With the increasing interest in research on the development of next-generation technologies such as flexible smartphones, displays, and wearable devices, interest in the development of materials and processes for transparent electrodes constituting them is also increasing. The most widely used material for manufacturing transparent devices is indium tin oxide (ITO). However, ITO is scarce, expensive, and brittle, making it is essential to replace it with new materials. In this study, we successfully fabricated a transparent electrode by electrospinning polyvinylpyrrolidone (PVP) and copper electroless deposition on the polyimide film. Especially, this study suggests a new combined heat treatment that uses both the hot plate and the convection oven. Through the combined heat treatment, the junctions between the nanofibers overlapped removed consequently reducing contact resistance. The mechanical stability of the fabricated electrode was evaluated by using a highly repeated bending test. Also, through the tape-peeling test, we confirmed that the adhesive strength of the electrode was high. This method can be applied to various polymer-based, substrate which are vulnerable to annealing process.

This study presents a transparent-patch antenna using a silver-mesh transparent electrode film with a high optical transmittance (87.7%), low haze (1.1%), and low sheet resistance (8.9 Ω/sq). The silver-mesh transparent electrode film is fabricated by using UV embossing and doctor blading without any high-temperature or vacuum processes. The UV resin pattern is transferred from a nickel mold to a plastic film, and then a silver paste is filled into the UV resin pattern. The transparent antenna patch and ground plane are obtained by repeating these processes on both sides of a single plastic film. The antenna patch is designed with a width of 44.8 mm and a height of 36.0 mm in order to obtain a resonant frequency at 2.45 GHz, which is a frequency of wireless LAN. As a result, the transparent-patch antenna has a reflection coefficient (S11 parameter) of -35.6 dB, a peak gain of -3.99 dBi, and a radiation efficiency of 6.2% at 2.45 GHz. Finally, a Wi-Fi router using the transparent-patch antenna is demonstrated.

Recently, the metal grid electrode drew attention as a flexible transparent conductive electrode for touch screen panels. In metal grid electrodes, various shapes of grid patterns were used to avoid the moiré phenomenon. In this study, we investigated the effects of the metal grid shapes - such as the honeycomb, diamond, and square - on the flexibility and durability of the metal grid film using an experimental and numerical analysis. The flexibility of the metal grid film was evaluated via the following: bending, cyclic bending fatigue and stretching tests; it was compared with the numerical stress analysis. In the bending test, the resistance of the honeycomb grid sample increased by 10% at a bending radius of 10 mm. On the other hand, the diamond grid showed almost no change in resistance up to a bending radius of 6 mm. When the substrate was stretched to 5%, many cracks appeared on the surface of the honeycomb pattern sample. On the other hand, no cracks were found in the diamond pattern sample. Therefore, the diamond pattern exhibited superior flexibility and durability to the honeycomb pattern. The numerical stress analysis also showed that the honeycomb pattern had the highest stress and the diamond pattern had the lowest stress during bending and stretching, which corresponded with the experimental results.