Measuring Surface Forces

2019 ◽  
pp. 234-258
Author(s):  
C. Mathew Mate ◽  
Robert W. Carpick
Keyword(s):  
Capillary Condensation ◽  
Surface Force ◽  
Liquid Films ◽  
Atomic Level ◽  
Surface Forces ◽  
Atomic Force ◽  
Measuring Surface ◽  
Frictional Forces ◽  
Repulsive Forces ◽  
Small Separation

This chapter focuses on the two experimental techniques—the surface force apparatus (SFA) and the atomic force microscope (AFM)—that are commonly used for measuring molecular level forces that act between two surfaces at small separation distances. The first part of this chapter covers the fundamental principles of SFA and AFM design. The second half of this chapter illustrates the application of AFM to measuring surface forces with examples the measurement of van der Waals forces, atomic level repulsive forces, frictional forces, electrostatic double-layer forces, and meniscus forces from liquid films and from capillary condensation.

scholarly journals Nanoscale Measurement of Surface Roughness and the existing Surface Forces of Aluminum by AFM

2011 ◽  
Vol 2 ◽  
pp. 76-79
Author(s):  
Purna B Pun ◽  
Shobha K Lamichhane
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscope ◽  
Thermal Oxidation ◽  
Surface Force ◽  
Surface Forces ◽  
Crystal Defects ◽  
Surface Contamination ◽  
Thermal Agitation ◽  
Atomic Force ◽  
Aluminum Sample

The surface contamination affects Atomic Force Microscope (AFM) performance. Thermal agitation during mapping doping, thermal oxidation, annealing impurities and crystal defects promotes the roughness; various kinds of forces on the surface can be detected by the interaction between tip of cantilever and sample. This interaction not only help us to understand the characteristics and morphology of the sample but also useful to measure the surface force of the aluminum sample too.Key words: Atomic Force Microscope (AFM) performance; Thermal oxidation; Annealing impurities; Crystal defectsThe Himalayan Physics Vol.2, No.2, May, 2011Page: 76-79Uploaded Date: 1 August, 2011

Nanotribological Investigation of the Role of Proteoglycans in Biolubrication

2008 ◽  
Author(s):  
Jasmine Seror ◽  
Nir Kampf ◽  
Alice Maroudas ◽  
Jacob Klein
Keyword(s):  
Polymer Brushes ◽  
Surface Force ◽  
Polymer Chains ◽  
Force Balance ◽  
Superficial Zone ◽  
Prosthetic Devices ◽  
Atomic Force ◽  
Frictional Forces ◽  
Human Joints ◽  
Hydration Layers

Articular joints in human body are uniquely efficient lubrication systems. While the cartilage surfaces slide past each other under physiological working conditions (pressure of tens of atmospheres and shear rates up to 106 – 107 Hz), the friction coefficient (μ) achieves extremely low values (down to 0.001) never successfully reached by mechanical prosthetic devices. Friction studies on polymer brushes attached to surfaces have recently demonstrated (17) their ability to reduce friction between the rubbing surfaces to extremely low values by means of the hydrated ions and the charges on the polymer chains. We propose that the extremely efficient lubrication observed in living joints arises from the presence of a brush-like phase of charged macromolecules at the surface of the cartilage superficial zone: hydration layers which surround the charges on the cartilage macromolecules might provide a lubricating ball-bearing-like effect as demonstrated for the synthetic polyelectrolytes (17). In this work macromolecules of the cartilage superficial zone (aggrecans) are extracted from human femoral heads and purified using well developed biochemical techniques (20). The extracted molecules are then characterized with atomic force microscope (AFM). By means of a surface force balance (SFB) normal and shear interactions between mica surfaces coated with these molecules are examined focusing on the frictional forces between such surfaces at normal stresses similar to those in human joints.

