GOALI: Delicate Material Characterization Using Tapping Mode AFM: Soft Impact and Nonlinear Dynamics

在过去的二十年中，原子力显微镜（AFM）已被用于测量各种纳米级样品的形貌，包括半导体表面特征，生物分子，碳纳米结构和有机单层。 尽管取得了巨大的进步，但纳米级生物和其他精细结构的温和表征仍然是一个挑战，因为它们容易受到尖端损坏。 位于学院公园的马里兰州大学与庇护研究机构合作应对这一挑战。 这是通过开发一个非线性动力学为基础的轻敲模式原子力显微镜计划，其中的悬臂梁是激发远离其基本共振和接近倍周期分岔点操作。 为了实现和证明这一方案，多尺度模拟将被用来确定尖端样品的相互作用力和实验进行微妙的材料，包括DNA，软蛋白分子（细菌视紫红质，肌动蛋白肌球蛋白），和鳞状癌细胞。 从基本的角度来看，所提出的研究可以帮助理解与软接触和非光滑机械系统相关的质的变化。 从应用的角度来看，AFM的功能扩展到表征更广泛的软材料可以帮助实现医疗保健，药物设计，病理学，组织工程，生物技术和其他高影响力的新兴技术领域的商业利益，这些技术与人类的福祉密切相关，错误表征可能会产生严重的后果，甚至包括死亡。 模拟方法的进一步发展也将有助于减少与大量实验有关的费用。最后，应用纳米科学的具体问题，以系统的方式将是有益的教育下一代的学生，这是必不可少的，以确保国家？在未来几十年内，中国在纳米技术方面的竞争力。

Over the last two decades, atomic force microscopy (AFM) has been used to measure the topography of a wide range of nanoscale samples, including semiconductor surface features, biomolecules, carbon nanostructures, and organic monolayers. Despite the tremendous progress, gentle characterization of nanoscale biological and other delicate structures remains a challenge since they are susceptible to tip damage. The University of Maryland at College Park has teamed up with Asylum Research to address this challenge. This is addressed by developing a nonlinear dynamics based tapping mode atomic force microscopy scheme, where the cantilever is to be excited away from its fundamental resonance and operated close to a period-doubling bifurcation point. In order to realize and demonstrate this scheme, multi-scale simulations are to be used to determine the tip-sample interaction forces and experiments are to be conducted with delicate materials including DNA, soft protein molecules (bacteriorhodpsin, actin & myosin), and squamous cancer cells. From a fundamental standpoint, the proposed study can help understand qualitative changes associated with mechanical systems with soft contacts and non-smoothness. From an application standpoint, the extension of AFM capabilities to characterize a wider range of soft materials can help realize commercial benefits in the areas of healthcare, drug design, pathology, tissue engineering, biotechnology, and other high-impact emerging technologies that are intimately related to the well-being of human beings and where mischaracterization can have severe consequences, even including death. Further development of simulation methodologies will also help reduce costs associated with extensive experimentation. Finally, the application of nanoscale science to specific problems in a systematic manner will be useful in the education of the next-generation of students, which is essential to ensure the nation?s competitiveness in nanotechnology in the next few decades.