Wireless Power Source Research Articles

Wireless LED controller IC for smart contact lens system

AbstractThis letter presents a wirelessly powered LED driving circuit for a smart contact lens system. Since photobiomodulation has been investigated for ocular disease treatment by irradiating light with a specific wavelength, a smart contact lens equipped with a µLED and its controller IC can be utilized as a phototherapy system. The proposed circuit design facilitates constant‐current generation to drive the LED and incorporates a wirelessly powered system. The system can be turned on and off in synchronization with an external wireless power source, providing controllability for the LED's irradiation period and intensity. The IC is fabricated in the 180‐nm CMOS process with a die area of 1.0 mm2 and integrated into the smart contact lens with an external loop antenna and a far red/NIR LED. The measurement demonstrates the irradiation period of the LED is successfully controlled by the external source, with current levels from 0.53 mA to 1.4 mA, thereby confirming the feasibility of the phototherapy system.

Stability and Reliability of Dye‐Sensitized Solar‐Cell Mini‐Module for Photocharging Li‐Ion‐Battery‐Connected Internet of Things

Dye‐sensitized solar cells (DSSCs)‐integrated Li‐ion batteries (LIBs) are considered a promising solution as a wireless power source for the increasing number of miniaturized portable devices and the internet of things (IoTs). However, DSSCs suffer from stability issues because of the using volatile electrolyte solvents that leak through the seal. To solve this problem, in this study, a polymer gel electrolyte based on the high‐boiling solvent 3‐methoxypropionitrile (bp = 164–165 °C) is used, and the backside of the cells are sealed by hot press using surlyn and Al foil. A highly stable and efficient counter electrode, Pt/porous carbon (Pt/PC), is also used to fabricate the devices, which show a high PCE of 25.7%–29.4% under the illumination of 500–2000 lux. The fabricated DSSC shows outstanding stability in the room condition and under the operating condition at 50 °C. A mini‐module of 13.3 cm2, PCE of 22.9–23.3%, and Pmax of 166.4–643.0 μW can recharge a LIB while powering an IoT device by producing an output greater than the IoT device consumes. The store charge can be used when the light source is cut off, indicating the reliability of the DSSC for photocharging the LIB as a wireless power source for IoT devices.

Wearable and long-range MXene 5G antenna energy harvester

Wireless and long-range energy transmission is an essential technology in the era of the Internet of Things, and currently it still relies on rigid and bulky metal antennas, which is incompatible with future wearable electronics. Here, we report a wearable and long-range MXene (Ti3C2Tx) 5G antenna energy harvester system that functions reliably as a wireless and battery-free power source for uninterrupted sensing and wireless data transmission. The MXene 5G antenna can efficiently harvest radio frequency (RF) electromagnetic energy at a 5G frequency range 1 band of 915 MHz, under a minimum input RF power density of 0.005 mW·cm−2, about 16 times lower than the threshold value for a control copper antenna. The device shows good mechanical bendability as it keeps over 99% power transfer efficiency at a bending angle of 90°. Our results open a new route for developing next-generation wireless powering for wearable electronics.

A Wirelessly-Powered Body-Coupled Data Transmission with Multi-Stage and Multi-Source Rectifier

This paper demonstrates body-coupled (BC) data transmission and multi-source power delivery systems for neural interface applications. The implanted data transmitter and power receiver utilize an electrode interface rather than an antenna or coil interface for battery-free wireless transmission, enabling the external data receiver and power transmitter with patch electrodes to be placed away from the implant without requiring precise alignment, which is a critical issue in the conventional communication modalities of inductive coupling. Significantly, the implanted power receiver produces the supply voltage using ambient body-coupled 50/60 Hz signals from the Mains, on top of the 40.68 MHz wireless power source from the external power transmitter, to increase the recovered power level and the voltage conversion efficiency (VCE). The body-coupled wireless systems for implanted and external devices are implemented with integrated circuits (ICs) fabricated in a 180 nm CMOS process. When 650 mVpp AC voltage is applied to the implanted device, the power receiver recovers up to 780 μW with ambient (60 Hz signals) BC energy harvesting, achieving 93% VCE, while 600 μW is recovered without ambient (60 Hz signals) signal. The recovered power supplies the regulated voltage to the direct-digital signaling transceiver, which consumes 460 μW with an uplink data rate of 10 Mbps and a downlink data rate of 200 kbps, corresponding to an energy efficiency of 46 pJ/b.

