Nanometer
Smooth, Macroscopic Spherical Cellulose Probes for Contact Adhesion
Measurements
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Abstract
Cellulose spheres were prepared by
dissolving cellulose fibers and subsequently solidifying the solution
in a nonsolvent. Three different solution concentrations were tested
and several nonsolvents were evaluated for their effect on the formation
of spheres. Conditions were highlighted to create cellulose spheres
with a diameter of ∼1 mm and a root-mean-square surface roughness
of ∼1 nm. These solid spheres were shown to be easily chemically
modified without changing the mechanical properties significantly.
Contact adhesion measurements were then implemented with these spheres
against a poly(dimethylsiloxane) (PDMS) elastomer in order to quantify
the adhesion. Using Johnson–Kendall–Roberts (JKR) theory,
we quantified the adhesion for unmodified cellulose and hydrophobic
cellulose spheres. We highlight the ability of these spheres to report
more accurate adhesion information, compared to spin-coated thin films.
The application of these new cellulose probes also opens up new possibilities
for direct, accurate measurement of adhesion between cellulose and
other materials instead of using uncertain surface energy determinations
to calculate the theoretical work of adhesion between cellulose and
different solid materials