Wearable Battery-Free Perspiration Analyzing Sites Based on Sweat Flowing on ZnO Nanoarrays

Integrated Wearable Flexible Hydrogel Patch Sensing System for the Detection of Physiological Markers

Conventional wearable flexible sensing systems typically comprise three components: a flexible substrate that contacts the skin, a signal processing module, and a signal output module. These components function relatively independently, resulting in a complex system that lacks sufficient integration. Therefore, developing an integrated wearable flexible sensing system by combining the flexible substrate, the signal processing module, and the signal output module not only enhances performance and comfort, but also reduces manufacturing costs and the risk of failure. Hydrogel substrates are particularly advantageous due to their excellent biocompatibility, flexibility, and encapsulation capabilities. Herein, we designed an integrated wearable flexible sensing system using an agarose hydrogel to encapsulate biological oxidative enzymes (e.g., glucose oxidase (GOx), lactate oxidase, and ethanol oxidase) and silver nanowires-polydopamine (Ag NWs-PB) as the signal processing module and a color-changing TMB probe as the signal output module. Additionally, we incorporated a polydimethylsiloxane-silicon dioxide patch to collect sweat for detecting physiological markers (e.g., glucose, lactate, and ethanol). An example of the application to facilitate visual detection of glucose in sweat was developed by encapsulating GOx as a biological oxidative enzyme in a sensing system. The system provides results within 3.5 min and operates within a linear range of 0.02 to 5.00 mmol/L, achieving a limit of detection of 0.011 mmol/L. This innovation not only presents a more integrated and portable solution for wearable hydrogel systems, but also introduces a new, feasible method for detecting human physiological markers through a straightforward detection process.

Recent Advances in Fibrous Materials for Hydroelectricity Generation

Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development. Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gaseous water has been considered a promising strategy for mitigating the energy crisis. Fibrous materials with unique flexibility, processability, multifunctionality, and practicability have been widely applied for fibrous materials-based hydroelectricity generation (FHG). In this review, the power generation mechanisms, design principles, and electricity enhancement factors of FHG are first introduced. Then, the fabrication strategies and characteristics of varied constructions including 1D fiber, 1D yarn, 2D fabric, 2D membrane, 3D fibrous framework, and 3D fibrous gel are demonstrated. Afterward, the advanced functions of FHG during water harvesting, proton dissociation, ion separation, and charge accumulation processes are analyzed in detail. Moreover, the potential applications including power supply, energy storage, electrical sensor, and information expression are also discussed. Finally, some existing challenges are considered and prospects for future development are sincerely proposed.

Recent advances in biosensors based on metal-oxide semiconductors system-integrated into bioelectronics

Metal-oxide semiconductors (MOSs) have emerged as pivotal components in technology related to biosensors and bioelectronics. Detecting biomarkers in sweat provides a glimpse into an individual's metabolism without the need for sample preparation or collection steps. The distinctive attributes of this biosensing technology position it as an appealing option for biomedical applications beyond the scope of diagnosis and healthcare monitoring. This review encapsulates ongoing developments of cutting-edge biosensors based on MOSs. Recent advances in MOS-based biosensors for human sweat analyses are reviewed. Also discussed is the progress in sweat-based biosensing technologies to detect and monitor diseases. Next, system integration of biosensors is demonstrated ultimately to ensure the accurate and reliable detection and analysis of target biomarkers beyond individual devices. Finally, the challenges and opportunities related to advanced biosensors and bioelectronics for biomedical applications are discussed.

A Bifunctional Wearable Sensor Based on a Nanoporous Membrane for Simultaneous Detection of Sweat Lactate and Temperature

Wearable sensors for non-invasive, real-time detection of sweat lactate have far-reaching implications in the fields of health care and exercise physiological responses. Here, we propose a wearable electrochemical sensor with gold nanoelectrode arrays fabricated on the nanoporous polycarbonate (PC) membrane by encapsulating lactate oxidase (LOx) in chitosan (CS) hydrogel for detecting body temperature and sweat lactate concurrently. Flexible gold nanoporous electrodes not only enhance electrode area but also offer a nanoconfined space to accelerate the catalytic reaction of LOx and control substrate concentration on the surface of LOx to decrease substrate inhibition. The proposed sensor has a long durability of 13 days and better selectivity for the detection of sweat lactate over a wide linear range (0.01-35 mM) with a low detection limit (0.144 μM). Furthermore, temperature-dependent transmembrane currents passing through the sensor are used to estimate body temperature. We then use multiple linear regression to adjust the effect of temperature on lactate detection and succeed in monitoring lactate molecules in sweat and body temperature during exercise.

Advanced and personalized healthcare through integrated wearable sensors (versatile)

Applications of integrated wearable sensors for the monitoring of human vital signs and clinically relevant biomarkers.

Screen-Printable Functional Nanomaterials for Flexible and Wearable Single-Enzyme-Based Energy-Harvesting and Self-Powered Biosensing Devices

Developing flexible bioelectronics is essential to the realization of artificial intelligence devices and biomedical applications, such as wearables, but their potential is limited by sustainable energy supply. An enzymatic biofuel cell (BFC) is promising for power supply, but its use is limited by the challenges of incorporating multiple enzymes and rigid platforms. This paper shows the first example of screen-printable nanocomposite inks engineered for a single-enzyme-based energy-harvesting device and a self-powered biosensor driven by glucose on bioanode and biocathode. The anode ink is modified with naphthoquinone and multiwalled carbon nanotubes (MWCNTs), whereas the cathode ink is modified with Prussian blue/MWCNT hybrid before immobilizing with glucose oxidase. The flexible bioanode and the biocathode consume glucose. This BFC yields an open circuit voltage of 0.45 V and a maximum power density of 266 μW cm-2. The wearable device coupled with a wireless portable system can convert chemical energy into electric energy and detect glucose in artificial sweat. The self-powered sensor can detect glucose concentrations up to 10 mM. Common interfering substances, including lactate, uric acid, ascorbic acid, and creatinine, have no effect on this self-powered biosensor. Additionally, the device can endure multiple mechanical deformations. New advances in ink development and flexible platforms enable a wide range of applications, including on-body electronics, self-sustainable applications, and smart fabrics.