Cellphone remote intelligent neuroregulation with self-powered piezoelectric wireless brain probe

The neural regulation that is tele-controlled remotely by medical professionals or artificial intelligence (AI) agents can meet the requirement of rapid, precise, personalized intervention and optimize the allocation of medical resources. Here, we develop a new self-powered wireless mini-invasive brain probe for remote intelligent neuroregulation. The probe can be wirelessly powered and controlled by cellphone audio tones (through piezoelectric effect) with the assistance of AI cellphone video analysis. The probe consists of a biocompatible pedestal integrated with implanting stimulation electrodes connected to embedded magnets and a magnetically coupled custom-designed signal-intensifying resonator integrated with a piezoelectric powered signal modulation circuit. A programmed audio tone functions as the wireless power source, and it can be tele-transmitted remotely from other cellphones with desired neural stimulation protocols. Combined with AI-enabled video monitoring of the epileptic tremor, we show that the probe can relieve the seizure events in the epileptic mice, and the therapeutic effect is confirmed by in-vivo electroencephalography and free-moving scenario. The multi-functionality of versatility, AI-assistance, wireless power transfer, and tele-transmission of the cellphone-interacted brain probe opens the possibility for remote precision neural modulation.

Build Charging Database of Linear-Motor Type Flux Pump and Analyze the Influence of DC-Bias Field Using Fixed Step Size Search Algorithm

The linear-motor type flux pump is a wireless DC power source for high-temperature superconducting coils, which is compact in size, efficient in energy use, fast in output control, etc. It consists of three major parts: DC windings, phase windings and iron circuit, which generates a DC-bias AC travelling wave in its airgap. In theory, there are three controllable parameters such as DC-bias field, amplitude of the AC travelling wave, and the field frequency (travelling speed). By changing those parameters, we change the applied fields and its DC output current into superconducting coils. For studying the impact of those parameters on its DC output, this paper uses a fixed step algorithm to collect the current charging data, by automatically controlling the flux pump device, and then establishes an output database. By using this algorithm, we have searched out the maximum pumped current and analyzed the impact of the three parameters. We have also found out that, in order to get maximum current output, the value of the DC-bias field should be close to the amplitude of AC magnetic field.

Promising Electrode and Electrolyte Materials for High‐Energy‐Density Thin‐Film Lithium Batteries

All‐solid‐state thin‐film lithium batteries (TFLBs) are the ideal wireless power sources for on‐chip micro/nanodevices due to the significant advantages of safety, portability, and integration. As the bottleneck for increasing the energy density of TFLBs, the key components of cathode, electrolyte, and anode are still underway to be improved. In this review, a brief history of TFLBs is first outlined by presenting several TFLB configurations. Based on the state‐of‐the‐art materials developed for lithium‐ion batteries (LIBs), the challenges and related strategies for the application of those potential electrode and electrolyte materials in TFLBs are discussed. Given the advanced manufacture and characterization techniques, the recent advances of TFLBs are reviewed for pursuing the high‐energy‐density and long‐term‐durability demands, which could guide the development of future TFLBs and analogous all‐solid‐state lithium batteries.

