3 research outputs found
Nanometer Smooth, Macroscopic Spherical Cellulose Probes for Contact Adhesion Measurements
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 polyÂ(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
Enhancing Adhesion of Elastomeric Composites through Facile Patterning of Surface Discontinuities
Patterning interfaces can provide
enhanced adhesion over a projected area. However, careful consideration
of the material properties and geometry must be applied to provide
successful reversible adhesives. We present a simple method to use
patterned, elastomeric fabric composites to enhance the shear adhesion
strength by nearly 40% compared to a non-patterned sample. We describe
how this enhancement depends on the pattern geometry, the velocity
dependence of the adhesive materials, and the controlled displacement
rate applied to the interface. Through these observations, we discuss
strategies for improving reversible adhesives
Robust and Tailored Wet Adhesion in Biopolymer Thin Films
Model layer-by-layer (LbL) assemblies
of polyÂ(allylamine hydrochloride)
(PAH) and hyaluronic acid (HA) were fabricated in order to study their
wet adhesive behavior. The film characteristics were investigated
to understand the inherent structures during the assembly process.
Subsequently, the adhesion of these systems was evaluated to understand
the correlation between the structure of the film and the energy required
to separate these LbL assemblies. We describe how the conditions of
the LbL fabrication can be utilized to control the adhesion between
films. The characteristics of the film formation are examined in the
absence and presence of salt during the film formation. The dependence
on contact time and LbL film thickness on the critical pull-off force
and work of adhesion are discussed. Specifically, by introducing sodium
chloride (NaCl) in the assembly process, the pull-off forces can be
increased by a factor of 10 and the work of adhesion by 2 orders of
magnitude. Adjusting both the contact time and the film thickness
enables control of the adhesive properties within these limits. Based
on these results, we discuss how the fabrication procedure can create
tailored adhesive interfaces with properties surpassing analogous
systems found in nature