Department of Civil and Environmental Engineering, National University of Kaohsiung, No. 700, Kaohsiung University Road, Nanzih District, 81148, Kaohsiung, Taiwan.
Sensors (Basel). 2012;12(5):6666-84. doi: 10.3390/s120506666. Epub 2012 May 22.
The dynamic behaviors of an Atomic Force Microscope are of interest, and variously unpredictable phenomena are experimentally measured. In practical measurements, researchers have proposed many methods for avoiding these uncertainties. However, causes of these phenomena are still hard to demonstrate in simulation. To demonstrate these phenomena, this paper claims the tip-jump motion is a predictable process, and the jumping kinetic energy results in different nonlinear phenomena. It emphasizes the variation in the eigenvalues of an AFM with tip-sample distance. This requirement ensures the phase transformations from one associated with the oscillation mode to one associated with the tip-jump/sample-contact mode. Also, multi-modal analysis was utilized to ensure the modal transformation in varying tip-sample distances. In the presented model, oscillations with various tip-sample distances and with various excitation frequencies and amplitudes were compared. The results reveal that the tip-jump motion separates the oscillation orbit into two regions, and the jumping kinetic energy, comparing with the superficial potential energy, leads the oscillation to be bistable or intermittent. The sample-contact condition associates to bifurcation and chaos. Additionally, the jumping is a strong motion that occurs before the tip-sample contacts, and this motion signal can replace the sample-contact-signal to avoid destroying the sample.
原子力显微镜的动态行为很有趣，各种不可预测的现象都在实验中进行了测量。在实际测量中，研究人员已经提出了许多方法来避免这些不确定性。然而，这些现象的原因在模拟中仍然难以证明。为了证明这些现象，本文声称尖端跳跃运动是一个可预测的过程，跳跃动能导致不同的非线性现象。它强调了针尖-样品距离对原子力显微镜特征值的变化。这一要求确保了从与振动模式相关的相位转变为与尖端跳跃/样品接触模式相关的相位转变。此外，还利用多模态分析来确保在不同的针尖-样品距离下的模态转换。在所提出的模型中，比较了具有不同针尖-样品距离、不同激励频率和振幅的振动。结果表明，尖端跳跃运动将振动轨道分为两个区域，跳跃动能与表面势能相比，使振动处于双稳态或间歇性。样品接触条件与分岔和混沌有关。此外，跳跃是在针尖-样品接触之前发生的强烈运动，这种运动信号可以代替样品接触信号，避免破坏样品。
