New Tools for Quantitative Nano-Mechanical Force Microscopy and
High-Speed High-Resolution AFM
Stefan B. Kaemmer
JPK Instruments, 4189 Carpinteria Ave. Suite 1, Carpinteria CA 93103
stefan.kaemmer@jpk.com
9-10AM on Tuesday, June 23 in MEC 301
Atomic Force Microscopy (AFM) is well known as a
multi-purpose tool for imaging a wide range of
different samples with nanometer scale resolution in
air and under controlled environmental conditions in
liquid using forces ranging from several pN to nN.
Optical tweezers extend the observable force range to
the sub-pN regime enabling applications from single
molecule interactions to rheological phenomena (see
fig 1).
Fig 1. Interaction forces ranging from sub pN to
several nN can be quantified and mapped using
Optical Tweezers and Atomic Force Microscopy.
A brief introduction to both techniques with
application examples will be given.
AFM can also be used to obtain mechanical
properties of different kinds of samples.
Nevertheless, the traditional imaging modes
demonstrated well known drawbacks for challenging
samples that have steep edges, as well as those that
are soft, sticky, or loosely attached to the surface.
A new imaging mode: “Quantitative Imaging” (QI)
combines nano-topography with the opportunity of
obtaining mechanical properties simultaneously. The
QI tip movement algorithm prevents lateral forces
and controls the vertical forces for nondestructive
imaging at each pixel
Information such as, topography, adhesion, slope and
even more complex data like contact point images,
Young´s moduli maps, or even recognition events
can be analyzed. Furthermore challenging samples
which are fragile or loosely attached, like fibers,
viruses, and bacteria can be measured by QI. A
comparison between QI, force spectroscopy and
traditional AFM imaging modes is given.
More than half a century after the first highresolution electron microscopy images of collagen
type I banding have been reported, high-speed AFM
enabled us to gain a high-resolution temporal insight
into the dynamics of collagen I fibril formation and
its characteristic 67nm banding hallmark as an
example of studying dynamic processes in fluids. The
literature still abounds with conflicting data regarding
the models of its fibril formation, structural
intermediates, and kinetics. AFM is the only
currently available high-resolution imaging technique
to offer insight into the collagen I fibrillogenesis by
operating in situ. The described technique could be
instrumental for future studies of the structural
dynamics in biology as well as material sciences.