Biomedical Engineering Reference
In-Depth Information
Drawing
The process of drawing can be used to fabricate nanofibers through dipping a micropipette
with a diameter of a few micrometers into the droplet near the contact line. The micropi-
pette is then withdrawn from the liquid and moved at a speed of approximately 1 × 10
−4
m s
−1
,
pulling out the nanofibers, which are then solidified by rapid evaporation of the solvent due
to the high surface area of the obtained fiber [9, 10]. The pulled fibers are deposited on a
surface by touching with the end of the micropipette, and drawing of nanofibers is repeated
several times for every droplet (Figure 8.2A). Drawing a fiber requires a material with a pro-
nounced visco-elastic behavior to undergo strong deformation, while being cohesive enough
to support the stresses developed during the pulling [11]. The solvent evaporates from the
deposited droplet and the viscosity of the droplet continuously increases with time, which is
a major disadvantage of this process. Due to this problem, there is also limited time within
which the fibers can be pulled out [10, 12].
Template Synthesis
Template synthesis entails synthesizing the desired material within the pores of a nanopo-
rous membrane, template, or mold. The membranes employed have cylindrical pores of
uniform diameter [13-15] and are used to make tubules and fibrils [16]. Because of the
monodispersed diameter of membrane pores, analogous monodispersed nanostructures can
(A)
(B)
(C)
Water
1
Polymer
Nano porous membrane
Solvent
Polymer
2
Solidification solution
Solution
(D)
Bioactive head
Gelation
Hydrophilic segment
3
hydrophobic tail
Porous
nanofibrous
structure
Figure 8.2
Nanofiber fabrication techniques: (A) drawing, (B) template synthesis, (C) phase separation,
and (D) self-assembly. With permission from Elsevier [3].
