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Graphene inks have recently attracted attention for the development of printed wearable and flexible electronics and sensors not only because of their high conductivity and low cost but also because they are suitable for high-speed printing. Although reliable and scalable printing technologies are well established, further improvement in graphene inks in terms of electrical conductivity, stretchability/flexibility, and mass production is necessary for sensors for real-time monitoring. Herein, highly stretchable and conductive graphene inks were prepared by an efficient and scalable fluid dynamics-assisted exfoliation of graphite and a mixing process with elastomeric Ecoflex. After printing inks onto textile substrates, the serpentine-patterned conductors exhibited high conductivity and stable resistance even under a mechanically stretched state (a strain of 150%). Electrochemical sensors that detect sodium ions were fabricated on this conducting platform. These sensors indicated high potentiometric sensing ability under different mechanical deformations. To demonstrate the on-body performance of the developed sensors, real-time monitoring of sodium-ion concentration in the sweat of a human subject was carried out during an indoor stationary cycling exercise.

Length–weight relations (LWRs) of 12 freshwater fish species from the Geum River, South Korea were estimated. The following species representing the family Cobitidae, Xenocyprididae, Acheilognathidae, and Gobionidae were studied: Cobitis choii Kim et Son, 1984; Opsariichthys uncirostris (Temminck et Schlegel, 1846); Zacco platypus (Temminck et Schlegel, 1846); Tanakia lanceolata (Temminck et Schlegel, 1846); Acheilognathus rhombeus (Temminck et Schlegel, 1846); Hemibarbus labeo (Pallas, 1776); Gobiobotia naktongensis Mori, 1935; Hemibarbus longirostris (Regan, 1908); Microphysogobio jeoni Kim et Yang, 1999; Pseudogobio esocinus (Temminck et Schlegel, 1846); Pseudorasbora parva (Temminck et Schlegel, 1846); Squalidus japonicus (Sauvage, 1883). Parameter b ranged from 2.820 (P. parva) to 3.485 (C. choii), and parameter a ranged from 0.0015 (C. choii) to 0.0145 (A. rhombeus). The LWR for C. choii and G. naktongensis, endangered species in South Korea, was estimated for the first time. Our results could be useful as baseline information for evaluating population status.

In this study, ultrathin and defect-free graphene (Gr) sheets were prepared through a fluid dynamics–induced shear exfoliation method using graphite. The high hydrophobicity and surface area of Gr make it attractive as a solid-contact ion-to-electron transducer for potentiometric K+ sensors, in which the electrodes are fabricated through a screen-printing process. The electrochemical characterization demonstrates that Gr solid contact results in a high double-layer capacitance, potential stability, and strong resistance against water layer, gases, and light. The Gr-based K+ sensors showed a Nernstian slope of 53.53 mV/log[K+] within a linear concentration range of 10−1–10−4 M, a low detection limit of 10−4.28 M, a fast response time of ~8 s, good repeatability, and excellent long-term stability. Moreover, the Gr-based K+ sensors provided accurate ion concentrations in actual samples of human sweat and sports drinks.

This paper proposes a batteryless chronic wound monitoring system to accurately diagnose the wound states with lowered cost. To acquire various biomarkers, the proposed system could interface different types of sensor signals (voltage, resistive, and capacitive) using dual-slope integrator circuit technology. A time-to-digital converter is used to digitize the acquired signals. The proposed system adopts 13.56-MHz near-field communication for energy harvesting and sending data. The proposed IC is implemented using the standard TSMC 0.18- $\mu \text{m}$ CMOS process and occupies an area of 0.5 mm2. The power consumptions of the proposed interface IC and total system are 1.9 and 3.9 mW, respectively.

We report potentiometric performances of ion-to-electron transducer based on reduced graphene oxide (RGO) for application of all-solid-state potassium ion sensors. A large surface area and pore structure of RGO are obtained by a hydrothermal self-assembly of graphene oxide. The extensive electrochemical characterization of RGO solid contact at the interface of ion-selective membrane and gold electrode shows that the potassium ion-selective electrode based on RGO had a high sensitivity (53.34 mV/log[K+]), a low detection of limit (− 4.24 log[K+], 0.06 mM) a good potential stability, and a high resistance to light and gas interferences. The potentiometric K+-sensor device was fabricated by combining of screen-printed electrodes and a printed circuit board. The K+-sensor device accurately measures the ion concentration of real samples of commercial sports drinks, coke and orange juice, and then transfers the collected data to a mobile application through a Bluetooth module. The screen-printed ion sensors based on RGO solid contact show a great potential for real-time monitoring and point-of-care devices in human health care, water-treatment process, and environmental and chemical industries.

