Capillarity-driven dynamics of water–alcohol mixtures in nanofluidic channels

Oh, Jung Min; Faez, T.; Beer, Sissi de; Mugele, Friedrich Gunther

doi:10.1007/s10404-009-0517-3

Cited by 50 publications

(41 citation statements)

References 26 publications

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“…Since the pioneering contributions of Lucas [1], Washburn [2], and Bosanquet [3], efforts have been made to describe the problem of capillary filling as a function of the balance between the driving surface tension forces and resisting viscous drag, resulting in the filling length ( ) becoming proportional to the square root of filling time (t) [2][3][4][5][6][7][8][9]. The proposed derivation necessarily assumes R (R is the capillary radius), so that one can consider the fully developed pressure-driven Poisseuille flow profile for explicit calculation of the viscous drag and thereby obtain the explicit form of the ∼ √ t variation [2,10].…”

Section: Introductionmentioning

confidence: 99%

Early regimes of capillary filling

Das

Waghmare²,

Mitra³

2012

Phys. Rev. E

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In this paper we analyze the inviscid regime (for which viscosity is unimportant and the flow occurs due to the balance between the capillary and the inertial effects) that invariably precedes the classical century-old Washburn regime during capillary filling. We demonstrate that a new nondimensional number, namely, the product of the Ohnesorge number and the ratio between the filling length (ℓ) and the radius of the capillary (R), dictates the occurrence of this regime and the other well-known regimes in a capillary filling problem. We also identify that this inviscid regime occurs for the time that is of the order of the capillary time scale and, as has been quantified before [Quere, Eur. Phys. Lett. 39, 533 (1997); Joly, J. Chem. Phys. 135, 214705 (2011)], is characterized by the filling length being linearly proportional to the filling time. We establish the universality of this regime by pinpointing the existence of this regime (showing appropriate dependencies of the capillary radii and density) from existing experimental and Molecular Dynamics Simulation results that signify disparate ranges of length and time scales.

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Section: Introductionmentioning

confidence: 99%

Early regimes of capillary filling

Das

Waghmare²,

Mitra³

2012

Phys. Rev. E

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“…These advances are leading to studies with microfluidic (e.g. Yang et al, 2011) and nanofluidic capillaries widths of a few tens of nm (Han et al, 2006) or with depths as small as 6 nm (Oh et al, 2009). Whilst non-constant channel cross sections have been a focus of study experimentally and theoretically (Legait, 1983;Staples andShaffer, 2002, Reysatt et al, 2008;Liou et al, 2009), increased solid-liquid contact area, and hence increased capillary pull can be achieved using a range of in-channel structures.…”

Section: Introductionmentioning

confidence: 99%

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Ouali

McHale

Javed

et al. 2013

Microfluid Nanofluid

149

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The spontaneous capillary-driven filling of microchannels is important for a wide range of applications. These channels are often rectangular in cross-section, can be closed or open, and horizontal or vertically orientated. In this work, we develop the theory for capillary imbibition and rise in channels of rectangular cross-section, taking into account rigidified and non-rigidified boundary conditions for the liquid-air interfaces and the effects of surface topography assuming Wenzel or Cassie-Baxter states. We provide simple interpolation formulae for the viscous friction associated with flow through rectangular cross-section channels as a function of aspect ratio. We derive a dimensionless cross-over time, T c , below which the exact numerical solution can be approximated by the Bousanquet solution and above which by the visco-gravitational solution. For capillary rise heights significantly below the equilibrium height, this cross-over time is T c  (3X e /2) 2/3 and has an associated dimensionless crossover rise height X c  (3X e /2) 1/3 , where X e =1/G is the dimensionless equilibrium rise height and G is a dimensionless form of the acceleration due to gravity. We also show from wetting considerations that for rectangular channels, fingers of a wetting liquid can be expected to imbibe in advance of the main meniscus along the corners of the channel walls. We test the theory via capillary rise experiments using polydimethylsiloxane oils of viscosity 96.0, 48.0, 19.2 and 4.8 mPa s within a range of closed square tubes and open rectangular cross-section channels with SU-8 walls. We show that the capillary rise heights can be fitted using the exact numerical solution and that these are similar to fits using the analytical visco-gravitational solution. The viscous friction contribution was found to be slightly higher than predicted by theory assuming a non-rigidified liquid-air boundary, but far below that for a rigidified boundary, which was recently reported for imbibition into horizontally mounted open microchannels. In these experiments we also observed fingers of liquid spreading along the internal edges of the channels in advance of the main body of liquid consistent with wetting expectations. We briefly discuss the implications of these observations for the design of microfluidic systems.

