All-oxide, fully-transparent thin film transistors and rectifiers, processed entirely by atomic layer deposition, have been developed for on-chip capacitive energy storage. Fully depleted thin film transistor (TFT) operation is achieved by optimizing the carrier concentration in the ZnO channels. The TFTs show an average saturation mobility of 10.5 cm2 V−1 s−1, a stable positive turn-on voltage of 0.88 V, a low subthreshold swing of 0.162 V dec−1, and the entire device achieves an overall transmittance of 85%. The field-effect rectifiers (FER) are fabricated based on short-circuiting the gate and drain electrodes of the TFT structure. Rectification ratio of 3.5 × 106 is achieved in DC measurements. Under AC input, the rectifiers can steadily operate at an input frequency up to 10 MHz and amplitude (peak to peak) up to 20 V. The rectifier can be used for signal processing applications with frequency up to 1 MHz. The energy storage utility of the rectifiers is demonstrated by rectifying AC input signals and successfully charging home-made electrochemical on-chip microsupercapacitors. The results demonstrate that integrated, all-oxide thin film rectifiers can be used for on-chip capacitive energy storage.
Monitoring, measuring, and controlling electronic systems in space exploration, automotive industries, downhole oil and gas industries, marine environment, geothermal power plants, etc., require materials and processes that can withstand harsh environments. Such harshness can come from the surrounding temperature, varying pressure, intense radiation, reactive chemicals, humidity, salinity, or a combination of any of these conditions. Here, recent progress in the development of flexible and stretchable electronic devices for harsh-environment applications is reviewed. Studies are considered on how the selection of a specific material is critical for a particular application and how the selection of the material plays a critical role in sustained performance. Certain examples are presented for selected applications. Works on methods and designs for achieving flexibility and stretchability in devices designed for harsh environments are also investigated. Finally, studies on packaging techniques that enable deployment of conventional electronic devices in harsh-environment applications are considered, with a few examples described.
Li, Wenjie; Kerr, Emily; Goulet, Marc Antoni; Fu, Hui-Chun; Zhao, Yuzhou; Yang, Ying; Veyssal, Atilla; He, Jr-Hau; Gordon, Roy G.; Aziz, Michael J.; Jin, Song(Advanced Energy Materials, Wiley, 2019-01-01)[Article]
Monolithically integrated solar flow batteries (SFBs) hold promise as compact stand-alone energy systems for off-grid solar electrification. Although considerable research is devoted to studying and improving the round-trip efficiency of SFBs, little attention is paid to the device lifetime. Herein, a neutral pH aqueous electrolyte SFB with robust organic redox couples and inexpensive silicon-based photoelectrodes is demonstrated. Enabled by the excellent stability of both electrolytes and protected photoelectrodes, this SFB device exhibits not only unprecedented stable continuous cycling performance over 200 h but also a capacity utilization rate higher than 80%. Moreover, through comprehensive study on the working mechanisms of SFBs, a new theory based on instantaneous solar-to-output electricity efficiency toward more optimized device design is developed and a significantly improved solar-to-output electricity efficiency of 5.4% from single-junction silicon photoelectrodes is realized. The design principles presented in this work for extending device lifetime and boosting round trip energy efficiency will make SFBs more competitive for off-grid applications.
Memristive devices have been extensively demonstrated for applications in nonvolatile memory, computer logic, and biological synapses. Precise control of the conducting paths associated with the resistance switching in memristive devices is critical for optimizing their performances including ON/OFF ratios. Here, gate tunability and multidirectional switching can be implemented in memristors for modulating the conducting paths using hexagonal α-In2Se3, a semiconducting van der Waals ferroelectric material. The planar memristor based on in-plane (IP) polarization of α-In2Se3 exhibits a pronounced switchable photocurrent, as well as gate tunability of the channel conductance, ferroelectric polarization, and resistance-switching ratio. The integration of vertical α-In2Se3 memristors based on out-of-plane (OOP) polarization is demonstrated with a device density of 7.1 × 109 in.−2 and a resistance-switching ratio of well over 103. A multidirectionally operated α-In2Se3 memristor is also proposed, enabling the control of the OOP (or IP) resistance state directly by an IP (or OOP) programming pulse, which has not been achieved in other reported memristors. The remarkable behavior and diverse functionalities of these ferroelectric α-In2Se3 memristors suggest opportunities for future logic circuits and complex neuromorphic computing.
