Fabricating Shaped Microfibers with Inertial Microfluidics

Nunes, Janine K.; Wu, Chueh‐Yu; Amini, Hamed; Owsley, Keegan; Carlo, Dino Di; Stone, Howard A.

doi:10.1002/adma.201400268

Cited by 64 publications

(74 citation statements)

References 19 publications

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“…Such an approach opens up the computer-aided design and manufacturing of shaped polymer fibers 13 and particles 14 for a range of applications. Additional uses in directing mass and heat transfer and transferring solutions for automation of biological sample preparation should also benefit.…”

Section: Discussionmentioning

confidence: 99%

“…uFlow is built on top of computationally expensive solutions to the Navier-Stokes equations, 12 but as a standalone product, it uses lightweight, pre-computed advection maps, relieving the end-user of time consuming calculations. Using this framework, manual pillar programming has been successfully employed for shaping polymer precursors for streams 13 and particles, 14,15 reducing inertial flow focusing positions, 16 and solution transfer around particles. 17 Such manual exploration of flow deformations will quickly run up against the combinatorial phase space of possible pillar combinations.…”

Section: Introductionmentioning

confidence: 99%

“…19 Decreasing the channel length can not only reduce the pressure drop to improve the performance of the device but also provide more space downstream for applications, for example, complex 3D shaped particle fabrication or particle separation and solution exchange. [13][14][15]17 Therefore, an optimization scheme is needed to enhance the capability of pillar programming while still remaining accessible to, and easily implementable by, an interested researcher with modest computing hardware. Although pillar diameter will play a role in the required pressure to drive flow through a micropillar sequence, we have determined that microchannel length has a greater overall impact on pressure drop (more information available in the supplementary material 20 ).…”

Section: Introductionmentioning

confidence: 99%

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Optimization of micropillar sequences for fluid flow sculpting

Stoecklein

Kim

et al. 2016

Physics of Fluids

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Inertial fluid flow deformation around pillars in a microchannel is a new method for controlling fluid flow. Sequences of pillars have been shown to produce a rich phase space with a wide variety of flow transformations. Previous work has successfully demonstrated manual design of pillar sequences to achieve desired transformations of the flow cross section, with experimental validation. However, such a method is not ideal for seeking out complex sculpted shapes as the search space quickly becomes too large for efficient manual discovery. We explore fast, automated optimization methods to solve this problem. We formulate the inertial flow physics in microchannels with different micropillar configurations as a set of state transition matrix operations. These state transition matrices are constructed from experimentally validated streamtraces for a fixed channel length per pillar. This facilitates modeling the effect of a sequence of micropillars as nested matrix-matrix products, which have very efficient numerical implementations. With this new forward model, arbitrary micropillar sequences can be rapidly simulated with various inlet configurations, allowing optimization routines quick access to a large search space. We integrate this framework with the genetic algorithm and showcase its applicability by designing micropillar sequences for various useful transformations. We computationally discover micropillar sequences for complex transformations that are substantially shorter than manually designed sequences. We also determine sequences for novel transformations that were difficult to manually design. Finally, we experimentally validate these computational designs by fabricating devices and comparing predictions with the results from confocal microscopy. C 2016 AIP Publishing LLC. [http://dx

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optimization of micropillar sequences for fluid flow sculpting

Stoecklein

Kim

et al. 2016

Physics of Fluids

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“…To explore the capabilities of this sequenced pillar microchannel, Amini et al 26 have successfully demonstrated the sculpture of crosssectional shape of a laminated stream into complex geometries, moving and splitting a fluid stream, solution exchange and particle separation. Nunes et al 96 utilized this microfluidic technique to fabricate polymeric microfibers with noncircular cross-sectional shape, Figure 9(d). The computer-aided design (CAD) tool uFlow has a stored library of pre-computed fluid deformations that are produced by individual pillars in the flow channel.…”

