Search

A letter to the editor is presented in response to the article "Adhesion-delamination mechanics of a presented rectangular film adhered onto a rigid substrate."

A prestressed rectangular film clamped at both ends delaminates from a rigid punch. Based on a thermodynamic energy balance, the delamination mechanics is derived to relate the simultaneous external tensile force applied to the punch, punch displacement, and contact area. Effects of the coupled tensile residual membrane stress and adhesion energy at the punch-film interface are investigated. A “pinch off” (stable shrinking of the contact area to a line) is predicted, contrasting the nonzero “pull-off” radius in a clamped circular film. The model is useful in understanding the behavior of various adhesion-delamination phenomena, especially in one dimensional capacitive microelectromechanical systems radio frequency switches, microstructure network, and nanostructures. [ABSTRACT FROM AUTHOR]

An array of gold nano-pillars is fabricated on silicon, before chemical vapor deposited graphene is transferred to the substrate. Intrinsic intersurface attraction pulls the monolayer into intimate contact conforming to the substrate geometry, but the pillars support an array of circular blisters. A simple delamination mechanics model is constructed to extract the materials and interface properties. The graphene-gold interfacial adhesion energy is found to be γ = 450 ± 100 mJ m-2 by measuring the blister dimension. Should the ratio of pillar height to inter-pillar separation falls short of (γ/Eh)1/4 with graphene elastic modulus, E and thickness, h, the blisters stay isolated; otherwise, adjacent blisters coalesce. Critical design guidelines are set for graphene devices. [ABSTRACT FROM AUTHOR]

A nano-cheese-cutter is fabricated to directly measure the adhesion between two freestanding nano-fibers. A single electrospun fiber is attached to the free end of an atomic force microscope cantilever, while a similar fiber is similarly prepared on a mica substrate in an orthogonal direction. External load is applied to deform the two fibers into complementary V-shapes, and the force measurement allows the elastic modulus to be determined. At a critical tensile load, 'pull-off' occurs when the adhering fibers spontaneously detach from each other, yielding the interfacial adhesion energy. Loading-unloading cycles are performed to investigate repeated adhesion-detachment and surface degradation. [ABSTRACT FROM AUTHOR]

We report a technique to characterize adhesion of monolayered/multilayered graphene sheets on silicon wafer. Nanoparticles trapped at graphene-silicon interface act as point wedges to support axisymmetric blisters. Local adhesion strength is found by measuring the particle height and blister radius using a scanning electron microscope. Adhesion energy of the typical graphene-silicon interface is measured to be 151±28 mJ/m2. The proposed method and our measurements provide insights in fabrication and reliability of microelectromechanical/nanoelectromechanical systems. [ABSTRACT FROM AUTHOR]