An autonomous wearable biosensor powered by a perovskite solar cell

Emerging innovations in portable chemical sensing devices: Advancements from microneedles to hydrogel, microfluidic, and paper-based platforms

With the public heightened emphasis on mitigating the occurrence risks of health-related ailment and optimizing personal physical performance, portable chemical sensing devices emerged as an indispensable component of pervasive health monitoring. Chemical sensing enabled the immediate and on-site identification of biomarkers in biological fluids by integrating colorimetry, fluorescence, electrochemical, and other methods into portable sensor devices. These sensor devices incorporated microneedles, hydrogels, microfluidic modules, and papers, facilitating conformal human-device contact and providing several visual sensing options for disease prevention and healthcare management. This review systematically overviewed recent advancements in chemical sensors for marker detection, categorizing them based on monitoring device types. Furthermore, we also offered recommendations and opportunities for developing portable chemical sensing devices by summarizing sensor integration methods and tracking sites on the human body.

Recent Progress on Flexible Self-Powered Tactile Sensing Platforms for Health Monitoring and Robotics

Over the past decades, tactile sensing technology has made significant advances in the fields of health monitoring and robotics. Compared to conventional sensors, self-powered tactile sensors do not require an external power source to drive, which makes the entire system more flexible and lightweight. Therefore, they are excellent candidates for mimicking the tactile perception functions for wearable health monitoring and ideal electronic skin (e-skin) for intelligent robots. Herein, the working principles, materials, and device fabrication strategies of various self-powered tactile sensing platforms are introduced first. Then their applications in health monitoring and robotics are presented. Finally, the future prospects of self-powered tactile sensing systems are discussed.

Designs and Applications for the Multimodal Flexible Hybrid Epidermal Electronic Systems

Research on the flexible hybrid epidermal electronic system (FHEES) has attracted considerable attention due to its potential applications in human-machine interaction and healthcare. Through material and structural innovations, FHEES combines the advantages of traditional stiff electronic devices and flexible electronic technology, enabling it to be worn conformally on the skin while retaining complex system functionality. FHEESs use multimodal sensing to enhance the identification accuracy of the wearer's motion modes, intentions, or health status, thus realizing more comprehensive physiological signal acquisition. However, the heterogeneous integration of soft and stiff components makes balancing comfort and performance in designing and implementing multimodal FHEESs challenging. Herein, multimodal FHEESs are first introduced in 2 types based on their different system structure: all-in-one and assembled, reflecting totally different heterogeneous integration strategies. Characteristics and the key design issues (such as interconnect design, interface strategy, substrate selection, etc.) of the 2 multimodal FHEESs are emphasized. Besides, the applications and advantages of the 2 multimodal FHEESs in recent research have been presented, with a focus on the control and medical fields. Finally, the prospects and challenges of the multimodal FHEES are discussed.

WSe2 Negative Capacitance Field-Effect Transistor for Biosensing Applications

Field-effect transistor (FET) biosensors based on two-dimensional (2D) materials are highly sought after for their high sensitivity, label-free detection, fast response, and ease of on-chip integration. However, the subthreshold swing (SS) of FETs is constrained by the Boltzmann limit and cannot fall below 60 mV/dec, hindering sensor sensitivity enhancement. Additionally, the gate-leakage current of 2D material biosensors in liquid environments significantly increases, adversely affecting the detection accuracy and stability. Based on the principle of negative capacitance, this paper presents for the first time a two-dimensional material WSe2 negative capacitance field-effect transistor (NCFET) with a minimum subthreshold swing of 56 mV/dec in aqueous solution. The NCFET shows a significantly improved biosensor function. The pH detection sensitivity of the NCFET biosensor reaches 994 pH-1, nearly an order of magnitude higher than that of the traditional two-dimensional WSe2 FET biosensor. The Al2O3/HfZrO (HZO) bilayer dielectric in the NCFET not only contributes to negative capacitance characteristics in solution but also significantly reduces the leakage in solution. Utilizing an enzyme catalysis method, the WSe2 NCFET biosensor demonstrates a specific detection of glucose molecules, achieving a high sensitivity of 4800 A/A in a 5 mM glucose solution and a low detection limit (10-9 M). Further experiments also exhibit the ability of the biosensor to detect glucose in sweat.