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“…Since the colloidal solution used in our experiments is more complex than pure liquid, the filling law for the relationship between S and t may deviate from the Lucas-Washburn equation, as discussed in Ref. 38. More fluid flow experiments will be performed in future to explore the relationship between the flow distance and time in the nanofluidic device.…”

Section: Fluid Flow Experiments Resultsmentioning

confidence: 99%

Fabrication of all-transparent polymer-based and encapsulated nanofluidic devices using nano-indentation lithography

Lin

Zhan

et al. 2017

Microsyst Nanoeng

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In this paper, we describe a novel and simple process for the fabrication of all-transparent and encapsulated polymeric nanofluidic devices using nano-indentation lithography. First, a nanomechanical probe is used to 'scratch' nanoscale channels on polymethylmethacrylate (PMMA) substrates with sufficiently high hardness. Next, polydimethylsiloxane (PDMS) is used twice to duplicate the nanochannels onto PDMS substrates from the 'nano-scratched' PMMA substrates. A number of experiments are conducted to explore the relationships between the nano-indentation parameters and the nanochannel dimensions and to control the aspect ratio of the fabricated nanochannels. In addition, traditional photolithography combined with soft lithography is employed to fabricate microchannels on another PDMS 'cap' substrate. After manually aligning the substrates, all uncovered channels on two separate PDMS substrates are bonded to achieve a sealed and transparent nanofluidic device, which makes the dimensional transition from microscale to nanoscale feasible. The smallest dimensions of the achievable nanochannels that we have demonstrated thus far are of~20 nm depth and~800 nm width, with lengths extendable beyond 100 μm. Fluid flow experiments are performed to verify the reliability of the device. Two types of colloidal solution are used to visualize the fluid flow through the nanochannels, that is, ethanol is mixed with gold colloid or fluorescent dye (fluorescein isothiocyanate), and the flow rate and filling time of liquid in the nanochannels are estimated based on time-lapsed image data. The simplicity of the fabrication process, bio-compatibility of the polymer substrates, and optical transparency of the nanochannels for flow visualization are key characteristics of this approach that will be very useful for nanofluidic and biomolecular research applications in the future. INTRODUCTIONThe field of nanofluidics is widely known as the research and application of the behaviors of liquid flow in a specific area that is confined to the nanoscale 1 . A significant research interest has risen in this field due to the unique nanofluidic phenomena and flow properties that are markedly different from those in the welldeveloped microfluidics field. For example, since the dimensions of typical nanochannels are comparable to those of biomolecules, such as proteins and DNAs, they may be used for the transportation of selective molecules and DNA stretching. Furthermore, similar to microchannels, the surface-to-volume ratio of nanochannel structures is ultra-high, which leads to a diffusionlimited reaction 2 and negative water pressure induced by capillarity 3 . Moreover, because the size of the electrical double layer formed by strong electrostatic interactions between ions and the charged surface is in the range of 1 − 100 nm (Refs. 4,5), nanoflows in nanochannels will have flow properties that significantly deviate from Newtonian fluids. Based on these novel dimensional effects, many significant applications have been explored over the past ...

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Capillarity-driven dynamics of water–alcohol mixtures in nanofluidic channels

Cited by 50 publications

References 26 publications

Early regimes of capillary filling

Early regimes of capillary filling

Wetting considerations in capillary rise and imbibition in closed square tubes and open rectangular cross-section channels

Fabrication of all-transparent polymer-based and encapsulated nanofluidic devices using nano-indentation lithography

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