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We proposed a sensing–transducing coupled strategy by embedding the high piezoresponse Sm-PMN-PT ceramic into a moisture-sensitive PEI via electrospinning to conjugate the humidity perception and signal transduction synchronously and sympatrically.

Degradable wearable electronics offer a promising route to construct sustainable cities and reduced carbon society. However, the difficult functionalization and the poor stability of degradable sensitive materials dramatically restrict their application in personalized healthcare assessment. Herein, we developed a scalable, low-cost, and porosity degradable MXene-polylactic acid textile (DMPT) for on-body biomonitoring via electrospinning. A combination of polydimethylsiloxane templating and MXene flake impregnation methods endows the fabricated DMPT with a sensitivity of 5.37/kPa, a fast response time of 98 ms, and a good mechanical stability (over 6000 cycles). An efficient degradation of as-electrospun DMPTs was observed in 1 wt % sodium carbonate solution. It is found that the incorporation of MXene nanosheets boosts the hydrophilicity and degradation efficiency of active polylactic acid nanofibrous films in comparison with the pristine counterpart. Furthermore, the as-received DMPT demonstrates great capability in monitoring physiological activities of wrist pulse, knuckle bending, swallowing, and vocalization. This work opens up a new paradigm for developing and optimizing high-performance degradable on-body electronics.

The high moisture level of exhaled gases unavoidably limits the sensitivity of breath analysis via wearable bioelectronics. Inspired by pulmonary lobe expansion/contraction observed during respiration, a respiration-driven triboelectric sensor (RTS) was devised for simultaneous respiratory biomechanical monitoring and exhaled acetone concentration analysis. A tin oxide-doped polyethyleneimine membrane was devised to play a dual role as both a triboelectric layer and an acetone sensing material. The prepared RTS exhibited excellent ability in measuring respiratory flow rate (2-8 L/min) and breath frequency (0.33-0.8 Hz). Furthermore, the RTS presented good performance in biochemical acetone sensing (2-10 ppm range at high moisture levels), which was validated via finite element analysis. This work has led to the development of a novel real-time active respiratory monitoring system and strengthened triboelectric-chemisorption coupling sensing mechanism.

Polyvinylidene fluoride (PVDF) is considered to be one of the most promising candidates for next-generation wearable sensors; however, the sensing ability of PVDF is worth expanding beyond its ferroelectricity. In this work, PVDF is used as matrix material for humidity detection by adding two other ingredients: lithium chloride (LiCl) and polyvinyl alcohol (PVA), optimal concentrations of LiCl and PVA are found by systematic investigation of the impact of the two inclusions on humidity sensing ability of the composites.

NiWO4 microflowers with a large surface area up to 79.77 m2·g-1 are synthesized in situ via a facile coprecipitation method. The NiWO4 microflowers are further decorated with multi-walled carbon nanotubes (MWCNTs) and assembled to form composites for NH3 detection. The as-fabricated composite exhibits an excellent NH3 sensing response/recovery time (53 s/177 s) at a temperature of 460 °C, which is a 10-fold enhancement compared to that of pristine NiWO4. It also demonstrates a low detection limit of 50 ppm; the improved sensing performance is attributed to the porous structure of the material, the large specific surface area, and the p-n heterojunction formed between the MWNTs and NiWO4. The gas sensitivity of the sensor based on daisy-like NiWO4/MWCNTs shows that the sensor based on 10 mol % (MWN10) has the best gas sensitivity, with a sensitivity of 13.07 to 50 ppm NH3 at room temperature and a detection lower limit of 20 ppm. NH3, CO2, NO2, SO2, CO, and CH4 are used as typical target gases to construct the NiWO4/MWCNTs gas-sensitive material and study the research method combining density functional theory calculations and experiments. By calculating the morphology and structure of the gas-sensitive material NiWO4(110), the MWCNT load samples, the vacancy defects, and the influence law and internal mechanism of gas sensitivity were described.

