具有高品质因数的剪切力扫描近场光学显微镜在液体中的生物成像

基于剪切力的探针-试样间距控制扫描近场光学显微镜用于生物材料在液体中的成像比在空气中难得多。液体的黏性阻尼和软的试样表面要求更高的力检测灵敏度。最近我们试验成功的压电双晶片剪切力检测器结合力反馈技术，可以大幅度提高双晶片的机械谐振品质因数，从而改善在粘滞液体中力检测灵敏度。当双晶片在它的某一本征频率下被激励，通过调节一个适当的反馈力，它的机械谐振品质因数在水中可以从40增强到10^3，因此成像灵敏度获得显著改善。上述力检测技术被用于一些生物试样在液体环境下的拓扑和近场光学成像。所得到的力、相位和光学图像显示了高的成像质量和分辨率。实验结果证明上述装置尤其适宜于近场光学显微镜在生物领域的应用。

Q-enhanced shear force near-field optical microscopy on biological imaging in liquid

Shear force scanning near-field optical microscopy (SNOM) on biological materials is more critical to implement in liquid than in air because of viscous damping and sample softness. The bimorph-based cantilever incorporating force feedback technique used for SNOM tip-sample distance regulation, that we recently developed, allows improving the force detection sensitivity through amplifying the sensor's quality factor Q (Q-factor) in viscous media. Driving the bimorph cantilever at one of its eigenfrequencies with an appropriate force feedback allows obtaining an effective Q-factor up to 103 in water from its original amount of ～ 40, that is, the sensitivity can be improved. The SNOM with above sensor was used for observing human skin tissues and adenocarcinoma ovarian cell membranes in aqueous environment. The obtained shear force, phase and optical images have shown a high imaging quality and resolution. These experimental results give further ewidence that our SNOM setup is particularly suitable for biological applications.