H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, UK.
Nanotechnology. 2012 Mar 2;23(8):085703. doi: 10.1088/0957-4484/23/8/085703. Epub 2012 Feb 1.
Shear force microscopy is not normally associated with the imaging of biomolecules in a liquid environment. Here we show that the recently developed scattered evanescent wave (SEW) detection system, combined with custom-designed vertically oriented cantilevers (VOCs), can reliably produce true non-contact images in liquid of DNA molecules. The range of cantilever spring constants for successful shear force imaging was experimentally identified between 0.05 and 0.09 N m(-1). Images of λ-DNA adsorbed on mica in distilled water were obtained at scan rates of 8000 pixels s(-1). A new constant-height force mapping mode for VOCs is also presented. This method is shown to control the vertical position of the tip in the sample plane with better than 1 nm accuracy. The force mode is demonstrated by mapping the shear force above λ-DNA molecules adsorbed on mica in a liquid environment at different tip-sample separations.
剪切力显微镜通常不适用于在液体环境下对生物分子进行成像。在这里，我们展示了最近开发的散射消逝波（SEW）检测系统，结合特制的垂直取向悬臂（VOCs），可以在液体中可靠地对 DNA 分子进行真正的非接触成像。成功进行剪切力成像的悬臂弹簧常数范围通过实验确定在 0.05 到 0.09 N m^-1 之间。在 8000 像素每秒的扫描速度下，获得了在去离子水中吸附在云母上的 λ-DNA 的图像。还提出了一种用于 VOCs 的新型恒高力映射模式。该方法显示可以以优于 1nm 的精度控制尖端在样品平面中的垂直位置。通过在不同的针尖-样品分离下在液体环境中对吸附在云母上的 λ-DNA 分子上方的剪切力进行映射，证明了该力模式。
