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Full-Text Articles in Biomedical Engineering and Bioengineering
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Nancy A. Burnham
It has long been recognized that the angular deflection of an atomic force microscope(AFM) cantilever under “normal” loading conditions can be profoundly influenced by the friction between the tip and the surface. It is shown here that a remarkably quantifiable hysteresis occurs in the slope of loading curves whenever the normal flexural stiffness of the AFM cantilever is greater than that of the sample. This situation arises naturally in cantilever-on-cantilever calibration, but also when trying to measure the stiffness of nanomechanical devices or test structures, or when probing any type of surface or structure that is much more compliant along …
Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell
Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell
Nancy A. Burnham
To have confidence in force measurements made with atomic force microscopes(AFMs), the spring constant of the AFM cantilevers should be known with good precision and accuracy, a topic not yet thoroughly treated in the literature. In this study, we compared the stiffnesses of uncoated tipless uniform rectangular silicon cantilevers among thermal, loading, and geometric calibration methods; loading was done against an artifact from the National Institute of Standards and Technology (NIST). The artifact was calibrated at NIST using forces that were traceable to the International System of units. The precision and accuracy of the thermal method were found to be …
Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson
Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson
Nancy A. Burnham
We describe an efficient method for determining the radii of spheres attached to atomic force microscope(AFM) cantilevers by minimizing the square root of the square error for a segment of circular arc cross-sectional data. The approach we present has benefits: (1) The method fits a function, with two fitting parameters, to a number of data points, rather than calculating the radius based on two points of cross-sectional data, (2) a fit is performed in a common spreadsheet application, using a solving feature, and (3) spheres of diameters 2 to 60 μm were measured to an accuracy of 9% and a …
Apparatus For Illuminating The Tip-Sample Interface Of An Atomic Force Microscope, Nancy Burnham, E Thoreson
Apparatus For Illuminating The Tip-Sample Interface Of An Atomic Force Microscope, Nancy Burnham, E Thoreson
Nancy A. Burnham
An apparatus for the delivery of radiation to the tip-sample interface of an atomic force microscope(AFM) is demonstrated. The pulsed light delivery system (PLDS) was fabricated to probe photoinduced conformational changes of molecules using an AFM. The system is 67 mm long, 59 mm wide, and 21 mm high, leaving clearance to mount the PLDS and a microscope slide coated with a thin film of photoactive molecules beneath the cantilever tip of a stand-alone AFM. The PLDS is coupled into a fiber pigtailed Nd:yttrium–aluminum–garnetfrequency doubled laser, operating at a wavelength of 532 nm. The radiation delivered to a sample through …
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.
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, …