Apply Novel Tapping Mode Atomic Force Microscope with DVD Pickup Head in Fluid
Date Issued
2009
Date
2009
Author(s)
shih-hsun, yen
Abstract
The system proposed here is a tapping mode scanning sample type Atomic Force Microscope (AFM) equipped with a CD/DVD pick-up-head (PUH) used to measure the deflection of the cantilever beam of the probe in the liquid. In order to realize the system mentioned above, we design an adaptive Quality-Factor-controller (Q-controller) to modulate the interaction force between the tip and the sample. And, increasing the quality factor will increase the oscillation amplitude of the probe in liquid and overcome the problem with high damping ratio in the fluid which tends to make the probe hard to oscillate. It is noteworthy that the tip-sample force can be decreased if the scanning is through tapping mode whereby the sample surface will not be easily hurt due to such tip-sample contact. Hence, this type of AFM can also be used to scan soft samples, which may lead to acquire more realistic topography. o implement the above systems, we have designed a novel AFM mechanism and used an adaptive sliding-mode controller which replaces the traditional manually-tuned proportion-integration (PI) controller. By using this controller, any user can still acquire high quality AFM images easily. his AFM will be used to help to observe the continuous interaction between the biology sample and the probe tip. Through adjusting the light path system and applying the controller, we can correctly measure the displacement of the probe in vertical direction in different kinds of fluid. The use of DVD pickup head minimizes the volume of the hardware system, and thus reduces the measurement error caused by heat expansion.or testing the system capability and analyzing the biomorphic change of the sample in liquid, we have conducted a series of experiments, and the results can help us to understand more about the mechanism of the sample in liquid.
Subjects
AFM
adaptive sliding-mode control
DVD pickup head
adaptive Q-control
Type
thesis
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