Human eyes possess exceptional image sensing characteristics such as spectacularly wide field of view (FOV), high resolution and sensitivity with low aberration. Biomimetic eyes with the same superior characteristics are highly desirable in many technological applications. However, the spherical nature of biological eyes, particularly the core component of retina, poses an enormous challenge for fabrication of biomimetic eyes. Herein, we demonstrate a unique biomimetic electrochemical eye using a hemispherical retina made of high-density array of nanowires mimicking photoreceptors on a real retina. The device design has a high degree of structural similarity to a real human eye with potency to achieve a high imaging resolution when individual nanowires are electrically addressed. Meanwhile, image sensing function of our biomimetic eye device is also demonstrated. The work here may lead to a new generation of photosensing and imaging devices based on a bioinspired design that can benefit a wide spectrum of technological applications.

Large-scale and highly ordered 3D perov-skite nanowire (NW) arrays are achieved in nanoengineering templates by a unique vapor-solid-solid reaction process. The excellent material properties, in conjunction with the high integration density of the NW arrays, make them promising for 3D integrated nanoelectronics/optoelectronics. Image sensors with 1024 pixels are assembled and characterized to demonstrate the technological potency.

Recent technological advancements in wearable sensors have made it easier to detect sweat components, but our limited understanding of sweat restricts its application. A critical bottleneck for temporal and regional sweat analysis is achieving uniform, high-throughput fabrication of sweat sensor components, including microfluidic chip and sensing electrodes. To overcome this challenge, we introduce microfluidic sensing patches mass fabricated via roll-to-roll (R2R) processes. The patch allows sweat capture within a spiral microfluidic for real-time measurement of sweat parameters including [Na+], [K+], [glucose], and sweat rate in exercise and chemically induced sweat. The patch is demonstrated for investigating regional sweat composition, predicting whole-body fluid/electrolyte loss during exercise, uncovering relationships between sweat metrics, and tracking glucose dynamics to explore sweat-to-blood correlations in healthy and diabetic individuals. By enabling a comprehensive sweat analysis, the presented device is a crucial tool for advancing sweat testing beyond the research stage for point-of-care medical and athletic applications.

Metal halide perovskite has emerged as a promising material for light-emitting diodes. In the past, the performance of devices has been improved mainly by optimizing the active and charge injection layers. However, the large refractive index difference among different materials limits the overall light extraction. Herein, we fabricate efficient methylammonium lead bromide light-emitting diodes on nanophotonic substrates with an optimal device external quantum efficiency of 17.5% which is around twice of the record for the planar device based on this material system. Furthermore, optical modelling shows that a high light extraction efficiency of 73.6% can be achieved as a result of a two-step light extraction process involving nanodome light couplers and nanowire optical antennas on the nanophotonic substrate. These results suggest that utilization of nanophotonic structures can be an effective approach to achieve high performance perovskite light-emitting diodes.

Wearable devices for health monitoring and fitness management have foreseen a rapidly expanding market, especially those for noninvasive and continuous measurements with real-time display that provide practical convenience and eliminated safety/infection risks. Herein, a self-powered and fully integrated smartwatch that consists of flexible photovoltaic cells and rechargeable batteries in the forms of a “watch strap”, electrochemical glucose sensors, customized circuits, and display units integrated into a “dial” platform is successfully fabricated for real-time and continuous monitoring of sweat glucose levels. The functionality of the smartwatch, including sweat glucose sensing, signal processing, and display, can be supported with the harvested/converted solar energy without external charging devices. The Zn-MnO2 batteries serve as intermediate energy storage units and the utilization of aqueous electrolytes eliminated safety concerns for batteries, which is critical for wearable devices. Such a wearable system in a smartwatch fashion realizes integration of energy modules with self-powered capability, electrochemical sensors for noninvasive glucose monitoring, and in situ and real-time signal processing/display in a single platform for the first time. The as-fabricated fully integrated and self-powered smartwatch also provides a promising protocol for statistical study and clinical investigation to reveal correlations between sweat compositions and human body dynamics.

Wearable and portable devices contribute to a rapidly growing emerging market for electronics and can find wide applications for wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. [1][2][3][4][5] Typically, wearable devices with attractive attributes such as flexibility, long cruising time, and operation safety are highly desirable. [6][7][8][9][10][11] Recent advances in fields of power generation devices enable sustainable energy harvesting from the environment, such as solar energy, mechanical vibrations and frictions, biofluid and thermal energy from human body, and converted into electricity without external power sources, which introduces the concept of "self-powered" systems. [12][13][14][15][16][17] To realize continuous operation of the entire self-powered devices without interruption from surrounding conditions variation, such as insufficient solar illumination, fully integrated self-powered systems that consist of energy harvesting/conversion devices (e.g., solar cells, nanogenerators, biofuel cells), energy storage devices as intermediate energy storage units (e.g., rechargeable batteries, supercapacitors) and functional devices (e.g., sensors, transistors, biomedical implants) are highly desirable. [18] Planar supercapacitors with interdigitated electrodes constructed on single substrate emerged as one of the highly competitive energy storage devices to complement/replace batteries, offering merits of high power density, separator-free architectures for device miniaturization, and favorable operational safety without using flammable electrolytes. [19][20][21][22] Especially for integration with energy harvesting devices dealing with highly volatile energy input, particularly in wearable applications, supercapacitors possess an appealing capability to accommodate fast and high charging current fluctuation. [23][24][25][26] Although self-sufficient energy modules (e.g., photovoltaic-batteries, nanogenerator-supercapacitors) and selfpowered sensors (e.g., nanogenerator-sensors, battery-sensors) have been reported previously, [12,23,[26][27][28][29][30][31][32] to our best knowledge, demonstration of a fully integrated self-powered sensor system on flexible substrate implemented via additive printable strategy is rarely achieved, mainly due to the challenges on fabrication procedures compatibility and system integration of different device components.Wearable and portable devices with desirable flexibility, operational safety, and long cruising time, are in urgent demand for applications in wireless communications, multifunctional entertainments, personal healthcare monitoring, etc. Herein, a monolithically integrated self-powered smart sensor system with printed interconnects, printed gas sensor for ethanol and acetone detection, and printable supercapacitors and embedded solar cells as energy sources, is successfully demonstrated in a wearable wristband fashion by utilizing inkjet printing as a proof-of-concept. In such a "wearable wristband", the harvested so...

Levodopa is the standard medication clinically prescribed to patients afflicted with Parkinson's disease. In particular, the monitoring and optimization of levodopa dosage are critical to mitigate the onset of undesired fluctuations in the patients' physical and emotional conditions such as speech function, motor behavior, and mood stability. The traditional approach to optimize levodopa dosage involves evaluating the subjects' motor function, which has many shortcomings due to its subjective and limited quantifiable nature. Here, we present a wearable sweat band on a nanodendritic platform that quantitatively monitors levodopa dynamics in the body. Both stationary iontophoretic induction and physical exercise are utilized as our methods of sweat extraction. The sweat band measures real-time pharmacokinetic profiles of levodopa to track the dynamic response of the drug metabolism. We demonstrated the sweat band's functionalities on multiple subjects with implications toward the systematic administering of levodopa and routine management of Parkinson's disease.

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.