A Wearable Wireless Energy Link for Thin-Film Batteries Charging

Abstract

A wireless charger for low capacity thin-film batteries is presented. The proposed device consists of a nonradiative wireless resonant energy link and a power management unit. Experimental data referring to a prototype operating in the ISM band centered at 434 MHz are presented and discussed. In more detail, in order to facilitate the integration into wearable accessories (such as handbags or suitcases), the prototype of the wireless energy link was implemented by exploiting a magnetic coupling between two planar resonators fabricated by using a conductive fabric on a layer of leather. From experimental data, it is demonstrated that, at 434 MHz, the RF-to-RF power transfer efficiency of the link is approximately 69.3%. As for the performance of the system as a whole, when an RF power of 7.5 dBm is provided at the input port, a total efficiency of about 29.7% is obtained. Finally, experiments performed for calculating the charging time for a low capacity thin-film battery demonstrated that, for RF input power higher than 6 dBm, the time necessary for recharging the battery is lower than 50 minutes.

Detecting Load Resistance and Mutual Inductance in Series-Parallel Compensated Wireless Power Transfer System Based on Input-Side Measurement

“…Assuming c = R 2 − λωL 2 = 0, λ = R 2 /ωL 2 > 0 and a = ωC 2 ωR 2 C 2 + λ 1 − ω 2 L 2 C 2 > 0 can be obtained. Solving (5), there are one zero root and one negative root for R L ; therefore this case is not existing.…”

“…When the operating frequency ω is higher than the receiving-side resonant frequency ω 2 (i.e., ω 2 = 1/ L 2 C 2 ), the numerical analysis indicates that there are two sets of positive roots in (5). For example, the same circuit parameters as listed in Section 4 are used, and the receiving-side resonant frequency is 209.6 kHz.…”

“…Recently, WPT has been extensively applied in household appliances, robotics, portable electronic products, underwater equipment, implantable medical devices, and electric vehicle charging [4][5][6][7][8] because of its convenience, flexibility, reliability, and safety.…”

Fully-Textile, Wearable Chipless Tags for Identification and Tracking Applications

“…Because clothing can be adapted to everyday life, wearables (combined with smart textiles) are arguably the best candidates to facilitate this process, possibly becoming the next interface between the real and the digital world [7]. As a result, the development of wearables that could allow to effectively engage the user into the IoT sensory environment without compromising their comfort has become a major interest of applied research [8][9][10]. Nevertheless, despite its potential, the use of wearable electronics has been hindered by some practical limitations, such as its robustness to basic but severe operations (e.g., washing, ironing) [11,12] and the need to tin solder the necessary integrated circuitry (IC).…”

Durability of Wearable Antennas Based on Nonwoven Conductive Fabrics: Experimental Study on Resistance to Washing and Ironing

“…As per the substrate, it is possible to employ materials that are typically used in the clothing industry, such as cotton, jeans, and pile, while, for implementing the conductive parts of the antenna, the use of different materials has been proposed and tested in the literature . Among these, particularly attractive are (i) nonwoven conductive fabrics (NWCFs) [12][13][14][15][16][17][18], (ii) conductive threads [19][20][21][22][23][24][25][26][27], and (iii) electrotextiles [28][29][30][31][32][33].…”