Wettability of AFM tip influences the profile of interfacial nanobubbles
Wettability of AFM tip influences the profile of interfacial nanobubbles
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DOI：
10.1063/1.5010131
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发表时间：
2018-02-07
影响因子：
3.2
通讯作者：
Nishiyama, Takashi
中科院分区：
文献类型：
--
作者：
Teshima, Hideaki;Takahashi, Koji;Nishiyama, Takashi
为了准确地表征使用原子力显微镜（AFM）的界面纳米气泡的形状，我们研究了在峰值力轻敲（PFT）模式下操作时AFM针尖的润湿性的影响。AFM针尖分别通过Teflon AF涂层和氧等离子体处理制成疏水和亲水的。结果发现，测得的纳米气泡的基底半径不同的AFM高度图像和粘附图像之间，这种差异取决于尖端的润湿性。在测量过程中获得的力曲线也是不同的，这取决于润湿性，特别是在尖端/纳米气泡相互作用的范围内，并在收缩期的最大吸引力的大小。这种差异表明，疏水尖端穿透纳米气泡的气/液界面，三相接触线固定在尖端表面上;另一方面，亲水尖端不穿透界面。然后，我们定量地估计了钉扎位置，并通过比较高度图像和粘附图像重新计算了纳米气泡的真实轮廓。随着AFM针尖变得更加亲水，穿透深度减小并最终接近零。该结果表明，使用亲水尖端的PFT测量对于获得可靠的纳米气泡轮廓是至关重要的。由AIP出版社出版。
To accurately characterize the shape of interfacial nanobubbles using atomic force microscopy (AFM), we investigated the effect of wettability of the AFM tip while operating in the peak force tapping (PFT) mode. The AFM tips were made hydrophobic and hydrophilic by Teflon AF coating and oxygen plasma treatment, respectively. It was found that the measured base radius of nanobubbles differed between AFM height images and adhesion images, and that this difference depended on the tip wettability. The force curves obtained during the measurements were also different depending on the wettability, especially in the range of the tip/nanobubble interaction and in the magnitude of the maximum attractive force in the retraction period. The difference suggests that hydrophobic tips penetrate the gas/liquid interface of the nanobubbles, with the three phase contact line being pinned on the tip surface; hydrophilic tips on the other hand do not penetrate the interface. We then quantitatively estimated the pinning position and recalculated the true profiles of the nanobubbles by comparing the height images and adhesion images. As the AFM tip was made more hydrophilic, the penetration depth decreased and eventually approached zero. This result suggests that the PFT measurement using a hydrophilic tip is vital for the acquisition of reliable nanobubble profiles. Published by AIP Publishing.