Difference between revisions of "Surface Forces Apparatus"

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== Definition ==
 
== Definition ==
The '''surface forces apparatus''' (SFA) is an instrument developed by ... for measuring the forces between surfaces at small distances. The challenges of such a measurement are accurately determining the distance between the surfaces and the forces applied to them. The SFA uses interferometry to obtain the distance between the surfaces and a spring to calculate the force applied.
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The '''surface forces apparatus''' (SFA) is an instrument developed by Israelachvili and Adams for measuring the forces between surfaces at small distances (between microns apart and contact) [1]. The challenges of such a measurement are accurately determining the distance between the surfaces and the forces applied to them. The SFA uses interferometry to obtain the distance between the surfaces and a spring to calculate the force applied.[2]
  
One of the ingenious things about the SFA is the geometry of surfaces used. The classic SFA surface geometry is two cylinders brought together perpendicularly. The forces between such objects are equivalent to the forces between two spheres. The cylinders are much easier to align than two spheres would be.
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One of the ingenious things about the SFA is the geometry of surfaces used. The classic SFA surface geometry is two cylinders brought together perpendicularly (forming an x-shape). The forces between two crossed cylinders are locally equivalent to the forces between two spheres [1]. Two cylinders should be easier to align than two spheres.
  
A drawback to the SFA is its reliance on molecularly smooth and semi-transparent materials. Many studies are performed on mica.
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A drawback to the SFA is its reliance on molecularly smooth and semi-transparent materials. Many studies are performed on mica [2].
  
 
== Examples ==
 
== Examples ==

Revision as of 15:28, 23 November 2009

Under construction

Definition

The surface forces apparatus (SFA) is an instrument developed by Israelachvili and Adams for measuring the forces between surfaces at small distances (between microns apart and contact) [1]. The challenges of such a measurement are accurately determining the distance between the surfaces and the forces applied to them. The SFA uses interferometry to obtain the distance between the surfaces and a spring to calculate the force applied.[2]

One of the ingenious things about the SFA is the geometry of surfaces used. The classic SFA surface geometry is two cylinders brought together perpendicularly (forming an x-shape). The forces between two crossed cylinders are locally equivalent to the forces between two spheres [1]. Two cylinders should be easier to align than two spheres.

A drawback to the SFA is its reliance on molecularly smooth and semi-transparent materials. Many studies are performed on mica [2].

Examples

As of November, 2009, many labs around the world were actively using SFA for research. Here are a few:

Swiss Federal Institute of Technology

University of Mexico

University of Illinois at Urbana-Champaign

KTH Royal Institute of Technology (Sweden)

References

-Review Article -Websites -Witten?