Kiracofe Daniel, Melcher John, Raman Arvind
School of Mechanical Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA.
Rev Sci Instrum. 2012 Jan;83(1):013702. doi: 10.1063/1.3669638.
Dynamic atomic force microscopy (dAFM) continues to grow in popularity among scientists in many different fields, and research on new methods and operating modes continues to expand the resolution, capabilities, and types of samples that can be studied. But many promising increases in capability are accompanied by increases in complexity. Indeed, interpreting modern dAFM data can be challenging, especially on complicated material systems, or in liquid environments where the behavior is often contrary to what is known in air or vacuum environments. Mathematical simulations have proven to be an effective tool in providing physical insight into these non-intuitive systems. In this article we describe recent developments in the VEDA (virtual environment for dynamic AFM) simulator, which is a suite of freely available, open-source simulation tools that are delivered through the cloud computing cyber-infrastructure of nanoHUB (www.nanohub.org). Here we describe three major developments. First, simulations in liquid environments are improved by enhancements in the modeling of cantilever dynamics, excitation methods, and solvation shell forces. Second, VEDA is now able to simulate many new advanced modes of operation (bimodal, phase-modulation, frequency-modulation, etc.). Finally, nineteen different tip-sample models are available to simulate the surface physics of a wide variety different material systems including capillary, specific adhesion, van der Waals, electrostatic, viscoelasticity, and hydration forces. These features are demonstrated through example simulations and validated against experimental data, in order to provide insight into practical problems in dynamic AFM.
动态原子力显微镜（dAFM）在许多不同领域的科学家中越来越受欢迎，对新方法和操作模式的研究不断拓展可研究样品的分辨率、能力及类型。但许多有前景的能力提升伴随着复杂性的增加。实际上，解释现代dAFM数据可能具有挑战性，尤其是在复杂材料系统中，或在液体环境中，其行为往往与在空气或真空环境中已知的情况相反。数学模拟已被证明是一种有效的工具，可用于深入了解这些非直观系统。在本文中，我们描述了VEDA（动态AFM虚拟环境）模拟器的最新进展，它是一套通过nanoHUB（www.nanohub.org）的云计算网络基础设施提供的免费开源模拟工具。在此我们描述三个主要进展。首先，通过改进悬臂动力学建模、激发方法和溶剂化壳层力，提升了在液体环境中的模拟能力。其次，VEDA现在能够模拟许多新的先进操作模式（双峰、相位调制、频率调制等）。最后，有19种不同的针尖 - 样品模型可用于模拟各种不同材料系统的表面物理，包括毛细力、特定粘附力、范德华力、静电力、粘弹性和水化力。通过示例模拟展示了这些特性，并与实验数据进行了验证，以便深入了解动态AFM中的实际问题。
