Contact angle static sessile drop

Fig. 2 Contact angle goniometry images of static sessile drop on glass slides, left column 5 A glass, right column ACP-coated glass (still photos extracted from a...

A distinction can be made among the available methods between static and dynamic contact angle determination methods. In the case of a static determination the contact angle of a drop with an immobile solid/liquid/gas interface is determined microscopically (sessile drop). In the captive bubble method the contact angle of an air bubble, which is located under the solid surface in contact with the liquid, is determined. In contrast to the sessile drop method, in the captive bubble method the contact angle is measured at a completely wet surface. 

Fig. 4 Comparison between single-fiber Wilhelmy, static sessile drop, and dynamic sessile drop contact angles for plain Toray TGP-H paper. The substrate on which the water droplet is sitting top-left comer) is plain TGP-H paper, with a single approximately 10 pm diameter TGP-H fiber penetrating the water droplet (the fiber was extracted from the paper substrate)...

Fig. 10 Before and after comparison of static sessile-drop contact angles of SGL SIGRACET GDL 24BC aged for 1,006 h in 80°C deionized water with air sparging gas Bars on left represent the MPL surface and bars on right represent the non-MPL sirrface...

Fig. 12 Cassie model of equilibrium static sessile drop water contact angles as a function of TGP-H fiber surface coverage for FEP (gray) and PTFE (black) (Wood 2007)...

Figure 6.1 schematically depicts the three interactions between a liquid droplet and a surface. These three interactions are actually governed by the movement of the contact line. When the liquid first wets the surface, the contact line advances outward, and the first information one seeks is wettability. The adjectives to describe the surface are wettable and non-wettable. As for the liquid, it will either wet or partially wet the surface or repel from it. As discussed in Chap. 5, wettability is measured by the advancing angle Oa- Once the liquid partially wets the surface, a static sessile drop is formed. There exist two interactions between the sessile drop and the surface. In the vertical direction, it is the adhesion and it is measured by the receding angle 0r. The only motion for the contact line is receding, and an interface (liquid-solid) is eliminated when the liquid droplet is detached from the surface. 

Far from a wellbore, the velocity of reservoir fluids is about one linear foot per day. Near a wellbore, the velocity can increase one-hundred fold. A static or quasi-static test such as the sessile drop (contact angle) test may not represent the dynamic behavior of the fluids in the field. The dynamic Wilhelmy device gives results which are comparable in interface velocity to the field displacement rate. The interface in the Wilhelmy test described here moved at a steady rate of 0.127 mm/sec or 36 ft/day. The wetting cycle for a hybrid-wetting crude oil system was not affected by moving at a rate less than 1 ft/day. 

The profiles of pendant and sessile bubbles and drops are commonly used in determinations of surface and interfacial tensions and of contact angles. Such methods are possible because the interfaces of static fluid particles must be at equilibrium with respect to hydrostatic pressure gradients and increments in normal stress due to surface tension at a curved interface (see Chapter 1). It is simple to show that at any point on the surface... 

Provides measuring techniques of contact angle, surface tension, interfacial tension, and bubble pressure. Suitable methods for both static and dynamic inteifacial tension of liquids include du Nous ring, Wilhelmy plate, spinning drop, pendant drop, bubble pressure, and drop volume techniques. Methods for solids include sessile drop, dynamic Wilhelmy, single fiber, and powder contact angle techniques. 

Static contact angle measurement of the sessile drop. The contact angle, 6C, is the angle formed by a liquid drop at the three-phase boundary where a liquid, a gas, and a solid intersect. It depends on the interfacial surface tensions between gas and liquid nGL, liquid and solid nLS, and gas and solid IIGS, as given by Young s6 equation of 1805 ... 

ADSA-P has been employed in various surface tension and contact angle studies, including static (advancing) contact angles [69.70], dynamic (advancing) contact angles at slow motion of the three-phase contact line [4, 71—74], and contact angle kinetics of surfactant solutions [75]. A schematic of the experimental setup for ADSA-P sessile drops is shown in Fig. 6. More details are available elsewhere [66[. 

Figure 4. Static test results. // is the parallel direction and is the perpendicular direction. The sessile drop data point is the contact angle measurement on a static, non-tilted drop. The rightmost 6 wafers shown are unpatterned.

Fig. 7. Schematic illustration of dynamic and static contact angle determinations using die Wihehny plate method, the sessile drop method and the captive huhhle method...

Static water contact angles were determined by the sessile-drop method employing a Rame-Hart goniometer (Rame-Hart Instrument Co., Model-100, Netcong, NJ) at all stages of the surface-modification process, i.e., after cleaning of the Si02 substrates, after vapor deposition of the photoiniferter, and after photopolymerization of the PMAA brushes. 

Contact-Angle Measurements. Static contact angles were measured at room temperature and ambient humidity. On gradient samples, a single measurement of sessile drops was... 

Values of advancing 0a, receding 0r, and static 0q contact angles measured for sessile droplets on a methylated quartz plate in dependence on surfactant concentration [22] are shown in Fig. 19. To determine 0a and 0r, the drop was disposed on a polished surface of a flat cut of a thick-walled quartz capillary over its orifice. For solution concentration Cq< 0.1%, advancing angles are higher than 90° and, therefore, the capillary suction is formally impossible. However, as is shown in Fig. 18, a slow penetration of low concentrated solutions takes place. Similar results were obtained in other experiments with... 

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