Rates of cavity filling by liquids

Seo, Dongjin; Schrader, Alex M.; Chen, Szu-Ying; Kaufman, Yair; Cristiani, Thomas R.; Page, Steven H.; Koenig, Peter H.; Gizaw, Yonas; Lee, Dong Woog; Israelachvili, Jacob N.

doi:10.1073/pnas.1804437115

Cited by 30 publications

(38 citation statements)

References 27 publications

(22 reference statements)

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“…To date, few publications discuss time dependent wetting based on the Cassie-Wenzel transition 26,27 for the viscous fluids, so this issue is left for future work. Also, it is needed for future studies to investigate wetting transitions in new factors such as the dissolution of the entrapped gas into the liquid, effects of mechanical vibrations, and breakthrough pressures 28,29 .…”

Section: Resultsmentioning

confidence: 99%

Microfabrication of re-entrant surface with hydrophobicity/oleophobicity for liquid foods

Yamaguchi

2020

Sci Rep

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Re-entrant texturing may potentially improve the hydrophobicity and oleophobicity of a surface. the food industry requires a microfabrication method to keep surfaces clean without leaving a packaging residue for applications such as food bottles, food containers, and preservation bags. the goal of this study is thus to establish a microfabrication method for re-entrant texturing with spherical curvature to produce hydrophobic/oleophobic surfaces for liquid foods, such as soy sauce and canola oil. Samples with a spherical curvature are created from an ultraviolet cure (UV-cure) resin and poly (tetrafluoroethylene) (PTFE) microbeads with diameters between 2.26 to 1,353 microns by spin coating on a glass substrate. the resin thickness, the mass and diameter of the microbeads, and the spin coater rotation speed are used as the microfabrication parameters. A side view of samples showing the spherical curvature reveals that a re-entrant texture indeed forms. Distilled water, soy sauce, and canola oil are dropped softly onto the re-entrant surface, however, the droplets cannot be placed stably. for appropriate microbead diameters, the apparent contact angles of soy sauce and canola oil showed 130.2 and 119.4 degrees, respectively. This facile fabrication method for re-entrant surfaces could prove useful for generating hydrophobic/oleophobic surfaces for newtonian liquid foods. Superhydrophobic surfaces exhibit apparent contact angles with water (surface tension γ LV = 72.1 mN/m) that exceed 150°, and low contact angle hysteresis is controlled by two factors: the chemical composition and the surface roughness. Barhlott presented technical applications for such features by using micro-and nano-sized particles for applications, including building materials and food containers 1. However, superhydrophobic surfaces with contact angles exceeding 150° are extremely rare in nature. Tuteja et al. reported that a third factor, the re-entrant surface curvature, can be used to design surfaces with extreme resistance to wetting for a number of liquids with low surface tension 2,3. For re-entrant curved surfaces (re-entrant texture), the net traction on the liquid-vapor interface is directed upwards, thereby supporting the formation of a composite interface 4. Additionally, four design criteria have been proposed to form an air-entrapped Cassie-Baxter state from the re-entrant texturing considering the pressure balance of liquids, such as Laplace pressure, gravity, surface curvature, pinning effects, and the suspending conditions 5. Several fabrication methods based on lithographic techniques have been proposed to produce re-entrant textures 6. Brown and Bhushan suggested that spherical and/or cylindrical curvatures are able to support high droplet contact angles 7. Ellinas et al. assembled a dual-scale texture by spin coating and etching on the surface of poly(methyl methacrylate) 8. Zhao et al. created a wavy structure at the top of pillars using photolithography as a model surface of re-entrant textures 9. An overhang structure us...

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Section: Resultsmentioning

confidence: 99%

Microfabrication of re-entrant surface with hydrophobicity/oleophobicity for liquid foods

Yamaguchi

2020

Sci Rep

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“…In order to quantitatively relate the progress of wetting transition to time, Arrhenius equation with an activation energy being the adhesion energy is used in a recent study by Seo et al 31 .…”

Section: Time-dependent Wetting Transition Modelmentioning

confidence: 99%

“…The typical time for wetting transition to complete ranges from seconds to days, depending on the aforementioned factors and liquid properties, including interfacial tension and viscosity. [28][29][30][31] It has been also found that hierarchical surface structure can dramatically increase the stability of the Cassie state, slowing the transition [46][47][48] . On the other hand, external excitations, such as vibration can help overcome the energy barrier, accelerating the wetting transition [49][50][51] .…”

Section: Introductionmentioning

confidence: 99%

Effect of Wetting Transition during Multiphase Displacement in Porous Media

2020

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The e↵ects of wettability on multiphase displacement in porous media have been studied extensively in the past, and the contact angle is identified as an important factor influencing the displacement patterns. At the same time, it has been found that e↵ective contact angle can vary drastically in a time-dependent manner on rough surfaces due to Cassie-Wenzel wetting transition. In this study, we develop a theoretical model at the pore scale describing the apparent contact angle on rough interface as a function of time. The theory is then incorporated into the Lattice Boltzmann method for simulation of multiphase displacement in disordered porous media. A dimensionless time ratio, Dy, describing the relative speed of wetting transition and pore invasion is defined. We show that the displacement patterns can be significantly influenced by Dy, where more trapped defending ganglia are observed at large Dy, leading to lower displacement e ciency. We investigate the mobilization of trapped ganglia through identifying di↵erent mobilization dynamics during displacement, including translation, coalescence, and fragmentation. Agreement is observed between the mobilization statistics and the total pressure gradient across a wide range of Dy. Understanding the e↵ect of wetting transition during multiphase displacement in porous media is of importance 1 for applications such as carbon geosequestration and oil recovery, especially for porous media where solid surface roughness cannot be neglected.

