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A new approach of electrostatically focusing nanoparticles through an electrical tape mask to form narrow <10 μm and conductive microstructures is developed and investigated in this work. The presented approach is similar to deposition of material through a stencil and allows one to obtain lines 15 times smaller than the width of the gap in the mask. It is proposed to use ordinary polyvinyl chloride (PVC) electrical tape as a mask instead of expensive photo or electronic resists. The work investigates the influence of a mask thickness (height) of 60–180 μm, a gap width of 120–380 μm, a substrate potential of 0.1–5 kV, and a deposition time of 10 and 120 min on the geometry and electrical properties of the lines. Charged Au nanoparticles 60 nm in size synthesized by spark discharge are the building blocks of microstructures. Numerical modeling of the process of focusing nanoparticles in COMSOL qualitatively confirms the found experimental dependencies. The electrical resistivity of the sintered lines is 6.34 times higher than that of bulk gold. The developed approach makes it possible to obtain high‐aspect microstructures and supports operation at atmospheric pressure. [ABSTRACT FROM AUTHOR]

The demand for the development of local laser sintering of nanoparticle arrays is explained by the expanding needs for printed electronics for functional microstructure formation, on heat-sensitive substrates in particular. This work is based on the research into the sintering of arrays of silver nanoparticles synthesized in a spark discharge and deposited on a substrate by focused aerosol flow. The sintering was done by continuous and pulsed lasers with wavelengths 527, 980 and 1054 nm. Sintered samples were studied by measuring the resistivity, cross-section profile area and microstructure features. The highest average conductivity, equal to the half of the bulk silver conductivity, was achieved when sintering by continuous radiation with a wavelength 980 nm. The results showed that when using pulsed radiation the direct heating of nanoparticles in the sample surface layer dominates with the formation of a pore-free conductive layer of around 0.5 μm thick and crystallite of 70–80 nm size. It was found that laser sintering by radiation with a wavelength 527 nm required an order of magnitude lower specific energy costs as compared to the longwave laser radiation. The high energy efficiency of laser sintering is explained by special conditions for radiation absorption at plasmon resonance. [ABSTRACT FROM AUTHOR]

In this paper we investigated the effect of substrate temperature (25-300°C) on the aspect ratio (thickness/width) of the silver lines formed by aerosol jet printing (AJP). This effect was studied by varying the speed of substrate (50-250 mm/min.) and the number of printing layers (1-25 layers) in order to obtain lines with high aspect ratio. It is shown that AJP on a heated substrate at a temperature equal to >100°C allows to increase the aspect ratio of the lines more than 17 times in comparison with conventional AJP. It is established that the aspect ratio of the lines increases with the increase in the number of printing layers and the decrease in the speed of substrate. Silver lines with high aspect ratio of 1.7 with a width of about 25 μm were formed. This result is important for the formation of current-carrying microcircuits with a high density of elements. [ABSTRACT FROM AUTHOR]

A simple unipolar needle-plate corona charger (NPC) was designed, fabricated and tested on aerosol Al2O3 particles in the size range 75-500 nm. The intrinsic charging efficiency, particle electrostatic losses, and extrinsic charging efficiency were investigated depending on the corona current (35-215 µA), corona polarity, and aerosol flow rate (12-250 l/min). It was found that the intrinsic charging efficiency of the NPC is growing with increase in the corona current and the particle size and decrease in the aerosol flow rate. However, the extrinsic charging efficiency is lower than intrinsic one due to the particle electrostatic losses. Although the NPC has very simple design, it provides the extrinsic charging efficiency comparable with that of unipolar corona chargers of other types having more complicated design. The maximum value of the extrinsic charging efficiency was more than 40% for particles in the size range from 98 to 210 nm. [ABSTRACT FROM AUTHOR]

We proposed a novel method of nanostructure preparation for observation of surface-enhanced Raman spectroscopy (SERS) and metal-enhanced fluorescence (MEF) based on the deposition of gold nanoparticles (GNPs) above the thin dye film by dry aerosol printing. We detected various enhanced SERS and MEF signals of films of malachite green (MG) and rhodamine B (RhB) mixtures, depending on the surface packing density of Au NPs on the strip, and found the optimum one to achieve the 3.5 × 105 SERS enhancement. It was shown that statistical methods of chemometrics such as projection on latent structures provided the opportunity to distinguish SERS of MG from 100 ppm RhB in a mixture, whereas separation of MEF signals are feasible even for a mixture of MG and 1 ppm RhB due to two-photon excitation. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the interaction of nanosecond pulsed-periodic infrared (IR) laser radiation at a 50 and 500 Hz repetition rate with aerosol platinum (Pt) and silver (Ag) nanoparticles agglomerates obtained in a spark discharge. Results showed the complete transformation of Pt dendrite-like agglomerates with sizes of 300 nm into individual spherical nanoparticles directly in a gas flow under 1053 nm laser pulses with energy density 3.5 mJ/cm2. Notably, the critical energy density required for this process depended on the size distribution and extinction of agglomerates nanoparticles. Based on the extinction cross-section spectra results, Ag nanoparticles exhibit a weaker extinction in the IR region in contrast to Pt, so they were not completely modified even under the pulses with energy density up to 12.7 mJ/cm2. The obtained results for Ag and Pt laser sintering were compared with corresponding modification of gold (Au) nanoparticles studied in our previous work. Here we considered the sintering mechanisms for Ag, Pt and Au nanoparticles agglomerates in the aerosol phase and proposed the model of their laser sintering based on one-stage for Pt agglomerates and two-stage shrinkage processes for Au and Ag agglomerates. [ABSTRACT FROM AUTHOR]

This study investigates the processes of interaction of nanosecond pulsed-periodic laser radiation with the flow of aerosol agglomerates of gold nanoparticles synthesized in a spark discharge. Nanoparticles in a gas flow are spatially separated nano-objects whose interaction with each other and with the walls of an experimental cell was insignificant. Therefore, the energy absorbed by nanoparticles was used only for their own heating with further shape and size modification and on heat transfer to the surrounding gas. In the research, we used laser radiation with wavelengths of 527 and 1053 nm at pulse energies up to 900 µJ and pulse repetition rates up to 500 Hz. The dynamics of changes in the nanoparticles size during their sintering process depending on the laser pulses energy is characterized by an S-shaped shrinkage curve. Complete sintering of the initial agglomerates with their transformation into spherical nanoparticles is achieved by a series of impacting laser pulses. The result of nanoparticles' laser modification is largely determined by the pulse energy and the efficiency of the nanoparticles' radiation absorption. [ABSTRACT FROM AUTHOR]

Printing nano-ink with platinum nanoparticles to generate conductive microstructures for electronics on different types of substrates has gained increasing interest in recent years. To solve the problem of the low conductivity of platinum (Pt) nano-ink, we synthesized chemically pure Pt nanoparticles with sizes of 18.2 ± 9.0 nm by spark discharge method. A low toxic solvent, ethylene glycol with water, was used to ensure the aggregation stability of Pt nanoparticles. Polyvinylpyrrolidone was used as an adhesive additive and binder in the nano-ink. Narrow and conductive Pt lines were generated by aerosol jet printing technology. The resistivity of the Pt lines sintered at 750 °C on alumina substrate was found to exceed the bulk Pt by about 13%. Moreover, the Pt film fabricated on polymer substrates has demonstrated excellent mechanical flexibility in terms of twisting tests. [ABSTRACT FROM AUTHOR]