Biomedical Engineering Reference
In-Depth Information
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Figure 12.3 Plot of surface free energy and the Mf values of the conventional
polymer surfaces. The reason for the straightforward relationships
between two factors is explained schematically.
As shown in Figure 12.2, two independent factors show similar tendency
(linear co-relationship) on the five different conventional polymer surfaces.
This similarity is possibly due to the difference in the swelled states on the
hydrophilic (high surface free energy) and hydrophobic (low surface free
energy) polymer surfaces. Since the side chain of hydrophilic polymer sur-
faces (e.g., hydroxyl group in pHEMA) might be highly hydrated, a more
swollen molecular layer will be formed at the outermost surface. This might
show a higher level of energy dissipation (larger DD) when the oscillation is
turned off, and this will give a large value of Mf as depicted in Figure 12.3. In
the case of hydrophobic polymer surface (e.g., n-butyl group in pBMA), the
side chain group might be rapidly shrunk when it is immersed in aqueous
medium. The shrunk surface molecules might show a low level of energy
dissipation (lower DD), and this will provide a low value of Mf. This linear
correlation between the Mf value and the traditional surface free energy
provides useful information. That is, the Mf value obtained by means of
QCM-D measurement could be an alternative method to estimate the po-
larity of polymer surfaces. However, this also indicates that the effect of Mf
value on the protein/cell responses on polymer biomaterials could not be
independently discussed from those of surface free energy. Namely, de-
signing a novel concept of polymer surfaces is essential to clearly understand
the relationship between the Mf value and biological responses.
.
12.3 Designing Dynamic Surface for Regulation of
Hydrated Viscoelastic Factor
In order to specifically understand the effect of the Mf value on protein/cell
responses, polymer surfaces with a much broader range of Mf values but a
narrow range of surface free energy must be considered as a model surface.
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