Porous textile antenna designs for improved wearability

Abstract

Textile antennas are an integral part of the next generation personalized wearable electronics system. However, the durability of textile antennas are rarely discussed in the literature. Typical textile antennas are prone to damage during normal wearable user scenarios, washing, and heat cycling over time. Fabricating a durable, washable, flexible, and breathable (like textile materials) antenna is challenging due to the incompatibility of the mechanical properties of conductive materials and soft textile materials. This paper describes a scalable screen printing process on an engineered nonwoven substrate to fabricate microstrip patch antennas with enhanced durability. This work used an Evolon® nonwoven substrate with low surface roughness (∼Ra = 18 μm) and high surface area (∼2.05 mm2 mm−2 of fabric area) compared to traditional textile materials, which allows the ink to penetrate evenly in the fiber bulk with its strong capillary wicking force and enhances print resolution. The composite layer of ink and fiber is conductive and enables the antennas to maintain high mechanical flexibility without varying its RF (Radio Frequency) properties. Additionally, the antennas are packaged by laminating porous polyurethane web to make the device durable and washable. The fully packaged antennas maintain the structural flexibility and RF functionality after 15 cycles of washing and drying. To improve the air permeability and enhance flexibility the antenna is also modified by incorporating holes in the both patch and ground layer of the antenna. The antennas were analyzed before and after submerging in water to observe the effect of wetting and drying with respect to frequency response. The porous antenna with holes recovered 3x times faster than the one without holes (solid) from fully wet state (saturated with water) to the dry state, demonstrating its potential use as a moisture sensor system.

Kirigami‐Inspired Textile Electronics: K.I.T.E.

“…Printing technology and its associated methods show promise as a postprocessing approach to compensate for the limitations in the integration of conductive fibers and yarns. By printing with conductive inks, researchers have developed functional materials for flexible electronics such as strain sensors, wearable antennas, electrocardiogram sensors, electromyography sensors, and energy harvesting devices . However, all these techniques utilize rigid conductive materials whose mechanical properties vastly differ from the integrated soft textile platform.…”

Inkjet Process for Conductive Patterning on Textiles: Maintaining Inherent Stretchability and Breathability in Knit Structures

“…While wearable technology is a highly intriguing and interdisciplinary field both in academic research and industry, incorporating desired properties of materials and efficient processing techniques is crucial and challenging . Achieving high electrical conductivity is not the only goal in wearable electronics, since maintaining flexibility, breathability, permeability, and durability, which are fundamental features, is characteristic to the textile itself to consider for the use case scenario …”

Recent Advances of Wearable Antennas in Materials, Fabrication Methods, Designs, and Their Applications: State-of-the-Art

“…In [ 183 ], a highly conductive patch antenna was designed using composite materials like graphene, polyaniline (PANI), and PDMS on textile material. Furthermore, an active and screen-printed antenna was designed on non-woven material (Evolon) [ 184 ]. The conductive ink was equally spread on the substrate material.…”