Colorimetric sensing for translational applications: from colorants to mechanisms

Colorimetric sensing offers instant reporting via visible signals. Versus labor-intensive and instrument-dependent detection methods, colorimetric sensors present advantages including short acquisition time, high throughput screening, low cost, portability, and a user-friendly approach. These advantages have driven substantial growth in colorimetric sensors, particularly in point-of-care (POC) diagnostics. Rapid progress in nanotechnology, materials science, microfluidics technology, biomarker discovery, digital technology, and signal pattern analysis has led to a variety of colorimetric reagents and detection mechanisms, which are fundamental to advance colorimetric sensing applications. This review first summarizes the basic components (e.g., color reagents, recognition interactions, and sampling procedures) in the design of a colorimetric sensing system. It then presents the rationale design and typical examples of POC devices, e.g., lateral flow devices, microfluidic paper-based analytical devices, and wearable sensing devices. Two highlighted colorimetric formats are discussed: combinational and activatable systems based on the sensor-array and lock-and-key mechanisms, respectively. Case discussions in colorimetric assays are organized by the analyte identities. Finally, the review presents challenges and perspectives for the design and development of colorimetric detection schemes as well as applications. The goal of this review is to provide a foundational resource for developing colorimetric systems and underscoring the colorants and mechanisms that facilitate the continuing evolution of POC sensors.

Adhesion-Controlled Heterogeneous Nucleation of Tin Halide Perovskites for Eco-Friendly Indoor Photovoltaics

The rapid development of the Internet of Things (IoT) has accelerated the advancement of indoor photovoltaics (IPVs) that directly power wireless IoT devices. The interest in lead-free perovskites for IPVs stems from their similar optoelectronic properties to high-performance lead halide perovskites, but without concerns about toxic lead leakage in indoor environments. However, currently prevalent lead-free perovskite IPVs, especially tin halide perovskites (THPs), still exhibit inferior performance, arising from their uncontrollable crystallization. Here, a novel adhesive bonding strategy is proposed for precisely regulating heterogeneous nucleation kinetics of THPs by introducing alkali metal fluorides. These ionic adhesives boost the work of adhesion at the buried interface between substrates and perovskite film, subsequently reducing the contact angle and energy barrier for heterogeneous nucleation, resulting in high-quality THP films. The resulting THP solar cells achieve an efficiency of 20.12% under indoor illumination at 1000 lux, exceeding all types of lead-free perovskite IPVs and successfully powering radio frequency identification-based sensors.

Wearable and Multiplexed Biosensors based on Oxide Field-Effect Transistors

Wearable sensors designed for continuous, non-invasive monitoring of physicochemical signals are important for portable healthcare. Oxide field-effect transistor (FET)-type biosensors provide high sensitivity and scalability. However, they face challenges in mechanical flexibility, multiplexed sensing of different modules, and the absence of integrated on-site signal processing and wireless transmission functionalities for wearable sensing. In this work, a fully integrated wearable oxide FET-based biosensor array is developed to facilitate the multiplexed and simultaneous measurement of ion concentrations (H+, Na+, K+) and temperature. The FET-sensor array is achieved by utilizing a solution-processed ultrathin (≈6 nm thick) In2O3 active channel layer, exhibiting high compatibility with standard semiconductor technology, good mechanical flexibility, high uniformity, and low operational voltage of 0.005 V. This work provides an effective method to enable oxide FET-based biosensors for the fusion of multiplexed physicochemical information and wearable health monitoring applications.

Advances in Energy Harvesting Technologies for Wearable Devices

The development of wearable electronics is revolutionizing human health monitoring, intelligent robotics, and informatics. Yet the reliance on traditional batteries limits their wearability, user comfort, and continuous use. Energy harvesting technologies offer a promising power solution by converting ambient energy from the human body or surrounding environment into electrical power. Despite their potential, current studies often focus on individual modules under specific conditions, which limits practical applicability in diverse real-world environments. Here, this review highlights the recent progress, potential, and technological challenges in energy harvesting technology and accompanying technologies to construct a practical powering module, including power management and energy storage devices for wearable device developments. Also, this paper offers perspectives on designing next-generation wearable soft electronics that enhance quality of life and foster broader adoption in various aspects of daily life.

