Contact area

About: Contact area is a research topic. Over the lifetime, 12358 publications have been published within this topic receiving 256401 citations. The topic is also known as: contact patch & contact region.

Effect of Ag particle size on electrical conductivity of isotropically conductive adhesives

Abstract: The present work is to introduce nanoparticles in micro-sized metal particles to study particle distribution in polymer matrix. Previous examinations of the silver-filled particles reveal that the micro-sized particle fillers appear as full density silver flakes, while nanoparticle fillers appear as highly porous agglomerates, similar to open-cell foams. Actually little work has been carried out to study the cross-sectional area of a particle-particle-contact in isotropically conductive adhesives (ICA). In this study, transmission electron microscope is chosen as a main measure to analyze the distribution of different-sized particles. The percentage of the nanoparticles varies from 20 wt% and 50 wt% to full percentage within micro-sized particles, and the total metal content in epoxy resin is 70 wt%. So the change of contact area and contact behavior with various volume ratio of nano-sized and micro-sized particles was investigated. At the same time, the electrical resistivity was measured, which is compared with the different level of the filler loading.

Biomechanics of smooth adhesive pads in insects: influence of tarsal secretion on attachment performance

Abstract: Many insects possess smooth adhesive pads on their legs, which adhere by thin films of a two-phasic secretion. To understand the function of such fluid-based adhesive systems, we simultaneously measured adhesion, friction and contact area in single pads of stick insects (Carausius morosus). Shear stress was largely independent of normal force and increased with velocity, seemingly consistent with the viscosity-effect of a continuous fluid film. However, measurements of the remaining force 2 min after a sliding movement show that adhesive pads can sustain considerable static friction. Repeated sliding movements and multiple consecutive pull-offs to deplete adhesive secretion showed that on a smooth surface, friction and adhesion strongly increased with decreasing amount of fluid. In contrast, pull-off forces significantly decreased on a rough substrate. Thus, the secretion does not generally increase attachment but does so only on rough substrates, where it helps to maximize contact area. When slides were repeated at one position so that secretion could accumulate, sliding shear stress decreased but static friction remained clearly present. This suggests that static friction which is biologically important to prevent sliding is based on non-Newtonian properties of the adhesive emulsion rather than on a direct contact between the cuticle and the substrate.

Computer touch screen adapted to facilitate selection of features at edge of screen

Abstract: In one embodiment of the invention, a hot spot is normally centered in an area of contact between a user's finger and a touch screen to position the hot spot on an icon or other feature thereby selecting a program or function corresponding to the icon or feature. When the contact area is near an edge, the hot spot is offset toward the edge so that it coincides more closely to the center of the users finger, thus allowing an icon or other feature adjacent the edge of the screen to be more easily selected. In another embodiment, a cursor is displayed on a touch screen at a location that is offset from the contact area between a finger and the screen. The cursor, which is used as the hot spot of the computer, is normally offset above the contact area except when the contact area is close to the bottom of the screen. The cursor is then offset to the left or right of the contact area depending on whether the contact are is to the left or right of the screen, respectively, so that icons or features adjacent the left or right edges of the screen can be selected. Similarly, when the contact area is very close to the bottom of the screen, the cursor is offset downwardly and to the right or left so that icons or features adjacent the bottom edge of the screen can be selected. Alternatively, a touch sensitive area incapable of displaying an image may be provided beneath a display area of the touch screen to allow icons or features adjacent the bottom edge of the display area to be selected.

Dynamics of precursors to frictional sliding.

Abstract: We measure the spatial and temporal behavior of the true contact area A along a rough spatially extended interface between two blocks in frictional contact. Upon the application of shear the onset of motion is preceded by a discrete sequence of cracklike precursors, which are initiated at shear levels that are well below the threshold for static friction. These precursors arrest well before traversing the entire interface. They systematically increase in length with the applied shear force and significantly redistribute the true contact area along the interface. Thus, when frictional sliding occurs, the initially uniform contact area along the interface has already evolved to one that is highly nonuniform in space.