Paper-based materials have attracted a great deal of attention in sensor applications because they are readily available, biodegradable, inexpensive, and mechanically flexible. Although paper-based sensors have been developed, but important obstacles remian, which include the retention of chemical and mechanical stabilities when paper is wetted. Herein, we develop a simple and scalable process for fabrication of newspaper-based platforms by coating of parylene C and patterning of metal layers. As-prepared parylene C-coated newspaper (PC-paper) provides low-cost, disposable, and mechanically and chemically stable electrochemical platforms for the development of potentiometric ion sensors for the detection of electrolyte cations, such as, H+ and K+. The pH and K+ sensors produced show near ideal Nernstian sensitivity, good repeatability, good ion selectivity, and low potential drift. These disposable, flexible ion sensors based on PC-paper platforms could provide new opportunities for the development of point-of-care testing sensors, for diagnostics, healthcare, and environment testing.

Sensors with autonomous self-healing properties offer enhanced durability, reliability, and stability. Although numerous self-healing polymers have been attempted, achieving sensors with fast and reversible recovery under ambient conditions with high mechanical toughness remains challenging. Here, a highly sensitive wearable sensor made of a robust bio-based supramolecular polymer that is capable of self-healing via hydrogen bonding is presented. The integration of carbon fiber thread into a self-healing polymer matrix provides a new toolset that can easily be knitted into textile items to fabricate wearable sensors that show impressive self-healing efficiency (>97.0%) after 30 s at room temperature for K+/Na+ sensing. The wearable sweat-sensor system-coupled with a wireless electronic circuit board capable of transferring data to a smart phone-successfully monitors electrolyte ions in human perspiration noninvasively in real time, even in the healed state during indoor exercise. Our smart sensors represent an important advance toward futuristic personalized healthcare applications.

Development of sensing technology with wearable chemical sensors is realizing non-invasive, real-time monitoring healthcare and disease diagnostics. The advanced sensor devices should be compact and portable for use in limited space, easy to wear on human body, and low-cost for personalized healthcare markets. Here, we report a highly sensitive, flexible, and autonomously self-healable pH sensor cable developed by weaving together two carbon fiber thread electrodes coated with mechanically robust self-healing polymers. The pH sensor cable showed excellent electrochemical performances of sensitivity, repeatability, and durability. Spontaneous and autonomous sensor healing efficiency of the pH sensor cable was demonstrated by measuring sensitivity during four cycles of cutting and healing process. The pH sensor cable could measure pH in small volumes of real human fluid samples, including urine, saliva, and sweat, and the results were similar to those of a commercial pH meter. Taken together, successful real-time pH monitoring for human sweat was demonstrated by fabricating a wearable sensing system in which the pH sensor cable was knitted into a headband integrated with wireless electronics.

This paper proposes a batteryless chronic wound monitoring system with commercial discrete components. To monitor the chronic wound, the proposed system acquires the pH and temperature of the chronic wound. The proposed system adopts 13.56-MHz NFC communications to supply power to an interface circuit and send data to mobile phones. The power consumption of the proposed system is 5.0 mW.

We report on the high-throughput production of heterogeneous catalysts of RuO2-deposited graphene using a hydrodynamic process for selective alcohol oxidation. The fluid mechanics of a hydrodynamic process based on a Taylor–Couette flow provide a high shear stress field and fast mixing process. The unique fluidic behavior efficiently exfoliates graphite into defect-free graphene sheets dispersed in water solution, in which ionic liquid is used as the stabilizing reagent to prevent the restacking of the graphene sheets. The deposition of RuO2 on a graphene surface is performed using a hydrodynamic process, resulting in the uniform coating of RuO2 nanoparticles. The as synthesized RuO2/IL–graphene catalyst has been applied efficiently for the oxidation of a wide variety of alcohol substrates, including biomass-derived 5-hydroxymethylfurfural (HMF) under environmentally benign conditions. The catalyst is mechanically stable and recyclable, confirming its heterogeneous nature.

Highly ordered and flexible nanopillar arrays have received considerable interest for many applications of electrochemical devices because of their unique mechanical and structural properties. Here, we report on highly ordered polyoxometalate (POM)-doped polypyrrole (Ppy) nanopillar arrays produced by soft lithography and subsequent electrodeposition. As-prepared POM-Ppy/nanopillar films show superior electrochemical performances for pseudocapacitor and enzymeless electrochemical sensor applications and good mechanical properties, which allowed them to be easily bent and twisted. Regarding electrochemical characteristics for pseudocapacitive electrodes, the POM-Ppy/nanopillar electrodes are capable of delivering high areal capacitance of 77.0 mF cm(-2), high rate performance, and good cycle life of ∼100% retention over 3500 cycles even when bent. Moreover, the study suggests that the POM-Ppy/nanopillar electrodes have an excellent electrocatalytic activity toward hydrogen.

BACKGROUND: Water quality is of concern to water utility operators, public health officials, and populations using the water. If any contaminant is released from a point of entry, it could be spread rapidly throughout the water stream. So the identification of the location of the points of entry and its release history are critical informations to establish the management strategy.METHODS AND RESULTS: Aniline, nonylphenol, pentachlorophenol and formaldehyde in 39 surface water samples were analysed using Gas chromatography-mass spectrometry (GC-MS) methods. Formaldehyde, aniline and nonylphenol were mainly detected in the near sites where industrial waste water and domestic sewage were discharged into stream. But pentachlorophenol was detected in the downstream samples where pulp manufacturing plants were operated.CONCLUSION: Results indicate that pentachlorophenol found in main stream of Guem river was mainly introduced from pulp manufacture industries. Otherwise, formaldehyde, aniline and nonylphenol were mainly contaminated from the industrial waste water and domestic sewage.