Hussain, Rifaqat; Raza, Ali; Khan, Muhammad U.; Shamim, Atif; Sharawi, Mohammad S.(International Journal of RF and Microwave Computer-Aided Engineering, Wiley, 2019-05-01)[Article]
In this article, a miniaturized 4-element frequency reconfigurable multiple-input-multiple-output (MIMO) antenna system is presented. The proposed design is low profile with planar configuration. The design consists of pentagonal slot-based frequency reconfigurable antenna elements. Varactor diodes are used to change the capacitive reactance of the slot. The MIMO antenna system can be tuned over a frequency band covering 3.2 to 3.9 GHz with at least 100 MHz bandwidth within each band. The proposed antenna covers several commercial standards including WiMAX (3.4-3.6 GHz), TDD LTE (3.6-3.8 GHz), and Wi-Fi 802.11y (3.65-3.7 GHz), along with several other bands. The proposed design was realized on a board of dimensions 60 × 120 mm2. The isolation between adjacent antenna elements is improved using slot-line based defected ground structures (DGS). The antenna maintains a minimum isolation of 10 dB in its entire covered operating bands. The antenna is also analyzed for its far-field characteristics and MIMO performance parameters. The proposed design is suitable to be used in mobile handsets for cognitive radio (CR) platforms.
Fu, Hui-Chun; Ramalingam, Vinoth; Kim, Hyunho; Lin, Chun-Ho; Fang, Xiaosheng; Alshareef, Husam N.; He, Jr-Hau(Advanced Energy Materials, Wiley, 2019-04-24)[Article]
MXene, a new class of 2D materials, has gained significant attention owing to its attractive electrical conductivity, tunable work function, and metallic nature for wide range of applications. Herein, delaminated few layered Ti3C2Tx MXene contacted Si solar cells with a maximum power conversion efficiency (PCE) of ≈11.5% under AM1.5G illumination are demonstrated. The formation of an Ohmic junction of the metallic MXene to n+-Si surface efficiently extracts the photogenerated electrons from n+np+-Si, decreases the contact resistance, and suppresses the charge carrier recombination, giving rise to excellent open-circuit voltage and short-circuit current density. The rapid thermal annealing process further improves the electrical contact between Ti3C2Tx MXene and n+-Si surface by reducing sheet resistance, increasing electrical conductivity, and decreasing cell series resistance, thus leading to a remarkable improvement in fill factor and overall PCE. The work demonstrated here can be extended to other MXene compositions as potential electrodes for developing highly performing solar cells.
Guler, Samet; Algarni, Mohammed Abdullah; Shaqura, Mohammad; Jaleel, Hassan; Mabrok, Mohamed A.; Jiang, Jiming; Lu, Yimeng; Shamma, Jeff S.(Journal of Field Robotics, Wiley, 2019-02-26)[Article]
The ground robotics challenge in the Mohammed Bin Zayed International Robotics Challenge required a ground vehicle equipped with a robotic arm to autonomously locate a panel, select a proper size wrench among several options mounted on the panel, and use the wrench to rotate a valve. Autonomy was the critical factor in this challenge, which required the teams to devise algorithms that can operate successfully in a semistructured environment without human supervision. This paper presents the approaches taken by team KAUST to meet this challenge, ranging from in-house hardware designs to algorithm integration and customization. We separated the whole objective into three interconnected tasks: Navigation, perception, and manipulation. For the navigation task, we developed a basic robotic exploration scheme to find the panel front side where the wrenches were present. For the perception task, we integrated common object detection algorithms with neural networks to identify the proper size wrench precisely. For successful manipulation, we designed and built a custom gripper, which was inspired by the common grasping behavior of a human hand under tight clearance conditions. The modular structure of the proposed approach allowed the team to progress in several subtasks simultaneously. However, the interconnection between the subtasks necessitated a reliable integration framework between these modules for effective implementation. We tuned our algorithms in extensive experimental studies and eventually obtained 10 consecutive successful navigation runs, 96% true wrench detection rate, and high success rate in wrench grasping. Furthermore, successful complete tests proved the reliability and repeatability of our system.
