Flexible Wearable Tri-notched UWB Antenna Printed with Silver Conductive Materials

The advancement of Internet of Things and associated technologies has led to the widespread usage of smart wearable devices, greatly boosting the demand for flexible antennas, which are critical electromagnetic components in such devices. Additive manufacturing technologies provide a feasible solution for the creation of wearable and flexible antennas. However, performance reliability under deformation and radiation safety near the human body are two issues that need to be solved for such antennas. Currently, there are few reports on compact, flexible ultrawideband (UWB) antennas with more notch numbers, reliable bendability, and radiation safety. In this paper, a UWB antenna with trinotched characteristics for wearable applications was proposed and developed using printable conductive silver materials consisting of silver microflakes or silver nanoparticles. The antenna has a compact size of 18 × 20 × 0.12 mm³ and adopts a gradient feeder and a radiation patch with three folding slots. It was fabricated on transparent and flexible poly(ethylene terephthalate) film substrates, using screen printing and inkjet printing. The measurement results demonstrated that the fabricated antennas could cover the UWB band (2.35-10.93 GHz) while efficiently filtering out interferences from the C-band downlink satellite system (3.43-4.21 GHz), wireless local area networks (4.66-5.29 GHz), and X-band uplink satellite system (6.73-8.02 GHz), which was consistent with the simulation results. The bendability and radiation safety of the antennas were evaluated, proving their feasibility for usage under bending conditions and near the human body. Additionally, it was found that the screen-printed antenna performed better after bending. The research is expected to provide guidance on designing flexible antennas that are both safe to wear and easily conformable.