Ma Chengfu, Zhou Feng
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Langmuir. 2025 Jun 24;41(24):15203-15220. doi: 10.1021/acs.langmuir.5c01456. Epub 2025 Jun 11.
Techniques capable of evaluating the surface and subsurface mechanical properties on the nanoscale are crucial for the advancement of many fields of nanoscience and nanotechnology, including nanomaterials, micro/nano-electronics, and nanobiology. To this end, several techniques combining atomic force microscopy (AFM) and ultrasonic excitation/detection, as we refer them collectively as ultrasonic AFMs, have been developed and have drawn great attention. By mechanically modulating the contact between the AFM tip and the sample surface at ultrasonic frequencies and then analyzing the responses of the AFM cantilever, ultrasonic AFMs show the capabilities of nondestructively measuring the elastic and viscoelastic properties of surfaces on the nanoscale resolution of a few nanometers. Parameters including the elastic modulus and the loss tangent of a broad range of materials from soft polymers (∼0.1 GPa) to hard coatings (>100 GPa) can be quantitatively characterized. In addition, ultrasonic AFMs also show potentials of nondestructively visualizing subsurface nanostructures that are embedded beneath the sample surfaces. Particle inclusions, void defects, adhesion interfaces, nanofillers, and subcellular structures can be revealed with detection depths up to a few micrometers, depending on the characteristics of the specimen and the imaging settings. In this article, we review the research on ultrasonic AFMs by concentrating on the imaging methods, the physics for surface and subsurface mechanical testing, and their applications.
能够在纳米尺度上评估表面和亚表面力学性能的技术对于纳米科学和纳米技术的许多领域的发展至关重要，这些领域包括纳米材料、微纳电子学和纳米生物学。为此，已经开发出了几种结合原子力显微镜（AFM）和超声激发/检测的技术，我们将它们统称为超声原子力显微镜，并且这些技术已经引起了极大的关注。通过在超声频率下机械调制AFM探针与样品表面之间的接触，然后分析AFM悬臂的响应，超声原子力显微镜显示出能够在几纳米的纳米尺度分辨率下无损测量表面的弹性和粘弹性特性。包括从软聚合物（约0.1 GPa）到硬涂层（>100 GPa）等多种材料的弹性模量和损耗角正切等参数都可以进行定量表征。此外，超声原子力显微镜还显示出无损可视化嵌入样品表面下方的亚表面纳米结构的潜力。根据样品的特性和成像设置，颗粒夹杂物、孔隙缺陷、粘附界面、纳米填料和亚细胞结构都可以在高达几微米的检测深度下被揭示出来。在本文中，我们将集中讨论超声原子力显微镜的成像方法、表面和亚表面力学测试的物理原理及其应用等方面的研究。