Raindrop contains a large amount of renewable mechanical energy. Acid rain has adverse impact on the plants, aquatic animals and infrastructure. In this work, a triboelectric raindrop generator (TRG) was developed to harvest raindrop energy on a large scale. The TRG consists of electrification layer, electrodes and substrate. At the rainfall rate of 53 mL/s, the open‐circuit voltage and short‐circuit currents of the device reaches 27 V and 4.6 μA, respectively, which can simultaneously drive 60 LED light‐emitting diodes or charge a 5 μF capacitor. In addition, relied on the electrostatic shielding effect of the solid–liquid interface, the pH value of ambient solution drops can be spontaneously detected to reveal the potential in real‐time monitoring of environmental quality. By integrating with a signal processing circuit, a self‐powered acid rain alert system was formed for real‐time monitoring the acidity of the falling raindrops. This work proposes a feasible and innovative approach for active environmental monitoring.

As humidity is one of the most widely demanded environmental parameters, the precision of its detection is significant. An advanced humidity sensor will improve the validity of the humidity monitoring system. In this study, a facile chemical layer-by-layer self-assembly (CLS) method was developed for fabricating graphene oxide (GO)/polyethyleneimine (PEI) multilayer films. Owing to the chemical bonding between the PEI and GO, and the intrinsic stickiness of the PEI, layered films with different numbers of layers were successfully prepared using the CLS method and confirmed through ultraviolet–visible (UV–Vis) spectroscopy and the mass loading of quartz crystal microbalance (QCM). Morphological measurements revealed that the roughness and thickness of the films increased exponentially with the number of bilayers. The GO/PEI films were deposited on QCM electrodes using the CLS method to produce the humidity sensors. The humidity measurement results showed a high sensitivity (37.84 Hz/%RH) and rapid response/recovery (

Due to the extensive energy consumption and high population density in modern cities, the collection and use of scattered walking energy from the stream of people is crucial for the development of a green ecological city. Herein, a flexible undulated electrode-based triboelectric nanogenerator (u-TENG) was integrated to the floor to scavenge walking energy from pedestrians, promoting the ordered collection of disordered and scattered energy. Driven by the steps of human walking, the output of the as-fabricated u-TENG are an open-circuit voltage of 86 V and a short-circuit current of 6.2 μA, which are able to continuously light up 110 light-emitting diode bulbs. In addition, a self-powered location-tracking system was prepared for pedestrian volume counting and passenger tracing with the purpose of reducing energy consumption in public areas. The proposed walking energy harvesting device is flexible, feasible, and unaffected by season, climate, or location. This work not only proposes a strategy for mechanical energy harvesting in public areas, including subway stations, hospitals, shopping malls, and business streets, but also offers a novel solution for smart cities and low-carbon transportation alternatives.

Spermatozoon represents a very special cell type in human body, and glycosylation plays essential roles in its whole life including spermatogenesis, maturation, capacitation, sperm-egg recognition, and fertilization. In this study, by mapping the most comprehensive N-glycoproteome of human spermatozoa using our recently developed site-specific glycoproteomic approaches, we show that spermatozoa contain a number of distinctive glycoproteins, which are mainly involved in spermatogenesis, acrosome reaction and sperm:oocyte membrane binding, and fertilization. Heavy fucosylation is observed on 14 glycoproteins mostly located at extracellular and cell surface regions in spermatozoa but not in other tissues. Sialylation and Lewis epitopes are enriched in the biological process of immune response in spermatozoa, while bisected core structures and LacdiNAc structures are highly expressed in acrosome. These data deepen our knowledge about glycosylation in spermatozoa and lay the foundation for functional study of glycosylation and glycan structures in male infertility.

NiWO

A flexible NO2 gas sensor based on a polypyrrole/nitrogen-doped multi-walled carbon nanotube (PPy/N-MWCNT) composite film was successfully prepared on PI substrates using a combined in situ self-assembly and annealing treatment method. After annealing at 350 °C, the gas sensor exhibited a high response of 24.82% ((Rg−Ra)/Ra×100%) under 5 ppm of NO2, which is 44.12 times greater than that of the unannealed sensor. The PPy/N-MWCNT gas sensor exhibited excellent repeatability, remarkable selectivity, good long-term stability, and acceptable flexibility. Furthermore, the effect of the relative humidity on the gas sensing properties was examined. The excellent gas sensing performances of the sensor were attributed to the enriched adsorption sites due to degradation of the amount of stacked PPy structures on the surface of the N-MWCNTs after the annealing treatment. The results demonstrated that PPy/N-MWCNT composite films are highly promising for potential applications in the field of NO2 gas sensing.

