1. SCANNING VOL. 30, 3 (2008) 271
Characterization of Sisal Fibers using
Dynamic Atomic Force Spectroscopy (DAFS)
F. L. LEITE
1,2*
, E. C. ZIEMATH
3
, P. S. P. HERRMANN
1
1
Embrapa Instrumentação Agropecuária,
2
Instituto de
Física de São Carlos,
Universidade de São Paulo (USP), Instituto de
Geociências e Ciências Exatas, Universidade
Estadual Paulista (UNESP).
Dynamic atomic force spectroscopy (DAFS) or
“damped oscillation” method consists of a vibrating
microcantilever after pull-off force, with a nanoscale
tip that interacts with a sample surface via short- and
long-range intermolecular forces. When the motion
of an oscillator is reduced by an external force, the
oscillator and its motion are said to be damped. This
work presents results of the characterization of
physicochemical properties of sisal fibers using
DAFS technique. To evaluate to adhesion and surface
energy were used as samples inorganic materials
(mica and quartz) as well as organic materials as sisal
fibers. Delignified, benzylated and in natura sisal
fiber were characterized by atomic force microscopy
(AFM), force spectroscopy (AFS) and DAFS. A very
large variation was observed among the DAFS
measures as can bee seen in the Fig. 1.
Understanding these phenomena can offer deep
insight into physics of DAFS and provide exciting
possibilities for achieving better materials
physicochemical information. The experiments were
carried out at environmental condition using the
silicon cantilever with rectangular shaped and spring
constant of 0.03 N m
-1
. Observe one that the adhesion
force and surface energy changes considerably the
oscillation amplitude, the frequency delay and curve
profile. The method open new possibilities to
evaluate the condition of the cantilever and could
supply information about the environment where the
experiment are made. With this technique can one
obtain viscosity values of gases and liquids, which
the liquid exerts a damping force that is proportional
in magnitude to the withdrawal velocity of the tip.
Figure 1. Damping oscillation profile of sisal fiber (a) in
natura, (b) delignified (60 minutes) and (c) benzilated (30
minutes). Physically, the actuating force perturbs the tip after
pull-off force (instant time t = 0s) – speed=10000 μm/s.
Physicochemical properties of sisal fiber influence drastically
in the dissipation of the damper.
OscillationAmplitude
Sample Displacement (nm)
In natura fiber
Pull-off Force
Envelope
Underdamped
(a)
OscillationAmplitude
Sample Displacement (nm)
Delignified Sisal (60 min.)
(b)
OscillationAmplitude
Sample Displacement (nm)
Benzilated Sisal (30 min.)