Atomic force microscopy and direct surface force measurements (IUPAC Technical Report)

2005 ◽  
Vol 77 (12) ◽  
pp. 2149-2170 ◽  
Author(s):  
John Ralston ◽  
Ian Larson ◽  
Mark W. Rutland ◽  
Adam A. Feiler ◽  
Mieke Kleijn
Keyword(s):  
Surface Force ◽  
Distinct Advantage ◽  
Adhesion Forces ◽  
Force Microscopy ◽  
Atomic Force ◽  
Technical Report ◽  
Relative Separation ◽  
Frictional Forces ◽  
Probe Microscope ◽  
Friction Measurements

The atomic force microscope (AFM) is designed to provide high-resolution (in the ideal case, atomic) topographical analysis, applicable to both conducting and nonconducting surfaces. The basic imaging principle is very simple: a sample attached to a piezoelectric positioner is rastered beneath a sharp tip attached to a sensitive cantilever spring. Undulations in the surface lead to deflection of the spring, which is monitored optically. Usually, a feedback loop is employed, which holds the spring deflection constant, and the corresponding movement of the piezoelectric positioner thus generates the image. From this it can be seen that the scanning AFM has all the attributes necessary for the determination of surface and adhesion forces; a sensitive spring to determine the force, a piezoelectric crystal to alter the separation of the tip and surface, which if sufficiently well-calibrated also allows the relative separation of the tip and surface to be calculated. One can routinely quantify both the net surface force (and its separation dependence) as the probe approaches the sample, and any adhesion (pull-off) force on retraction. Interactions in relevant or practical systems may be studied, and, in such cases, a distinct advantage of the AFM technique is that a particle of interest can be attached to the end of the cantilever and the interaction with a sample of choice can be studied, a method often referred to as colloid probe microscopy. The AFM, or, more correctly, the scanning probe microscope, can thus be used to measure surface and frictional forces, the two foci of this article. There have been a wealth of force and friction measurements performed between an AFM tip and a surface, and many of the calibration and analysis issues are identical to those necessary for colloid probe work. We emphasize that this article confines itself primarily to elements of colloid probe measurement using the AFM.

scholarly journals Surface Forces between Nanomagnetite and Silica in Aqueous Ca2+ Solutions Studied with AFM Colloidal Probe Method

2020 ◽  
Vol 4 (3) ◽  
pp. 41
Author(s):  
Illia Dobryden ◽  
Elizaveta Mensi ◽  
Allan Holmgren ◽  
Nils Almqvist
Keyword(s):  
Iron Ore ◽  
Adhesion Force ◽  
Surface Forces ◽  
Adhesion Forces ◽  
Interaction Forces ◽  
Colloidal Probe ◽  
Force Microscopy ◽  
Atomic Force ◽  
Repulsive Forces ◽  
Qualitative Changes

Dispersion and aggregation of nanomagnetite (Fe3O4) and silica (SiO2) particles are of high importance in various applications, such as biomedicine, nanoelectronics, drug delivery, flotation, and pelletization of iron ore. In directly probing nanomagnetite–silica interaction, atomic force microscopy (AFM) using the colloidal probe technique has proven to be a suitable tool. In this work, the interaction between nanomagnetite and silica particles was measured with AFM in aqueous Ca2+ solution at different pH levels. This study showed that the qualitative changes of the interaction forces with pH and Ca2+ concentrations were consistent with the results from zeta-potential measurements. The repulsion between nanomagnetite and silica was observed at alkaline pH and 1 mM Ca2+ concentration, but no repulsive forces were observed at 3 mM Ca2+ concentration. The interaction forces on approach were due to van der Waals and electrical double-layer forces. The good fitting of experimental data to the DLVO model and simulations supported this conclusion. However, contributions from non-DLVO forces should also be considered. It was shown that an increase of Ca2+ concentration from 1 to 3.3 mM led to a less pronounced decrease of adhesion force with increasing pH. A comparison of measured and calculated adhesion forces with a few contact mechanics models demonstrated an important impact of nanomagnetite layer nanoroughness.