A UV-activated room temperature chemiresistive gas sensor based on ZnO nanocrystals film was fabricated. Its gas sensing properties under various conditions were also investigated in detail. The results shed new insight into the adsorption behaviors of gas molecules on the surface of ZnO nanocrystals under UV irradiation. The chemisorbed oxygen species (O2(ads)−(hv)) induced by UV light govern the adsorption and desorption ways of other gas molecules on the surface of ZnO nanocrystals, which is dependent on the electron affinity of gas molecules. Gas molecules with higher electron affinity than oxygen molecules can be adsorbed on the surface by the competitive adsorption way, extracting electrons from the surface. Gas molecules with lower electron affinity than oxygen molecules are attracted by the adsorbed O2(ads)−(hv) layer, releasing electrons to the surface. These processes can influence the gas sensing properties of the sensor. Our findings will pave the way for the fundamental understanding and design of UV-activated gas sensor in the future.

A fast and simple method using co-grinding with Fe powder followed by heat treatment is developed to regulate surface oxygen vacancy content of ZnO nanoparticles. The moderately increased surface oxygen vacancy is conducive to shortening the adsorption and desorption times of NO2 molecules, arising from the enhanced O2 adsorption. Therefore, the response and recovery speeds of ZnO nanoparticle-based sensor under UV irradiation were significantly promoted. Our findings not only offer a feasible strategy to modulate surface oxygen vacancy content of nanostructured oxides, but also provide a novel approach to improve the response and recovery speeds of light-activated NO2 sensor.

Respiration is an important physiological process of human body that can not only act as vital signs for physical health management or “biomarkers” of some diseases, but also as a kind of energy that can be utilized to drive triboelectric nanogenerator (TENG). It is particularly desirable to develop a facile TENG that can be driven by human respiration itself for multifunctional human respiratory monitoring. In this work, a respiration-driven TENG based on Ce-doped ZnO-PANI nanocomposite film that can convert respiratory airflow energy into electric signals was developed for the detection of multiple respiratory parameters including trace-level NH3 concentration, human respiratory flow and respiratory frequency. It was found that the as-designed TENG exhibited excellent ability for respiratory flow monitoring (2–6 L/min), identification of human breathing frequency and recognition of different breathing patterns. Furthermore, output voltage of the self-powered NH3 sensor monotonously decreases with the increase of NH3 concentrations from 0.1 to 25 ppm. Especially, a good NH3-sensing performance was exhibited when exposed to a trace-level NH3 atmosphere ranging from 0.1 to 1 ppm, implying a promising potential in self-powered disease screening related to the detection of exhaled NH3 in human breathing. This research offers a facile method to establish a multifunctional respiratory monitoring system driven by respiration itself, which is of significant importance in self-powered human health monitoring through non-implantable respiratory diagnosis.

In mammals, physiological respiration involves respiratory cycles of inhaled and exhaled breaths, which has traditionally been an underutilized resource potentially encompassing a wealth of physiologically relevant information as well as clues to potential diseases. Recently, triboelectric nanogenerators (TENGs) have been widely adopted for self-powered respiration monitoring owing to their compelling features, such as decent biocompatibility, wearing comfort, low-cost, and high sensitivity to respiration activities in the aspect of low frequency and slight amplitude body motions. Physiological respiration behaviors and exhaled chemical regents can be precisely and continuously monitored by TENG-based respiration sensors for personalized health care. This article presents an overview of TENG enabled self-powered respiration monitoring, with a focus on the working principle, sensing materials, functional structures, and related applications in both physical respiration motion detection and chemical breath analysis. Concepts and approaches for acquisition of physical information associated with respiratory rate and depth are covered in the first part. Then the sensing mechanism, theoretical modeling, and applications related to detection of chemicals released from breathing gases are systemically summarized. Finally, the opportunities and challenges of triboelectric effect enabled self-powered respiration monitoring are comprehensively discussed and criticized.