A skin-interfaced, miniaturized platform for triggered induction, capture and colorimetric multicomponent analysis of microliter volumes of sweat

Eccrine sweat can serve as a source of biomarkers for assessing physiological health and nutritional balance, for tracking loss of essential species from the body and for evaluating exposure to hazardous substances. The growing interest in this relatively underexplored class of biofluid arises in part from its non-invasive ability for capture and analysis. The simplest devices, and the only ones that are commercially available, exploit soft microfluidic constructs and colorimetric assays with purely passive modes of operation. The most sophisticated platforms exploit batteries, electronic components and radio hardware for inducing sweat, for electrochemical evaluation of its content and for wireless transmission of this information. The work reported here introduces a technology that combines the advantages of these two different approaches, in the form of a cost-effective, easy-to-use device that supports on-demand evaluation of multiple biomarkers in sweat. This flexible, skin-interfaced, miniaturized system incorporates a hydrogel that contains an approved drug to activate eccrine sweat glands, electrodes and a simple circuit and battery to delivery this drug by iontophoresis through the surface of the skin, microfluidic channels and microreservoirs to capture the induced sweat, and multiple colorimetric assays to evaluate the concentrations of chloride, zinc, and iron. As demonstrated in healthy human participants monitored before and after a meal, such devices yield results that match those of traditional laboratory analysis techniques. Clinical studies that involve cystic fibrosis pediatric patients illustrate the use of this technology as a simple, painless, and reliable alternative to traditional hospital systems for measurements of sweat chloride.

Efficient Homojunction Tin Perovskite Solar Cells Enabled by Gradient Germanium Doping

P-type self-doping is known to hamper tin-based perovskites for developing high-performance solar cells by increasing the background current density and carrier recombination processes. In this work, we propose a gradient homojunction structure with germanium doping that generates an internal electric field across the perovskite film to deplete the charge carriers. This structure reduces the dark current density of perovskite by over 2 orders of magnitude and trap density by an order of magnitude. The resultant tin-based perovskite solar cells exhibit a higher power conversion efficiency of 13.3% and excellent stability, maintaining 95% and 85% of their initial efficiencies after 250 min of continuous illumination and 3800 h of storage, respectively. We reveal the homojunction formation mechanism using density functional theory calculations and molecular level characterizations. Our work provides a reliable strategy for controlling the spatial energy levels in tin perovskite films and offers insights into designing intriguing lead-free perovskite optoelectronics.

Improvement of Thermal Stability and Photoelectric Performance of Cs2PbI2Cl2/CsPbI2.5Br0.5 Perovskite Solar Cells by Triple-Layer Inorganic Hole Transport Materials

Conventional hole transport layer (HTL) Spiro-OMeTAD requires the addition of hygroscopic dopants due to its low conductivity and hole mobility, resulting in a high preparation cost and poor device stability. Cuprous thiocyanate (CuSCN) is a cost-effective alternative with a suitable energy structure and high hole mobility. However, CuSCN-based perovskite solar cells (PSCs) are affected by environmental factors, and the solvents of an HTL can potentially corrode the perovskite layer. In this study, a Co3O4/CuSCN/Co3O4 sandwich structure was proposed as an HTL for inorganic Cs2PbI2Cl2/CsPbI2.5Br0.5 PSCs to address these issues. The Co3O4 layers can serve as buffer and encapsulation layers, protecting the perovskite layer from solvent-induced corrosion and enhancing hole mobility at the interface. Based on this sandwich structure, the photovoltaic performances of the Cs2PbI2Cl2/CsPbI2.5Br0.5 PSCs are significantly improved, with the power conversion efficiency (PCE) increasing from 9.87% (without Co3O4) to 11.06%. Furthermore, the thermal stability of the devices is also significantly enhanced, retaining 80% of its initial PCE after 40 h of continuous aging at 60 °C. These results indicate that the Co3O4/CuSCN/Co3O4 sandwich structure can effectively mitigate the corrosion of the perovskite layer by solvents of an HTL and significantly improves the photovoltaic performance and thermal stability of devices.

