高成像速率和高力灵敏度的I-2形原子力显微镜探针研究

Atomic force microscopy (AFM) has unique advantages in the field of biomedical research. The existed AFM system, however, still can not perform the real-time imaging of the biological process over a living cell. This is because the resonance frequency (f) and the quality factor (Q) of current cantilever AFM probes can not be effectively increased by existing research efforts, leading to a low AFM imaging rate and a low imaging quality in liquid. In the light of that MEMS resonators benefit from high f , high Q and integrated transduction functions, a new idea for developing a MEMS-based I-2 shaped oscillating AFM probe is proposed. Effective promotion of f , Q and force sensitivity of the proposed I-2 shaped probe are determined as the research objectives of this project. All round improvements on mechanical structure, transducer construction and signal processing electronic circuit designs are taken to be the main measures. A structure and geometry parameter-based design method for obtaining high f and Q values will be put forward. An improved transducer design method for achieving the higher transmission efficiency and better output signal quality will also proposed. A design method of proper signal processing electronic circuit specially for the I-2 shaped probe with a high signal to noise ratio will be provided as well. The previous exploratory research results show that the f and Q values of the first version of I-2 shaped probe are 10 times higher than those of the most commercial cantilever probes. It can be expected that the force sensitivity of I-2 shaped probe could be further increased to fN/√Hz range through the further research of this project, realizing the eager desire of bio-scientists for real-time observation of the biological process over a living cell.

原子力显微镜(AFM)在生物医学研究领域具有独特优势，但由于微悬臂探针的谐振频率(f)和品质因数(Q值)偏低，制约AFM的成像速率以及在液体中的成像性能。既有AFM尚无法克服对活细胞表面及内部生物进程进行观测的瓶颈问题。鉴于MEMS谐振器具有高f和Q值以及可集成的传感功能等优点，本项目提出一种基于MEMS谐振器的I-2形探针的研发新思路，以提高f、Q值和力灵敏度为目标，全面改进机械结构、传感结构以及检测电路的设计。提出高f、Q值的结构参数设计方法；提出高传输效率与高品质输出信号的传感结构改进设计方法；提出高信噪比检测电路设计方法；从而实现f、Q值和力灵敏度的全面提升。预研结果显示，首批I-2形探针的f和Q值均为大多数商用悬臂探针的十倍以上。预计经本项目研究改进后，I-2形探针力灵敏度有望达到fN/√Hz，实现生命科学界对活细胞表面及内部的生物进程实时观测的迫切愿望。

原子力显微镜(AFM)在生物医学研究领域具有独特优势，但由于微悬臂探针的谐振频率f和品质因数（Q值）偏低，制约AFM的成像速率以及在液体中的成像性能。鉴于MEMS谐振器具有高f和Q值以及可集成的传感功能等优点，本项目在原有基于MEMS谐振器的I2形探针的基础上，通过对结构的锚损分析，确定了高Q值谐振器的尺寸参数；通过对谐振器在工作模态的应力分布分析，采用局部离子注入的方式有效提高谐振器的机电转换效率，从而使力灵敏度提高10倍以上；通过利用反偏P-N结界面处的势垒效应，抑制了热驱动激励信号与压阻敏感信号间的耦合效应，输出信号品质获得大幅提高；设计并实现电阻差分检测电路，获得对耦合信号的调节方法；研究了I2形探针针尖与液滴间的固液接触特性，对后续探针在液体中成像方式的实现提供有益帮助。