A magnetic microstirrer and array for microfluidic mixing

Lu, Liang-Hsuan; Ryu, Kee Suk; Liu, Chang

doi:10.1109/jmems.2002.802899

Cited by 375 publications

(47 citation statements)

References 25 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%

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%

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

Morrissette

Mahapatra

Ghosh

et al. 2017

Sci Rep

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“…In order to efficiently mix reagents and samples, many active mixers have been designed and tested, such as ultrasonic, 8 magnetic stirring, 9 and bubble-induced acoustic actuation 10 . However, compared to active mixers, passive mixers are preferred due to their low-cost, ease of fabrication, and integration within microfluidics.…”

Section: Introductionmentioning

confidence: 99%

A “twisted” microfluidic mixer suitable for a wide range of flow rate applications

et al. 2016

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This paper proposes a new “twisted” 3D microfluidic mixer fabricated by a laser writing/microfabrication technique. Effective and efficient mixing using the twisted micromixers can be obtained by combining two general chaotic mixing mechanisms: splitting/recombining and chaotic advection. The lamination of mixer units provides the splitting and recombination mechanism when the quadrant of circles is arranged in a two-layered serial arrangement of mixing units. The overall 3D path of the microchannel introduces the advection. An experimental investigation using chemical solutions revealed that these novel 3D passive microfluidic mixers were stable and could be operated at a wide range of flow rates. This micromixer finds application in the manipulation of tiny volumes of liquids that are crucial in diagnostics. The mixing performance was evaluated by dye visualization, and using a pH test that determined the chemical reaction of the solutions. A comparison of the tornado-mixer with this twisted micromixer was made to evaluate the efficiency of mixing. The efficiency of mixing was calculated within the channel by acquiring intensities using ImageJ software. Results suggested that efficient mixing can be obtained when more than 3 units were consecutively placed. The geometry of the device, which has a length of 30 mm, enables the device to be integrated with micro total analysis systems and other lab-on-chip devices.

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“…Given the latter, the average mixing time τ mix can be calculated using the following equation:

τ_{italicmix} \propto x^{2} / D

where x is the diffusion length (the distance that the solute needs to travel during the diffusion), and D is the diffusion coefficient. In low Re microfluidic systems, various mixing mechanisms have been demonstrated [17] using active approaches, such as magnetic [18,19], electrokinetic [20], acoustic [21–23], optical based [24] as well as passive approaches such as tesla microstructures [25,26], serpentine channels [27], and lamination [28]. These approaches either require an external mechanism to induce mixing or lacks the dynamic control of the fluid interface.…”

Section: Hydrodynamic Focusing (Hf) Devicesmentioning

confidence: 99%

Microfluidic hydrodynamic focusing for synthesis of nanomaterials

et al. 2016

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Microfluidics expands the synthetic space such as heat transfer, mass transport, and reagent consumption to conditions not easily achievable in conventional batch processes. Hydrodynamic focusing in particular enables the generation and study of complex engineered nanostructures and new materials systems. In this review, we present an overview of recent progress in the synthesis of nanostructures and microfibers using microfluidic hydrodynamic focusing techniques. Emphasis is placed on distinct designs of flow focusing methods and their associated mechanisms, as well as their applications in material synthesis, determination of reaction kinetics, and study of synthetic mechanisms.

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A magnetic microstirrer and array for microfluidic mixing

Cited by 375 publications

References 25 publications

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

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

A “twisted” microfluidic mixer suitable for a wide range of flow rate applications

Microfluidic hydrodynamic focusing for synthesis of nanomaterials

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