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Full-Text Articles in Biomedical Engineering and Bioengineering
Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin
Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin
Nancy A. Burnham
Roughness has a significant affect on adhesion. The authors used a single-asperity model to describe a smooth tip in contact with a rough surface and predicted that an optimal size of asperity yields a minimum of adhesion. Experimentally, adhesive forces on silicon wafers with varying roughness were measured using atomic-force-microscopy cantilevers with varying tip radii. It was found that minima do exist, and for all tip radii, the adhesion falls significantly for roughness greater than 1–2nm and drops at higher roughness for larger tips. This work should help minimize stiction in microelectromechanical systems and progress the understanding of nanoscale-contact mechanics.
Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet
Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet
Nancy A. Burnham
Phase images acquired while intermittently contacting a sample surface with the tip of an atomic force microscope cantilever are not easy to relate to material properties. We have simulated dynamic force curves and compared simulated with experimental results. For some cantilever–sample combinations, the interaction remains a surface effect, whereas for others, the tip penetrates the sample significantly. Height artifacts in the “topography” images, and the role of the sample stiffness, work of adhesion, damping, and topography in the cantilever response manifest themselves to different extents depending on the indentation depth.
Stiffness Of Measurement System And Significant Figures Of Displacement Which Are Required To Interpret Adhesional Force Curves, Nancy Burnham, Kunio Takahashi, Hubert Pollock, Tadao Onzawa
Stiffness Of Measurement System And Significant Figures Of Displacement Which Are Required To Interpret Adhesional Force Curves, Nancy Burnham, Kunio Takahashi, Hubert Pollock, Tadao Onzawa
Nancy A. Burnham
Force curves obtained from an elastic contact theory are shown and compared with experimental results. In the elastic contact theory, a pin-on-disk contact is assumed and the following interaction are taken into consideration; (i) elastic deformation, (ii) the specific energy of adhesion in the area of the contact, which is expressed as the difference between the surface energies and the interface energy, (iii) the long-range interaction outside the area of contact, assuming the additivity of the Lennard-Jones type potential, and (iv) another elastic term for the measurement system such as the cantilever stiffness of an atomic force microscope (AFM). In …
Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton
Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton
Nancy A. Burnham
An atomic force microscope(AFM) has been configured so that it measures the force between a tip mounted on a cantilever beam and a sample surface as a function of the tip–surface separation. This allows the AFM to study both the nanomechanical properties of the sample and the forces associated with the tip–surface interaction. More specifically, the AFM can measure the elastic and plastic behavior and hardness via nanoindentation,van der Waals forces, and the adhesion of thin‐film and bulk materials with unprecedented force and spatial resolution. The force resolution is currently 1 nanonewton, and the depth resolution is 0.02 nm. Additionally, …