Elastic menisci

Texture modifications occur mainly during the first step of drying (the constant rate period) and are related to the visco-elastic properties of the gel network [6]. During the second step of drying (the falling rate period), liquid water leaves the capillaries and the pore walls can be damaged by forces linked to the existence of liquid-gas meniscus [6, 7],... 

In the case of protein adsorption layers, the surface elasticity is so strong that the particle (Figure 5.21) is arrested in the adsorption him. Nevertheless, with heavier particles and at larger meniscus slopes, it is possible to break the protein adsorption layer. Based on such experiments, a method for determining surface elasticity and yield stress has been developed. ... 

Liquids behave as if they have an elastic skin, which holds the liquid molecules together and tries to minimize its surface area. This property is the surface tension (for a liquid surrounded by gas). The surfaee tension is responsible for many well-known properties of liquids, e.g. the bulge of liquid (the meniscus) above a cup that has been overfilled and the fact that flat stones can be bounced off the surface of a lake. Just as the surface of a liquid has a surface tension, the interface between two immiscible liquids, such as oil and water, has an interfacial tension. This arises because water molecules prefer to be surrounded by other water molecules rather than oil molecules. 

The physical dimension of a template defines the boundary of regeneration. Thus, the size of the collagen template should match the tissue defect to be repaired. A properly sized meniscal substitute has been found to function better than a substitute which mismatches the physical dimension of the host meniscus [Rodkey et al., 1998 Sommerlath et al., 1991]. For a porous, elastic matrix such as the one designed from collagen for meniscal tissue repair, the shape of the meniscus is further defined in vivo by the space available between the femoral condyles and tibial plateau within the synovial joint. 

As with the meniscus, strength and modulus of discal tissue vary with location and orientation of the specimen (Table B2.7). Lin et al [15, 16] have however shown that elastic moduli of annular specimens are independent of disc level. 

It is unexpected that the droplet would jump away from the surface when encountering the unpattemed strips, since the strips were measured to be more hydrophflic than the patterned squares. The high speed videos show that the unpattemed strips suddenly pulled a portion of liquid adhered to the smooth surface. In many cases, the droplet elasticity due to surface tension was overcome, resulting in a separated droplet. In other cases, the droplet pulled the adhered liquid back to the droplet until a sudden detachment (jumping) event from the surface. Cases where a detached droplet was propelled towards the meniscus due to surface tension forces acting on it or off the surface were observed when the adhered liquid was pulled towards the droplet but still pinched off. 

It is interesting to compare the elasticity of a meniscus with another elasticity involved in wetting processes the CL spring constant. It was shown experimentally that the elasticity energy of a CL is not Hookean. By studying the relaxation of a CL deformed periodically, Ondarfuhu and Veyssie verified that this energy has a nonclassical expression given by ... 

Another issue of particular interest is the determination of the smallest size of a meniscus as a function of the tip geometry and the RH, which is relevant for the experimental results described before. Whatever the process involved, with a surface exhibiting an elastic-like behavior, the force at which the tip detaches from a surface, that is, the adhesion force measured, occurs when the tip reaches a critical contact area that corresponds to the smallest contact area between the tip and the meniscus. Therefore, the... 

The last part of the separation process is important in the framework of the elasticity of meniscus since it corresponds to the stretching of the meniscus. The slope of the curve is a direct determination of the meniscus spring constant. In Fig. 9.12 is reported this part for two different liquids (heptadecane and glycerol). The spring constant values determined with several tips for each liquid are heptadecane = 8 3 mN/m and kgiyceroi = 18 3 mN/m. 

A typical sequence of dipping events in water is displayed in Fig. 9.14. The liquid is approached with a step motor toward the nanoneedle. When the tip is far from the surface, that is, more than a few nanometers, there is no interaction between the needle and the air-liquid interface and thus no frequency shift (phase 1). As soon as the tip touches the liquid, the elastic response of the meniscus induces a positive shift of the resonance frequency (phase 2). Because of the water evaporation, the average contact angle decreases with time leading to a decrease of the frequency shift (phase 3). The phase 4 is identical to phase 1 with no significant interaction between the tip and the liquid. 

The rectangular channel is covered by an elastic membrane that is pulled downward due to the negative pressure inside the liquid. This downward deflection can be written as u(x, z). If we make the assumption that, the z-derivatives of u are much smaller than the x-derivatives and that the length of the meniscus is not much larger than the channel width w, then the deflection in the elasticity problem is virtually independent of z and we are left with a quasi one-dimensional problem, the so-called cylindrical bending of a long, rectangular plate. The equation of elasticity for the deflection... 

Mechanical properties of the knee components are derived from selected referred articles (See Table 1). Bone s density and its mechanical properties varied along its length, but in this study tibia and femur simplified as a non-linear isotropic material. Meniscus is composed of fibrocartilage, an anisotropic nonlinear viscoelastic material and its viscoelastic behavior make constant after 1500s [2]. Because an instance load applied in the dynamic analysis, so the properties variation is neglected. Articular cartilage and tibia plateau cartilage are assumed as isotropic elastic material. 

The wicking rate from an infinite liquid reservoir depends on the capillary dimensions of the substrate and the viscosity of the liquid [37,38]. For a theoretical treatment of capillary flow in fabrics, the fibrous assemblies are usually considered to consist of a number of parallel capillaries [39]. The advancement of the liquid front in a capillary occurs in small jumps. The advancing wetting line in a single capillary stretches the meniscus of the liquid until the elasticity of the... 

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