Self-Powered Wearable Biosensor in a Baby Diaper for Monitoring Neonatal Jaundice through a Hydrovoltaic-Biosensing Coupling Effect of ZnO Nanoarray

Neonatal jaundice refers to the abnormality of bilirubin metabolism for newborns, and wearable transcutaneous bilirubin meters for real-time measuring the bilirubin concentration is an insistent demand for the babies' parents and doctors. In this paper, a self-powered wearable biosensor in a baby diaper for real-time monitoring neonatal jaundice has been realized by the hydrovoltaic-biosensing coupling effect of ZnO nanoarray. Without external power supply, the system can work independently, and the hydrovoltaic output can be treated as both the power source and biosensing signal. The working mechanism is that the hydrovoltaic output arises from the urine flowing on ZnO nanoarray and the enzymatic reaction on the surface can influence the output. The sensing information can be transmitted through a wireless transmitter, and thus the parents and doctors can treat the neonatal jaundice of babies in time. This work can potentially promote the development of next generation of biosensors and physiological monitoring system, and expand the scope of self-powered technique and smart healthcare area.

Light-Weight, Self-Powered Sensor Based on Triboelectric Nanogenerator for Big Data Analytics in Sports

With the rapid development of the Internet of Things (IoTs), big data analytics has been widely used in the sport field. In this paper, a light-weight, self-powered sensor based on a triboelectric nanogenerator for big data analytics in sports has been demonstrated. The weight of each sensing unit is ~0.4 g. The friction material consists of polyaniline (PANI) and polytetrafluoroethylene (PTFE). Based on the triboelectric nanogenerator (TENG), the device can convert small amounts of mechanical energy into the electrical signal, which contains information about the hitting position and hitting velocity of table tennis balls. By collecting data from daily table tennis training in real time, the personalized training program can be adjusted. A practical application has been exhibited for collecting table tennis information in real time and, according to these data, coaches can develop personalized training for an amateur to enhance the ability of hand control, which can improve their table tennis skills. This work opens up a new direction in intelligent athletic facilities and big data analytics.

Nanogenerator-based self-powered sensors for data collection

Self-powered sensors can provide energy and environmental data for applications regarding the Internet of Things, big data, and artificial intelligence. Nanogenerators provide excellent material compatibility, which also leads to a rich variety of nanogenerator-based self-powered sensors. This article reviews the development of nanogenerator-based self-powered sensors for the collection of human physiological data and external environmental data. Nanogenerator-based self-powered sensors can be designed to detect physiological data as wearable and implantable devices. Nanogenerator-based self-powered sensors are a solution for collecting data and expanding data dimensions in a future intelligent society. The future key challenges and potential solutions regarding nanogenerator-based self-powered sensors are discussed.

Antipathogenic properties and applications of low-dimensional materials

A major health concern of the 21st century is the rise of multi-drug resistant pathogenic microbial species. Recent technological advancements have led to considerable opportunities for low-dimensional materials (LDMs) as potential next-generation antimicrobials. LDMs have demonstrated antimicrobial behaviour towards a variety of pathogenic bacterial and fungal cells, due to their unique physicochemical properties. This review provides a critical assessment of current LDMs that have exhibited antimicrobial behaviour and their mechanism of action. Future design considerations and constraints in deploying LDMs for antimicrobial applications are discussed. It is envisioned that this review will guide future design parameters for LDM-based antimicrobial applications.

Mineralized Soft and Elastic Polymer Dot Hydrogel for a Flexible Self-Powered Electronic Skin Sensor

We propose an integrated, self-powered, flexible electronic skin device containing an alginate-derived polymer dot (A-PD)-incorporated mineralized hydrogel-based energy storage unit and a chitosan-derived n-type carbon dot (N-CD)-based solar cell for an energy-harvesting unit. This study demonstrates a unique architecture of mineralized hydrogel comprising A-PD-incorporated poly(acrylic acid) (PAA)/CaCO₃/laponite containing soft and sensitive layers, deposited with a polyaniline electrode to serve as an energy storage unit. The self-assembly was achieved through the ionic cross-linking between A-PD and PAA driven by the mineralization process, resulting in excellent dimensional stability and improved mechanical properties of the hydrogel. The sp² carbon-rich A-PD enhances the electrochemical performance and the overall photon-to-electrical conversion and storage efficiency for self-powered devices by the formation of the bridge of electrons between the ionized polymer and metal ion. The capacitive sensor developed in this study exhibits high sensitivity in detecting small pressure changes, such as the falling of small water droplets. The self-powered sensing device can detect and monitor various human motions continuously by harvesting light energy from outdoor sunlight. Furthermore, the energy-autonomous device exhibits unique responses for handwriting characters stably and repeatedly. The proposed system may be applicable to human-machine interfaces, biomonitoring systems, secure communication, and wearable devices.