in numerous fields, including point-of-care (POC) diagnostics 1 , lab-on-a-chip (LOC) applications 2-5 , and micro total analysis systems (μTAS) 6 . Although most conventional microfluidics devices have historically deployed flow-through systems, a more recent strategy of handling liquid samples in the form of discrete droplets has gained popularity 7 . Droplet-based microfluidics is advantageous over flow-through microfluidics, since the liquid sample handling in the former is relatively free from the common problems of the latter, such as axial dispersion, sample dilution, and cross-contamination 8, 9 . In droplet-based microfluidics, individual (or sequences of) droplets of the sample liquid may be handled either within an immiscible liquid in a closed microchannel 10 or on open surfaces 11 . The dispensed liquid volumes range from 1 μL to 1 mL; the lower range is common to many microfluidic applications 12 , while the larger volumes are relevant to on-chip liquid storage 13 , or some specialized microfluidic applications that require larger samples (e.g. whole-blood assays 14,15 ). Open-surface type microfluidic devices offer the possibility of low-cost fabrication -these devices can be built on low-cost, paper or plastic surfaces and do not require elaborate fabrication of embedded microchannels -and hence, are ideally suited for POC diagnostics 16 .Like the flow-through microfluidic devices, rapid and efficient mixing is also an essential pre-requisite for open-surface microfluidic platforms. Open-surface micromixers may be of active or passive type, depending on whether external energy input is required or not, respectivel...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Rapid, Self-driven Liquid Mixing on Open-Surface Microfluidic Platforms

Morrissette

Mahapatra

Ghosh

et al. 2017

Sci Rep

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“…When a droplet is released from a critical height on a liquid layer, the substrate behaves similar to an elastic membrane; thus after several oscillations its amplitude dies out, and droplet stays floating on the liquid surface. , However, this configuration is not stable, and as soon as the supporting air film beneath the droplet ruptures, two liquids coalesce. In the well-studied Leidenfrost effect, the rapid evaporation of liquid as it approaches the hot surface helps squeezing lubricant gas between two media and avoid direct contact of them .…”

Section: Resultsmentioning

confidence: 99%

The Role of Liquid Properties on Lifetime of Levitated Droplets

Davanlou

2016

Langmuir

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It is known that the temperature difference between a droplet and a liquid surface can extend the levitation time of that droplet by providing a thin air film between the surface and the droplet. However, the effect of fluid properties, liquid surface velocity, and air film thickness on the lifetime of droplets is still not well understood. Also, there is inconsistency in the literature about the role of vapor pressure in noncoalescence. Here we test a variety of liquids including silicone oil, Fluorinert, and water to understand the effect of surface tension, density ratio, viscosity, and heat capacity on the lifetime of a droplet. Droplets with larger heat capacity and vapor pressure like water remain floating for a longer time compared to oils. Similarly, higher surface velocity, which is seen in low viscous liquids, helps the air to replenish into the interstices beneath droplet and delay the drainage process. We also discuss the air film variation with temperature manipulation, and propose a correlation for the minimum thickness required to balance the droplet weight.

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“…Most of evaluation methods are based on the principle of the non-homogeneous level of the tracer concentration distribution in a certain droplet. Standard deviation is an important parameter reflecting the uniformity of the tracer distribution, and sometimes it is adopted directly as a criterion of the mixing efficiency (Equation (1)) [ 40 ]. In Equation (1),

is called standard deviation.…”

Section: Characterization Of Mixing In Microdropletsmentioning

confidence: 99%

Passive Mixing inside Microdroplets

et al. 2018

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Droplet-based micromixers are essential units in many microfluidic devices for widespread applications, such as diagnostics and synthesis. The mixers can be either passive or active. When compared to active methods, the passive mixer is widely used because it does not require extra energy input apart from the pump drive. In recent years, several passive droplet-based mixers were developed, where mixing was characterized by both experiments and simulation. A unified physical understanding of both experimental processes and simulation models is beneficial for effectively developing new and efficient mixing techniques. This review covers the state-of-the-art passive droplet-based micromixers in microfluidics, which mainly focuses on three aspects: (1) Mixing parameters and analysis method; (2) Typical mixing element designs and the mixing characters in experiments; and, (3) Comprehensive introduction of numerical models used in microfluidic flow and diffusion.

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Passive mixing enhancement of microliter droplets in a thermocapillary environment

Cited by 13 publications

References 27 publications

Rapid, Self-driven Liquid Mixing on Open-Surface Microfluidic Platforms

Rapid, Self-driven Liquid Mixing on Open-Surface Microfluidic Platforms

The Role of Liquid Properties on Lifetime of Levitated Droplets

Passive Mixing inside Microdroplets

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