Nanocellulose based carbon ink and its application in electrochromic displays and supercapacitors.

Conventional electronics have been highlighted as an unsustainable technology; hazardous wastes are produced both during their manufacturing but also, due to their limited recyclability, during electronic end of life cycle (e.g., disposal in landfill). In recent years additive manufacturing processes have attracted significant interest as a more sustainable approach to electronic manufacturing. Despite the field of printed electronics addressing some of the issues related to the manufacturing of electronics, many components and inks are still considered hazardous to the environment and are difficult to recycle. Here we present the development of a low environmental impact carbon ink based on a non-hazardous solvent and a cellulosic matrix and its implementation in electrochromic displays and supercapacitors. As part of the reported work, a different protocol for mixing carbon and cellulose nanofibrils (CNF) (rotation mixing and high shear force mixing), nanocellulose of different grades and different carbon: nanocellulose ratio were investigated and optimized. The rheology profiles of the different inks showed good shear thinning properties, demonstrating their suitability for screen-printing technology. The printability of the developed inks was excellent and in line with those of reference commercial carbon inks. Despite the lower electrical conductivity (400 S/m for the developed carbon ink compared to 1000 S/m for the commercial inks), which may be explained by their difference in composition (carbon content, density and carbon derived nature) compared to the commercial carbon, the developed ink functioned adequately as the counter electrode in all screen-printed electrochromic displays and even allowed for improved supercapacitors compared to those utilizing commercial carbon inks. In this sense, the supercapacitors incorporating the developed carbon ink in the current collector layer had an average capacitance = 97.4 mF/cm2 compared to the commercial carbon ink average capacitance = 61.6 mF/cm2). The ink development reported herein provides a step towards more sustainable printed electronics.

Research on Frequency Doubling Effect of Thermoacoustic Speaker Based on Graphene Film

In this work, the frequency doubling effect of thermoacoustic speakers is studied, and a method is analyzed to suppress the frequency doubling effect. Three cases were analyzed by superimposing the DC bias on the AC excitation: (1) DC is less than AC; (2) DC is equal to AC; (3) DC is greater than AC. We found that the frequency doubling effect can be well suppressed by superimposing a larger DC excitation on the AC excitation. The laser scribing technology was used to prepare graphene film in only one step, and the screen printing technology was used to prepare conductive electrodes. The microphone and B&K system was used to record the sound pressure level and study the suppression of frequency doubling effect. Finally, the sound pressure levels with the three different kinds of excitations were measured. The measured results show that they have a good agreement with the theoretical results. The suppression effect will be better when DC amplitude is greater than AC amplitude. Therefore, this work has certain reference significance for the further study and application of thermoacoustic speakers.

High-Performance Temperature Sensor by Employing Screen Printing Technology

In the present study, a high-performance n-type temperature sensor was developed by a new and facile synthesis approach, which could apply to ambient temperature applications. As impacted by the low sintering temperature of flexible polyimide substrates, a screen printing technology-based method to prepare thermoelectric materials and a low-temperature heat treatment process applying to polymer substrates were proposed and achieved. By regulating the preparation parameters of the high-performance n-type indium oxide material, the optimal proportioning method and the post-treatment process method were developed. The sensors based on thermoelectric effects exhibited a sensitivity of 162.5 μV/°C, as well as a wide range of temperature measurement from ambient temperature to 223.6 °C. Furthermore, it is expected to conduct temperature monitoring in different scenarios through a sensor prepared in masks and mechanical hands, laying a foundation for the large-scale manufacturing and widespread application of flexible electronic skin and devices.

