Permanent encapsulation of nanoparticle patterns formed by inkjet printer for transparent and flexible anti-counterfeit applications
01 Jun 2017-pp 1316-1319
TL;DR: In this article, the authors describe the underlying lack mechanisms of the self-assembly and deposition behavior of nanoparticles in inkjet-printed droplets and demonstrate the development of flexible and photonic crystal structural color based on self-assembled silica photonic crystals.
Abstract: The self-assembly and deposition mechanisms of nanoparticles in droplets on a substrate are significant in many inkjet printing-based industrial applications such as microelectronics, display systems, and paint manufacturing. In this study, we describe the underlying lack mechanisms of the self-assembly and deposition behavior of nanoparticles in inkjet-printed. We also demonstrate the development of flexible and photonic crystals structural color based on self-assembled silica photonic crystals.
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TL;DR: Variations in the deposit patterns can be explained in terms of competing effects between the convective and Marangoni flows, which vary with the types of the high-boiling-point solvent added to the ink.
Abstract: Particle deposit morphologies that resulted from evaporating ink-jetted microdroplets were controlled by varying the ink compositions and concentrations. The ink was a well-dispersed aqueous dispersion of monodisperse silica microspheres. Silica particles suspended in the microdroplet undergo self-assembly upon the evaporation of the solvent. A ringlike deposit of the self-assembled silica particles was produced from the water-based ink, while a uniform two-dimensional monolayer with a well-ordered hexagonal structure was obtained from the mixed-solvent-based inks. Variations in the deposit patterns can be explained in terms of competing effects between the convective and Marangoni flows, which vary with the types of the high-boiling-point solvent added to the ink. The macroscopic shape and microstructure of the silica colloidal deposits were observed by SEM, AFM, and a confocal microscope.
695 citations
TL;DR: It is demonstrated that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques.
Abstract: Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique.
150 citations
TL;DR: In this article, controllable footprint lines were fabricated by adjusting the ink droplets' dynamic wettability which is depended on the surface tension difference between the two droplets.
Abstract: Inkjet printing lines with controllable footprints is the prerequisite of fabricating high-quality patterns. However, achieving precise footprints of lines by inkjet printing is still a challenge because of the difficulty in controlling coalescences of ink droplets. Here, controllable footprint lines were fabricated by adjusting the ink droplets’ dynamic wettability which is depended on the ink droplets’ surface tension difference. The experimental surface tension difference of 0.77–1.50 mN/m leads to appropriate surface dynamic wettability to ink droplets and the formation of straight lines, which agrees well with the theoretical results. These results will pave the way for printing electronics and patterns.
72 citations