Flexible Wearable\nTri-notched UWB Antenna Printed\nwith Silver Conductive Materials

The advancement of Internet of Things and associated\ntechnologies\nhas led to the widespread usage of smart wearable devices, greatly\nboosting the demand for flexible antennas, which are critical electromagnetic\ncomponents in such devices. Additive manufacturing technologies provide\na feasible solution for the creation of wearable and flexible antennas.\nHowever, performance reliability under deformation and radiation safety\nnear the human body are two issues that need to be solved for such\nantennas. Currently, there are few reports on compact, flexible ultrawideband\n(UWB) antennas with more notch numbers, reliable bendability, and\nradiation safety. In this paper, a UWB antenna with trinotched characteristics\nfor wearable applications was proposed and developed using printable\nconductive silver materials consisting of silver microflakes or silver\nnanoparticles. The antenna has a compact size of 18 × 20 ×\n0.12 mm<sup>3</sup> and adopts a gradient feeder and a radiation patch\nwith three folding slots. It was fabricated on transparent and flexible\npoly­(ethylene terephthalate) film substrates, using screen printing\nand inkjet printing. The measurement results demonstrated that the\nfabricated antennas could cover the UWB band (2.35–10.93 GHz)\nwhile efficiently filtering out interferences from the C-band downlink\nsatellite system (3.43–4.21 GHz), wireless local area networks\n(4.66–5.29 GHz), and X-band uplink satellite system (6.73–8.02\nGHz), which was consistent with the simulation results. The bendability\nand radiation safety of the antennas were evaluated, proving their\nfeasibility for usage under bending conditions and near the human\nbody. Additionally, it was found that the screen-printed antenna performed\nbetter after bending. The research is expected to provide guidance\non designing flexible antennas that are both safe to wear and easily\nconformable.