Biomedical Engineering Reference
In-Depth Information
that contains a ballistic fabric impregnated with
shear thickening fluid has been invented
[22]
.
other natural actuator that has been studied is
that of the octopus
[25]
. In these instances, it
was the structure of these types of appendages,
as known to biologists, that led the engineering
researchers to design an arm that would be as
mobile.
10.3.3.2 Biomedical Materials
As discussed by Sinclair
[23]
, the alignment
of cells in the direction of the grooves on an
etched surface, i.e., contact guidance, gov-
erns the growth behavior of many cell types,
including epithelial cells, oligodendrocytes,
astrocytes, and fibroblasts. Capillary-Chan-
neled Polymer™ (C-CP™) fibers are fabri-
cated with micrometer-scale surface channels
aligned parallel to the fiber axis by melt-extru-
sion through Clemson University proprietary
spinnerets at Specialty Custom Fibers (
www.
specialtycustomibers.com
)
. The microscale
surface topography and comparable groove
dimensions of the C-CP fibers provide the sur-
face topography necessary to align cells along
the axis of each fiber. The specific target for this
work was the anterior cruciate ligament (ACL),
which is composed primarily of fibroblasts
and extracellular matrix (ECM) organized in
parallel structural alignment consistent with
their biomechanical function in resisting ten-
sile loading. Sinclair
et al.
concluded that the
deep channels of the C-CP fibers appeared to
be potential candidates to serve as scaffolding
for a tissue engineering approach to ligament
regeneration.
SELF-CLEANING MATERIALS
Researchers at Clemson University developed a
super-hydrophobic fabric based on the “lotus”
effect. To create the lotus effect on a fabric sur-
face, they employed the deposition of both
polystyrene (PS) and the triblock copolymer
polystyrene-
β
-(ethylene-co-butylene)-
β
-styrene
(SEBS) simultaneously on a model substrate.
The selective dissolution of PS by ethyl acetate
(EA), which acts as a solvent for PS and as a non-
solvent for SEBS, created a porous hydrophobic
rough surface on the substrate. This method of
surface modification was applied to a polyester
fabric and resulted in a practically nonwettable
textile material
[26, 27]
.
RESPONSIVE MATERIALS
Observation of the spontaneous unfolding of
tree leaves led Kornev of Clemson University
to develop deployable wet-responsive fibrous
materials
[28]
. This is an application of super-
absorbency in which the physicochemical
energy of wetting is converted into mechani-
cal energy to effect fabric bending. Electrospun
nanofibers of alginate, a natural biopolymer
extracted from seaweed and that a gels upon
cross-linking with calcium chloride, were incor-
porated between fabric layers. When wetted,
the alginate layer swells to orders of magnitude.
One result of this work is a scroll that unrolls
itself upon wetting.
Natural mechanical deformation sensors use
filiform hairs (cilia) as the transducer. One
common example is the inner ear of humans.
The cilia are responsible for acoustic perception
as well as for balance. Other examples include
the detection of flow or inertial forces in other
vertebrates and insects. Optimized through
10.3.3.3 Technical Materials
ACTUATORS
The pneumatic muscle, which incorporates a
braid and a bladder, as mentioned in Section
10.1
, is one type of actuator. However, actua-
tors modeled after squid tentacles provide us
with an excellent example of biomimicry
[24]
.
Whereas the braid/bladder muscle is an exam-
ple of mimicking rudimentary muscle action
using the textile structure of a braid, those work-
ers report using the more complex structure of
the squid tentacle as a versatile mobile arm. The
