Biomedical Engineering Reference
In-Depth Information
20.0 nm
10.0 nm
0.0 nm
1.00
1.00
0.75
0.75
0.50
0.50
0.25
0.25
0
0
0.25
0.25
0.50
0
0.50
0
0.75
0.75
1.00
µ
m
1.0
µ
m
(A)
(B)
FIGURE 18.2
Tapping AFM scans of 1 1
μ
m area at 1 Hz of the (A) no heat-treated surface with an Ra of 1.9 nm and
(B) the heat-treated surface with an Ra of 2.8 nm
[15]
.
Mechanical, chemical, or electrochemical surface modification techniques are commonly used to pro-
vide surface textures that are deemed to be more biocompatible or osteoconductive. Surface chem-
istry modification, most commonly as organic treatments, can also be used such as immobilizing
peptides or proteins onto an implant surface. These surfaces can be tailored as biomimetic surfaces
that control or aim to trigger cascading events that would occur when cells reach the surface. In the
work of Wang et al.
[15]
a modified AFM setup (cyto-detacher) was used to measure cell adhesion
forces. Another AFM was used in this work to image the surface topology before and after cell incu-
bation in a bioactivity assay. Surgical grade Ti6Al4V alloy was used without any surface treatment
and with modification by oxidizing at 400°C in an atmosphere furnace for 45 min. Roughness (Ra)
values of 1.9
0.1 nm and 2.8
0.1 nm were measured, respectively, for these surfaces. Lateral and
vertical resolutions of 2 and 0.01 nm were reported for this AFM work.
Figure 18.2
shows the AFM-
recorded surface profiles for the nonheat-treated surface and the surface after heat treatment. In this
work, an SPM IIIa Dimension™ 3000 (Digital Instruments Inc., New York, USA) instrument was
used with scanning conducted using etched silicone tips (NSC15, MikroMasch Co., Spain) with the
spring constant range capability of 20-100 N/m.
18.1.3
Confocal Microscopy and Interferometry
18.1.3.1 Confocal Microscopy
In confocal microscopy two focusing arrangements are used to focus on the point in a sample to be
imaged
[16,17]
. One focuses laser light through an objective lens to the point of interest, and the
other focuses the reflected light to the imaging sensor. Light from the point to be imaged is passed
through a pinhole such that all extraneous out-of-focus light is removed. This allows lateral reso-
lutions approximately 1.4 times greater than in conventional microscopes to be achieved with con-
focal microscopy. The depth of the focal plane depends on the specimen's optical properties and
importantly on the squared value of the objective lens' numerical aperture. Three-dimensional
