Ultra Small Surface Force Measurements in Vacuum

在纳米尺度上对粘合剂相互作用的深刻理解对于各种应用都很重要，例如在微和纳米组装过程中处理颗粒和构建块，用于工业清洁过程和医疗药物输送。基于原子力显微镜的力谱与胶体探针技术和其他力测量工具在理解基本粘合剂相互作用方面取得了巨大进展，并验证了该领域的理论考虑。然而，环境大气中的力谱总是只产生范德华效应、静电效应和毛细效应的叠加。此外，颗粒直径小于1微米的胶体探针研究很少，因为没有复杂的湿化学过程和几何形状和材料选择的限制，制造这种小探针的能力有限。在含水介质中进行测量可以减少毛细力，但同时也可以引入新的力贡献并改变化学环境。此外，在环境或水介质中获得的数据并不完全适用于扫描电子显微镜内部的处理过程，扫描电子显微镜已成为纳米操作和纳米组装的首选环境，因为它们不考虑电子束和真空环境的影响。该项目有两个主要目标：在没有毛细管力和水介质影响的情况下直接研究范德华和静电相互作用，以及在扫描电子显微镜下探索电子束诱导效应对粘附和粘附的影响。此外，将在通常由毛细相互作用和跳跃到接触效应叠加的力范围内验证常见的粘附理论和近似。为了实现这一目标，将结合高分辨率扫描电子显微镜/聚焦离子束仪器，建立一个超越当前力分辨率限制的专用力谱装置。通过这种方式，在扫描电子显微镜的真空室中系统地研究粘附力，使用定制的衬底和胶体探针，在尺寸、几何形状和材料方面具有迄今为止无法实现的多样性，这将是可行的，从而允许更深入地了解毛细力和粘附相互作用，并为新的微纳米处理策略铺平道路。

Profound understanding of adhesive interactions on the nanoscale is important for a variety of applications as for example for handling of particles and building blocks during micro- and nanoassembly, for industrial cleaning processes and for medical drug delivery.Atomic force microscope based force spectroscopy with the colloidal probe technique and other force measurement tools have led to great advances in the understanding of fundamental adhesive interactions and verified theoretical considerations in this field. However, force spectroscopy in ambient atmosphere always yields only a superposition of van der Waals, electrostatic and capillary effects. Moreover, colloidal probe studies with particles below 1 micrometer in diameter are rare due to the limited ability to fabricate such small probes without a complicated wet-chemical process and restrictions regarding geometry and material selection. Measurements in an aqueous medium reduce the capillary forces, but at the same time they can introduce new force contributions and alter the chemical environment. Furthermore, data gained in ambient or an aqueous medium is not fully applicable to handling processes inside the scanning electron microscope, which has become a preferred environment for nanomanipulation and nanoassembly, as they do not take into account the influence of the electron beam and the vacuum environment.This project aims at two main objectives: directly investigating the van der Waals and electrostatic interactions without the influence of capillary forces and the need for an aqueous medium, and exploring the influence of electron beam induced effects on adhesion and stiction inside a scanning electron microscope. Furthermore, the common adhesion theories and approximations will be validated in the force range that is normally superimposed by capillary interaction and jump to contact effects. To achieve this goals a dedicated force spectroscopy setup surpassing the current force resolution limits will be combined with a high resolution scanning electron microscope/focused ion beam instrument. In this way, systematic adhesion force studies inside the vacuum chamber of the scanning electron microscope employing tailored substrates and colloidal probes with hitherto unachievable variety regarding size, geometry, and material will be feasible, thus allowing for deeper understanding of capillary forces and adhesive interactions in general, and making way for new micro- and nanohandling strategies.