Microstructure-induced helical vortices allow single-stream and long-term inertial focusing

Chung, Aram J.; Pulido, Dianne; Oka, Justin C.; Amini, Hamed; Masaeli, Mahdokht; Carlo, Dino Di

doi:10.1039/c3lc41227j

Cited by 94 publications

(96 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

Optimization of micropillar sequences for fluid flow sculpting

Stoecklein

Kim

et al. 2016

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

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

show abstract

Section: Introductionmentioning

confidence: 99%

Optimization of micropillar sequences for fluid flow sculpting

Stoecklein

Kim

et al. 2016

Physics of Fluids

Self Cite

View full text Add to dashboard Cite

show abstract

“…This type of high quality focusing is important for both high precision positional focusing and due to the correlation between this single point focusing and consistent longitudinal ordering between particles 23,36 . It is also of note that single point particle focusing is possible in simple curved channels not requiring the more complicated structures required for the other known techniques for sheathless alignment of particles 26,37,38 . For the current data set these single point focusing conditions also represent the minimum streak width over the entire parameter space for each particle size Not all of the smallest particles are forced to a single point in this device, however, the existence of the streak near the inner wall indicates that the equilibrium position is present but perhaps the channel was not long enough for all particles to traverse to this position.…”

Section: Resultsmentioning

confidence: 99%

Particle Focusing in Curved Microfluidic Channels

Martel

Toner

2013

Sci Rep

174

173

View full text Add to dashboard Cite

The decoupled effects of Reynolds and Dean numbers are examined in inertial focusing flows. In doing so, a complex set of inertial focusing behavioral regimes is discovered within curved microfluidic channels over a range of channel Reynolds numbers, curvature ratios and particle confinement ratios. These regimes are characterized by particle migration either towards or away from the center of curvature as the channel Reynolds number is increased. The transition between these two regimes is shown to be a set of conditions where single-point equilibrium position focusing of particles of different sizes is achieved. A mechanism describing the observed motion of particles in such flows is hypothesized incorporating the redistribution of the main flow velocities caused by Dean flow and its effect on the balance forces on suspended particles.I nertial focusing is an area of significant interest in the realm of microfluidics because it combines high throughput capability with precision particle positioning and offers theoretical intrigue due to the seemingly endless surprises that accompany experimental results. Inertial focusing occurs under certain conditions as particles flowing through a microchannel migrate across streamlines to equilibrium positions within the flow. This migration is due to inertial effects of the fluid motion around the particle and the interaction of this flow field with the walls of the channel 1-5 . Equilibrium positions arise from a balance between two distinct effects; a shear gradient lift force directed towards the walls of the channel and an opposing wall effect 6,7 . These forces allow for the precise alignment of particles in a flow at throughputs orders of magnitudes higher than in previous microfluidic technologies. The high throughput nature of inertial focusing has enabled a range of microfluidic technologies for biomedical applications from separation technologies [8][9][10][11][12] , to automated sample preparations 13,14 , to novel cell analysis techniques such as cell deformability cytometry 15 and the isolation of circulating tumor cells from blood 16,17 .It is generally accepted that inertial focusing in straight channels is dependent on two main parameters: Reynolds number, defined as Re C 5 rU Max D h /m, where r is the fluid density, m is the fluid viscosity, U Max > 3/2U Avg is the maximum velocity of the fluid and D h is the hydraulic diameter of the channel defined as D h 5 2hw/(h 1 w) where h and w are the height and width of the channel cross section respectively, and the particle confinement ratio, l 5 a/D h , where a, is the particle size. Prior research has determined a minimum threshold for inertial focusing to occur such that l . 0.07 and Re C l 2 , also known as the particle Reynolds number, Re P , is $1 18 . The equilibrium positions can be further controlled using curved channels, where a secondary flow called Dean flow is established at finite Re C . The strength of this secondary flow is characterized by the inertia of the fluid and the curvature of the cha...

show abstract

“…Inertial microfluidic devices can employ various channel structures for different functions. Straight channels with fine-tuned aspect ratios 14,22,28 or microstructures 15,18,29 are frequently used as particle focusers by reducing the focusing positions. Straight channels have the best parallelizability and the simplest design rules among all structure types.…”

Section: Introductionmentioning

confidence: 99%

Inertial focusing of spherical particles in rectangular microchannels over a wide range of Reynolds numbers

et al. 2015

View full text Add to dashboard Cite

Inertial microfluidics has emerged as an important tool for manipulating particles and cells. For a better design of inertial microfluidic devices, we conduct 3D direct numerical simulations (DNS) and experiments to determine the complicated dependence of focusing behaviour on the particle size, channel aspect ratio, and channel Reynolds number. We find that the well-known focusing of the particles at the two centers of the long channel walls occurs at a relatively low Reynolds number, whereas additional stable equilibrium positions emerge close to the short walls with increasing Reynolds number. Based on the numerically calculated trajectories of particles, we propose a two-stage particle migration which is consistent with experimental observations. We further present a general criterion to secure good focusing of particles for high flow rates. This work thus provides physical insight into the multiplex focusing of particles in rectangular microchannels with different geometries and Reynolds numbers, and paves the way for efficiently designing inertial microfluidic devices.

show abstract

Microstructure-induced helical vortices allow single-stream and long-term inertial focusing

Cited by 94 publications

References 42 publications

Optimization of micropillar sequences for fluid flow sculpting

Optimization of micropillar sequences for fluid flow sculpting

Particle Focusing in Curved Microfluidic Channels

Inertial focusing of spherical particles in rectangular microchannels over a wide range of Reynolds numbers

Contact Info

Product

Resources

About