Section: Straight Channel With Pillar Arrays or Expansion-contractionmentioning

confidence: 99%

Fundamentals and applications of inertial microfluidics: a review

et al. 2016

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In the last decade, inertial microfluidics has attracted significant attention and a wide variety of channel designs that focus, concentrate and separate particles and fluids have been demonstrated. In contrast to conventional microfluidic technologies, where fluid inertia is negligible and flow remains almost within the Stokes flow region with very low Reynolds number (Re < 1), inertial microfluidics works in the intermediate Reynolds number range (~1 < Re < ~100) between Stokes and turbulent regimes. In this intermediate range, both inertia and fluid viscosity are finite and bring about several intriguing effects that form the basis of inertial microfluidics including (i) inertial migration and (ii) secondary flow. Due to the superior features of high-throughput, simplicity, precise manipulation and low cost, inertial microfluidics is a very promising candidate for cellular sample processing, especially for samples with low abundant targets. In this review, we first discuss the fundamental kinematics of particles in microchannels to familiarise readers with the mechanisms and underlying physics in inertial microfluidic systems. We then present a comprehensive review of recent developments and key applications of inertial microfluidic systems according to their microchannel structures. Finally, we discuss the perspective of employing fluid inertia in microfluidics for particle manipulation. Due to the superior benefits of inertial microfluidics, this promising technology will still be an attractive topic in the near future, with more novel designs and further applications in biology, medicine and industry on the horizon. ABSTRACT:In the last decade, inertial microfluidics has attracted significant attention and a wide variety of channel designs that focus, concentrate and separate particles and fluids have been demonstrated. In contrast to conventional microfluidic technologies, where fluid inertia is negligible and flow remains almost within Stokes flow region with very low Reynolds number Re <<1, inertial microfluidics works in the intermediate Reynolds number range (~1 < Re < ~100) between Stokes and turbulent regimes. In this intermediate range, both inertia and fluid viscosity are finite, and bring about several intriguing effects that form the basis of inertial microfluidics including: (i) inertial migration and (ii) secondary flow. Due to the superior features of high-throughput, simplicity, precise manipulation and low cost, inertial microfluidics is a very promising candidate for cellular sample processing, especially for sample with low abundant targets. In this review, we first discuss the fundamental kinematics of particles in microchannels to familiarise readers with mechanisms and underlying physics in inertial microfluidic systems. We then present a comprehensive review of recent developments and key applications of inertial microfluidic systems according to their microchannel structures. Finally, we discuss the perspective of employing fluid inertia in microfluidics for particle manipu...

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“…3 The most common methods by which fluid parcels have been diverted across a channel cross section to shape a stream make use of asymmetric structured channels (e.g. grooves, chevrons) in Stokes flow 4 or curved channels with finite inertia.…”

Section: Introductionmentioning

confidence: 99%

Micropillar sequence designs for fundamental inertial flow transformations

Stoecklein

Owsley

et al. 2014

Lab Chip

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The ability to control the shape of a flow in a passive microfluidic device enables potential applications in chemical reaction control, particle separation, and complex material fabrication. Recent work has demonstrated the concept of sculpting fluid streams in a microchannel using a set of pillars or other structures that individually deform a flow in a predictable pre-computed manner. These individual pillars are then placed in a defined sequence within the channel to yield the composition of the individual flow deformations -and ultimately complex user-defined flow shapes. In this way, an elegant mathematical operation can yield the final flow shape for a sequence without an experiment or additional numerical simulation. Although these approaches allow for programming complex flow shapes without understanding the detailed fluid mechanics, the design of an arbitrary flow shape of interest remains difficult, requiring significant design iteration. The development of intuitive basic operations (i.e. higher-level functions that consist of combinations of obstacles) that act on the flow field to create a basis for more complex transformations would be useful in systematically achieving a desired flow shape. Here, we show eight transformations that could serve as a partial basis for more complex transformations. We initially used inhouse, freely available custom software (uFlow), which allowed us to arrive at these transformations that include making a fluid stream concave and convex, tilting, stretching, splitting, adding a vertex, shifting, and encapsulating another flow stream. The pillar sequences corresponding to these transformations were subsequently fabricated and optically analyzed using confocal imaging -yielding close agreement with uFlowpredicted shapes. We performed topological analysis on each transformation, characterizing potential sequences leading to these outputs and trends associated with changing diameter and placement of the pillars. We classify operations into four sets of sequence-building concatenations: stacking, recursion, mirroring, and shaping. The developed basis should help in the design of microfluidic systems that have a phenomenal variety of applications, such as optofluidic lensing, enhanced heat transfer, or new polymer fiber design.

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Fabricating Shaped Microfibers with Inertial Microfluidics

Cited by 64 publications

References 19 publications

Optimization of micropillar sequences for fluid flow sculpting

Optimization of micropillar sequences for fluid flow sculpting

Fundamentals and applications of inertial microfluidics: a review

Micropillar sequence designs for fundamental inertial flow transformations

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