Photonics-powered augmented reality skin electronics for proactive healthcare: multifaceted opportunities

Rapid technological advancements have created opportunities for new solutions in various industries, including healthcare. One exciting new direction in this field of innovation is the combination of skin-based technologies and augmented reality (AR). These dermatological devices allow for the continuous and non-invasive measurement of vital signs and biomarkers, enabling the real-time diagnosis of anomalies, which have applications in telemedicine, oncology, dermatology, and early diagnostics. Despite its many potential benefits, there is a substantial information vacuum regarding using flexible photonics in conjunction with augmented reality for medical purposes. This review explores the current state of dermal augmented reality and flexible optics in skin-conforming sensing platforms by examining the obstacles faced thus far, including technical hurdles, demanding clinical validation standards, and problems with user acceptance. Our main areas of interest are skills, chiroptical properties, and health platform applications, such as optogenetic pixels, spectroscopic imagers, and optical biosensors. My skin-enhanced spherical dichroism and powerful spherically polarized light enable thorough physical inspection with these augmented reality devices: diabetic tracking, skin cancer diagnosis, and cardiovascular illness: preventative medicine, namely blood pressure screening. We demonstrate how to accomplish early prevention using case studies and emergency detection. Finally, it addresses real-world obstacles that hinder fully realizing these materials' extraordinary potential in advancing proactive and preventative personalized medicine, including technical constraints, clinical validation gaps, and barriers to widespread adoption.

E-Tattoos: Toward Functional but Imperceptible Interfacing with Human Skin

The human body continuously emits physiological and psychological information from head to toe. Wearable electronics capable of noninvasively and accurately digitizing this information without compromising user comfort or mobility have the potential to revolutionize telemedicine, mobile health, and both human-machine or human-metaverse interactions. However, state-of-the-art wearable electronics face limitations regarding wearability and functionality due to the mechanical incompatibility between conventional rigid, planar electronics and soft, curvy human skin surfaces. E-Tattoos, a unique type of wearable electronics, are defined by their ultrathin and skin-soft characteristics, which enable noninvasive and comfortable lamination on human skin surfaces without causing obstruction or even mechanical perception. This review article offers an exhaustive exploration of e-tattoos, accounting for their materials, structures, manufacturing processes, properties, functionalities, applications, and remaining challenges. We begin by summarizing the properties of human skin and their effects on signal transmission across the e-tattoo-skin interface. Following this is a discussion of the materials, structural designs, manufacturing, and skin attachment processes of e-tattoos. We classify e-tattoo functionalities into electrical, mechanical, optical, thermal, and chemical sensing, as well as wound healing and other treatments. After discussing energy harvesting and storage capabilities, we outline strategies for the system integration of wireless e-tattoos. In the end, we offer personal perspectives on the remaining challenges and future opportunities in the field.

Monitoring of Sweat Ions and Physiological Parameters via a Reconfigurable Modular System

In recent years, wearable sensors have revolutionized health monitoring by enabling continuous, real-time tracking of human health and performance. These noninvasive devices are usually designed to monitor human physical state and biochemical markers. However, enhancing their functionalities often demands intricate customization by designers and additional expenses for users. Here, we present a strategy using assembled modular circuits to customize health monitoring wearables. The modular circuits can be effortlessly reconfigured to meet various specific requirements, facilitating the incorporation of diverse functions at a lower cost. To validate this approach, modular circuits were employed to develop four distinct systems for in vitro evaluations. These systems enabled the detection of sweat biomarkers and physical signals under various scenarios, including sedentary state, exercise, and daily activities with or without incorporating iontophoresis to induce sweat. Four key sweat markers (K+, Ca2+, Na+, and pH) and three essential physical indicators (heart rate, blood oxygen levels, and skin temperature) are selected as the detection targets. Commercial methods were also used to evaluate the potential for effective health monitoring with our technique. This reconfigurable modular wearable (ReModuWear) system promises to provide more easy-to-use and comprehensive health assessments. Additionally, it may contribute to environmental sustainability by reusing modules.

