Preparation Technology And Imaging Study Of Large-area Micro/nanoparticle Arrays Based On Gravity-assisted Self-assembly Method

Dielectric-microsphere-assisted super-resolution optical microscopy has been a hot topic in the microscopy community.Compared with other super-resolution technologies,microsphere-assisted-microscopy has the merits of white light illumination,label-free imaging,wide-field observation and no need of sophisticated equipment.In this work,a gravity-assisted self-assembly technique has been proposed to fabricate large-area microsphere arrays.Then,the influence of the diameter of microspheres and the refractive index of the immersion liquid on the imaging was studied.The work done in this dissertation are as below:1.A gravity-assisted self-assembly method is developed in this work.Si O₂microsphere monolayers with an area of several centimeter squares were fabricated by using colloidal suspensions of Si O₂ microspheres which have a diameter of 0.61?0.81 and4.87?m.The influence of the capillary cell position and the colloidal suspension concentration on the self-assembly process were studied.The sample quality was characterized both by recording samples'laser diffraction patterns and by measuring the transmission spectrum between 400 nm and 1800 nm wavelength and the reflection spectrum between 400 nm and 800 nm wavelength.2.The imaging properties of barium titanate glass microspheres fully immersed in various liquid immersion were studied.Barium titanate glass microspheres were self-assembled on substrates with periodic patterns,and were observed under reflective microscope using deionized water,ethanol,ethylene glycol and cedar oil,respectively.In addition,the effects of microsphere size and refractive index of immersion liquid on magnification factors were studied.The experimental results show that the magnification factor decreases with the increase of the diameter of barium titanate glass microspheres or with the increase of the refractive index of immersion liquid.We also performed simulation with finite-difference time-domain method and found that the photonic nanojet of the dielectric microsphere is affected by the refractive index ratio between the microsphere and the immersed liquid.A larger refractive index ratio causes a closer photon nanojet and a greater magnification factor of the imaging system.3.The imaging properties of close-packed microsphere arrays fully immersed with various liquids are studied.Monolayers of polystyrene and silica microsphere arrays were prepared on stripe samples by self-assembly technique.Deionized water,cedar oil and deionized water near boiling point were used to immerse microsphere arrays,and their imaging characteristics were observed under microscopic objective lens.The experimental results suggest that the observation range of the sample can be effectively increased by using the microsphere lens array to observe the sample.In addition,the refractive index of deionized water is inversely proportional to its temperature,so the magnification of the microsphere imaging system increases with the increase of deionized water temperature.Moreover,the periodic structure of the sample has a bright structure color due to the existence of Bragg diffraction,which will also change with the change of the refractive index of the immersed liquid.