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- 2016 (2) (entfernen)
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- Englisch (2)
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- AFM (1)
- DySEM (1)
- FIB patterning (1)
- Modal analysis (1)
- Plasmid DNA (1)
- Sample AFM preparation (1)
- Structured cantilever (1)
We use a dynamic scanning electron microscope (DySEM) to map the spatial distribution of the vibration of a cantilever beam. The DySEM measurements are based on variations of the local secondary electron signal within the imaging electron beam diameter during an oscillation period of the cantilever. For this reason, the surface of a cantilever without topography or material variation does not allow any conclusions about the spatial distribution of vibration due to a lack of dynamic contrast. In order to overcome this limitation, artificial structures were added at defined positions on the cantilever surface using focused ion beam lithography patterning. The DySEM signal of such high-contrast structures is strongly improved, hence information about the surface vibration becomes accessible. Simulations of images of the vibrating cantilever have also been performed. The results of the simulation are in good agreement with the experimental images.
Tapping mode AFM (TM-AFM) is a standard technique to image biomolecules and cells avoiding damage to susceptible samples.
For preparing AFM samples we fixed (untreated and radiated) plasmids chemically on ultra-smooth mica silanized with APTES.
The recorded AFM images were examined concerning the contour length, the conformation and the writhing number of the plasmids.
We found that the measured contour length is in accordance with the number of base pairs. Apart from that, we indicate different structures of plasmids from our AFM images, which were assigned to our plasmid data from agarose gel-electrophoresis.