Exploring the Boundaries of Ambient RF Energy Harvesting With LoRaWAN

Environmental monitoring is an important application for wireless sensing devices. Battery power requires in-the-field replacement, and the chemicals involved are environmentally harmful, so harvested energy is a useful alternative. Previous research has shown the feasibility of powering LoRaWAN sensors using high-energy ambient or wireless transfer power sources. This article extends this work by exploring the boundaries of using low-energy radio-frequency (RF) ambient sources. Ambient RF energy harvesting is an attractive option, but it is more challenging due to the low levels of energy density typically available.Using an analytical LoRaWAN device model and RF energy data collected from around the world, a systematic investigation of the design and environmental space is performed. The main contribution of this article is to identify the boundaries of feasibility for powering LoRaWAN sensor nodes from ambient RF energy. These boundaries include design and environmental factors.

Wireless Qi-powered, Multinodal and Multisensory Body Area Network for Mobile Health.

Wireless, battery-free Body Area Networks (BAN) enable reliable long-term health monitoring with minimal intervention, and have the potential to transform patient care via mobile health monitoring. Current approaches for achieving such battery-free networks are limited in the number, capability, and positioning of sensing nodes-this is related to constraints in power supply, data rate, and working distance requirements between the wireless power source and sensing nodes. Here, we investigate a Qi-based, near-field power transfer scheme that can effectively drive wireless, battery-free, multi-node and multi-sensor BAN over long distances. This consists of a single Qi power source (such as a cellphone), a detached/untethered Passive Intermediate Relay (PIR) (facilitates power transfer from a central Qi source to multiple nodes on the body), and finally individual/detached sensing nodes placed throughout the body. Alongside this power scheme we implement the star network topology of a Gazell protocol to enable the continuous connection of one host to many sensing nodes while minimizing data loss over long temporal periods. The high-power transmission capabilities of Qi enables wireless support for a multitude of sensors (up to 12), and sensing nodes (up to 6) with a single transmitter at long distances (60 cm) and a sample rate of 20 Hz. This scheme is studied both in-vitro and in-vivo on the body.

Conjunction of triboelectric nanogenerator with induction coils as wireless power sources and self-powered wireless sensors

Here we demonstrate a magnetic resonance coupling based wireless triboelectric nanogenerator (TENG) and fully self-powered wireless sensors. By integrating a microswitch and an inductor with the TENG, the pulsed voltage output is converted into a sinusoidal voltage signal with a fixed frequency. This can be transmitted wirelessly from the transmit coil to the resonant-coupled receiver coil with an efficiency of 73% for a 5 cm distance between the two coils (10 cm diameter). Analytic models of the oscillating and coupled voltage signals for the wireless energy transfer are developed, showing excellent agreement with the experimental results. A TENG of 40 × 50 mm2 can wirelessly light up 70 LEDs or charge up a 15 μF capacitor to 12.5 V in ~90 s. The system is further utilized for two types of fully self-powered wireless chipless sensors with no microelectronic components. The technologies demonstrate an innovative strategy for a wireless ‘green’ power source and sensing.

Optimal UAV Route in Wireless Charging Sensor Networks

An unmanned aerial vehicle (UAV) can be utilized as a flying data collector and wireless power source in wireless charging sensor networks (WCSNs). Different from conventional studies that focused on maximizing the efficiency of wireless power transfer (WPT) for UAV route design, in this article, we maximize the lifetime of WCSNs by considering sensor energy consumption and energy harvesting simultaneously. We consider simultaneous wireless information and power transfer (SWIFT), where data collection capability guarantees power leftover for UAV to complete its round-trip flight. Our objective is to jointly optimize the UAV hovering location and duration to maximize the minimum energy of sensors after data transmission and energy harvesting under data collection and UAV energy consumption constraints. To tackle this nonconvex optimization problem, we first assume that the UAV hovering location for each sensor is fixed and optimize UAV hovering duration by the Lagrange multiplier method. Next, for each UAV hovering location, we propose a geometry-based update algorithm, which can be used to find initial feasible UAV routes to the problem. Last, a near-optimal UAV route is determined by adjusting the initial feasible UAV route iteratively, where UAV hovering locations and duration are updated at each iteration. The numerical results are provided to validate the performance of our proposed algorithm.

