Printable Silver Nano Ink for Bendable Ultrawideband Antenna with Triple-Notch Characteristics

Flexible antennas based on the printed flexible electronic technology are of great interest for important applications in wireless communication systems due to their distinctive features over traditional rigid-based antennas. The ultrawideband (UWB), notch characteristics, and bending capabilities of such antennas are crucial for flexible and wearable applications. Currently, only a few are focused on the printed flexible electronics technology with printable ink materials for UWB antenna applications. In addition, flexible UWB antennas with triple-notch characteristics and good bending performance are rarely reported. Thus, there is a need to make advances in this area. Here, we describe the application of a printable silver nanoparticle-based ink for rapidly fabricating an antenna with bendable and triple-notch characteristics designed for UWB communication systems. The ink, composed of monodisperse silver nanoparticles, isopropanol, and ethyl glycol, can easily produce favorable conductive patterns at a sintering temperature below 130 °C after inkjet printing. The antenna is designed on a flexible polyethylene terephthalate (PET) substrate and has a moderate size of 27 mm × 38 mm × 0.12 mm. It operates at a frequency range of 1.9–10.75 GHz, which covers the desired UWB frequency band. By loading a “U”-like slot and two “C”-like slots on the radiating patch, band rejections were generated at 3.2–3.8, 5.3–6.2, and 7.8–8.5 GHz, shielding the interference from world interoperability for microwave access, wireless local area networks, and X uplink bands. The bending results show that the antenna retains good UWB and triple-notch performance even after bending along the Y - or X -axis for different degrees. An antenna prototype was finally fabricated by inkjet printing of the silver nano ink on the PET substrate, exhibiting the desired notch characteristics and excellent bendability. The fabricated antenna prototype proved the feasibility of use as a flexible device at an ultrawide frequency band. The research provides a design guide for flexible antennas with notch features toward flexible and wearable electronics.