Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of ...consensus on how to incorporate a description of contact angle hysteresis into physical models. To clarify this, starting from the basic definition of contact angle hysteresis, we introduce the formalism and models for implementing contact angle hysteresis into relevant physical phenomena. Furthermore, we explain the influence of the contact angle hysteresis in physical phenomena relevant for industrial applications such as sliding drops, coffee stain phenomenon (in general evaporative self-assembly), and curtain and wire coating techniques.
CO
geo-sequestration is a promising technology to permanently store CO
in geological formations to control the atmospheric carbon footprint. In addition, CO
is frequently utilized in enhanced oil ...recovery operations to accelerate oil production. Both, CO
geo-storage and EOR, are significantly influenced by the wettability of the associated rock/CO
/brine systems. Wettability drives the multiphase flow dynamics, and microscopic fluid distribution in the reservoir. Furthermore, while wettability is known to be influenced by varying in-situ conditions and surface chemistry of the rock/mineral, the current state-of-the-art indicates wider variabilities of the wetting states. This article, therefore, critically reviews the published datasets on CO
wettability of geological formations. Essentially, the rock/CO
/brine and rock/crude-oil/CO
-enriched-brine contact angle datasets for the important reservoir rocks (i.e. sandstone and carbonate rocks), as well as for the key minerals quartz and calcite are considered. Also, the parameters that influence wettability are critically analyzed, and the associated parametric trends are discussed and summarized. Finally, we identify pertinent research gaps and define the outlook of future research. The review, therefore, establishes a repository of the recent contact angle data, which thus assists to enhance our current understanding of the subject.
•A new variable solid-fluid interaction strength scheme is incorporated to a multicomponent/multiphase lattice Boltzmann method to simulate contact angle hysteresis.•Droplet sliding on a inclined ...isothermal non-ideal/ideal flat plate is simulated showing the decrease/increase in receding/advancing contact angle as the droplet slides along the inclined plate.•Droplet evaporation on a horizontal heated non-ideal flat plate is simulated showing constant contact line and constant contact angle periods.•Good agreements with the previous results are shown.
A variable solid-fluid interaction strength scheme compatible with the lattice Boltzmann method is introduced to investigate contact angle hysteresis phenomena numerically. This method is applied to study two problems: (i) droplet sliding on inclined isothermal plates and (ii) droplet evaporating on horizontal heated plates. It is demonstrated that this method is capable of reproducing the decrease in the receding contact angle and the increase in the advancing contact angle during droplet sliding on an inclined isothermal plate, and the constant contact line (CCL) and constant contact angle (CCA) evaporation periods during droplet evaporation on a horizontal heated plate. These simulated results are in agreement with previous experimental investigations.
Surface roughness is an important factor that affects dynamic wetting behavior, which can improve the surface hydrophobicity, so it is of great significance to obtain a better understanding of ...roughness effect from both theoretical and practical perspectives. In this paper, we studied the influence of macro-size surface roughness on contact angle hysteresis and spreading work and analyzed the relationship between contact angle hysteresis and spreading work. Results showed that as the surface roughness increased, both the advancing contact angle and the receding contact angle continued to increase until their maximum values were reached, and then started to decrease within the range of surface roughness studied, while the contact angle hysteresis presented the opposite trend. In addition, with the increase of surface roughness the spreading work initially increased to a certain maximum value, then continuously decreased to the minimum value, and then began to increase within the range of the surface roughness studied. These trends could be attributed to the surface wetting state (Wenzel state, Cassie state, and transition state) changing with the change of surface roughness. These findings can provide guidance for the preparation of wetted surfaces with specific functions, especially when it is required to change the wettability without changing the surface chemical properties.
Superhydrophobic-superhydrophilic patterned surfaces have attracted more and more attention due to their great potential applications in the fog harvest process. In this work, we developed a simple ...and universal electrochemical-etching method to fabricate the superhydrophobic-superhydrophilic patterned surface on metal superhydrophobic substrates. The anti-electrochemical corrosion property of superhydrophobic substrates and the dependence of electrochemical etching potential on the wettability of the fabricated dimples were investigated on Al samples. Results showed that high etching potential was beneficial for efficiently producing a uniform superhydrophilic dimple. Fabrication of long-term superhydrophilic dimples on the Al superhydrophobic substrate was achieved by combining the masked electrochemical etching and boiling-water immersion methods. A long-term wedge-shaped superhydrophilic dimple array was fabricated on a superhydrophobic surface. The fog harvest test showed that the surface with a wedge-shaped pattern array had high water collection efficiency. Condensing water on the pattern was easy to converge and depart due to the internal Laplace pressure gradient of the liquid and the contact angle hysteresis contrast on the surface. The Furmidge equation was applied to explain the droplet departing mechanism and to control the departing volume. The fabrication technique and research of the fog harvest process may guide the design of new water collection devices.
