18 novembre 2010, Luminy, CINAM, Salle Kern, 16h00, thé à 15h45
ALI PASSIAN - Oak Ridge National Laboratory, TN 37831 USA
SUMMARY :
In a series of theoretical and experimental work, we will discuss both
optical and mechanical micro- and nano-structures that are of current
interest in many nanoscale imaging and sensing applications. When the
distance between two material domains is reduced, the two objects interact
via a number of various forces. Such forces depend, among others, upon the
local geometry of the two approaching points. This is the principle behind
the Scanning Probe Microscope (SPM), where one of the objects (the
probe) is a tiny sharp piece of a material that moves very closely to the
second object. Microfabricated cantilever probes have proven to be an
effective tool for investigating nanoscale phenomena. A cantilever is an
integral part of the scanning probe microscopes, where it is used for
measuring van der Waals, and many other forces between the atoms
on the tip and the surface. The response of a microcantilever used in
scanning probe imaging shows rich data indicative of properties of materials
underneath the cantilever tip. For example, the dynamic response in the MHz
regime can be used for obtaining subsurface images of materials. In
addition, microcantilever sensors have been used as a highly sensitive
sensor platform for high-throughput, multiplexed, label-free detection of
chemicals, proteins, and nucleic acids. Molecular adsorption, when
restricted to a single side of a deformable cantilever, results in
measurable displacement. Mass-produced,
microcantilever arrays offer a clear path to the development of miniature
sensors with unprecedented sensitivity for chemical and biological
applications. However, one area that is neglected so far is sample
collection, which we will discuss. We will then continue
by presenting some recent results on the use of mechanical probes in
subsurface imaging. Specific examples include the visualizations of both
buried nanoparticles in fabricated samples and of inhaled nanoparticles in
cells. Finally, when discussing the optical probes, the conditions for
obtaining resonant response from an isolated single probe as well as a
multilayered probe-sample system are presented and the concept of plasmon
coupling, interference, and photon tunneling are discussed.
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