Meniscus slip

The ACL conies into adjacency with the anterior horn of the lateral meniscus under gross observation, and parts of the ACL fiber are attached to the anterior horn with an anterior width ranging from 1/3-1/2 of its surface. Moreover, fat and scar tissues cover its border, and the border between the anterior horn of the lateral meniscus and ACL attachment cannot be grossly identified. When these surface layers of soft tissues are carefully detached, both structures are overlapped anteriorly and the lateral meniscus slips under the substratum of the ACL posteriorly (Fig. 4.3). The anterior horn of the lateral meniscus was attached on the base of the lateral groove and lateral aspect of the aforementioned bony protrusion, and the attachment was... 

Macroscopic observation of ACL tibial footprint, (a) ACL and lalraal meniscus arc overlapped anteriOTly, and the lateral meniscus slips under the substratum of the ACL posteriOTly. (b) After resection of ACL and lateral moiiscus attachmenL AH anterior hom of lateral mcmiscus, MM medial meniscus, UT lateral intercondylar tubercle, M7T medial intercondylar tubtucle, white dot area ACL tibial footprint, blue dot area attachment of anterior hom of lateral meniscus... 

The existence of a stress-free meniscus introduces a boundary discontinuity on both upper and lower rims. This discontinuity is bound to result in sharply enhanced stress build-up at the upper and lower contact lines. It may produce an effective slip layer on the sample/plate interfaces at the meniscus, yielding an overall torque, which is less than anticipated on the basis of Fig. 7a, since a large portion of the measured torque on the plate arises from the stress contribution at the rim r=R. This correction may increase with lowering the gap distance. Without a proper analytical treatment, it remains unknown how the magnitude of such an apparent slip depends on the rheological properties of the sample and whether the reported slip like behavior [ 19,33] is a manifestation of such a plausible edge effect. 

In the second method a small sample of the material is placed in the well of a hot stage containing a quantity of low-viscosity silicone oil (Fig. 28). The test piece is prepared by a special cutter of diameter 1.6 mm from a granule that will pass through a 0.80 mm sieve but is retained on a 0.63 mm sieve. The disk so formed is cut into quarters to form the test piece. A cover slip is placed over the test piece to form a wedge-shaped gap. and the oil is present in sufficient quantity to form a meniscus between the cover slip and the cell floor. The hot stage is heated in the same way as the previous method and, as the test piece begins to melt, the meniscus of the oil moves across the field of view of a low power lens... 

In practice it is essential that the manometer and mercury be thoroughly clean to eliminate. stick-slip effects in the movement of the mercury meniscus. A tipping manometer is frequently used to transfer mercury from the reservoir into the arms of the manometer after evacuation. During the tipping operation it is essential that the mercury not reach the stopcock, because this is always greased and the resulting contamination will spread rapidly through the manometer [27],... 

With the initial conditions of ds/dt = 0 at t = 0 and s = So at t = 0, Eq. 23 can be numerically solved to yield the displacement and velocity characteristics of the advancing capillary meniscus. Since the effect of added mass is not incorporated in Eq. 22, a nonzero value of sq is required to avoid the prediction of an unrealistic initial burst at t = 0, as explained earlier. One major cmiclusimi that can be drawn from the numerical simulatimi studies of Yang et al. [8] is, based on the above model, that while liquid slip on hydrophobic surfaces may increase the flow velocity, the presence of a capillary pressure across the liquid—vapor interface can suppress the electroosmotic flow and significantly decrease the flow performance. 

From a fluid physics perspective, rigorous solutions to the Navier-Stokes equations are not immediately realizable as a consequence of the poor understanding of slip velocities associated with boundary conditions in microfluidic systems. However, alternative approaches toward developing dynamic flow models indicate meniscus position progresses according to the square... 

The results obtained in our experiments are in agreement with the pinning depiiming model published by Adachi and coworkers [22] where the meniscus is pinned by the assembling colloidal crystal. This model was designed to describe the stripe pattern observed in monolayer formation prepared by horizontal deposition. Also here the stick-slip motion is explained by a competition be-... 

A set of microposts made of pH-responsive hydrogel was constructed in a microfluidic chamber. A circular aperture was formed in a flexible polymer slip. The sidewall and top side of the aperture were treated to be hydrophilic and hydrophobic, respectively. Again, since aqueous solutions remained only on hydrophilic pathways at pressures below a critical value, part of the water-based liquid attached to the sidewall could form a liquid meniscus protruding downward at low pressures and upward at high pressures. 

Experiments in thick channels - have established that hydrodynamic flows are generally slower than one would expect from theory. Current analytical models of the superhydrophobic effective slip are based on the idealized model of a heterogeneous surface with patches of boundary conditions and mostly neglect a number of dissipation mechanisms in the gas phase and at the interface. The effects associated with different aspects of the gas flow and meniscus curvature must be included in the models. Regardless of recent semianalytical and numerical analyses,the goal should remain to find simple analytical formulas, with as few adjustable parameters as possible, to fit experimental data. 

Figure 10.2 Shape of a meniscus inside a nanochannel representing slip and no slip.

Careful investigations of the particle transport phenomena close to the meniscus showed that an additional mechanism is competing with particle accumulation. Indeed, due to a no-slip condition at the surface of the substrate, a recirculation flow /r of liquid is induced while the droplet is dragged over the substrate. As a consequence, because of stokes drag, particles are dragged from the meniscus region back to the suspension (See Fig. 15.11). This particle flow competes with the accumulation process created by evaporation. To start accumulation, Ji has to compensate for the depletion of the accumulation region created both by deposition particles... 

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