Research On The Controllable Assembly And Optical Properties Of Colloidal Microspheres Induced By Fiber Liquid Bridge

With the continuous development of science and technology,people's awareness of intellectual property protection continues to increase,and the requirements for anti-counterfeiting are increasing.Optical anti-counterfeiting technology is to print a film with anti-counterfeiting function on a specific part of a specific object through a device with different patterns,which identifies photoelectric identification through the photoelectric recognition of the instrument to achieve the purpose of anti-counterfeiting.Optical anti-counterfeiting technology is based on the color change of multi-angle diffraction of light.Compared with ordinary anti-counterfeiting technology,it has better security and identification,and plays an increasingly important role in the field of anti-counterfeiting.Photonic crystals(Photonic Crystals)as thin-film structures are widely used in light-emitting display,optical anti-counterfeiting,solar cells,biological detection and other fields due to their superior performance,In recent years,due to the increasing demand for anti-counterfeiting,PCs films have played an important role in the field of optical anti-counterfeiting.The PCs films of different layers have rich structural color depth changes due to the difference in light diffraction,which is of great significance for improving optical anti-counterfeiting performance.There are a variety of commonly used construction methods for PCs films,such as dielectric rod stacking,precision mechanical drilling,colloidal self-assembly method,and semiconductor technology.Among these methods,the colloid-based self-assembly preparation method is one of the commonly used methods for constructing PCs membranes due to its unparalleled advantages such as simple colloidal self-assembly technology and wide range of available materials.The main methods based on the self-assembly of colloidal particles including dipping and pulling method,spin coating method,inkjet printing method,doctor blade coating method,LB method,etc.These methods have their own advantages,but there is a problem that the layer-by-layer microstructure cannot be realized precise control.Because it is difficult for these methods to control the stable and continuous dewetting of the three-phase line during the evaporation assembly process,and the fiber's super handling ability of the liquid enables it to achieve better control during the construction of thin film structure.As a traditional calligraphy and painting tool,the Chinese writing brush composed of animal hair fiber provides a good example for the preparation of nanomaterial film.However,there are two problems in the original research based on tapered fiber.One is that the writing system only depends on the solution stored among the fiber to achieve liquid supply.The lack of a continuous solution storage system limits the continuity of the writing process;the other one is the fiber are all perpendicular to the substrate,although relying on the tiny scale of the tip of the fiber can effectively achieve precise structural control,it also limits the area of the prepared film.Based on these,the research group early developed the method of the fiber liquid-bridge constructed by the capillary and the fiber,obtained a large-area uniform continuous quantum dot film,realized the construction of QLED device,and this method can control the stable dewetting of the three-phase line,which provided a way to realize for good model system and technical means the preparation of large-area film.In response to the above problems,in order to establish a more complete colloidal particle controllable assembly system,we developed an efficient,simple and new method for the preparation of orderly,finely controllable PCs based on the precise control of the liquid and three-phase lines by the fiber liquid bridge method which is of great significance to realize the controllable assembly of the number of layers of colloidal particle microsphere structure and to realize its application in the field of optical anti-counterfeiting.The main research contents of this paper are as follows:(1)Controllable preparation and system construction of different layers of PCs film of colloidal particles based on fiber liquid bridge method.Based on the guidance of the new device in the fiber liquid bridge method,the PS microspheres solution forms a stable liquid-bridge,realizing the construction of a single layer of PCs film by the traction of the three-dimensional mobile platform.Choosing different substrates,different speeds,concentration ranges and adding different surface tension adjustment solvents are tried and explored.The study found that adding the appropriate type of surface tension adjusting solvent isopropanol in the specific range of speed and concentration on a normal glass substrate can realize the preparation of single-layer ordered PCs film.In addition,through the investigation of other particle sizes,it was found that a single-layer ordered film structure can also be stably constructed.On the basis of this investigation,a multilayer PS microsphere film with controllable number of layers was successfully constructed and characterized accordingly by changing the conditions of speed and concentration parameters.Afterwards,summary statistics were made on the concentration and speed conditions for the proper film formation of PS microspheres with different particle diameters to construct PCs membranes,and an accurate and controllable membrane structure system was established.Through this system,a film structure with a specific number of layers can be accurately constructed under corresponding conditions.Finally,on the basis of the previous chapter,in the third chapter,through further analysis of the experimental results and related theories,the film-forming mechanism for constructing elaborately controlled PCs thin-film materials is proposed.(2)Research and application of properties of PCs films with different layers fabricated by fiber liquid bridge method.The optical properties of the constructed PS microspheres film were characterized,and it was found that the single-layer PCs film have good transparency which can achieve optical hiding at a certain angle.Multi-layer PCs films of different structural colors do not have transparency,and there are blue-shift in their reflection spectra.Therefore,we are expected to build patterns of PCs films of different layers and different structural colors on the same substrate using the different optical properties of mono-layer and multi-layers PCs which can prepare patterned anti-counterfeit labels to improve optical anti-counterfeiting performances and achieve their optical properties and applications in the field of anti-counterfeiting.