Sustainable functional finishing for cotton fabrics using screen-printing process and gallotannin

To seek a more environmentally friendly textile finishing technique, the screen-printing method was adopted to apply functional material to cotton fabrics. In addition, gallotannin was used as a functional material because it is naturally abundant in many plant-derived substances and shows various health-promoting features such as antimicrobial, antioxidant, and other attractive properties. Therefore, a gallotannin/thickener paste was applied to the surface of cotton fabrics through the screen-printing technique, and the gallotannin-printed cotton fabrics were thoroughly investigated using scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), and other methods. The gallotannin printed area was substantially brown in appearance, and gallotannin moiety appeared to combine with cotton cellulose through heat treatment. Furthermore, functional properties of the gallotannin-printed cotton fabrics were examined in terms of antibacterial activity, deodorizing property, and ultraviolet-blocking property, of which it demonstrated excellent abilities. However, the antibacterial ability toward Gram-negative bacteria (K. pneumoniae) decreased as the laundry cycle increased.

The pursuit of further miniaturization of screen printed micro paper-based analytical devices utilizing controlled penetration towards optimized channel patterning

One of the main objectives of microfluidic paper-based analytical devices is to present solutions particularly, for applications in low-resource settings. Therefore, screen-printing appears to be an attractive fabrication technique in the field, due to its overall simplicity, affordability, and high-scalability potential. Conversely, the minimum feature size attained using screen-printing is still rather low, especially compared to other fabrication methods, mainly attributed to the over-penetration of hydrophobic agents, underneath defined patterns on masks, into the fiber matrix of paper substrates. In this work, we propose the use of the over-penetration to our advantage, whereby an appropriate combination of hydrophobic agent temperature and substrate thickness, allows for the proper control of channel patterning, rendering considerably higher resolutions than prior arts. The implementation of Xuan paper and nail oil as novel substrate and hydrophobic agent, respectively, is proposed in this work. Under optimum conditions of temperature and substrate thickness, the resolution of the screen-printing method was pushed up to 97.83 ± 16.34 μm of channel width with acceptable repeatability. It was also found that a trade-off exists between achieving considerably high channel resolutions and maintaining high levels of repeatability of the process. Lastly, miniaturized microfluidic channels were successfully patterned on pH strips for colorimetric pH measurement, demonstrating its advantage on negligible sample-volume consumption in nano-liter range during chemical measurement and minimal interference on manipulation of precious samples, which for the first time, is realized on screen-printed microfluidic paper-based analytical devices.

Development and Characteristics of Multipurpose Transparent Polyurethane Film

In industry, recent research developments include flexible films and foldable films. The next step is the development of stretchable films, and studies are being intensively carried out. Research on the development of stretchable and transparent materials is also increasing greatly. Currently, polydimethylsiloxane (PDMS) is the most commonly used film in the industry. However, PDMS surfaces are hydrophobic, so their use is limited to making materials and compounds with hydrophilic properties. In this study, we developed a transparent polyurethane film that can be used for multiple purposes. A transparency comparison between the transparent polyurethane film and the general polyurethane film was used to verify their future application. The conventional polyurethane films showed a transmittance rate of 2.2 percent, but the transparent polyurethane films achieved a high transmittance rate of 85 percent. To determine whether the film can be realized, we produced a conductive paste using resin for the transparent polyurethane film. In addition, a conductive paste was made based on the material used in the transparent polyurethane film to verify the hardness and reliability of the adhesion of electrodes, and we confirmed this with thermogravimetric analysis (TGA). The transparent polyurethane based paste was made with stretchable electrodes through a screen printing method. The manufactured stretchable electrodes were demonstrated by mechanical and adhesion tests. Finally, a permittivity test was conducted to determine the suitability of the film for application to printed electrodes for antennas in the future. The genetic rate of transparent polyurethane films was better than that of conventional polyurethane films. Moreover, the adhesion of the transparent polyurethane film and stretchable electrodes was as good as that of conventional polyurethane film and stretchable electrodes, and observation by optical microscopy confirmed that the printing performance was also excellent. In addition, the conductive paste made based on the transparent polyurethane film material was cured for 1 hour at 120 °C, and TGA analysis confirmed that both the binders and curing agent responded well in the test for curing the developed stretchable electrodes and transparent polyurethane.

Modifying Precursor Solutions to Obtain Screen-Printable Inks for Tungsten Oxides Electrochromic Film Preparation

Tungsten trioxide (WO3) is used to prepare the important electrochromic layer of the electrochromic device as a wide bandgap semiconductor material. In this study, WO3 electrochromic film was successfully prepared by screen printing. To modify the thixotropy and wettability of the ink, polyvinyl alcohol (PVA) and 2-perfluoroalkyl ethanol (FSO) were added in the ammonium meta-tungstate (AMT) solution. We found that the PVA additive could improve the dynamic viscosity of the solution and modify the uniformity of the film. 2-Perfluoroalkyl ethanol (FSO) could lower the surface tension and increase the wettability of the AMT solution on the substrate. By observing the morphology of the printed films, the ink formulas for screen printing were selected. We found the annealing process could help remove PVA. Through characterization of electrochromic performance, it was found that the best performing device had 42.57% modulation and 93.25 cm2·C−1 coloration efficiency (CE) for 600 nm light. This study showed great potential in the preparation of WO3 electrochromic devices by a low-cost screen-printing method.

Enhancing Formaldehyde Selectivity of SnO2 Gas Sensors with the ZSM-5 Modified Layers

High performance formaldehyde gas sensors are widely needed for indoor air quality monitoring. A modified layer of zeolite on the surface of metal oxide semiconductors results in selectivity improvement to formaldehyde as gas sensors. However, there is insufficient knowledge on how the thickness of the zeolite layer affects the gas sensing properties. In this paper, ZSM-5 zeolite films were coated on the surface of the SnO2 gas sensors by the screen printing method. The thickness of ZSM-5 zeolite films was controlled by adjusting the numbers of screen printing layers. The influence of ZSM-5 film thickness on the performance of ZSM-5/SnO2 gas sensors was studied. The results showed that the ZSM-5/SnO2 gas sensors with a thickness of 19.5 μm greatly improved the selectivity to formaldehyde, and reduced the response to ethanol, acetone and benzene at 350 °C. The mechanism of the selectivity improvement to formaldehyde of the sensors was discussed.

Miniaturization and Electromagnetic Reliability of Wearable Textile Antennas

The wearable textile antenna plays a decisive role in the currently increasingly wireless communication network area. To realize the miniaturization and electromagnetic reliability, a slotted full-textile microstrip antenna was designed and fabricated using the screen printing method. The measured return loss and radiation pattern were tested and compared with the simulated results. Additionally, the adhesion between the silver paste coating as the radiation element and the textile substrate was detected using sticking tape as well as observation by the microscope. To develop the designed antenna in the on-body application, the artificial magnetic conductor (AMC) was designed, optimized and fabricated. The antenna performance results showed that the existence of the AMC had a significant effect in reducing the body coupling and antenna backward radiation.