Deformation‐Resilient Embroidered Near Field Communication Antenna and Energy Harvesters for Wearable Applications

Abstract

E‐Textiles have gained increasing momentum in wearable electronics recently. Conductive‐yarn‐based embroidered devices, with the advantages of being soft, deformable, breathable, and protective for the skin, play an important role in replacing many metallic counterparts. However, embroidered devices face many new challenges in their design methodology and fabrication processes, such as high resistivity and low Q value of the conductive yarns, as well as deformation of device geometries during wearing. Herein, a strain‐free, deformation‐resilient embroidery process for near field communication (NFC) coil antennas is introduced. Coil geometry can endure extreme deformation by stretching with up to 50% elongation, bending with curvature as small as 16 mm in radius, and can still maintain a relatively small variation in its inductance, resonant frequency, Q value, as well as its energy‐harvesting capabilities. The embroidered coil antenna is used in an NFC‐based battery‐free body sensor system. Experiments demonstrate that the system can maintain a stable performance (voltage supply, temperature sensing, and reading range) under various deformation conditions.

A New Class of Electronic Devices Based on Flexible Porous Substrates

“…Other types of NG based on flexible porous substrates, including thermoelectric, [ 262 ] moist‐electric, [ 263 ] and near field communication‐based generators [ 264 ] can collect energy from human body waste heat, moisture, and magnetic fields. In addition, hybrid NGs can be manufactured by integrating multiple electrical energy conversion materials.…”

Electronic-components less fully textile multiple resonant combiners for body-centric near field communication

“…An experimental model to determine the antennas geometry versus the using constraint has been realized and expressed in Eqs. (14). Figure 7 shows the evolution of the inductance versus (a) the number of turns and (b) the radius where Nb is the number of turns and r (mm) is the radius of the coil.…”

“…This is made possible by a power adaptation of the different system components (relay/ combiner, source, and sensor node) very accurate. The three previous prototypes are quite different in their construction, the first 14 includes an additional capacity to reach a resonant frequency of 13.56 MHz, consequently, it is not fully textile. The second 15 focuses on the adaptation of intrinsic parameters to reach the resonant frequency without a precise characterization of energy and data transfer.…”

“…Finally, the military also uses these materials to improve its camouflage, communication, and protection capabilities 12,13 .Recent researches have highlighted the development possibilities of wearable sensor networks in textile materials. Lulu Xu et al 14 have developed a textile NFC coil, handling small fabric deformations, that is combined with an adapted solid-state capacitor to create an antenna resonating at 13.56 MHz. However, the addition of a classic capacitor makes the antenna none fully textile and requires few connection points.…”

Advances in Wearable Sensors: Signalling the Provenance of Garments Using Radio Frequency Watermarks

“…To counter the effects of fabric deformation and strain, two approaches are being pursued. Firstly, by using zigzag stiches during the embroidery process [ 18 ], the strain will be distributed evenly during elongation and stretching. In addition, by introducing a sine-wave modulation in the conventional spiral coil, the geometry deforms evenly in all directions with the least strain [ 19 ].…”