Design Of Measurement And Control System For Self-assembly And Study On Self-assembly Process Of PS Colloids

Self assembly is an efficient method for constructing ordered microstructures using micro particles,and it has attracted more and more attention with the development of nanotechnology.The method of obtaining ordered structure by colloid self-assembly which has been widely used in physics,chemistry,biology,materials,medicine and other fields can be accomplished without manpower.And it has the advantages of simple operation,various manufacturing structures and good repeatability.The self-assembly methods include template method,template free method,field oriented method and other physical methods.Among them,the self-assembly of PS colloids by solvent evaporation on planar substrate is the most widely used one because of its simple operation.The evaporation rate of the solvent,the temperature of the assembly environment and the concentration of PS solution affect the result of self-assembly by solvent evaporation method.The solvent-evaporation method is sensitive to variations of temperature,impurity and ambient humidity,and the quality of the crystalline films depends on these factors intensely.And it is hard to tailor the sickness and the crystallinity,so it is very significant to discuss the influence of these factors on colloidal crystal growth.In this thesis,the temperature controlling of the self-assembly environment was studied firstly,and then the effects of sealing modes,ambient temperature and solution concentration on the periodic constants and integrality of colloidal crystals were studied.The main work contents and achievements are summarized as follows:1.Design of a temperature measurement and control system based on FPGA and SHT20.The system framework was firstly designed using top-down strategy.Then the design and simulation verification of PID controller and other modules of the system were carried out.Finally,PID parameters were adjusted by an engineering way,and the control precision reaches 0.1 oC.2.A formula indicates the relationship between the central wavelength of photonic band gap and the volume fraction of PS nanospheres,the size of PS nanospheres was deduced.Using the designed temperature measurement and control system,PS colloidal crystal films were obtained by solvent evaporation on a planar substrate under three environmental sealing modes of unsealed,sealed and with-water-sealed.The surface morphology of colloidal crystal was obtained by scanning electron microscopy,and the optical properties were analyzed by UV-VIS spectrometer.The behavior mechanism of PS nanoparticles during the self-assembly process under different sealing conditions was analyzed,and the influence of sealing modes on the assembly of colloidal crystal structure morphology and optical properties was summarized.3.The self-assembly experiment of solvent evaporation under different temperatures wascarried out under with-water-sealed mode for its best assembling effect.The influence of temperature and concentration of PS solution on the behavior of particles during the assembly process were respectively analysed,and the influence to surface morphology,structure characteristics,periodic constant,filling rate and integrality of photonic crystal were studyed.