Nanomechanics
Fundamental research and technological applications involve
exceedingly small mechanically moving components. This requires an
improved understanding of mechanical, and tribological properties
appearing at the relevant length scales. In biology, understanding the
mechanical behavior of nanotubulus such as acquaporine and DNA strands
is crucial to comprehend the structural dynamics of cellular processes.
Our goal is to measure quantitatively, the Young and shear moduli of
nanotubes (C, SiC, Si, etc), and biological tubulus by means of a new
powerful method: modulated nanoindenting. With this method, we will also
investigate the mechanical properties of new and interesting nano-objects,
namely oxides nanosprings, nanobelts and nanorings, which can have
future applications in NEMS (nano-electrical-mechanical systems), nano-electronic
devices and nano-sensors.
Modulated nanoindenting is based on the atomic force microscopy (AFM)
which permits to image and manipulate nano-objects and at the same time
to measure normal and lateral forces with pico-Newton resolution.
We are able to acquire a map of the topography (with nanoscopic
resolution) and at the same time a map of the transversal Young modulus
and shear moduli of the nano-object. This gives access to the mechanical
properties of each point of the nano-object, which is particularly
interesting for inhomogeneous samples such as DNA.
Furthermore, during these experiments we can measure the area of contact
along with friction and adhesion forces between the AFM tip and the
object. Friction forces are usually a convolution of contact area and
shear strength t . This prevents to relate the friction behavior to the
structural properties of the materials. Our measurements, giving access
to the area of contact, will permit to determine the nanoscopic value of
t, which characterizes the intrinsic friction properties of a material.
This opens up new possibilities to understand the atomic processes
occurring at the tip-sample interface when they are in contact,
separated or moved with respect to one another. These processes are
central for fundamental and technological problems including
nanoelasticity, adhesion, friction, wear and lubrication.
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