Optimization Of Near-field Microwave Microscopy And Morphological Electromagnetic Parameters

As an emerging microscopic imaging technology,near-field microwave microscopy systems can break through the spatial resolution limit of far-field microscopy.Using the good penetration performance of microwave,the parameter information of the surface and subsurface of the sample to be measured can be detected.Near-field microwave scanning microscope systems have achieved some research breakthroughs and progress in the fields of life science applications,semiconductor device damage detection,and electromagnetic properties of microstructure materials.The electromagnetic properties of biological tissues are described in many literatures,but little data is available for single cells or subcellular structures.Traditional cell imaging methods include mitochondrial dyes or fluorescent labeling techniques.This method typically uses a compound microscope to observe the growth or movement of cells.The cells to be tested themselves can be contaminated or damaged by the use of fluorescent reagents.The detection of biological cells by microwave is characterized by non-invasive,rapid,label-free,etc.,and the tissues(cells)of the organism to be tested are not stained and other related operations that may lead to damage.To further improve the spatial resolution of electrical characterization techniques to the subcellular level or even the nanoscale,we use nearfield microwave scanning microscopy to perform experiments.In this thesis,the established near-field scanning microwave microscopy test system was used to perform scanning imaging experiments of plant cells to further verify the feasibility of this method.Based on the resonant cavity perturbation theory and near-field microwave theory,the electromagnetic simulation analysis software was used to establish an electromagnetic simulation model of the near-field microwave response between the sample to be measured(plant cells)and the tip of the needle,obtain the electromagnetic parameters of plant epithelial cells,and analyze the electric field near the tip of the needle.Onion epidermal cells were scanned at point,line and surface to obtain their near-field imaging results,and compared with cell optical photos,a near-field scanning microwave microscopy system could characterize cell morphology.In order to enable near-field scanning microwave microscopy to make more breakthroughs in the field of higher resolution imaging,we propose to add a Z-axis linear piezoelectric ceramic positioning stage controlled by a piezoelectric controller with higher resolution to the original approximation scanning system,which can make the distance change between the probe and the sample to be measured more accurate.A set of scanning programs with higher accuracy in the vertical direction that can be used for "tapping mode" was designed and built,and the optimized system used an operating program to resonate between the tip and the sample to be measured.Finally,we design and simulate a small circuit board based magnetic field probe with octagonal coil,this small circuit board magnetic field probe based on the automatic measurement of near-field EMI measurement system,can measure near-field electromagnetic interference,further improve the sensitivity and resolution of the magnetic field probe,and achieve accurate positioning of the EMI radiation position of the circuit board under test.