Biomedical Engineering Reference
In-Depth Information
(a)
(b)
-NH 2 -NH 2
NH +
NH +
R -
R -
-NH 2
NH +
R
R -
R
NH +
-NH 2
NH +
NH +
R
-NH 2
R -
R
-NH 2
Figure 5.21
Bending motion of amphoteric chitosan/polyanion hydrogels in different electrolyte pH solutions. (a) Acidic
medium and (b) basic medium.
increasing ionic strength, which is because a shielding effect of the polyions, by the other
ions in the electrolytic solute, would occur, leading to a reduction in the electrostatic repul-
sion of the polyions. For example, Kim et al. [77] found that the equilibrium bending angle
of the chitosan/poly(hydroxyethyl methacrylate) semi-IPN hydrogel showed an apparent
peak with a 1.0 wt% aqueous NaCl solution; (3) the electric voltage: the effect of electric
voltage was quite simple; that is, the higher the electric voltage applied, the higher the
bending rate and the greater the equilibrium bending angle the hydrogel shows. And it
exhibits a reversible bending behavior in proportion to the applied electric field. For exam-
ple, the chitosan/hyaluronic acid PEC hydrogels showed a reversible bending behavior
during voltage cyclic loading ( cf. Figure 5.22 ) [78].
Chitosan-based electric-sensitive hydrogels could be used in drug delivery systems.
Control of the “on-off” of drug release is achieved by varying the intensity of electric stim-
ulation. And reversible behaviors endow it with potential applications in artificial muscles.
However, at present, this application-based electric-sensitive chitosan-based hydrogels are
still in their infancy because these hydrogels require a controllable voltage source [79].
100
80
60
40
20
0
On
D.C.
electric
field
Off
0
2
4
6
8
10
12
Time (t/s)
Figure 5.22
Reversible bending behavior of the chitosan/hyaluronic acid PEC hydrogels in a 0.8 wt% aqueous NaCl solu-
tion with changes in the applied voltage.
Search WWH ::




Custom Search