Construction Of Responsive Photonic Crystals And Its Application In Structure Color Printing

Responsive photonic crystal is a kind of smart material whose stop band can be manipulated under external stimulus.It is widely used in various fields such as sensing,display and anti-counterfeiting and thus is a hot research topic in chemical and material science.Photonic crystal printing is a key technique to apply this new material to real-world applications.Up to now,reported printing methods can be classified into two categories.In one category,based on swelling or deforming process,the pattern could be obtained by selectively modulating the crystal structure of a part of prepared photonic crystal paper.In the other,colloidal particles were partially assembled into pattern under external filed.However,the currently reported methods still need to be improved in terms of printing efficiency,precision,and ability to tune structure colors.Based on this situation,we developed two new printing methods in this essay.In second chapter,we develop a printing method based on electric field response photonic crystals.Firstly,the SiO2 colloids were supersaturated and participated in the mixture of propylene carbonate(PC)and trimethylolpropane ethoxy triacrylate(ETPTA)to form the electric responsive,structural color and greyscale tunable,photo-curable E-ink.With the help of photomasks,an external electric field(0-3V)and ultraviolet radiation are cooperatively applied to the above-mentioned electronic ink to print a multicolor pattern that is previously drawn on the mask.The printed pattern and the background have different crystal structures,and thus show a distinct structural color difference.By building a miniature electric field array,pixel-level high-resolution pattern can also be achieved without mask assistance.In chapter 3,we develop a printing method based on solvent-responsive photonic crystals and prepare the invisible photonic crystal patterns that appear after wetting.Firstly,a hard template method was used to prepare the inverse polyurethane photonic crystal film,which has collapsing structure in normal circumstances.This colorless film has reversible solvent response characteristics.In swelling state,it recovers the ordered three-dimensionally macroporous structure and exhibits a structural color,whereas this structure collapses and the film become colorless again after being dried.When dropped with printing solvent and heated sequentially,the corresponding part on photonic paper will retain the solvent responsibility;However,in the area without the solvent protection,the thermoplasticization process will cause the film to lose the solvent responsibility;Thus,a transparent photonic crystal pattern that responds to solvent asymmetry can be printed.This invisible pattern appears rapidly when the soaking into developing solvent(alcohol and water mixture)and hides again after dried.