Nanoscale Surface Force Measurement

2005 ◽  
Author(s):  
Seung Ho Yang ◽  
Stephen M. Hsu
Keyword(s):  
Surface Roughness ◽  
Force Measurement ◽  
Laser Interferometry ◽  
Surface Force ◽  
Surface Forces ◽  
Control Force ◽  
Force Sensitivity ◽  
Measuring Surface ◽  
Colloidal Probes ◽  
Roughness Control

At nanoscale, surface forces often dominate or exert significant influence on contact interfaces. Adhesion and stiction in micro- and nanodevices are important technological challenges in nanotechnology and they are closely linked to our ability to control the surface forces. Yet our understanding of surface forces in nanoscale contacts is lacking, especially the interplay between surface roughness, material properties, contact geometry and the environment. Traditional means of measuring surface forces use a macrocontact with atomically flat mica surfaces and the forces measured by laser interferometry. Semiconductor and insulator materials cannot be measured by this technique. We have developed a preliminary AFM-based technique using colloidal probes capable of directly measure the surface forces at nanoscale. The difficulties are surface roughness control, force sensitivity of the cantilevers, the control of snapon, and the size of the probe tip. We have demonstrated that all these issues can be controlled to a large extent and reasonable surface forces can be measured between a probe tip and a flat surface down to a nanometer distance to the surface.

Simulations of Nanometer-Thick Lubricating Films

MRS Bulletin ◽  
1993 ◽  
Vol 18 (5) ◽  
pp. 45-49 ◽  
Author(s):  
Mark O. Robbins ◽  
Peter A. Thompson ◽  
Gary S. Grest
Keyword(s):  
Dynamic Properties ◽  
Surface Force ◽  
Confined Geometries ◽  
Fluid Films ◽  
Lubricated Contacts ◽  
Atomic Force ◽  
Crystal Oscillators ◽  
Frictional Forces ◽  
Mixed Lubrication Regime ◽  
Continuum Theories

Hydrodynamics and elastohydrodynamics have been successful in describing lubrication by micron-thick films. However, these continuum theories begin to break down as film thicknesses become comparable to molecular dimensions. An increasing number of applications require an understanding of lubricants in such severely confined geometries. Examples include lubrication of nanoscale bearings in micromachinery or high-density magnetic disk drives, as well as asperity interactions in macroscopic bearings that operate in the mixed lubrication regime.Development of new experimental and theoretical techniques for studying thin lubricant films has paralleled the growing interest in their properties. The surface force apparatus (SFA) allows normal and shear forces to be measured between atomically flat solid surfaces while their separation is determined to within 0.1 nm using interferometry or capacitance. The contact area in the SFA is typically 100 μm across, much larger than the separation between solid walls. The atomic force microscope (AFM) can be used to explore friction in lubricated contacts whose diameter is comparable to the separation (5 nm). This allows spatial resolution of the frictional force on a molecular scale. Quartz-crystal oscillators have been used to determine the frictional forces between a surface and an adsorbed film of one or more monolayers. Theoretical advances have been aided by the advent of supercomputers that allow thin films to be simulated at the molecular level using molecular dynamics. These new experimental and theoretical techniques reveal a sequence of dramatic changes in the static and dynamic properties of fluid films as their thickness approaches molecular scales.

Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy

1996 ◽  
Vol 54 ◽  
pp. 866-867
Author(s):  
H. Kinney ◽  
M.L. Occelli ◽  
S.A.C. Gould
Keyword(s):  
Surface Roughness ◽  
Zeolite Y ◽  
Atomic Level ◽  
Microporous Structure ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Roughness Measurements ◽  
Cracking Catalysts

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.

Case Studies in Atomic Force Probe Analysis

2006 ◽  
Author(s):  
Randal Mulder ◽  
Sam Subramanian ◽  
Tony Chrastecky
Keyword(s):  
Failure Analysis ◽  
Case Studies ◽  
Light Emission ◽  
Electrical Characterization ◽  
Logic Circuits ◽  
Contrast Imaging ◽  
Atomic Force ◽  
Measuring Surface ◽  
Analysis Environment

Abstract The use of atomic force probe (AFP) analysis in the analysis of semiconductor devices is expanding from its initial purpose of solely characterizing CMOS transistors at the contact level with a parametric analyzer. Other uses found for the AFP include the full electrical characterization of failing SRAM bit cells, current contrast imaging of SOI transistors, measuring surface roughness, the probing of metallization layers to measure leakages, and use with other tools, such as light emission, to quickly localize and identify defects in logic circuits. This paper presents several case studies in regards to these activities and their results. These case studies demonstrate the versatility of the AFP. The needs and demands of the failure analysis environment have quickly expanded its use. These expanded capabilities make the AFP more valuable for the failure analysis community.

Sign in / Sign up

Export Citation Format

Share Document