Characterization of Underwater Stability of Superhydrophobic Surfaces Using Quartz Crystal Microresonators

We synthesized porous aluminum oxide nanostructures directly on a quartz crystal microresonator and investigated the properties of superhydrophobic surfaces, including the surface wettability, water permeation, and underwater superhydrophobic stability. After increasing the pore diameter to 80 nm (AAO80), a gold film was deposited onto the AAO80 membrane, and the pore entrance size was reduced to 30 nm (AAO30). The surfaces of the AAO80 and AAO30 were made to be hydrophobic through chemical modification by incubation with octadecanethiol (ODT) or octadecyltrichlorosilane (OTS), which produced three different types of superhydrophobic surfaces on quartz microresonators: OTS-modified AAO80 (OTS-AAO80), ODT-modified AAO30 (ODT-AAO30), and ODT–OTS-modified AAO30 (TS-AAO30). The loading of a water droplet onto a microresonator or the immersion of a resonator into water induced changes in the resonance frequency that corresponded to the water permeation into the nanopores. TS-AAO30 exhibited the best performance, with a low degree of water permeation, and a high stability. These features were attributed to the presence of sealed air pockets and the narrow pore entrance diameter

Hybrid Copper–Silver Conductive Tracks for Enhanced Oxidation Resistance under Flash Light Sintering

We developed a simple method to prepare hybrid copper–silver conductive tracks under flash light sintering. The developed metal nanoparticle-based ink is convenient because its preparation process is free of any tedious washing steps. The inks were composed of commercially available copper nanoparticles which were mixed with formic acid, silver nitrate, and diethylene glycol. The role of formic acid is to remove the native copper oxide layer on the surface of the copper nanoparticles. In this way, it facilitates the formation of a silver outer shell on the surface of the copper nanoparticles through a galvanic replacement. In the presence of formic acid, the copper nanoparticles formed copper formate, which was present in the unsintered tracks. However, under illumination by a xenon flash light, the copper formate was then converted to copper. Moreover, the resistance of the copper-only films increased by 6 orders of magnitude when oxidized at high temperatures (∼220 °C). However, addition of silver nitrate to the inks suppressed the oxidation of the hybrid copper–silver films, and the resistance changes in these inks at high temperatures were greatly reduced. In addition, the hybrid inks proved to be advantageous for use in electrical circuits as they demonstrated a stable electrical conductivity after exposure to ambient air at 180 °C

Magnetorheological Elastomer Films with Tunable Wetting and Adhesion Properties

We fabricated magnetorheological elastomer (MRE) films consisting of polydimethyl­siloxane and various concentrations of fluorinated carbonyl iron particles. The application of a magnetic field to the MRE film induced changes in the surface morphology due to the alignment of the iron particles along the magnetic field lines. At low concentrations of iron particles and low magnetic field intensities, needle-like microstructures predominated. These structures formed more mountain-like microstructures as the concentration of iron particles or the magnetic field intensity increased. The surface roughness increased the water contact angle from 100° to 160° and decreased the sliding angle from 180° to 10°. The wettability and adhesion properties changed substantially within a few seconds simply upon application of a magnetic field. Cyclical measurements revealed that the transition was completely reversible

Hybrid Copper–Silver–Graphene Nanoplatelet Conductive Inks on PDMS for Oxidation Resistance Under Intensive Pulsed Light

A simple, low-cost, and reliable process of production for conductive tracks and their transfer to poly­(dimethylsiloxane) (PDMS) substrate has been proposed. Flexible electrodes were fabricated using conductive nanoparticulates under intensive pulsed light, which were then transferred on to a PDMS substrate via a pouring, curing, and peeling process. The combination of copper–silver nitrate–graphene nanoplatelets (GnPs) provided multiple benefits to the conductive tracks, such as oxidation resistance and increased durability on PDMS. The addition of silver nitrate reduced the speed of oxidation during the curing process of PDMS in the presence of heat and air. The addition of GnPs then increased the stability of conductive tracks on PDMS, whereas the films without GnPs were not conductive on PDMS due to mechanical cracks. The copper–silver–GnP electrodes on PDMS were successfully demonstrated as flexible electrodes and reveal the enhancement of oxidation resistance during thermal oxidation for Joule heater application