Performance enhancement of triboelectric nanogenerators based on polyvinylidene fluoride/graphene quantum dot composite nanofibers

Wearable mechanical energy harvesting technologies have been achieved much attention for the wireless sustainable power source applications. In this study, we have fabricated polyvinylidene fluoride (PVDF)/graphene quantum dot (GQD) composite nanofibers (NFs), which showed improved triboelectric nanogenerator (TENG) performance. PVDF/GQD composite NFs were fabricated by an electrospinning method. Structural and chemical investigations show that the GQDs were embedded in the PVDF NFs and promoted the formation of polar β-phase when an optimal amount of GQDs was incorporated. The PVDF/GQD NFs showed strong photoluminescence at a wavelength of 453 nm, which was attributed to the electronic transitions in the GQDs. As the GQD content increased from 0 to 5 vol%, the maximum output power from TENG devices increased from 35 to 97 μW but decreased with further additions of GQDs. The enhancement and degradation of the TENG performance with increasing the GQD contents were due to the enhanced formation of polar β-phase and the detrimental effect of conductive GQDs for charge trapping, respectively.

Resource Allocation in Wireless-Powered Mobile Edge Computing Systems for Internet of Things Applications

Wireless devices in Internet of Things (IoT) applications, such as wireless sensors and Radio Frequency Identifications (RFIDs), are faced with challenges of heavy computation tasks and limited energy, which can be solved by the importation of mobile edge computing (MEC) and wireless power transfer (WPT) techniques. As MEC can effectively enhance computation capability, and the wireless power transfer can ensure a sustainable supply of energy, it has drawn significant research interest in IoT applications. In this paper, we will study the resource allocation problem in the wireless-powered MEC system for IoT applications with one access point (AP) and many other wireless devices, and propose a Stackelberg dynamic game model to obtain the optimal allocated resource for the nodes in the IoT environment. The AP is a wireless power source that can charge wireless devices based on wireless power transfer techniques. The AP is also integrated with a MEC server that can carry out computation tasks that offload from wireless devices. The wireless devices can use the harvested energy to execute and offload computation tasks to the AP. Based on the proposed game model, the AP and wireless devices can control their optimal transmit power for energy transfer, and computation tasks offloading to the AP, respectively. The numerical simulation results show the correctness and effectiveness of the proposed model.

Age of Information in Wireless Powered Networks in Low SNR Region for Future 5G.

Wireless powered communication technology has a great potential to power low-power wireless sensor networks and Internet of Things (IoT) for real-time applications in future 5G networks, where age of information (AoI) plays a very important performance metric. This paper studies the system average AoI of a wireless powered network, where a wireless-powered user harvests energy from a wireless power source (WPS) and then transmits data packets to its access point (AP) by using the harvested energy. The user generates data packets with some probability and adopts the first-come-first-served (FCFS) service policy. For such a system, by using the queuing theory and the probability models, we derive a closed-form expression of the system average AoI. We also formulate an optimization problem to minimize the AoI by optimizing the data packet generating probability, and find its solution by simple calculation and search. Simulation results demonstrate the correctness of our obtained analytical results. It also shows that, when the total distance of the two hops is fixed, the system average AoI increases linearly with the increment of the distance of the first hop, and a smaller data packet generating probability should be selected to match a bigger first-hop distance for achieving a smaller system average AoI. Moreover, a smaller data packet size also contributes to a smaller system average AoI.

A Review on the Fundamentals and Practical Implementation Details of Strongly Coupled Magnetic Resonant Technology for Wireless Power Transfer

Users are increasing their demands on the home appliances they utilize by requiring them to be powered anywhere and anytime. In order to satisfy this need, wireless power transfer helps transfer energy between objects without conductors. For domestic scenarios, strongly magnetic resonant technology offers a method to enable wireless power transfer, even when there exist intermediate non-metallic objects between the wireless power source and the load. This paper reviews this technology with a comprehensive explanation about its fundamentals and physical principles. Some practical issues are also analyzed in this work. Particularly, how the control can be designed and how the coils are built. Finally, this paper also addresses the study about the features of other technologies to power home appliances without conductors. They can be foreseen as the technological competitors of strongly coupled magnetic resonant systems.

