Sboros V, Glynos E, Pye S D, Moran C M, Butler M, Ross J, Short R, McDicken W N, Koutsos V
Medical Physics, School of Clinical Sciences and Community Health, University of Edinburgh, Edinburgh, UK.
Ultrasound Med Biol. 2006 Apr;32(4):579-85. doi: 10.1016/j.ultrasmedbio.2005.12.016.
Predicting the acoustic response of an encapsulated microbubble to ultrasound requires an accurate assessment of the mechanical properties of the microbubble shell. Atomic force microscopy (AFM) provides an unprecedented spatial and force resolution of the order of Angstroms and subnanonewtons, respectively. It is introduced here as a means to interrogate microbubbles manufactured for ultrasonic imaging. The advantage of AFM over scanning electron microscopy (SEM) is that the microbubbles need not be subjected to a low temperature or low-pressure environment. The microbubbles were interrogated in a liquid environment, which could potentially be a simulated physiological environment. AFM was used in tapping mode imaging to reveal topographical detail of biSphere microbubbles. Because microbubbles are large objects compared with the overall size of usual AFM tips, a convolution between the AFM tip and the microbubble was typical of the acquired topographies. However, a part of the top half of the bubble was imaged with nanometer resolution, and roughness measurements are reported. Force-distance curves were captured using contact mode AFM. The range of stiffness or effective spring constant of biSphere was found to be between 1 and 6 N m(-1). In conclusion, the AFM is proposed here for the first time as a tool to image the surface of bubbles at the nanometer range in liquid and to perform reproducible measurements on the mechanical properties of individual microbubbles.
预测包封微泡对超声的声学响应需要准确评估微泡壳的力学性能。原子力显微镜（AFM）分别提供了前所未有的空间分辨率和力分辨率，空间分辨率可达埃量级，力分辨率可达亚纳牛顿量级。本文介绍将其作为一种检测用于超声成像的微泡的方法。与扫描电子显微镜（SEM）相比，AFM的优势在于微泡无需处于低温或低压环境。微泡在液体环境中接受检测，该液体环境可能是模拟生理环境。AFM用于轻敲模式成像以揭示生物微泡的形貌细节。由于与普通AFM探针的整体尺寸相比，微泡是较大的物体，因此AFM探针与微泡之间的卷积是所采集形貌的典型特征。然而，气泡上半部分的一部分以纳米分辨率成像，并报告了粗糙度测量结果。使用接触模式AFM捕获力-距离曲线。发现生物微泡的刚度范围或有效弹簧常数在1至6 N m⁻¹之间。总之，本文首次提出将AFM作为一种工具，用于在液体中对气泡表面进行纳米级成像，并对单个微泡的力学性能进行可重复测量。
