Printing metal nanowires are particularly attractive as compared to conventional coating methods due to the ease of processing, direct patterning, and large-scale fabrication capability. However, it is still challenging to print metal nanowire patterns that simultaneously have high conductivity, high transparency, flexibility, and stretchability. Three steps have been taken in this work to balance the transparency and conductivity of the screen-printed flexible and stretchable silver nanowire films, (1) selection of the ink formulation, (2) optimization of the printing parameters, and (3) posttreatment with a laser. The as-obtained silver nanowire patterns are large-area and demonstrate an ultralow sheet resistance of 1.9 ohm/sq, high transmittance (73%) at the wavelength of 550 nm, and an ultrahigh figure of merit (~136) as compared to the printed silver nanowire electrodes in the literature. The screen-printed transparent patterns exhibit excellent electrical stability and mechanical repeatability when subjected to 1000 bending cycles with a bending radius of 28 mm and 1000 stretch-release cycles with 10% strain, which makes the transparent patterns suitable for the fabrication of flexible, transparent microwave absorbers. The absorption performance of the prepared frequency selective surface absorbers indicates no obvious degradation after various manipulating configurations and multiple bending and stretching cycles. The results are promising enough to make this ink and screen-printing process suitable for many applications of flexible, stretchable, and transparent electronics.

This paper proposes a single-layer, dual-band, optically transparent frequency selective surface (FSS) for GSM shielding. The design evolves from a fractal cross dipole to achieve dual band response, polarization insensitivity and wide angle of incidence stability with a miniaturized size. A two-axis symmetric structure helps to provide a stable frequency response for incident waves with different polarization angles up to 60°. Capacitive loading further reduces the unit size and extends the maximum stable incident angle. The working mechanism of the design has been explained through an equivalent lumped element circuit model (ECM), which provides a generic approach to retune or optimize the design for another frequency band. Both the full-wave EM and circuit simulations are in good agreement. A prototype has been realized by screen-printing a custom silver nanowires (Ag NWs) based transparent ink on a flexible polymer substrate. A decent reflection performance has been achieved from 0.71 to 1.25 GHz and from 1.73 to 2.16 GHz in measurements, which are consistent with the simulations. Optical measurements reveal a transparency of 81.6%. Printed FSS is completely flexible and the performance does not deteriorate after bent or rolled up conditions. Field testing on a glass box demonstrate decent shielding from the incoming GSM signals. The highly transparent and flexible nature of the FSS structure makes it suitable for mounting on glass windows of cars or home environments for EM shielding purposes.

Silver nanowires (Ag NWs) possess excellent optoelectronic properties, which have led to many technology-focused applications of transparent and flexible electronics. Many of these applications require patterning of Ag NWs into desired shapes, for which mask-based and printing-based techniques have been developed and widely used. However, there are still several limitations associated to these techniques. These limitations, such as complicated patterning procedures, limited patterning area, and compromised optical transparency, hamper the efficient fabrication of high-performance Ag NW patterns. Here, we propose a coat-and-print approach for effectively patterning Ag NWs. We printed a polymer-based ink on the spin-coated Ag NW films. The ink acts as a protective layer to help remove excess Ag NWs from the substrate and then dissolves itself into an organic solvent. In this way, we can take advantage of both coating-based techniques (lead to Ag NWs with high transparency) and printing-based techniques (efficiently pattern diverse shapes). The resultant Ag NW patterns exhibit comparable conductivity (sheet resistance: 7.1 to 30 Ohm/sq) and transparency (transmittance: 84 to 95% at λ = 550 nm) to those made by conventional coating methods. In addition, the patterned Ag NWs exhibit robust mechanical stability and reliability, surviving extensive bending and peeling tests. Due to higher conductivity, efficient patterning ability and inherent transparency, this material system and application method is highly suitable for transparent and flexible electronics. As a proof of concept, this research demonstrates a wide-band antenna, operating in the mm-wave range that includes the 5G communication band. The proposed antenna exhibits a wide bandwidth of 26 GHz (from 17.9 GHz to 44 GHz), robust return loss under 1000 cyclic bending (bending radius of 3.5 mm), and decent transparency over the entire visible wavelength (86.8% transmittance at λ = 550 nm). This work’s promising results indicate that this method can be adapted for roll-to-roll manufacturing to efficiently produce patterned and optically transparent devices.

A flexible, wideband, and screen-printed antenna is proposed. The antenna is coplanar-waveguide (CPW) and composed of two inverted L-shape elements, a matching stub, and a defected ground structure (DGS), with a total area of 55 40 0.125 mm3. Studies show that the DGS can significantly increase the antenna bandwidth from 30% to 119% without sacrificing the size. The antenna has a wide measured bandwidth of 1.77 - 6.95 GHz, and a measured peak gain and efficiency in the ranges of 2.5-5.9 dBi and 60%-90%, respectively. Furthermore, both simulation and measurement confirm that the performance of the antenna is relatively stable under the bending conditions with various curvature radii.

Smart materials that can change their properties based on an applied stimulus are in high demand due to their suitability for reconfigurable electronics, such as tunable filters or antennas. In particular, materials that undergo a metal–insulator transition (MIT), for example, vanadium dioxide (VO₂) (M), are highly attractive due to their tunable electrical and optical properties at a low transition temperature of 68 °C. Although deposition of this material on a limited scale has been demonstrated through vacuum-based fabrication methods, its scalable application for large-area and high-volume processes is still challenging. Screen printing can be a viable option because of its high-throughput fabrication process on flexible substrates. In this work, we synthesize high-purity VO₂ (M) microparticles and develop a screen-printable VO₂ ink, enabling the large-area and high-resolution printing of VO₂ switches on various substrates. The electrical properties of screen-printed VO₂ switches at the microscale are thoroughly investigated under both thermal and electrical stimuli, and the switches exhibit a low ON resistance of 1.8 ohms and an ON/OFF ratio of more than 300. The electrical performance of the printed switches does not degrade even after multiple bending cycles and for bending radii as small as 1 mm. As a proof of concept, a fully printed and mechanically flexible band-pass filter is demonstrated that utilizes these printed switches as reconfigurable elements. Based on the ON and OFF conditions of the VO₂ switches, the filter can reconfigure its operating frequency from 3.95 to 3.77 GHz without any degradation in performance during bending.