This article presents a method for the development of an exhalation sensor consisting of a printed conductive cantilever that was embedded into the sponge part of a headset microphone. The cantilever was printed onto the sponge surface by using a printing method based on a technique known as Lift-On Offset Printing and was improved to achieve strong adhesion between the ink layer and the roughness of the sponge surface. The sensor clearly changed its capacitance in correspondence to the user’s exhalation distinguishing the user’s states. The developed sensor can be used to monitor a user’s health condition for improved safety.

Ga-doped zinc oxide (GZO) transparent conducting thin films were prepared by a polymer-assisted solution (PAS) process. The Ga concentration in the film was varied from 1 to 5 at.% by adjusting the mixing ratio of Zn- and Ga-source solutions formulated by coordinating Zn- and Ga-anionic complexes with a water-soluble polymer. The GZO-source solutions were spin-coated on glass substrates and heat-treated at elevated temperatures. The optimum Ga concentration was investigated by analyzing the electrical and optical properties of the PAS-coated films. The GZO film with 1 at.% Ga showed the lowest resistivity of 7.49 × 10⁻²Ω-cm and an optical transmittance of 85% at 550 nm with a film thickness of 107 nm. X-ray diffraction analysis revealed that the PAS-coated GZO films had the wurtzite crystal structure with a preferred orientation of (002). Higher post-annealing temperatures resulted in larger grain sizes and discontinuities were observed among the grains in the films. Multiple spin-coating steps were employed to increase the film thickness, resulting in the reduction in the sheet resistance of the PAS-coated GZO films from 7.0 kΩ∕sq. (single layer of GZO) to 0.7 kΩ∕sq. (four layers of GZO) without noticeable reduction in film transmittance.

In this study, the authors propose a new design for an external counter electrode for electrohydrodynamic (EHD) printing by considering two important aspects: robustness of EHD jetting and real-time monitoring for jetting reliability. For this purpose, the authors investigated the EHD jetting behavior in both cases: the external counter electrode positioned below and that positioned above the nozzle tip. It is well known that the ring electrode should be symmetric around the nozzle tip to ensure jet straightness. However, they found that a non-symmetric electrode can also produce straight jetting in the case when the external electrode is installed above the nozzle tip. In this way, real-time jetting monitoring based on the external camera view can be implemented by cutting part of the electrode without affecting jetting performance.

The authors report that the conversion of the charge-transfer characteristics in benzodithiophene–thiadiazoloquinoxaline (BDT-TAQ)-based donor (D)–acceptor (A) semiconducting copolymer, wherein the BDT moiety functions as the donor part and the TAQ block functions as the acceptor unit, is possible by adding trifluoromethyl groups to the TAQ-acceptor unit. The charge-transport characteristics of the BDT-TAQ films were investigated using a transistor platform, where the semiconducting films served as the active channel layer. The BDT-TAQ-based polymeric thin-film transistors (PTFTs) clearly show ambipolar characteristics that enable both electron and hole transport in the semiconducting polymer channel. By contrast, the PTFTs with BDT-TAQ-CF₃ as an active layer exhibit only n-type transport characteristics. These results suggest that the trifluoromethyl groups added to the acceptor unit of the BDT-TAQ-based D–A semiconductor copolymer change (reduce) the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the semiconductor copolymer film.

