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We propose a novel technique of integrating silica nanowires to carbon microelectrode arrays on silicon substrates. The silica nanowires were grown on photoresist-derived three-dimensional carbon microelectrode arrays during carbonization of patterned photoresist in a tube furnace at 1000 °C under a gaseous environment of N(2) and H(2) in the presence of Cu catalyst, sputtered initially as a thin layer on the structure surface. Carbonization-assisted nucleation and growth are proposed to extend the Cu-catalyzed vapor-liquid-solid mechanism for the nanowire integration behaviour. The growth of silica nanowires exploits Si from the etched silicon substrate under the Cu particles. It is found that the thickness of the initial Cu coating layer plays an important role as catalyst on the morphology and on the amount of grown silica nanowires. These nanowires have lengths of up to 100 µm and diameters ranging from 50 to 200 nm, with 30 nm Cu film sputtered initially. The study also reveals that the nanowire-integrated microelectrodes significantly enhance the electrochemical performance compared to blank ones. A specific capacitance increase of over 13 times is demonstrated in the electrochemical experiment. The platform can be used to develop large-scale miniaturized devices and systems with increased efficiency for applications in electrochemical, biological and energy-related fields.

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Electrohydrodynamic (EHD) jet printing is a highly effective technique for micro/nanoscale three-dimensional manufacturing. However, due to the complicated electrohydrodynamic mechanisms behind liquid deformation and jet emission, the printing process with remarkable droplet consistency and excellent controllability is still under investigation. In this work, a numerical analysis is conducted on EHD jet printing under constant and step change of electric voltages. We first examine constant-voltage-based pulsating EHD jet printing and explain the impacts of voltage on the regimes, deposited droplet volumes, and durations of the three key printing stages, namely cone formation, jetting, and jet/meniscus retraction and oscillation. After that, we carry out a comprehensive investigation on EHD jet printing under various step changes of voltages, while focusing on the jet behaviors at the voltage switch and after detaching from the Taylor cone. With the assistance of the electric field distribution, interface charge density, velocity fields, and very clear liquid motion images obtained from the numerical data, we fully inspect the pulsed printing processes and elucidate the influences of the pulse time, bias voltage, and peak voltage on the printing behaviors, durations of the three printing stages, and deposited droplet volumes. Finally, based on the obtained results, we make a comparison of the printing outcomes between these two techniques. The findings discovered in this work can be used for advancing the understanding and controlling methods of this complicated but very useful manufacturing technology.

Large amounts of amorphous silicon oxynitride nanowires have been synthesized on silicon wafer through carbon-assisted vapor-solid growth avoiding the contamination from metallic catalysts. These nanowires have the length of up to 100 μm, with a diameter ranging from 50 to 150 nm. Around 3-nm-sized nanostructures are observed to be homogeneously distributed within a nanowire cross-section matrix. The unique configuration might determine the growth of ternary amorphous structure and its special splitting behavior. Optical properties of the nanowires have also been investigated. The obtained nanowires were attractive for their exceptional whiteness, perceived brightness, and optical brilliance. These nanowires display greatly enhanced reflection over the whole visible wavelength, with more than 80% of light reflected on most of the wavelength ranging from 400 to 700 nm and the lowest reflectivity exceeding 70%, exhibiting performance superior to that of the reported white beetle. Intense visible photoluminescence is also observed over a broad spectrum ranging from 320 to 500 nm with two shoulders centered at around 444 and 468 nm, respectively.