In-atmosphere electrohydrodynamic propulsion aircraft with wireless supply onboard

Electrohydrodynamic flow generation systems are widely investigated in aerodynamic application due their high reliability, simplicity and effectiveness. This paper describes a heavier-than-air non-aerodynamic aircraft on the basis of in-atmosphere electrohydrodynamic propulsion system with wireless power system onboard. Inspired by the fundamental knowledge of air propulsion principles, we numerically and then on a prototype demonstrated the possibility of creating such a device. It is achieved by a combination of the ionocraft airframe composed of symmetric drop-shaped collectors carrying a part of the mechanical load and the developed wireless power source with a high power density per unit mass.

Power-Reduced Monolithic Wireless Sensor

Future wireless sensor networks require reliable, batteryless, miniaturized, low-cost sensor nodes with ultralow power consumption. Remote RF powering provides a reliable wireless power source for such monolithically integrated sensor nodes. Combining highly integrated ultralow power millimeter-wave (mm-wave) sensing, wireless power transfer, and on-chip antenna is a path toward batteryless, fully monolithically integrated, millimeter-sized sensor nodes with only a few milligrams of weight. In this paper, a passive fully integrated monolithic wireless sensor for mm-wave sensing is presented in a 65-nm CMOS technology, including an on-chip wireless power receiver, on-chip antenna, and a low-power transmitter.

Charging 2G HTS Double Pancake Coils With a Wireless Superconducting DC P ower Supply for Persistent Current Operation

We have designed and built a novel high-temperature superconducting (HTS) flux pump device to charge a second-generation (2G) HTS double pancake coil (DPC). This device generates dc-biased ac travelling wave on sections of 2G HTS coated conductor (superconducting stator), which pumps flux into the superconducting closed loop formed by the DPC and superconducting stator. In this paper, we discuss the importance of the dc-biased field, ac travelling wave, and the travelling direction in the flux pump process, and how to control the magnetization of an HTS coil with the above factors. We have found that a pure ac travelling wave can only transport net flux into the superconducting closed loop in the presence of dc-bias field. The magnetization direction of the DPC can be reversed by reversing the dc-bias direction of the dc background field or travelling direction of the ac travelling wave. This paper shows the versatility and flexibility of this novel flux pump device in controlling the magnetization of the HTS coils, which will work as a wireless dc power source to help persistent current mode operation of a small-scale MRI magnet built by HTS DPCs later in this project.

Disposable Wireless Immuno-Sensing Chips

A disposable immuno-sensor chip which is proposed for use in continuous health monitoring and for early diagnosis of infectious disease. On-chip high-power density wireless power sources and on-chip wireless data transfer technologies are developed to minimize chip production costs.

Application of wireless power transfer technologies and intermittent energy harvesting for wireless sensors in rotating machines

Battery-powered wireless sensor networks have been extensively deployed in condition monitoring and structural health monitoring systems, but the performance of wireless sensors are limited by battery capacity and difficulty of application in rotating machines. In this paper, a variety of commercial wireless charging solutions and coil-shaft configurations for magnetic coupling are compared, having in mind of the application of continuously charging wireless sensors on rotating machines. For the co-axial configuration of the transmitter coil and the receiver coil, a Qi standard compliant wireless charging kit and a custom charging circuit are successfully applied to charge wireless sensors on small rotating test rigs. In order to harvest and store intermittent energy input from the wireless power source, a prototype receiver circuit using a supercapacitor and low-dropout regulator is designed and validated. Based on the prototype circuit, the radial configuration of single transmitter coil and multiple receiver coils is demonstrated for wireless power transfer to the sensor nodes on the drivetrain of a small wind turbine test rig.