【作者】 秦岭；

【导师】 Daniel Mark Czajkowsky；

【作者基本信息】 上海交通大学 ， 生物学， 2016， 硕士

【摘要】 原子力显微镜已经成为科研工作者研究样品表面形貌特征的一种强有力的工具,尤其在材料科学和生物科学领域得到了广泛的关注。虽然原子力显微成像技术已经被广泛应用于探测各种不同类型的生物大分子,并取得了许多令人欣慰的成果,但是,稳定、可靠、可重复地获取1纳米,尤其是小于1纳米的精细结构仍然是目前的一大难点。针对这一难点问题,我们自主研发了一种具有超高分辨率成像能力的低温调频非接触原子力显微镜系统。首先,我们利用探针悬臂共振频率的变化作为反馈信号,通过精确控制探针和样品表面的距离,使其工作在非接触模式下,成功实现了调频非接触原子力显微镜的搭建。然后将显微镜置于77K的低温环境中,并使其正常工作。为了保证仪器能够在低温下工作,我们重新设计了一种不同于商业化原子力显微镜的头部,并增加了磁阻尼悬挂系统,以降低机械噪音与振动耦合;同时,我们通过适当增压的方式控制液氮沸点从而有效的压制了液氮气化在成像中造成的振动;设计了齿轮组合达到样品与探针间支撑点的三点联动以实现探针与样品间平行进退;通过增加光杠杆光程、高效聚焦等方法达到了必要的检测灵敏度。另外,我们重新设计了电路等来进一步减少噪声,提高整个系统的信噪比。通过测试,仪器的本底噪声可以达到12fm/√Hz,远远低于常规商业原子力显微镜的噪声值。我们利用搭建的低温调频非接触模式原子力显微镜成功探测了生物样品的表面形貌,成功证明了相对于接触模式,低温调频非接触模式更容易获得高分辨率图像。更多还原

【Abstract】 Atomic force microscopy has been a powerful tool for the study of the surface topography of the samples,especially in the field of material science and biological science.Although atomic force microscopy has been widely applied to the detection of a variety of different types of biological macromolecules,and made many commendable success,getting the resolution to 1 nm,especially less than 1 nm of the fine structures stably and reliably is still very difficult and challenging.To resolve the problem described above,we developed the cryogenic non-contact atomic force microscope which is capable of high resolution imaging.Firstly,we utilize the change of the resonant frequency of the cantilever probe as the feedback signal,through the precise control of the probe and sample surface distance,to achieve the non-contact mode AFM successfully.Then,we put the instrument into the cryogenic environment and ensured it to work well.To accomplish this goal,we redesigned a different AFM head compared with the commercial AFM head.We designed the magnetic damping suspension system in order to reduce the mechanical noise and coupling vibration.Moreover,controlling pressure properly so as to effectively suppress the boiling point of liquid nitrogen and reduce liquid nitrogen gasification which can bring more noise in the imaging process was designed.And the gear group can help us ensure that the probe and the sample is parallel when the probe is approaching the sample surface because of the linkage of three supporting points.Through increasing the optical path of optical lever and the highly efficient focusing method,we got the necessary detection sensitivity.In addition,we also redesigned the circuit to reduce the noise,improving the ratio of signal to noise of the whole system.The deflection noise density of our system can achieve 12fm/√Hz which are smaller than the values of commercial atomic force microscope.With this cryogenic non-contact frequency modulation atomic force microscope,we successfully detected the topography of the biological sample surfaces in high resolution and demonstrated that cryogenic noncontact AFM is much easier to obtain high resolution images compared with contact AFM.更多还原