El Astal, Mohammed-Taha; Ismail, Amr; Alouini, Mohamed-Slim; Olivier, Jan Corne(Transactions on Emerging Telecommunications Technologies, Wiley, 2019-03-05)[Article]
In this paper, the multiuser interference of wireless relaying networks (WRNs) is considered. Two transmission protocols with an interference cancellation scheme are proposed, namely, the concurrentS − R−D-PICR,D protocol for decode-and-forward WRNs and the concurrentS − R − D-PICD protocol for amplify-and-forward WRNs. Unlike the existing protocols, these protocols allow the concurrent transmission in both phases of the transmission, and hence, higher spectral efficiency is offered while maintaining low decoding complexity. The concurrentS − R − D-PICR,D protocol achieves interference-free diversity without imposing any condition on the node's antenna number. However and similar to most existing protocols, this protocol requires the channel state information (CSI) of the users-relay links at the relay. In contrast, the concurrentS − R − D-PICD protocol achieves a better diversity order, given that the relay's antenna >8, whereas CSI is required only at the destination. Although the diversity's upper bound is not achieved, this protocol uses a simple relay as no CSI or encoding is required at the relay. In addition and unlike the existing protocols, the achievable diversity is determined by both the user's and the destination's antennas, and it is not sacrificed while the number of users is increased. This paper also establishes sufficient conditions for a space-time block code to achieve the mentioned diversity gain of the proposed protocols.
The development of self-powered electronic systems requires integration of on-chip energy-storage units to interface with various types of energy harvesters, which are intermittent by nature. Most studies have involved on-chip electrochemical microsupercapacitors that have been interfaced with energy harvesters through bulky Si-based rectifiers that are difficult to integrate. This study demonstrates transistor-level integration of electrochemical microsupercapacitors and thin film transistor rectifiers. In this approach, the thin film transistors, thin film rectifiers, and electrochemical microsupercapacitors share the same electrode material for all, which allows for a highly integrated electrochemical on-chip storage solution. The thin film rectifiers are shown to be capable of rectifying AC signal input from either triboelectric nanogenerators or standard function generators. In addition, electrochemical microsupercapacitors exhibit exceptionally slow self-discharge rate (≈18.75 mV h-1 ) and sufficient power to drive various electronic devices. This study opens a new avenue for developing compact on-chip electrochemical micropower units integrated with thin film electronics.
Wearable electrochemical biosensors for sweat analysis present a promising means for noninvasive biomarker monitoring. However, sweat-based sensing still poses several challenges, including easy degradation of enzymes and biomaterials with repeated testing, limited detection range and sensitivity of enzyme-based biosensors caused by oxygen deficiency in sweat, and poor shelf life of sensors using all-in-one working electrodes patterned by traditional techniques (e.g., electrodeposition and screen printing). Herein, a stretchable, wearable, and modular multifunctional biosensor is developed, incorporating a novel MXene/Prussian blue (Ti3 C2 Tx /PB) composite designed for durable and sensitive detection of biomarkers (e.g., glucose and lactate) in sweat. A unique modular design enables a simple exchange of the specific sensing electrode to target the desired analytes. Furthermore, an implemented solid-liquid-air three-phase interface design leads to superior sensor performance and stability. Typical electrochemical sensitivities of 35.3 µA mm-1 cm-2 for glucose and 11.4 µA mm-1 cm-2 for lactate are achieved using artificial sweat. During in vitro perspiration monitoring of human subjects, the physiochemistry signals (glucose and lactate level) can be measured simultaneously with high sensitivity and good repeatability. This approach represents an important step toward the realization of ultrasensitive enzymatic wearable biosensors for personalized health monitoring.
The export option will allow you to export the current search results of the entered query to a file. Different
formats are available for download. To export the items, click on the button corresponding with the preferred download format.
By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.
For anonymous users the allowed maximum amount is 50 search results.
To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export.
The amount of items that can be exported at once is similarly restricted as the full export.
After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.