The impact of physiological variations on personalized reference intervals and decision limits: an in-depth analysis

The interpretation of laboratory data is a comparative procedure. Physicians typically need reference values to compare patients' laboratory data for clinical decisions. Therefore, establishing reliable reference data is essential for accurate diagnosis and patient monitoring. Human metabolism is a dynamic process. Various types of systematic and random fluctuations in the concentration/activity of biomolecules are observed in response to internal and external factors. In the human body, several biomolecules are under the influence of physiological rhythms and are therefore subject to ultradian, circadian and infradian fluctuations. In addition, most biomolecules are also characterized by random biological variations, which are referred to as biological fluctuations between subjects and within subjects/individuals. In routine practice, reference intervals based on population data are used, which by nature are not designed to capture physiological rhythms and random biological variations. To ensure safe and appropriate interpretation of patient laboratory data, reference intervals should be personalized and estimated using individual data in accordance with systematic and random variations. In this opinion paper, we outline (i) the main variations that contribute to the generation of personalized reference intervals (prRIs), (ii) the theoretical background of prRIs and (iii) propose new methods on how to harmonize prRIs with the systematic and random variations observed in metabolic activity, based on individuals' demography.

Stability of organic solar cells: toward commercial applications

Organic solar cells (OSCs) have attracted a great deal of attention in the field of clean solar energy due to their advantages of transparency, flexibility, low cost and light weight. Introducing them to the market enables seamless integration into buildings and windows, while also supporting wearable, portable electronics and internet-of-things (IoT) devices. With the development of photovoltaic materials and the optimization of fabrication technology, the power conversion efficiencies (PCEs) of OSCs have rapidly improved and now exceed 20%. However, there is a significant lack of focus on material stability and device lifetime, causing a severe hindrance to commercial applications. In this review, we carefully review important strategies employed to improve the stability of OSCs over the past three years from the perspectives of material design and device engineering. Furthermore, we analyze and discuss the current important progress in terms of air, light, thermal and mechanical stability. Finally, we propose the future research directions to overcome the challenges in achieving highly stable OSCs. We expect that this review will contribute to solving the stability problem of OSCs, eventually paving the way for commercial applications in the near future.

A wearable aptamer nanobiosensor for non-invasive female hormone monitoring

Personalized monitoring of female hormones (for example, oestradiol) is of great interest in fertility and women's health. However, existing approaches usually require invasive blood draws and/or bulky analytical laboratory equipment, making them hard to implement at home. Here we report a skin-interfaced wearable aptamer nanobiosensor based on target-induced strand displacement for automatic and non-invasive monitoring of oestradiol via in situ sweat analysis. The reagentless, amplification-free and 'signal-on' detection approach coupled with a gold nanoparticle-MXene-based detection electrode offers extraordinary sensitivity with an ultra-low limit of detection of 0.14 pM. This fully integrated system is capable of autonomous sweat induction at rest via iontophoresis, precise microfluidic sweat sampling controlled via capillary bursting valves, real-time oestradiol analysis and calibration with simultaneously collected multivariate information (that is, temperature, pH and ionic strength), as well as signal processing and wireless communication with a user interface (for example, smartphone). We validated the technology in human participants. Our data indicate a cyclical fluctuation in sweat oestradiol during menstrual cycles, and a high correlation between sweat and blood oestradiol was identified. Our study opens up the potential for wearable sensors for non-invasive, personalized reproductive hormone monitoring.