In 1892, in his classical work, L. Rayleigh considered the instability of a cylinder of viscous liquid under capillary force, the so-called Plateau–Rayleigh instability. In this work, in linear approximation, he obtained a dispersion equation describing the increment of this instability as a function of wavelength, the radius of cylinder, the mass density, surface tension, and viscosity of the liquid. Hundreds of authors referred to this work, but none of them used his dispersion equation in its complete form; they used only the asymptotic solutions of his equation for zero or infinitely large viscosities. A reason for this is, probably, that Rayleigh’s writing is difficult and his dispersion equation is quite complex. Then, in 1961, S. Chandrasekhar, in his monograph, also considered the stability of a viscous cylindrical jet and obtained his dispersion equation which is also quite complex and differs from the one obtained by Rayleigh. As in the case of Rayleigh’s dispersion equation, other works use only the asymptotic solution of Chandrasekhar’s equation that corresponds to the case where the viscosity is very large in comparison to inertia. In this article, the author demonstrates that Chandrasekhar’s dispersion equation is equivalent to Rayleigh’s and then simplifies their dispersion equations to a form which can be easily solved numerically for arbitrary values of viscosity. He also presents a Mathematica code to calculate the maximum increment of the Plateau–Rayleigh instability for given parameters of the jet. To illustrate how the code works, he applies it to a cylindrical jet to estimate its breakup.

This work demonstrated printed metallic bridge wire and spark gap igniters suitable for use with energetic materials. These devices were fabricated from an aqueous dispersion of silver nanoparticles on a flexible, mesoporous substrate using a piezoelectric inkjet printer. This manufacturing process resulted in precise samples fabricated without the need for thermal curing. Geometric parameters were varied for the devices to determine the design criteria of importance and to quantify the electrical excitation needed for optimal performance. The work successfully demonstrated the integration of bridge wires and spark gaps with energetic material to produce fully printed igniters that are of practical use in applications ranging from munitions to vehicle airbags.

The technological advancement in the field of printed electronics over roll-to-roll (R2R) platform has become very attractive, because of the several advantages such as mass production, large area application, cost-saving and high-speed capabilities. The inkjet technology, on the other hand, among other printing technologies promotes individualization and contact-less deposition process qualities. In this article, the authors demonstrate the state of the art R2R setup for printing silver (Ag) conductive patterns on PEN substrate using inkjet and infra-red technologies. The deposition of the conductive patterns was accomplished using a nanoparticle-based Ag ink and industrial printheads from Fujifilm Dimatix. The novelty of the research work is realization of a print setup, consisting of an industry relevant flexible printhead assembly and drop evaluation station, which are mounted over a R2R printing system. The entire setup allows the user to first evaluate the ejection of the droplets and then stabilize the print parameters without involving the web substrate, followed by re-positioning of the inkjet assembly back to the R2R printing system. The capability of the print setup is exhibited by varying the printing resolution for the defined digital patterns. In addition, the post-treatment of the conductive patterns was tailored with the implementation of an infra-red based sintering module from Heraeus Noblelight GmbH. The power density of the filaments from the sintering module was varied to achieve the maximum conductivity and to ensure no physical damage to the patterns and substrate. The results indicate that such a print setup is very flexible and can offer several benefits to the printing process of conductive patterns, e.g., obtaining line width below 80 μm and sheet resistance of about 0.5 Ω∕□, with the advantage of sintering the patterns within 20 s.

In this article, the author describes a set of models of particle transport in microchannels that has been recently developed at FUJIFILM Dimatix for design and optimization inkjet print heads. The models are used to estimate the modes of particle transport in horizontal channels, the times for particles to settle at the bottom of a channel, and the fluidization flow velocity. The Rouse number is commonly used to estimate the mode of sediment transport in horizontal turbulent flow with large Reynolds number. However, in microchannels such as in modern inkjet systems, the liquid flows are usually laminar. In this article, the author uses a modified Rouse number that is expanded to the case of weakly turbulent and laminar flows. To illustrate the applicability of the modified Rouse number, he applies it to the transport of pigment particles in a horizontal channel in the FUJIFILM inkjet print head and compares theoretical results with experimental observations. In the article, he also constructs a model to estimate two settling times in rectangular channels: the time of formation of a monolayer of particles at the bottom of a channel and the required time for all particles to settle at the channel bottom. In design and optimization of a print jet head, it is also important to know the critical fluidization flow velocity of the ink to prevent sedimentation of ink pigment particles in vertical channels. In this article, the author constructs a simple model to estimate the maximum fluidization flow velocity as well. The modified Rouse number constructed in this article, as well as presented models, can be used in other applications as well.