Self-assembly Of Colloidal Crystals With Wrinkles

Wrinkle is one of common natural phenomenon, which usually caused by stress mismatchin flexible substrate/stiff film system, and has important application in cell culture template,colloidal particles separation and ordered structure template areas. In this paper, PDMS flexiblesubstrate/Pt stiff film system was adopted, and the ordered wrinkle pattern were realized viaprepatterning boundaries. Generation and degeneration of wrinkle were observed in real time,and evolution law and wrinkle formation mechanism were obtained which was meaning forpreparing large-scale ordered wrinkles of low defect ratio. Based on reversal phenomenon,binary colloidal particles assembly were conducted, which assembled multielement colloidalcrystals on the same plane with a new approach. The main content as follows:1. Through cooling30°C to0°C and reheating25°C, the reversible process of orderedwrinkle were realized in PDMS substrate/Pt film embossed patterns. The wrinkle wavelengthwas controlled by film thickness and Young’s module of substrate, whose experimental resultswere diverged from theoretical results caused by interlayer during spurring. The wrinkle patternswere controlled by prepatterning boundaries, such as stripes, herringbones and labyrinths, whichwere explained from theoretical mechanics. At the same time, the law of generation anddegeneration of ordered wrinkles, the mechanism of formation and evolution, the effect oftemperature on wavelength and amplitude, and relationship of cooling speed and defect werewell explained using mechanics theory. It is meaning for physical formation mechanism ofnatural parallel veins.2. The law and defects of colloidal crystals assembled on stressed wrinkle surfaces wereresearched. Firstly, uniform polystyrene microspheres of average diameter at200nm,230nm,260nm,300nm and370nm were prepared by emulsion polymerization respectively, whoserelative standard deviations were all inferior to5%. Then, the two-dimensional unitarymonolayer colloidal crystals were prepared by lift-up method on the surface of PDMSsubstrate/Pt film structure, to form ordered colloidal layer between air-liquid interface undericewater bath. The best experimental parameter of lauryl sodium sulfate and ethanol wereobtained. And the band width, distribution spaces and arranged patterns of band-like colloidal crystals were controlled by wavelengths and patterns of substrates. The defects were studied bycontrolling by diameters of colloidal particles.3. Based on reversible behavior of wrinkle, the two-dimensional binary monolayer colloidalcrystals epitaxial grew on the surface of PDMS substrate/Pt film structure prepatterned unitarycolloidal crystals under room temperature with lift-up method. Via controlling the film coatingprocesses, the best experimental conditions were obtained. The band-like monolayer colloidalcrystals of stripes and herringbones were regulated by wrinkle patterns of substrate andstructures of extensional colloidal crystals were studied.