Biological health assessment (BHA) has developed as an imperative gauge in efficient management of freshwater resources and fish assemblages. The principal objective of this research is directed at the development and application of a new index under the umbrella of the famous index of biological integrity (IBI). Further, we intended to carry out comparative assessments of the new index with two existing indices and testified to their rational in Geum River watershed, which is the third largest river water basin in South Korea. We analyzed the biotic integrity of 149 different study sites in the streams and rivers of Geum River watershed, perusing fish assemblages and water quality data. The results revealed the newer index, i.e., multi-metric (mm) IBI 06 (mmIBI 06 metrics), as comparatively more efficient than previously used indices, i.e., mmIBI 08 and mmIBI 11. Furthermore, the linear regression and correlational analyses indicated harmonic relation of mmIBI 06 with mmIBI 08 (R2 = 0.85) and mmIBI 11 (R2 = 0.87). Nonetheless, linear regression modeling discovered a very strong positive relation between mmIBI 08 and mmIBI 11 (R2 = 0.91), thereby implying previously used indices demonstrate better approximation. In significant contrast to both old indices, the newer index exhibited improved facility to better classify the study sites between the assortments of &lsquo, excellent to very poor&rsquo, compared to old indices elucidated one-step lower, i.e., from &lsquo, excellent to poor&rsquo, For instance, the newer index categorized 60 sites as &lsquo, very poor&rsquo, requiring immediate attention owing to biological degradation. Additionally, the newer index endures grander ability to indicate sites requiring immediate management or restoration attention with a plausible site classification, especially in relation to the invasive alien species (IAS). The water chemistry was mainly influenced by rampant anthropogenic actions compounded by intensive monsoon precipitation that may relinquish highly suitable grounds for invasive alien fish species. This may eventually lead to severe biological degradation and successive deterioration of habitat by the IAS. In conclusion, the newer index endures ample capacity to indicate the fish community disturbances in rivers and streams. Further, correlation, linear regression, as well as principal component analysis (PCA) analyses on biotic indices and water chemistry showed higher approximations. Therefore, our newer index would be a valuable BHA tool to classify and elucidate the streams and rivers by indicating sites necessitating preferred attention and restoration measures.

Flexible pH sensor technologies have attracted a great deal of attention in many applications, such as, wearable health care devices and monitors for chemical and biological processes. Here, we fabricated flexible and thin pH sensors using a two electrode configuration comprised of a polyaniline nanopillar (PAN) array working electrode and an Ag/AgCl reference electrode. In order to provide nanostructure, soft lithography using a polymeric blend was employed to create a flexible nanopillar backbone film. Polyaniline-sensing materials were deposited on a patterned-nanopillar array by electrochemical deposition. The pH sensors produced exhibited a near-Nernstian response (∼60.3mV/pH), which was maintained in a bent state. In addition, pH sensors showed other excellent sensor performances in terms of response time, reversibility, repeatability, selectivity, and stability.

Design and fabrication of electrodes is key in the development of electrochemical sensors with superior electrochemical performances. Herein, an enzymeless electrochemical sensor is developed for detection of hydrogen peroxide based on the use of highly ordered polyoxometalate (POM)-doped polyaniline (PANI) nanopillar films. The electrodeposition technique enables the entrapment of POMs into PANI during electropolymerization to produce thin coatings of POM-PANI. Electrochemical investigations of the POM-PANI/nanopillar electrode showed well-defined multiple pairs of redox peaks and rapid electron transfer. The nanopillar structure facilitated the diffusion of the electrolyte and thus, enhanced the redox reaction. In particular, the POM-PANI/nanopillar electrode was incorporated into a flow injection biosensor and it demonstrates its electrocatalytic activity to detect hydrogen peroxide with high sensitivity, rapid response time, and low detection limit.

Most lakes are more than 50 years old in Korea, and the vulnerability to water pollution in lake areas has increased due to the increase of inflow pollutant loads caused by human activities. This study has investigated water quality characteristics for the six lakes in Geum River basin through an analysis of long-term water quality trends. It is observed that most results from the six lakes show unstable periodicities in long-term water quality observations and all lakes have low water quality with a level IV and above. Water quality improvement is required for the four lakes except Tapjeong Lake and Boryeong Lake, and water quality management plans are urgently needed especially for Sapgyo Lake where the water quality has been continuously deteriorating. On the other hand, Boryeong Lake well managed for water control and use in multi-purpose dam operations keeps water quality high compared with other lakes under study. It is expected that the results in this study can make a contribution to the water quality management plan incorporating long-term seasonal water quality changes.