Biomedical Engineering Reference
In-Depth Information
predict, as it depends on many factors, including the way the instrument is set up, and the
scanning parameters [462].
Because of its ability to distinguish many materials, phase imaging has been applied to
an enormous number of samples; just some examples include differentiation of semicon-
ductor films [196], detection of water in cracks in glasses [463, 464], nanoparticle
characterization and counting [217, 465], observation of spherulites in polymer crystal-
lization [466], polymer blend and composite composition [467-469] (see Figure 7.10),
protein adsorption to biomaterials [411, 470], self-assembled monolayers [462, 471, 472],
and many more systems [473]. Due to its dependence on topography, phase imaging is
mostly applied to flat surfaces such as films. However, with care, phase imaging can even
be applied to image differences in composition on the surfaces of small features such as
microspheres [474] or micro-organisms [475].
Phase imaging is particularly useful for imaging dynamic systems, as phase images
collected by high-speed AFM are often of better quality than the corresponding topog-
raphy images [476]. For example, with IC-AFM scanning at high speed often means the z
piezo cannot respond fast enough to allow the probe to fully track the sample surface,
meaning that height images will be of poor quality. Thus while scanning at high speeds,
topography images can show artefacts that are not present in the phase images [477, 478].
Fig. 7.10. Examples of using phase imaging to characterize heterogeneous polymers. Left: phase
imaging is sensitive to crystallinity via viscoelastic properties. In the height image (top left), it's hard
to distinguish the lamellae of the polymer due to macroscopic height differences. The phase image
(below) shows themmuch more clearly. Right: example of phase imaging of a nanocomposite. Phase
images of sliver nanoparticle/SBS nanocomposite films containing: (a) 0.5, (b) 3, (c) 7, and (d) 10 w.t%
Ag nanoparticles. Block copolymers such as this are simply characterized by phase imaging.
Reproduced with permission from [466] and [469].
 
Search WWH ::




Custom Search