Personalized laboratory medicine in the digital health era: recent developments and future challenges

Interpretation of laboratory data is a comparative procedure and requires reliable reference data, which are mostly derived from population data but used for individuals in conventional laboratory medicine. Using population data as a "reference" for individuals has generated several problems related to diagnosing, monitoring, and treating single individuals. This issue can be resolved by using data from individuals' repeated samples, as their personal reference, thus needing that laboratory data be personalized. The modern laboratory information system (LIS) can store the results of repeated measurements from millions of individuals. These data can then be analyzed to generate a variety of personalized reference data sets for numerous comparisons. In this manuscript, we redefine the term "personalized laboratory medicine" as the practices based on individual-specific samples and data. These reflect their unique biological characteristics, encompassing omics data, clinical chemistry, endocrinology, hematology, coagulation, and within-person biological variation of all laboratory data. It also includes information about individuals' health behavior, chronotypes, and all statistical algorithms used to make precise decisions. This approach facilitates more accurate diagnosis, monitoring, and treatment of diseases for each individual. Furthermore, we explore recent advancements and future challenges of personalized laboratory medicine in the context of the digital health era.

Materials-Driven Soft Wearable Bioelectronics for Connected Healthcare

In the era of Internet-of-things, many things can stay connected; however, biological systems, including those necessary for human health, remain unable to stay connected to the global Internet due to the lack of soft conformal biosensors. The fundamental challenge lies in the fact that electronics and biology are distinct and incompatible, as they are based on different materials via different functioning principles. In particular, the human body is soft and curvilinear, yet electronics are typically rigid and planar. Recent advances in materials and materials design have generated tremendous opportunities to design soft wearable bioelectronics, which may bridge the gap, enabling the ultimate dream of connected healthcare for anyone, anytime, and anywhere. We begin with a review of the historical development of healthcare, indicating the significant trend of connected healthcare. This is followed by the focal point of discussion about new materials and materials design, particularly low-dimensional nanomaterials. We summarize material types and their attributes for designing soft bioelectronic sensors; we also cover their synthesis and fabrication methods, including top-down, bottom-up, and their combined approaches. Next, we discuss the wearable energy challenges and progress made to date. In addition to front-end wearable devices, we also describe back-end machine learning algorithms, artificial intelligence, telecommunication, and software. Afterward, we describe the integration of soft wearable bioelectronic systems which have been applied in various testbeds in real-world settings, including laboratories that are preclinical and clinical environments. Finally, we narrate the remaining challenges and opportunities in conjunction with our perspectives.

Thiol-Functionalized Conjugated Metal-Organic Frameworks for Stable and Efficient Perovskite Photovoltaics

Metal-organic frameworks (MOFs) have been investigated recently in perovskite photovoltaics owing to their potential to boost optoelectronic performance and device stability. However, the impact of variations in the MOF side chain on perovskite characteristics and the mechanism of MOF/perovskite film formation remains unclear. In this study, three nanoscale thiol-functionalized UiO-66-type Zr-based MOFs (UiO-66-(SH)2 , UiO-66-MSA, and UiO-66-DMSA) are systematically employed and examined in perovskite solar cells (PSCs). Among these MOFs, UiO-66-(SH)2 , with its rigid organic ligands, exhibited a strong interaction with perovskite materials with more efficient suppression of perovskite vacancy defects. More importantly, A detailed and in-depth discussion is provided on the formation mechanism of UiO-66-(SH)2 -assisted perovskite film upon in situ GIWAXS performed during the annealing process. The incorporation of UiO-66-(SH)2 additives substantially facilitates the conversion of PbI2 into the perovskite phase, prolongs the duration of stage I, and induces a delayed phase transformation pathway. Consequently, the UiO-66-(SH)2 -assisted device demonstrates reduced defect density and superior optoelectronic properties with optimized power conversion efficiency of 24.09% and enhanced long-term stability under ambient environment and continuous light illumination conditions. This study acts as a helpful design guide for desired MOF/perovskite structures, enabling further advancements in MOF/perovskite optoelectronic devices.

