A tool used in nano-biotechnology

1. ATOMIC FORCE
MICROSCOPE
Ghalia Nawal
Roll # 32

2. What is AFM?
 Atomic Force Microscope
(AFM) traces the
topography of samples
with extremely high- up to
atomic- resolution by
recording the interaction
forces between the surface
and a sharp tip mounted
on a cantilever.

3. Invention
First AFM was made by Gerd Binnig and Cristoph
Gerber in 1985.

4. Principle of operation

5. Construction
 Ability of an AFM to achieve near atomic level
resolution depends on following essential
components:
1. Probe
2. Scanner
3. Optical lever (Laser and photo detector)

7. Probe :cantilever with a sharp
tip
 probe is a sharp tip, which is a 3-6
um tall pyramid with 15-40nm end
radius.
 It carefully maintains the force
between the probe and surface at
a set, low level.
 Usually, the probe is formed by a
silicon or silicon nitride cantilever
with a sharp integrated tip, and the
vertical bending (deflection) of the
cantilever due to forces acting on
the tip is detected by a laser
focussed on the back of the
cantilever.

8. Scanner
 The movement of the tip or sample in the the x-y-z
direct on is controlled a piezo-electric tube
scanner.
 Thin cylinders of radially poled piezoelectric
material with four external electrodes and a solid
or quadrant internal electrode. When a voltage is
applied to one of the external electrodes, the
actuator wall expands which causes a vertical
contraction and a large lateral deflection of the
tube tip. A circumferential electrode can be used
for vertical or radial extension and contraction.
 For typical AFM scanner,the maximum ranges are
80mmX 80mm in the x-y plane and 5mm for z
plane.

9. Optical Lever
 The laser is reflected by the cantilever onto a
distant photodetector. The movement of the
laser spot on the photodetector gives a greatly
exaggerated measurement of the movement of
the probe. This set-up is known as an optical
lever.

13. Applications of AFM
 Observance and imaging
characteristic D-banding
of type I collagen.
 Prof. Snedeker's research group
at the ETH Zürich. His research
area is tendon mechanics and
biology.
 The 3D representation of the
AFM topography image nicely
shows the typical periodic D-
banding of type I collagen on all
fibrils.

14. Studying Evolution of Biofilms
In situ AFM imaging of
bacteria on a substrate
immersed in solution
can give access to
online monitoring of
bacterial adhesion,
division and the growth
of the biofilm.
Dynamic mode image of untreated
electrogenic bacteria
Electrochemically deposited on
gold substrate
©Dr. I. Pobelov and M. Füeg, University of Berne

15. Miscellaneous
 Used to analyze DNA, RNA, protein-nucleic acid
complexes, chromosomes, cell membranes,
proteins and peptides, molecular crystals,
polymers, biomaterials, ligand-receptor binding.
 Nanometer resolved images of nucleic acids
 Imaging of cells
 Quantification of molecular interactions in
biological systems
 Quantification of electrical surface charge
 measures physical properties including elasticity,
adhesion, hardness, friction and chemical
functionality
 Can be used as a tool for controlled mechanical
nano stimulation and manipulation.