3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

Gazzola, Daniele; Scarselli, Eleonora Franchi; Guerrieri, R.

doi:10.1007/s10404-009-0426-5

Cited by 18 publications

(15 citation statements)

References 30 publications

(38 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, total reflexion and the Fresnel effect will limit the maximum angle. Two mirrors under an angle of 90°were used by Gazzola et al (2009) to track single particles in an open capillary. However, due to image aberrations and the lack of a sophisticated calibration they were just able to visualize the evolving vortex flow.…”

Section: (Scanning) Stereoscopic Imagingmentioning

confidence: 99%

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Cierpka

Kähler

2011

J Vis

128

View full text Add to dashboard Cite

The reliable measurement of the 3D3C velocity field in microfluidic devices becomes more and more important for future optimization and developments for lab-on-a-chip applications or point-of-care medical diagnosis systems. In the past years, different particle-based imaging methods, such as confocal scanning microscopy, holography, stereoscopic and tomographic imaging or approaches based on defocused particle images or optical aberrations have been developed and applied successfully to measure velocity fields in microfluidic systems. The benefits and drawbacks of these methods will be discussed in detail as the proper understanding of the measurement principle is essential to select the most appropriate technique for a desired measurement application. Once an imaging method is chosen, the velocity can be estimated by correlation-based methods or tracking approaches. The advantages and disadvantages of both methods and the importance of image preprocessing will also be discussed in detail.

show abstract

Section: (Scanning) Stereoscopic Imagingmentioning

confidence: 99%

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Cierpka

Kähler

2011

J Vis

128

View full text Add to dashboard Cite

show abstract

“…The measured region was not on the meniscus but far away (2-4 times of the channel diameter) from the meniscus. The authors didn't focus on the Marangoni symmetry issue, but it was concluded that the increase of the solute concentration increased both the speed at which the vortex invaded the channel and its flowing speed, which therefore, the solute concentration and buoyancy played a role (Gazzola et al 2009). Most recently in authors' previous work in this journal , a 3D numerical simulation was conducted for a convex meniscus with pure water as working fluid.…”

Section: Introductionmentioning

confidence: 98%

“…Recently Gazzola et al (2009) made a flow measurement in an open microchannel when developing a visualization system. The liquid was saline solution and the meniscus was at the top of the vertical channel.…”

Section: Introductionmentioning

confidence: 99%

“…Suman (2008) discussed the micro pumping and heat transfer enhancement ability of the Marangoni effect in micro channels. Gazzola et al (2009) investigated the influence of the Marangoni convection when controlling cell positions in micro channels with open outlets. Ranjan et al (2009) numerically accounted the importance of the Marangoni effect in micro-scale heat transfer enhancement.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Instability of Marangoni toroidal convection in a microchannel and its relevance with the flowing direction

Zhang

Wang

2011

Microfluid Nanofluid

View full text Add to dashboard Cite

The instability of the Marangoni toroidal flows in microchannels is of interest in various areas such as microfluidics and heat transfer. Using pure liquid as working fluid in this study, the phenomena of Marangoni symmetry-to-asymmetry transition which does not arise from the buoyancy was observed. The experiments used a vertical cylindrical channel and the meniscus was formed at the bottom outlet to minimize the buoyant influences. Two microscopes were used to have top view and side view of the meniscus simultaneously. The Marangoni flow field on the meniscus was obtained by means of tracing particles. It was observed that the Marangoni flow on a concave meniscus was always nearly symmetrical, while that on a convex meniscus was out of symmetry with only one single vortex occupying the whole channel. The experimental results were highly consistent to the simulation results of authors' previous 3D numerical model (Pan and Wang in Microfluid Nanofluid 9:657, 2010). Theoretical analysis together with newly developed numerical models is employed to dig into the mechanisms. The inward (from the meniscus edge to the center) Marangoni flow is found not as stable as the outward one. Based on the heat transfer analysis, a concave meniscus always has a colder edge thus the flow is outward and stable; while a convex enough meniscus could have an inward flow thus not stable and tends to lose the symmetry. The amplification mechanism of the inward Marangoni flow is comprehensively explained. Two conditions are required for the inward flow to lose the symmetry, i.e., the bulk liquid must be warmer than the meniscus, and the Marangoni number must be above a certain small value.

show abstract

“…Recently in this journal Gazzola et al (2009) reported an asymmetrical flow pattern generated at a convex meniscus while the boundary conditions were symmetrical. In their experiment a vertical micro well was filled up with liquid and the meniscus was held convex above the well outlet.…”

mentioning

confidence: 97%

Symmetry-to-asymmetry transition of Marangoni flow at a convex volatizing meniscus

Zhang

Wang

2010

Microfluid Nanofluid

View full text Add to dashboard Cite

Plenty of studies have been made to have a comprehensive understanding of heat and mass transport at an evaporating meniscus. Recently in this journal Gazzola et al. (2009) reported an asymmetrical flow pattern generated at a convex meniscus while the boundary conditions were symmetrical. In their experiment a vertical micro well was filled up with liquid and the meniscus was held convex above the well outlet. The flow pattern at the meniscus was found having only one single vortex, which was distinct from those symmetrical paired vortexes in literatures (Buffone and Sefiane 2004). In the present work a simulation is conducted to clarify the mechanisms behind the abnormality. Factors including liquid evaporation, vapor transport, and Marangoni effect are considered. It is found that for a convex meniscus as that in the experiment, symmetrical flow pattern is not stable. The transition of symmetry to asymmetry occurs and this is greatly affected by random perturbations. After the asymmetrical flow pattern is established, the perturbations have relatively minor effects on the flow pattern. Keywords Meniscus Á Marangoni Á Asymmetry Á Evaporation Á Liquid layer Á Vapor transport List of symbols A Area (m 2 ) C Vapor molar concentration (mol/m 3 ) D Diffusion coefficient in air (m 2 /s) J Molar flux (mole/m 2 s) h fg Latent heat of evaporation (J/kg) k Thermal conductivity (W/m K) l Characteristic length (m) m Mass (kg) m net Mass flow rate (kg/s) m 00 net Mass flux (kg/m 2 s) M Molecular weight (kg/mol) M Molecular weight (kg/kmol) n Interface normal coordinate (m) p Pressure (N/m 2 ) R Radius (m) or Universal gas constant (J/mol K) R Universal gas constant (J/kmol K) Re Reynolds number S h Heat source term (W/m 3 ) T Temperature (K) t Time (s) V Fluid velocity (m/s) Greek b Thermal expansion coefficient (1/K) d Thickness (m) h Contact angle m Kinematic viscosity (m 2 /s) l Dynamic viscosity (Ns/m 2 ) q Density (kg/m 3 ) r Surface tension coefficient (N/m) r Interface accommodation coefficient s Shear stress (N/m 2 ) Subscript diff Diffusion e Evaporation equ Equilibrium g Gas (vapor/air mixture) l Liquid lv Interface out Outlet

show abstract

3D visualization of convection patterns in lab-on-chip with open microfluidic outlet

Cited by 18 publications

References 30 publications

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Instability of Marangoni toroidal convection in a microchannel and its relevance with the flowing direction

Symmetry-to-asymmetry transition of Marangoni flow at a convex volatizing meniscus

Contact Info

Product

Resources

About