Measurement of adhesion forces

The studies on adhesion are mostly concerned on predictions and measurements of adhesion forces, but this section is written from a different standpoint. The author intends to present a dynamic analysis of adhesion which has been recently published [7], with the emphasis on the mechanism of energy dissipation. When two solids are brought into contact, or inversely separated apart by applied forces, the process will never go smoothly enough—the surfaces will always jump into and out of contact, no matter how slowly the forces are applied. We will show later that this is originated from the inherent mechanical instability of the system in which two solid bodies of certain stiffness interact through a distance dependent on potential energy. 

As described in the last section, the adhesion forces between the particles and the polished surface can provide insight into post-CMP cleaning mechanism and efficiency. As a matter of fact, measurements of adhesion force and alike can directly help in the understanding of CMP and post-CMP cleaning processes. In this section, some basic principles and applications of adhesion and friction force measurements in copper CMP will be presented. The discussion is certainly applicable to post-CMP cleaning processes when similar systems are involved. 

With calibrated detection system and cantilevers at hand, the measurement of adhesive forces can be carried out as outlined in Chap. 4. 

A Quantitative Measurement of Adhesion Force between Cell Adhesion... 

TABLE 11.1. Values of Constant A Obtained as a Result of Measurements of Adhesive Force. 

Fig. 111.14. Apparatus for measurement of adhesive force by use of plane-parallel disks (1, 2) disks (3) liquid (4) compressive load (5) counterweight (6) thermostat.

We see from these data that the values of surface tension calculated from known forces of adhesion (which are equal to the capillary forces) are low in comparison with the actual values. The point is that these investigators failed to account for the disjoining pressure of the thin layer of liquid (see Fig. IV.6.c), which weakens the capillary interaction. This is why their method for determining surface tension by measurement of adhesive force did not give accurate results. 

In later work [193], the chemically pure surfactant was a 3% solution of sodium dodecyl sulfate in distilled water. The results from measurements of adhesive force for yp = 50% are Hsted below. Also shown for comparison are results on the adhesion of aqueous solutions of a complex-forming substance, sodium tripolyphosphate (NasPaOio). The adhesion of 3-/xm gold particles in water and in aqueous solutions is illustrated by the following data ... 

Normal Forcos. In the treatment of normal forces, a differentiation into the measurement of adhesive forces, related to, eg, surface chemistry, quantification of entropic and enthalpic forces, dealing with single polymer chain properties, and finally indentation measurements, yielding surface mechanical properties, has been made. 

SIMBO G., ASAKAWA S., SOGA N. "Measurement of adhesion force of powder particles by powdered tensile strength method" J. Soc. Mater. Sc. Japan 1968 n 17 540-544. 

Snow Adhesion Tester For the measurement of adhesive force of snow, test apparatus dcviced by Ohishi was used. This apparatus,as shown in Fig.3, consists of refregerator, blower, ultra sonic steam generator and load sensor. 

Measurements of adhesion forces and contact deformations for single macro-, micro- and nanocontacts carried out with instruments as the JKR test, the SFA, or the AFM have shown good agreement with the JKR and DMTcontinuum theories even on the nanoscale. 

This chapter and the two that follow are introduced at this time to illustrate some of the many extensive areas in which there are important applications of surface chemistry. Friction and lubrication as topics properly deserve mention in a textbook on surface chemistiy, partly because these subjects do involve surfaces directly and partly because many aspects of lubrication depend on the properties of surface films. The subject of adhesion is treated briefly in this chapter mainly because it, too, depends greatly on the behavior of surface films at a solid interface and also because friction and adhesion have some interrelations. Studies of the interaction between two solid surfaces, with or without an intervening liquid phase, have been stimulated in recent years by the development of equipment capable of the direct measurement of the forces between macroscopic bodies. 

Standard Test Method for Adhesion Between Steel Tire Cords and Rubber. Steel cords are vulcanised into a block of mbber and the force necessary to pull the cords linearly out of the mbber is measured as adhesive force. ASTM method D2229-93a can be used for evaluating mbber compound performance with respect to adhesion to steel cord. The property measured by this test method indicates whether the adhesion of the steel cord to the mbber is greater than the cohesion of the mbber, ie, complete mbber coverage of the steel cord or less than the cohesion of mbber (lack of mbber coverage). 

Overall, the AFM is a powerful tool that can provide very high force and spatial resolution measurements of adhesion and mechanical properties. The reader is... 

New experimental techniqnes for the direct measurement of interparticle forces are now available and can be nsed to nnderstand the physicochemical factors that control adhesion, coating phenomena, tribology, and others. 

An important consideration for the direct physical measurement of adhesion via pull-off measurements is the influence of the precise direction of the applied force. In AFM the cantilever does not usually lie parallel to the surface, due to the risk that another part of the cantilever chip or chip holder will make contact with the surface before the tip. Another problem relates to the fact that the spot size in the optical beam deflection method is usually larger than the width of the lever. This can result in an interference effect between the reflection from the sample and the reflection from the cantilever. This is reduced if the cantilever and sample are not parallel. Most commercial AFM systems use an angle in the range of 10°-15° between the sample and the cantilever. Depending on this angle and the extent to which the cantilever is bent away from its equilibrium position, there can be a significant fraction of unintentional lateral forces applied to the contact. 

Stuart and Hlady [37] found that unintentional lateral forces influenced their measurements of adhesion between surface-bound protein molecules and colloid probe-bound ligands. They noted a greatly exaggerated separation distance and a stick-shp behavior in their adhesion curves, which they attribute to roUiug and buckling of the cantilever under the influence of lateral forces as the sample was retracted with the probe stuck to it. 

Determination of adhesion between textile and rubber in tyres, hose, belting, etc., by measurement of the force necessary to strip one from the other. 

Coefficient of variation for dust (dry assay) and dust (wet assay) was 8.5 and 8.7%, respectively. The range of trash contents is about 50 compared to about four for dust content. As explained by Montalvo (12). differences in dust content by the dry and wet assay methods are a result of a geometry effect associated with the former technique and the variation of adhesion force of dust on cotton with environment. Only one airborne dust measurement was taken on five of the six cottons. 

Another example of the use of DOE during pilot studies is the study of factors affecting the ejection and take-off force. Measurement of ejection force and take-off force will determine if the formula is sufficiently lubricated. Ejection force is measured as an indication of the release of the tablet from the die wall forces, and the take-off force related to the adhesion forces to the punch face. Take-off force is an appropriate measurement to determine if a formula has a tendency to stick. Based on these designs, an optimal formula, including the lubricant level, and process can be predicted for scale-up (Figs. 12 and 13). 

Various mechanical testing methods have been used to assess the bioadhesive properties of materials and formulations. Review of the literature reveals that the technique most commonly used is the tensile test [82,85]. This test provides the measure of the force needed to detach a layer of the tested material or formulation from a mucosal substrate as a function of the displacement occurring at the bioadhesive interface. Besides maximum force of detachment, another parameter provided by tensile test is the work of adhesion calculated as the area under the force versus displacement curve. Such a parameter gives more complete... 

Abstract. Quantitative measurements of lateral force required for displacement of SWNTs bundle on the surface of highly oriented pyrolytic graphite with the help of atomic force microscope (AFM) were performed in real time . New method of quantitative calibration of lateral forces was used for interpretation results of lateral force microscopy (LFM). It allows us to receive numerical values of adhesion force of bundle to substrate easy and without specific equipment. 

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