The wetting of solid surfaces is treated. The Young and receding contact angles are experimentally unattainable values for the majority of solid surfaces. Actually, we always observe the apparent ...contact angle. This makes the characterization of wetting of real surfaces problematic. It is proposed in this paper to characterize wetting of real surfaces with the advancing contact angle and the minimum work of adhesion calculated according to the Dupre equation. The advancing contact angle, which depends slightly on the experimental technique used for its measurement, corresponds to the maximal solid/liquid surface tension and correspondingly to the minimal work of adhesion, calculated according to the Dupre equation.
Thin-film composite (TFC) membranes are the most widely used membranes for low-cost and energy-efficient water desalination processes. Proper control over the three influential surface parameters, ...namely wettability, roughness, and surface charge, is vital in optimizing the TFC membrane surface and permeation properties. More specifically, the surface properties of TFC membranes are often tailored by incorporating novel special wettability materials to increase hydrophilicity and tune surface physicochemical heterogeneity. These essential parameters affect the membrane permeability and antifouling properties. The membrane surface characterization protocols employed to date are rather controversial, and there is no general agreement about the metrics used to evaluate the surface hydrophilicity and physicochemical heterogeneity. In this review, we surveyed and critically evaluated the process that emerged for understanding the membrane surface properties using the simple and economical contact angle analysis technique. Contact angle analysis allows the estimation of surface wettability, surface free energy, surface charge, oleophobicity, contact angle hysteresis, and free energy of interaction; all coordinatively influence the membrane permeation and fouling properties. This review will provide insights into simplifying the evaluation of membrane properties by contact angle analysis that will ultimately expedite the membrane development process by reducing the time and expenses required for the characterization to confirm the success and the impact of any modification.
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•Recent advancements in surface characterization of water treatment membranes are critically reviewed.•New insights into evaluation of membrane properties by contact angle analysis are provided.•The use of contact angle analysis to evaluate the membrane performance parameters are presented.•Estimation of surface free energy, surface charge, oleophobicity, and contact angle hysteresis are provided.•The challenges and opportunities in implicating specially wettable interfacial materials to develop next-generation membranes are discussed.
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Wetting phenomena play a significant role in oil recovery from complex carbonate reservoirs under harsh conditions. The potential to being able to alter the rock wettability from ...oil-wet to water- or neutral-wet is often considered the pre-requisite to a successful Enhanced Oil Recovery (EOR) process. Hence, there arises the importance of understanding the (static) wetting and (dynamic) wettability alteration of the reservoir rock when the rock comes in contact with injected modified brines, oilfield chemicals, and/or nanofluids. In this study, we investigate the effect of three Carbon nanodots in high salinity brines with and without surfactant on static wetting and dynamic wettability alteration of carbonate reservoirs. Outcrop Indiana limestone and reservoir crude oil samples were used in these tests. The contact angle of the rock-oil-brine system is measured as a function of the nanodot concentration, saturating fluid in the rock matrix and aging, surfactant concentration, temperature, pressure, and brine salinity. The upper limits for the values for temperature, pressure, and salinity are set to be representative of the Saudi Arabian harsh reservoir conditions. The use of Carbon nanofluids demonstrated a clear shift in both static and dynamic measurements towards a more favorable water-wet condition for EOR. Statically, the contact angle of an oil-saturated carbonate rock exhibited a change from a strongly oil-wet condition to slightly water wet (with more than 50 % drop in the contact angle value) in 200 ppm (0.02 wt/v%) solution of carbon nanodot (CND) in seawater (SW) over 24 hours. Dynamically, a smaller but still remarkable change (a shift in the order of 20 %) in the contact angle is noted for a sister rock sample over the same period when a solution at the same concentration of CND in SW is introduced to replace the SW base fluid. Nanofluid spreading experiments on oil-coated glass slides supported our dynamic wettability studies. The spreading efficiency of the Carbon nanofluid was analyzed using optical and confocal microscopy with a clear and remarkable oil dislodging effect. Zeta potential measurements of the different systems were made to aid in the interpretations. The combined mechanistic actions of the various factors, including reservoir environment, disjoining pressure, interfacial tension, capillary pressure alterations and nanodots interactions with the oil/water interface, contributed to this change in wettability. Our study supports a strong and favorable EOR impact of CND as an effective and economically viable additive to waterflood operations in carbonate reservoirs.
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