Approach to Performance Rating of Retroreflective Textile Material Considering Production Technology and Reflector Size

The study investigates retroreflective fabrics’ efficiency from the point of view of the interaction of their visibility, thermo-physiological comfort properties, and durability (represented by physical-mechanical performance). The effect of the combination of two production technologies (reflective transfer films and screen printing method) and two reflector covering sizes (25% and 85%) was examined. Technique for order of preference by similarity to ideal solution (TOPSIS) method was used to determine the best solution considering the abovementioned tested categories of properties. Retroreflective performance was in congruence with the used design coverage factor of the tested pattern. It was found that retroreflection of the tested pattern produced using screen printing technology was significantly lower than retroreflection of an identical pattern made by a transfer film. On the contrary, in terms of thermo-physiological comfort and physical-mechanical performance of the tested samples, screen printing technology shows significantly better results in almost all tested properties, especially in water vapor permeability, moisture management, and physical-mechanical performance. The solution for the abovementioned contradictory results can be achieved by using a combination of the advantages associated with each of these technology methods. Screen printing can be applied to specific regions of clothing that are exposed to extreme loading or sweating, and the transfer of film elements ensures high visibility with respect to the standards and biomotion principles that are deployed as prevalent benchmarks in the industry.

Description of a New Methodology for Baking Products from Wheat and Rye Flour by the Sour Dough Method

Introduction. The article presents the results of a study of using various methods for thermal processing of bakery products. It is shown that the infrared method is one of the most promising methods of heat treatment. The analysis showed that when combining different methods of heat treatment, the products retain their consumer qualities and the time of the technological cycle is reduced. The author proposes to use the method of thermal processing in the fast food industry. Materials and Methods. The subject of the study is a new method of thermal processing of bakery products made from wheat-rye flour using infrared radiation. For the study, a heating unit was manufactured in accordance with the patent for utility model No. 199820, where heating elements made using the grid-screen printing technology were installed; the performance of heating elements was controlled by a device with a PID controller of the TRM 148-T brand with an RS-485 interface. Results. The article shows that this method can be used to create a uniform product heating. The results of studies on the control of temperature conditions for baking bread are presented. It has been shown that the time of baking bread decreased by more than 25%, while the consumer quality of the product did not change. Discussion and Conclusion. The studies have shown that the use of the method for thermal processing opens up new opportunities for the fast food industry and other sectors of the national economy. The results of the study showed that together with a set of experimental data, this method will be possible to use in the individual sector and to carry out the intellectualization of the process of preparing various food products.

Semiconductor Oxide Gas Sensors: Correlation between Conduction Mechanisms and Their Sensing Performances

In this work, a variety of semiconducting oxides were prepared and principally characterized by means of spectroscopic techniques (absorbance FT-IR, diffuse reflectance UV-Vis-NIR) to shed light on the electronic properties and defects involved at the roots of gas sensing capabilities. The thick films were obtained by screen printing technology on which electrical characterization and gas sensing measurements were performed. From the cross analysis of the results, a description of the specific sensing mechanism for each material is proposed.

Fabrication and characterization of printed zinc batteries

Zinc batteries are a more sustainable alternative to lithium-ion batteries due to its components being highly recyclable. With the improvements in the screen printing technology, high quality devices can be printed with at high throughput and precision at a lower cost compared to those manufactured using lithographic techniques. In this paper we describe the fabrication and characterization of printed zinc batteries. Different binder materials such as polyvinyl pyrrolidone (PVP) and polyvinyl butyral (PVB), were used to fabricate the electrodes. The electrodes were first evaluated using three-electrode cyclic voltammetry, x-ray diffraction (XRD), and scanning electron microscopy before being fully assembled and tested using charge-discharge test and two-electrode cyclic voltammetry. The results show that the printed ZnO electrode with PVB as binder performed better than PVP-based ZnO. The XRD data prove that the electro-active materials were successfully transferred to the sample. However, based on the evaluation, the results show that the cathode electrode was dominated by the silver instead of Ni(OH)2, which leads the sample to behave like a silver-zinc battery instead of a nickel-zinc battery. Nevertheless, the printed zinc battery electrodes were successfully evaluated, and more current collector materials for cathode should be explored for printed nickel-zinc batteries.