A wireless sensor based on bioresponsive DNA hydrogel provides smartphone-based detection of wound infection.

This paper presents a novel wearable antenna sensor based on localized surface plasmons (LSPs) for communication and non-invasive sweat monitoring. The sensor is made up of corrugated plasmonic structures based on the conventional printed monopole antenna, which achieves multi-band and miniaturization. The physical dimensions of the antenna sensor are 35 × 34 mm ² , with a thickness of only 0.13 mm. Simulated and measured results demonstrate that the proposed antenna sensor covers triple operating bands, including 2.4 GHz and 5.8 GHz ISM bands, as well as high frequency ultra-wideband ranging from 7.89 GHz to 9.56 GHz. The antenna sensor exhibits a good radiation pattern with a peak gain of 3.02 dBi and a high quality factor (Q) up to 35. The use of polyimide as a dielectric substrate enables the antenna sensor to achieve flexibility and conformality, maintaining stable operating states even when bent and deformed. The specific absorption rate (SAR) values in three frequency bands are simulated and evaluated to ensure its safety for human health. Moreover, the resonant frequency of antenna sensor significantly shifts with the volume and concentration of sweat, indicating that the proposed sensor is highly sensitive to sweat volume and concentration with a sensitivity of 120 MHz/1mm and 4.57 MHz/1, respectively. The proposed wearable antenna sensor is a promising candidate for a sweat monitoring system for athletes or patients, allowing for health monitoring at any time and place.

Misalignments between the transmitting and receiving coils of a wireless power system can significantly reduce power transfer efficiency (PTE). In this paper, we propose a novel magnetically coupled resonant wireless power transfer (MCR-WPT) system with good misalignment tolerance for wireless charging applications. Specifically, we employ three interconnected planar coils to form a transmitter that produce multiple paths of magnetic flux linkages and power to the receiver even in angular and lateral misalignment positions. Unlike other methods, no additional control circuits are needed so that the circuit can be easily realized and implemented. A prototype is simulated, fabricated, and tested. It has a wide angular misalignment range of 165° for the power transfer efficiency of 20% or higher, which is 30% higher than 126° of the conventional system. It also has a wide lateral misalignment range of 180 mm for the power transfer efficiency of 20% or higher, which is 73% higher than 104 mm of the conventional system. Thus, the proposed system presents a good and simple wireless power delivering system for practical applications, in particular in the situations where angular and lateral misalignments occur in various degrees without prior acknowledge.

A wearable radio-frequency (RF) energy-localized harvester with multiple antennas and spoof surface plasmon (SSP) structure for multibeam radiation is presented to power the Bluetooth sensor module. The harvester contains four separate antennas connected by SSP waveguides, while the loop is applied to excite the structure to generate multibeam radiation and improve energy harvesting. The radiative waves will be harvested and converted into surface waves on the SSP waveguides, then, confined in a localized area of the structure through the evanescent field interactions between the current of SSP and the loop in a contactless way. More importantly, it is free of RF connectors and soldering works on the interface between the energy harvester and clothing. In addition, the wearable energy harvester is entirely made of flexible materials, such as conductive fabrics, polyimide, and nylon fabrics in a compact and low-profile structure. The loop can easily be integrated with the rectify circuit and power management unit (PMU) to provide direct-current (dc) power for different kinds of wireless sensor modules. In this design, the harvested power can support a battery-free Bluetooth temperature and humidity sensor with a power density of 2.75 $\mu \text{W}$ /cm ² . The complete system-level demonstration of RF energy harvesting shows the potential to power small electronic devices for wearable applications.

This letter presents a tank system for wireless power transfer with magnetically coupled resonance. It contains two interconnected transmitting resonant coils placed perpendicular to each other and forms a magnetic resonant tank. Due to the combined effects of these two transmitting coils, there will always be magnetic flux that goes through the receiver regardless of axial misalignment between the transmitter and the receiver. The transfer efficiency thus improves and becomes less sensitive to axial misalignment than the conventional system. A prototype is fabricated on FR4 printed circuit boards and tested. Both the simulation and test results show that the proposed system can enhance power transfer performances over a relatively good distance and a large range of misalignment angles. The receiver is functional even when it is perpendicular to the transmitter. Therefore, the proposed system can serve as a good candidate for applications such as wireless power supply to underwater motors.

Research and development of wireless power transfer (WPT) systems has attracted much attention in recent years for their potential widespread applications. One of the much desirable features of a WPT system is load-independence. In this letter, we propose the insertion of a simple T-type network into a multi-receiver WPT magnetically coupled resonant WPT system to achieve the load-independence. We then present theoretical analysis, simulation, and experimental verifications; as a result, they lay the foundation for further investigations, improvements, and implementations of realistic WPT systems.