tailieunhanh - Atomic Force Microscopy in Cell Biology Episode 2 Part 4

Tham khảo tài liệu 'atomic force microscopy in cell biology episode 2 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 246 Sheng and Shao chamber which is suspended through thin-wall stainless-steel tubings to the top flange. The remotely operated control shafts used to align the laser and the photo-diode detector to the cantilever as well as tip engagement are in these tubings. In the chamber the AFM is further suspended by several steel springs tuned to 1 Hz with magnetic damping to isolate the AFM from mechanical vibrations of the environment. To minimize any electronic noise coupling to the signal and to improve the laser stability the laser driver based on field-effect transistors and the preamplifier are built right into the optical head. For simplicity in design the laser diode is also mounted on the AFM head. Such simple designs apparently provide a stable platform sufficient for high-resolution imaging. It should be mentioned that the scanning range is reduced to about one-third of the range at room temperature for the same size piezo-tube due to its reduced sensitivity Mou et al. 1993 . Furthermore the time response in the laser driver circuit should be optimized because the electrostatic build up in the dewar can often lead to the failure of laser diodes. For the optical assembly glass or quartz lenses should be used to minimize any misalignment due to differential shrinkage. We do not find it necessary to use Invar as the primary material for the AFM frame and both brass and aluminum have yielded acceptable performance based on the quality of the images. This has reduced the cost considerably. The cantilever is preloaded by a spring clip to the tip holder which is mounted magnetically on the base plate of the AFM. For tapping mode operations a small piezo-element is embedded below the magnet which is driven directly by a NanoScope IIIa controller. The electrical leads to the piezo-element are separated from other signal leads to minimize cross-talk between weak signals and high-voltage signals. The optical head can be lifted manually from the scanner base to allow .