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“…These bio‐inspired [ 18,23 ] microtextures are known as doubly reentrant cavities (DRCs), and they can entrap air inside them on immersion in liquids due to their topography, regardless of their surface make‐up. [ 21 ] In fact, the transition of these air‐filled cavities—Cassie‐states [ 24–26 ] to the fully‐filled or the Wenzel‐state [ 27 ] depends on a number of factors, such as the compressibility of the trapped air, liquid vapor pressure, capillary condensation, the solubility of the trapped air in the liquid, and the cavity geometry. [ 20 ] For instance, when hexadecane (vapor pressure at NTP, P V = 0.01 kPa) was used to immerse silica surfaces adorned with circular DRCs (apparent advancing contact angle on flat silica, θ A ≈ 20°), they robustly entrapped air, which remained intact even after 27 days.…”

Section: Introductionmentioning

confidence: 99%

Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make‐Up, Hydrostatic Pressure, and Cavity Aspect Ratio

Arunachalam

Ahmad

Das

et al. 2020

Adv Materials Inter

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applications. Thus, new approaches for the long-term entrapment of air on submersion in water that does not entirely depend on coatings are needed. In this context, a new class of microtextures has been developed, comprising microcavities that broaden below the inlets such that the cross-section of the space between adjacent cavities spanning cavity inlets and the intervening wall resembles the serif-T shape [7,16-22] (Figure 1A-C). These bio-inspired [18,23] microtextures are known as doubly reentrant cavities (DRCs), and they can entrap air inside them on immersion in liquids due to their topography, regardless of their surface makeup. [21] In fact, the transition of these air-filled cavities-Cassie-states [24-26] to the fully-filled or the Wenzel-state [27] depends on a number of factors, such as the compressibility of the trapped air, liquid vapor pressure, capillary condensation, the solubility of the trapped air in the liquid, and the cavity geometry. [20] For instance, when hexadecane (vapor pressure at NTP, P V = 0.01 kPa) was used to immerse silica surfaces adorned with circular DRCs (apparent advancing contact angle on flat silica, θ A ≈ 20°), they robustly entrapped air, which remained intact even after 27 days. [20] In stark contrast, circular SCs of similar chemical make-up, diameter, and pitch as the DRCs got fully-filled by hexadecane within t ≈ 0.2 s, that is, a factor of ≈10 7 faster (or 10 9 % faster). Indeed, these observations are quite exciting because the function, that is, the entrapment of air underwater, can now be realized by the microtexture alone. A variety of materials and techniques have thus been explored toward proof-of-concept demonstrations of this approach, for example, with silica-on-silicon wafers (SiO 2 /Si) and photolithography and dry etching, [7,19,22,28-31] perfluoropolyether dimethacrylate and reverse imprint litho graphy, [32] and polypropylene and crack formation/propagation [33] among others. Thus, there is a growing expectation that this approach would yield greener and low-cost technologies. Even if a Cassie state is achieved on an intrinsically wetting material, this scenario does not pertain to the global minimum on the thermodynamic energy landscape; in fact, such a system will eventually transition to the Wenzel-state to reach thermodynamic equilibrium. [25,34] However, these wetting transitions could be impeded by kinetic barriers by controlling the micro/ nano texture-cavities/pillars, reentrant/simple profile, and Surfaces that entrap air underwater serve numerous practical applications, such as mitigating cavitation erosion and reducing frictional drag. These surfaces typically rely on perfluorinated coatings. However, the non-biodegradability and fragility of the coatings limit practical applications. Thus, coating-free, sustainable, and robust approaches are desirable. Recently, a microtexture comprising doubly reentrant cavities (DRCs) has been demonstrated to entrap air on immersion in wetting liquids. While this is a promising approach, insights into th...

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Rates of cavity filling by liquids

Cited by 30 publications

References 27 publications

Microfabrication of re-entrant surface with hydrophobicity/oleophobicity for liquid foods

Microfabrication of re-entrant surface with hydrophobicity/oleophobicity for liquid foods

Effect of Wetting Transition during Multiphase Displacement in Porous Media

Counterintuitive Wetting Transitions in Doubly Reentrant Cavities as a Function of Surface Make‐Up, Hydrostatic Pressure, and Cavity Aspect Ratio

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