Fossil fuel internal combustion engines generate and release a huge amount of nitrogen dioxide, leading to respiratory and allergic diseases such as asthma, pneumonia, and possibly tuberculosis. Here we develop an alveolus-inspired membrane sensor (AIMS) for self-powered wearable nitrogen dioxide detection and personal physiological assessment. The bionic AIMS exhibits an excellent sensitivity up to 452.44%, a good linearity of 0.976, and superior selectivity under a NO

An ultrasensitive self-powered ammonia (NH3) sensing system based on a vertical contact-separate mode triboelectric nanogenerator (TENG) has been proposed for room temperature detection of NH3 concentrations both in the ambient environment and in human exhaled gases. Owing to the special output characteristics of the TENG adjusted by the load resistance of the NH3 sensor, output voltage of the fabricated gas sensor has a proportional relationship with NH3 concentration, which is the fundamental working mechanism of the self-powered gas-sensing system. The triboelectric ammonia sensor (TEAS) based on PANI-MWCNTs composite thin film possesses a NH3-sensing response of 10% at 0.01 ppm NH3 and exhibits a great response of 255% at 100 ppm NH3. Meanwhile, the TEAS also holds fast response/recovery time (89–120 s/103–127 s for 0.6–100 ppm NH3), excellent long-term stability, satisfactory selectivity and good anti-bending ability. Furthermore, a preliminary test of human exhaled NH3 concentration has been carried out to further expand the practical application of the developed TEAS. The results not only provide an effective technique in ultrasensitive NH3 sensing but also greatly broaden the applicability of TENG in the detection of human kidney health through comparing to average NH3 concentrations within exhaled gases of healthy people.

Flexible nitrogen dioxide (NO2) gas sensors based on organic thin-film transistors (OTFTs) were developed in this work, in which conductive indium tin oxide (ITO) coated polyethylene naphthalene-2,6-dicarboxylate (PEN) was designed for the flexible substrates, and poly methyl methacrylate (PMMA) and poly(3-hexylthiophene) (P3HT) was spin-coated as the gate dielectric layer and spray-deposited as the active layer, respectively. The effects of PMMA concentrations and P3HT solution volume on performances of flexible OTFTs were systematically investigated. The results showed that the optimized flexible OTFT exhibited high field-effect mobility (9.51×10–3 cm2/(V s) at a gate bias of –50 V) and excellent response characteristics, including high sensitivity (up to 0.169 ppm–1), good repeatability and selectivity. The flexibility of the developed OTFT sensor was also investigated, and the results showed that the electrical and gas-sensing properties were affected by the bending cycles, thus further work should be done for improving the flexibility of the sensor. This work provides an effective approach in developing high performance flexible OTFT NO2 gas sensor.

In this paper, a two-step method is proposed to optimize the layout of the conventional serpentine film heater thus to improve the temperature uniformity. The optimization is made on transverse direction firstly with varied linewidths and pitches, and then on longitudinal direction with varied line shapes. Based on finite element simulation using a flow field approach, the heater geometry evolution dependent on temperature uniformity is investigated. The results show that the isothermal region extends greatly in transverse direction by the first step, while it extends subsequently in longitudinal direction by the second step and simultaneously shrinks in transverse direction. By a proper tradeoff between these two modification steps, the substrate area within 96.4% temperature uniformity increases by more than five times in comparison to the conventional serpentine heater. This area is even larger by 5% than that achieved by an optimized spiral heater, indicating that the serpentine heater is more powerful to adjust the temperature uniformity. Moreover, the optimized serpentine heater realizes a coverage ratio as high as 86.64% on a rectangular membrane, demonstrating that serpentine heaters are more flexible to substrate shapes than spiral heaters to achieve a uniform and large area temperature distribution.

The triboelectric nanogenerator (TENG) driven self-powered gas sensor has been developed for room temperature nitrogen dioxide (NO2) detection under UV illumination (365 nm). Powered by TENG, the concentration of NO2 can be spontaneously detected via chemoresistive gas sensor based on Zinc Oxide-Reduced graphene oxide (ZnO-RGO) hybrid films, where the voltage drop across the interdigital electrodes (IDEs) has a proportional relationship with NO2 concentration. The self-powered triboelectric gas sensor (TGS) composed by ZnO-RGO composite films exhibit superior response (~ 16.8) and sensitivity as well as selectivity than that for pure ZnO film. With respect to selectivity, the response of ZnO-RGO composite film based TGS to NO2 was at least 49-fold higher than those for other gases. Furthermore, through a signal processing circuit, a self-powered NO2 gas alert system was developed for real-time monitoring the ambient NO2 concentration. This work not only promotes the applicability of TENGs as self-powered sensors but also pushes forwards the active sensing network node for environmental monitoring by harvesting ambient energy.