Metal particle compaction during drop-substrate impact for inkjet printing and drop-casting processes

Direct coating methods using metal particles from aqueous solutions or solvent-based inks become central in the roll-to-roll fabrication processes as these methods can lead to continuous or pre-defined conductive layers on a large variety of substrates. For good electrical conductivity, the metal particles have to be brought into contact, and traditionally, additional sintering treatments are required. Such treatments can degrade the sensitive substrates as paper or polymer films. In this study, the possibility of obtaining conductive layers at room temperature is investigated for direct coating methods with an emphasis on drop-casting and inkjet printing. Thus, it is shown that electrical conductive layers can be achieved if the metal particles can compact during the drop-substrate impact interaction. It is theoretically shown that the compaction process is directly related to the particle and ink drop size, the initial fractional particle loading of the ink, solvent viscosity, and drop velocity. The theoretical predictions on compaction are experimentally validated, and the particle compaction's influence on changes in the electrical conductivity of the resulting layers is demonstrated. (C) 2016 AIP Publishing LLC

Electrochemical impedance spectroscopy investigations on glassy carbon electrodes modified with poly(4-azulen-1-yl-2,6-bis(2-thienyl)pyridine)

A characterization of glassy carbon (GC) electrodes modified by controlled potential electrolysis of 4-azulen-1-yl-2,6-bis(2-thienyl)pyridine (L) in acetonitrile solutions containing tetra-n-butylammonium perchlorate is presented. The electrochemical properties of bare and modified GC electrodes were investigated by electrochemical impedance spectroscopy (EIS) in acetate buffer solutions. EIS data were fitted using the Zview fitting program and the appropriate equivalent electrical circuit. Small variations in the electrochemical properties of the interface during the steps of preparation of the modified electrodes with polyL films were observed. The EIS parameters of the polyL film have no regular variation with the increase in film thickness, most probably due to significant effect of polyL films porosity

Stability of ultrathin nanocomposite polymer films controlled by the embedding of gold nanoparticles

Thin and ultrathin polymer films combined with nanoparticles (NPs) are of significant interest as they are used in a host of industrial applications. In this paper we describe the stability of such films (hpoly ≤ 30 nm) to dewetting, specifically, how the development of a spinodal instability in a composite NP–polymer layer is controlled by the embedding of Au NPs. At working temperatures (T = 170 °C) above the polymer glass transition temperature (Tg ≈ 100 °C) the absence of Au NPs leads to film rupture by nucleation dewetting, while their presence over a large surface area enhances the development of a spinodal instability without destroying the film continuity. When the NPs embed, the surface undulations are suppressed. The dynamics change from an unstable to a stable state, and the thin composite NP–polymer layer returns to a flat configuration, while the wavelength of the pattern remains constant. Moreover, we demonstrate from a thermodynamic perspective that NPs will remain on the surface or embed in the polymer film depending on their free energy, which is determined by the NP interactions with the underlying polymer, the native SiOx layer, and the Si substrate