The Contact Adhesion Testing Device is based on the contact mechanics
principles of Johnson, Kendall, and Roberts (often referred to as JKR
testing).  This instrument was fabricated by the Crosby group for the
purpose of characterizing the interfacial properties of materials,
specifically the stiffness and adhesion of elastomers and gels. It is
comprised of a nanopositioner, load cell, and a rigid indenter mounted
axially over an inverted microscope.  The nanopositioner controls the
vertical displacement of the probe while the load cell records the
compressive and tensile forces applied to the probe. The contact or
interfacial area between the material being tested and the indenter is
imaged from below and recorded by a CCD camera.  The test is completely
automated and run by a custom LabView program.  By combining displacement,
force, and contact geometry information, Hertz and JKR Contact theories
can be used to measure and calculate interfacial properties.