Influence of patterned surface in the rheometry of simple and complex fluids

Broboana, Diana; Tanase, Nicoleta Octavia; Bălan, Corneliu

doi:10.1016/j.jnnfm.2014.10.006

Cited by 13 publications

(2 citation statements)

References 32 publications

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“…Therefore, the control of wall adherence and degree of slipping become central topics for this sort of applications application of microfluidics [18][19][20]. In this sense, the application of superhydrophobic surfaces can potentially help to investigate and analyze the influence of patterned surfaces in microrheometry.…”

Section: Introductionmentioning

confidence: 99%

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

2016

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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.

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Section: Introductionmentioning

confidence: 99%

Superhydrophobic Surfaces Created by Elastic Instability of PDMS

2016

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“…Vayssade et al [53] showed for aqueous suspensions of microgel particles that heterogeneity in the slip conditions at the wall has a substantial influence on the velocity profile, in particular for confined systems. Recently, Broboana et al [54] investigated both Newtonian and non-Newtonian shear flow between patterned and liquid-filled parallel plates of a rheometer. Their results underline that surface heterogeneity leads to local variations in shear stress and viscosity, in particular for a shear-thinning liquid.…”

Section: Introductionmentioning

confidence: 99%

Inelastic non-Newtonian flow over heterogeneously slippery surfaces

et al. 2017

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In this study, we investigated inelastic non-Newtonian fluid flow over heterogeneously slippery surfaces. First, we simulated the flow of aqueous xanthan gum solutions over a bubble mattress, which is a superhydrophobic surface consisting of transversely positioned no-slip walls and no-shear gas bubbles. The results reveal that for shear-thinning fluids wall slip can be increased significantly, provided that the system is operated in the shear-thinning regime. For a 0.2 wt% xanthan gum solution with a power-law index of n=0.4, the numerical results indicate that wall slip can be enhanced 3.2 times when compared to a Newtonian liquid. This enhancement factor was also predicted from a theoretical analysis, which gave an expression for the maximum slip length that can be attained over flat, heterogeneously slippery surfaces. Although this equation was derived for a no-slip/no-shear unit length that is much larger than the typical size of the system, we found that it can also be used to predict the enhancement in the regime where the slip length is proportional to the size of the no-shear region or the bubble width. The results could be coupled to the hydrodynamic development or entrance length of the system, as maximum wall slip is only reached when the fluid flow can fully adapt to the no-slip and no-shear conditions at the wall.

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