Papers by Keyword: Surface Stress

Abstract: Based on the two distinct solutions, as classical solution for an elastic half space containing a circular hole at nanoscale, the complex variable and superposition method was proposed and employed to investigate the state of stress and displacement in an half space with surface tension for nanoelastic material.The results indicate some characteristics in half space which are different from those in classical elasticity theory .

Abstract: Surface stress-based biosensors as a crucial part of micro-scale and label-free system, use free energy change, the underlying concept in any binding reaction, have been investigated extensively in recent years. In this paper, a new bi-micro-cantilever surface stress biosensor is proposed which can be used to detect cells. Some fundamental study has been done, especially for the micro-cantilever due to its crucial role in the whole system. To acquiring the optimal material for more sensitive sensor, four material, Si, SiN, AlN, PMMA(polymethylmethacrylate), were contrastively analyzed under the same conditions (loads, size, environmental factor. etc) by finite element (FE) method. This study could provide some foundation for the biosensor design and fabrication.

Abstract: Atomic/molecular adsorption on a microcantilever surface can cause the cantilever to deflect as a result of the adsorption-induced surface stress. In this paper, based on atomic/molecular interactions, an energy-based model is proposed to calculate the chemisorption-induced surface stress. The connection between the chemisorption-induced surface stress and the covalent bond interactions is established. The results are consistent with relevant experimental observations. This study is helpful for characterizing and optimizing the mechanical response of cantilever-based sensors.

Abstract: In this paper, we analyze the influence of surface effects including residual surface stress, surface piezoelectric and surface elasticity on the buckling behavior of piezoelectric nanobeams by using the Timoshenko beam theory and surface piezoelectricity model. The critical electric potential for buckling of piezoelectric nanobeams with different boundary condition is obtained analytically. From the results, it is found that the surface piezoelectric reduces the critical electric potential. However, a positive residual surface stress increases the critical electric potential. In addition, the shear deformation reduces the critical electric potential, and the influence of shear deformation become more significant for a stubby piezoelectric nanobeam.

Abstract: Three-point bending tests of nanowires with Contact atomic force microscopy reveal that the Young’s modulus of a nanowire is size-dependent. The modulus changes with the diameter of a nanowire. This size dependency can be explained within the framework of classical continuum mechanics by including the effects of surface stress. In this study, an analytical solution has been derived for the elastic strain energy of a nanowire with both ends clamped and contacted by an AFM tip at its midpoint. Different from previous theoretical models, the present model can handle the case of large deflection, where the displacement of the nanowire is in the same order of the diameter. Based on the equivalence of elastic strain energy, the apparent Young’s modulus of a nanowire is expressed as a function of the elastic modulus of the bulk and that of the surface, and the dimensions of a nanowire.

Abstract: Started from structure construction ,this paper carried out numerical analysis about the test members through computer simulation and studied the influence of cover thickness and stirrup spacing on the rust expansion crack by means of rapid electrifying for accelerating the corrosion of longitudinal reinforcement. Based on this, it established the correlativity between member surface stress and concrete cover thickness, stirrup spacing. And this paper found the influence law of cover thicknesses and stirrup spacing on rust expansion crack on specimen surface.

Abstract: With new applications in the area of diagnostics, drug discovery and genetics, the need for Biological Micro-Electro-Mechanical Systems (BioMEMS) has increased tremendously in the last decade. Especially, surface stress-based BioMEMS has been investigated extensively in the recently years. In this paper, a new BioMEMS is proposed, which can be used to detect cells. It consists of microfluidics, square membrane and a fiber optic interferometer. The square membrane as the crucial and sensitive part includes three layers, self-assembled monolayer (SAM), gold and substrate material. Based on the BioMEMS, some fundamental study has been done, especially for the membrane due to its crucial role in the whole system. The finite element (FE) method has been used to study the membrane with different substrates. By the fundamental study, some important conclusions have been acquired: (1) The square membrane will reach maximal deflection at different ratio values (P: membrane size) to different substrates; (2) To a certain substrate, such as PDMS, the ratio making the membrane reach maximal deflection is different to dissimilar PDMS layer thickness; (3) If young’s modulus (E) of the substrate is too small, separation may happen between the gold layer and substrate layer when the gold size becomes smaller.

Abstract: The purpose of this work is to extend the equations of linear poroelasticity to the case of materials with nanopores. We consider a model of microstructure which corresponds to an assemblage of hollow spheres saturated by a fluid. The solid phase is linearly elastic and isotropic; pores are assumed to be of nanometric size. To account for the pore surface stresses, the Young-Laplace model is used. The nanopore size effects on the effective bulk modulus, Biot’ modulus and coefficient are shown. When pores are sufficiently large, the classical relations of linear poroelasticity are retrieved.

Abstract: The coherent phase equilibria of binary nanoparticles, in which three phases can be formed, were examined by accounting for the particle size effect engendered by the surface stress. Considering the system geometry exhibiting radial symmetry, coherent phase diagrams could be constructed for different particle sizes. The phase diagrams exhibited several characteristics of phase equilibria unique to coherent systems. It was found that a positive surface stress results in a radial compressive stress in the particle that is inversely proportional to the particle radius, thereby increasingly stabilizing the phase having a lower molar volume as the particle size decreases.

Abstract: A new formulation for an adhesive force between a substrate and an indenter is presented. The boundary condition taking into account surface stresses is used for the present analysis. The surface stress is originated from surface energy. A paraboloidal indenter is pressed to the substrate, and then adhesion occurs between both surfaces. Surface energy and surface stress will vary at the adhesion surface, and then the surfaces deform in a concave way. An attractive force occurs to keep the contact of two adhesion surfaces. In the present paper, an effect of surface stress on the adhesive force will be clarified.