Session 23: RF Technology
Direct-Write Flexible Meshed Patch Antenna on Nonwoven Material
Thursday, June 22, 2017
11:20 AM - 11:40 AM
Conformal and flexible radio frequency (RF) devices have drawn the interest for communication applications in wearable electronics, including sensing and health monitoring. Of particular interest is the use of a textile as a platform for these devices, but is challenged by the impact of the antenna design on the properties of the textile. This paper presents the fabrication of a meshed patch antenna on an Evolon® nonwoven textile by using a high-throughput direct-write process. For comparison, screen printed patch antennas on the same nonwoven fabric are first fabricated to demonstrate the effect of materials properties (effective permittivity of dielectric materials, conductivity the conductive ink) and impact of mechanical deformation on RF properties of printed antennas. While screen printing is a simple fabrication method for the textile patch antenna, the process can be limited by the excess use of the expensive conductive inks and the simple customization for the antenna design. As such, a direct-write process is employed as a method to improve the materials use efficiency and facilitate a facile customized design process. The challenge with printing on textiles is the poor resolution due to high surface roughness and surface energy of textile. In this work, Evolon® is used as the print media as this nylon-polyester fabric has a unique surface structure (high surface area & low surface roughness) in addition to having a high fluid absorption capacity. Therefore, the solvent of the particle based ink is absorbed very quickly by the high capillary pulling force of the fabric leaving the ink outer textile surface. Direct Jet printing of the conductive ink (DuPont) was performed used Nordson Asymtek Conformal Coating System with a delivery head speed of 50 mm/sec. In the formation of the grid-based antenna, the delivery fluid pressure is a critical process metric that affects the antenna’s resolution, which impacts the characteristic impedance and matching. For example, measured reflection co-efficient (S11) of the printed meshed antennas shows that the center frequency of the antennas changes with the change of fluid pressure used during printing process. A full wave electromagnetic simulation (HFSS) is done and compared with the experimented results which proves that, these printed meshed antennas can be modeled to resonate at desired frequency range. The direct-write printed mesh antennas on Evolon® are flexible and breathable having the ink coverage of only 47.47% of the patch area of antenna. Being porous and highly breathable in the conductor areas, these antennas provide a unique platform for textile-based sensors that are sensitive to the moisture and gasses in the surrounding environment.
Hasan Shahariar is a PhD student at North Carolina State University, where he is pursuing his degree with a major in Fiber and Polymer Science and minor in Electrical Engineering. He has received MS degree in Textile Engineering from the same university. His research interest is focused on development of functional materials and fabrication processes of printing devices for wireless communication and smart sensing applications.
North Carolina State University