Microfluidic rheometry

Pipe, Christopher; McKinley, Gareth H.

doi:10.1016/j.mechrescom.2008.08.009

Cited by 225 publications

(170 citation statements)

References 83 publications

(137 reference statements)

Supporting

Mentioning

161

Contrasting

Unclassified

Order By: Relevance

“…Superhydrophobic surfaces created by elastic instability can contribute to the recent advances in microfluidics which allowed the development of rheometers on a chip [15][16][17], where microfluidics is a competitive platform for performing rheometry. Therefore, the control of wall adherence and degree of slipping become central topics for this sort of applications application of microfluidics [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

2016

View full text Add to dashboard Cite

Lotus flowers, rose petals, some plant leaves and insects have a naturally super-hydrophobic surface. In fact, the surface of a Lotus leaf is covered by micro and nano structures mixed with wax, which makes its surface superhydrophobic. In microfluidics, superhydrophobicity is an important factor in the rheometers on a chip. It is also sought in other complex fluids applications like the self-cleaning and the antibacterial materials. The wettability of the surface of solid support can be modified by altering its chemical composition. This means functionalizing the interface molecules to different chemical properties, and/or forming a thin film on the surface. We can also influence its texturing by changing its roughness. Despite considerable efforts during the last decade, superhydrophobic surfaces usually involve, among others, microfabrication processes, such as photolithography technique. In this study, we propose an original and simple method to create superhydrophobic surfaces by controlling elastic instability of poly-dimethylsiloxane (PDMS) films. Indeed, we demonstrate that the self-organization of wrinkles on top of non-wettable polymer surfaces leads to surperhydrophobic surfaces with contact angles exceeding 150˝. We studied the transition Wenzel-Cassie, which indicated that the passage of morphology drops "impaled" to a type of morphology "fakir" were the strongest topographies.

show abstract

Section: Introductionmentioning

confidence: 99%

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

2016

View full text Add to dashboard Cite

show abstract

“…An overview of several canonical flow types and the challenges associated with quantitative microfluidic rheometry can be found in [8]. In the present work, we focus on two different T-shaped microchannels that are specially constructed to enable an investigation of viscoelastic effects on the stability of planar elongation flows.…”

Section: Introductionmentioning

confidence: 99%

Investigating the stability of viscoelastic stagnation flows in T-shaped microchannels

Soulages

Oliveira

Sousa

et al. 2009

Journal of Non-Newtonian Fluid Mechanics

View full text Add to dashboard Cite

We investigate the stability of steady planar stagnation flows of a dilute polyethylene oxide (PEO) solution using T-shaped microchannels. The precise flow rate control and well-defined geometries achievable with microfluidic fabrication technologies enable us to make detailed observations of the onset of elastically-driven flow asymmetries in steady flows with strong planar elongational characteristics. We consider two different stagnation flow geometries; corresponding to T-shaped microchannels with, and without, a recirculating cavity region. In the former case, the stagnation point is located on a free streamline, whereas in the absence of a recirculating cavity the stagnation point at the separating streamline is pinned at the confining wall of the microchannel. The kinematic differences in these two configurations affect the resulting polymeric stress fields and control the critical conditions and spatiotemporal dynamics of the resulting viscoelastic flow instability. In the free stagnation point flow, a strand of highly-oriented polymeric material is formed in the region of strong planar extensional flow. This leads to a symmetry-breaking bifurcation at moderate Weissenberg numbers followed by the onset of three-dimensional flow at high Weissenberg numbers, which can be visualized using streak-imaging and microparticle image velocimetry. When the stagnation point is pinned at the wall this symmetry-breaking transition is suppressed and the flow transitions directly to a threedimensional time-dependent flow at an intermediate flow rate. The spatial characteristics of these purely elastic flow transitions are compared quantitatively to the predictions of two-dimensional viscoelastic numerical simulations using a single-mode simplified PhanThien-Tanner (SPTT) model.

show abstract

“…7 A different class of instruments for probing elongational properties of dilute solutions is based on steady flow of viscoelastic fluids through a contraction or a contraction/expansion. 18,30,44 Imposing a sudden contraction on a fully developed channel flow induces streamwise extensional kinematics that can cause significant stretching in the microstructure of the fluid, which then results in an extra pressure drop across the contraction/expansion. Essentially, this is the microfluidic analog of the "orifice plate" widely used for inline measurement of the flow rate of the Newtonian fluids (with constant rheology).…”

Section: Introductionmentioning

confidence: 99%

“…Considering the recent developments in microfluidic devices/flows for biological applications and the fact that many of the relevant liquids are of a weakly viscoelastic nature 30,44,[58][59][60][61][62] it is important for the rheologist to develop a comprehensive understanding of the relative merits of different devices available for measuring the elongational rheology of dilute solutions. This situation is complicated by the knowledge that the extensional viscosity of a microstructured material is typically a time-varying function of both the strain rate _ ðtÞ and the total strain ¼ Ð t 0 _ ðt 0 Þdt 0 imposed on a material element.…”

Section: Introductionmentioning

confidence: 99%

Micro-scale extensional rheometry using hyperbolic converging/diverging channels and jet breakup

Keshavarz

McKinley

2016

Biomicrofluidics

Self Cite

View full text Add to dashboard Cite

Understanding the elongational rheology of dilute polymer solutions plays an important role in many biological and industrial applications ranging from microfluidic lab-on-a-chip diagnostics to phenomena such as fuel atomization and combustion. Making quantitative measurements of the extensional viscosity for dilute viscoelastic fluids is a long-standing challenge and it motivates developments in microfluidic fabrication techniques and high speed/strobe imaging of millifluidic capillary phenomena in order to develop new classes of instruments. In this paper, we study the elongational rheology of a family of dilute polymeric solutions in two devices: first, steady pressure-driven flow through a hyperbolic microfluidic contraction/expansion and, second, the capillary driven breakup of a thin filament formed from a small diameter jet (D j $ Oð100 lmÞ). The small length scale of the device allows very large deformation rates to be achieved. Our results show that in certain limits of low viscosity and elasticity, jet breakup studies offer significant advantages over the hyperbolic channel measurements despite the more complex implementation. Using our results, together with scaling estimates of the competing viscous, elastic, inertial and capillary timescales that control the dynamics, we construct a dimensionless map or nomogram summarizing the operating space for each instrument. Published by AIP Publishing. [http://dx

show abstract

Microfluidic rheometry

Cited by 225 publications

References 83 publications

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

Investigating the stability of viscoelastic stagnation flows in T-shaped microchannels

Micro-scale extensional rheometry using hyperbolic converging/diverging channels and jet breakup

Contact Info

Product

Resources

About