SkinAid: A Wirelessly Powered Smart Dressing Solution for Continuous Wound-Tracking Using Textile-Based Frequency Modulation.

In this article, SkinAid, a battery-free, low-cost, robust, and user-friendly smart bandage for electrochemical monitoring and sensing of chronic wounds is proposed. The working principle of the bandage is based on direct frequency modulation of a tri-electrode electrochemical sensing of wound data. The electronics and biotelemetry links were realized using low-cost manufacturing process of textile embroidery onto fabric substrate. The transmitter was represented by a bedsheet with novel corrugated crossed-dipole made of Elektrisola-7 embroidered onto gauze fabric. An input RF signal of 1 W was transmitted at 462 MHz from the bedsheet to the all-textile bandage featuring a rectifying circuit, a voltage-controlled oscillator (VCO), an electrochemical sensor, and a 915-MHz dipole for re-transmission of the modulated wound data. We demonstrate that for wound fluid emulated by various uric acid concentrations from 0.2 mM to 1.2 mM, corresponding modulated frequency varies from 1090 MHz to 1145 MHz for signals captured at 25 cm away from the bandage. For pH modulation ranging from 2 to 10, the corresponding modulated frequency was between 800 MHz and 830 MHz for signals received at more than 6 feet away from the bandage. For quick and reliable assessment, two empirical models were developed for the direct frequency modulation as a function of uric acid and pH. To the best of our knowledge, this is the first time an all-textile (fabric-integrated), battery-free and wirelessly powered smart bandage have been proposed for wound monitoring. This result can be used as a first step in developing RFID-type, battery-free, and low-cost 5G/6G smart bandages using millimeterwave and terahertz frequencies where the bedsheet can be host to a MIMO-aided beamforming.

Generation of vector vortex wave modes in cylindrical waveguides.

In this paper, we propose a method to generate Vector Vortex Modes (VVM) inside a metallic cylindrical waveguide at microwave frequencies and demonstrate the experimental validation of the concept. Vector vortex modes of EM waves can carry both spin and orbital angular momentum as they propagate within a tubular medium. The existence of such waves in tubular media can be beneficial to wireless communication in such structures. These waves can carry different orbital angular momentum and spin angular momentum, and therefore, they feature the ability to carry multiple orthogonal modes at the same frequency due to spatial structure of the phase and polarization. In essence, high data rate channels can be developed using such waves. In free space, Orbital Angular Momentum carrying vortex waves have beam divergence issues and a central field-minima, which makes these waves unfavorable for free space communication. But vector vortex mode waves in guided structures do not suffer from these drawbacks. This prospect of enhancement of communication spectrum in waveguides provides the background for the study of vortex wave in circular waveguides. In this work, new feed structures and a radial array of monopoles are designed to generate the VVM carrying waves inside the waveguide. The experimental findings on the distribution of the amplitude and phase of the electromagnetic fields inside the waveguide are presented and the relationship between the waveguide fundamental modes and VVMs are discussed for the first time. The paper also presents methods for varying the cutoff frequency of the VVMs by introducing dielectric materials in the waveguide.

Adhoc mobile power connectivity using a wireless power transmission grid.

Wireless charging of devices has significant outcomes for mobile devices, IoT devices and wearables. Existing technologies consider using Point to Point type wireless transfer from a transmitter Tx (node that is sending Power) to a receiver Rx (node that receives power), which limits the area of coverage for devices. As a result, existing systems are forced to use near field coupling to charge such devices. Fundamental limitation is also that such methods limit charging to a small hotspot. In partnership with Wireless Electrical Grid LANs (WiGL pronounced "wiggle"), we demonstrate patented Ad-hoc mesh networking method(s) to provide wireless recharging at over 5 feet from the source, while allowing significant lateral movement of the receiver on the WiGL (Wireless Grid LAN or local area network). The transmitter network method leverages a series of panels, operating as a mesh of transmitters that can be miniaturized or hidden in walls or furniture for an ergonomic use. This disruptive technology holds the unique advantage of being able to provide recharging of moving targets similar to the cellular concept used in WiLAN, as opposed to prior wireless charging attempts, which only allow a hotspot-based charging. Specifically, we demonstrate the charging of a popular smartphone using the proposed system in the radiating near field zone of the transmitter antennas, while the user is free to move in the space on the meshed network. The averaged received power of 10 dBm is demonstrated using 1W RF-transmitter(s), operating in the 2.4 GHz ISM band. The proposed hardware consists of antennas arrays, rectennas, power management and USB 2.0 interfaces for maintaining a voltage between 4.2 and 5.3 V and smooth charging. We also show extending the wireless grid coverage with the use of multiple transmitting antennas, and mechanical beam-steering even further an increased coverage using the proposed system.