Biomedical Engineering Reference
In-Depth Information
atom. Samples can be analysed in air or liquids however; a vacuum is typi-
cally used to prevent sample contamination. h is technique is not limited
to information gathering, the STM can also be used to manipulate atoms
at the nanolevel [75]. h is technique has been used for the observation of
DNA deposited on graphene, but not yet on chitosan derived materials [82].
Figure 5.5 shows examples of images obtained using SEM, TEM and AFM.
Magnetic Resonance Force Microscopy (MRFM) is a technique which
uses the three dimensional imaging abilities of magnetic resonance imag-
ing (MRI) together with AFM. h is leads to a technique which is non-
destructive and chemical-specii c which can produce high resolution
images of many dif erent materials potentially at the atomic scale [85].
Low-voltage electron microscopes (LVEM) have also been used to
image samples at the nanoscale. h ese microscopes can operate in TEM,
STEM, SEM and electron dif raction modes. h is instrument produces
images with better spatial resolution by reducing the beam/sample interac-
tion volume and the lower voltage allows for a longer collecting time espe-
cially in cases where samples are beam sensitive. h is instrument is also
Figure 5.5
Representative images generated using SEM (A), TEM (B) and AFM (C &
D). h e SEM and TEM images show Ag nanoparticles which have been stabilized using
chitosan [83]. h e AFM images show chitosan/ halloysite nanotube nanocomposites
produced by Liu
et al.
where image (C) and (D) show the height and three dimensional
topography of the sample [84].