Soft Epidermal Paperfluidics for Sweat Analysis by Ratiometric Raman Spectroscopy

The expanding interest in digital biomarker analysis focused on non-invasive human bodily fluids, such as sweat, highlights the pressing need for easily manufactured and highly efficient soft lab-on-skin solutions. Here, we report, for the first time, the integration of microfluidic paper-based devices (μPAD) and non-enhanced Raman-scattering-enabled optical biochemical sensing (Raman biosensing). Their integration merges the enormous benefits of μPAD, with high potential for commercialization and use in resource-limited settings, with biorecognition-element-free (but highly selective) optical Raman biosensing. The introduced thin (0.36 mm), ultra-lightweight (0.19 g), and compact footprint (3 cm2) opto-paperfluidic sweat patch is flexible, stretchable, and conforms, irritation-free, to hairless or minimally haired body regions to enable swift sweat collection. As a great advantage, this new bio-chemical sensory system excels through its absence of onboard biorecognition elements (bioreceptor-free) and omission of plasmonic nanomaterials. The proposed easy fabrication process is adaptable to mass production by following a fully sustainable and cost-effective process utilizing only basic tools by avoiding typically employed printing or laser patterning. Furthermore, efficient collection and transportation of precise sweat volumes, driven exclusively by the wicking properties of porous materials, shows high efficiency in liquid transportation and reduces biosensing latency by a factor of 5 compared to state-of-the-art epidermal microfluidics. The proposed unit enables electronic chip-free and imaging-less visual sweat loss quantification as well as optical biochemical analysis when coupled with Raman spectroscopy. We investigated the multimodal quantification of sweat urea and lactate levels ex vivo (with syntactic sweat including +30 sweat analytes on porcine skin) and achieved a linear dynamic range from 0 to 100 mmol/L during fully dynamic continuous flow characterization.

Molecular Engineering of Photosensitizers for Solid-State Dye-Sensitized Solar Cells: Recent Developments and Perspectives

Dye-sensitized solar cells (DSSCs) are a feasible alternative to traditional silicon-based solar cells because of their low cost, eco-friendliness, flexibility, and acceptable device efficiency. In recent years, solid-state DSSCs (ss-DSSCs) have garnered much interest as they can overcome the leakage and evaporation issues of liquid electrolyte systems. However, the poor morphology of solid electrolytes and their interface with photoanodes can minimize the device performance. The photosensitizer/dye is a critical component of ss-DSSCs and plays a vital role in the device's overall performance. In this review, we summarize recent developments and performance of photosensitizers, including mono- and co-sensitization of ruthenium, porphyrin, and metal-free organic dyes under 1 sun and ambient/artificial light conditions. We also discuss the various requirements that efficient photosensitizers should satisfy and provide an overview of their historical development over the years.

Amphibious epidermal area networks for uninterrupted wireless data and power transfer

The human body exhibits complex, spatially distributed chemo-electro-mechanical processes that must be properly captured for emerging applications in virtual/augmented reality, precision health, activity monitoring, bionics, and more. A key factor in enabling such applications involves the seamless integration of multipurpose wearable sensors across the human body in different environments, spanning from indoor settings to outdoor landscapes. Here, we report a versatile epidermal body area network ecosystem that enables wireless power and data transmission to and from battery-free wearable sensors with continuous functionality from dry to underwater settings. This is achieved through an artificial near field propagation across the chain of biocompatible, magneto-inductive metamaterials in the form of stretchable waterborne skin patches-these are fully compatible with pre-existing consumer electronics. Our approach offers uninterrupted, self-powered communication for human status monitoring in harsh environments where traditional wireless solutions (such as Bluetooth, Wi-Fi or cellular) are unable to communicate reliably.

3D-printed epifluidic electronic skin for machine learning-powered multimodal health surveillance

The amalgamation of wearable technologies with physiochemical sensing capabilities promises to create powerful interpretive and predictive platforms for real-time health surveillance. However, the construction of such multimodal devices is difficult to be implemented wholly by traditional manufacturing techniques for at-home personalized applications. Here, we present a universal semisolid extrusion-based three-dimensional printing technology to fabricate an epifluidic elastic electronic skin (e3-skin) with high-performance multimodal physiochemical sensing capabilities. We demonstrate that the e3-skin can serve as a sustainable surveillance platform to capture the real-time physiological state of individuals during regular daily activities. We also show that by coupling the information collected from the e3-skin with machine learning, we were able to predict an individual's degree of behavior impairments (i.e., reaction time and inhibitory control) after alcohol consumption. The e3-skin paves the path for future autonomous manufacturing of customizable wearable systems that will enable widespread utility for regular health monitoring and clinical applications.