Research Of High Resolution Imaging Method Of SICM

There are two aspects of Single-cell analysis including observation and manipulation.Microscopic technology with a resolution of Micro-nanoscale is the key to single-cell observation.There are several Microscopic techniques including optical microscopy,scanning electron microscopy(SEM)and scanning probe microscopy(SPM).Scanning ion conductance microscopy(SICM),one form of SPM,has become a significant technique in the research of biology and medicine,which allows imaging of the cell surface under physiological conditions without physical contact and with a resolution of nanometer scale.Traditional scanning mode has always been suffering from the contradiction of scanning speed and anti-interference capability.Direct current(DC)mode provides a high scanning speed but is affected by current instability(dc drift),distance modulation mode and hopping mode offer strong anti-interference capability but can only work at a low scan speed.Recently,In-Phase Bias modulation(IPBM)mode has been presented,which is less prone to DC drift and electronic noise while maintains a high scanning speed.But in comparison with DC mode,IPBM is still a mode with low scan speed and imaging resolution.Aiming at the problems above,some research on SICM scanning method has been done in this dissertation.The main work is as follows:First,a novel signal optimization method,Opposed-Phase Bias modulation signal optimization method,is presented,which is based on the IPBM mode.Scan speed and Vertical resolution are further improved with an increased signal to noise ration and high anti-interference capability.Meanwhile,it optimizes the tip set point positon to a better tip-sample distance.Imaging quality is further enhanced by these advantages.Secondly,a smearing phenomenon on the downward step has been noticed during the fast scanning experiments.We propose a Prior-knowledge-based Adaptive Strategy for SICM tip-sample distance control,which has effectively solved this problem,to ensure the accuracy of imaging.Thirdly,a new imaging mode,Capacitance mode,is introduced.In this mode,a AC current is applied between the electrodes and one component of the current is used as feedback.We improve the circuit model to explain the principle of this mode.Experimental results show that in comparison with the traditional modes,Capacitance mode has a better performance at higher lateral resolution imaging or at higher modulation frequency.In this dissertation,we use theoretical analysis,modeling and experimental verification for the research of SICM imaging method.Scanning speed and imaging quality are both improved while the system maintains a strong anti-interference capability,making SICM a better technical support for the research in nanoscale observation and single-cell analysis and promoting the development of related fields.