Blood platelet count signiflcantly affects the development of severe conditions like myocardial infarction, peripheral arterial ischemia, respiratory compromise, stroke, diabetes, coronavirus disease 2019 (COVID-19), along with chemotherapy patients and those suffering cardiovascular diseases (CVDs). These conditions necessitate frequent monitoring of platelet counts to guide diagnostic and therapeutic decisions. However, existing techniques are relatively time-consuming, lack of accuracy and require precise operation. The emergence of these severe diseases underscored the need to develop advanced platelet count-monitoring techniques which are rapid, highly precise, and conveniently portable for point-of-care applications. In this study, we emphasized the development of a triboelectric microfluidic nanosensor (TMNS) for platelet quantiflcation through the assessment of flow resistance. The functionality of TMNS device is based on immobilization of platelets on a collagen layer coated inside a microfluidic channel. The triboelectric voltage output is measured as a detection signal of the flow resistance and is enhanced by incorporating high surface area copper oxide nanowires (CuO NWs) on the interior of copper tubes. These copper tubes serve as terminal electrodes and for flow guiding. The flow resistance of plasma solutions is elevated when the platelet concentration increases due to heightened adherence of platelets onto the collagen layer. Variations in flow resistance induce alterations in contact electriflcation, causing changes in output voltage at load terminals. Fine-tuning of the TMNS device was achieved by optimizing the channel width and length, flowing liquid viscosity, and voltage measurement technique. Platelet quantiflcation sensing data were acquired through the combination of platelet-rich plasma (PRP) and platelet-poor plasma (PPP) solutions. The described device exhibits promising capabilities for platelet-count monitoring in whole-blood samples collected from three distinct patient groups, showcasing its potential impact in precise point-of-care applications.

BaTiO3 octahedra, edge-, and corner-truncated cubes, and cubes with four tunable sizes from 132 to 438 nm are synthesized by a solvothermal growth approach. Acetic acid treatment can cleanly remove BaCO3 impurity. Rietveld refinement of X-ray diffraction patterns and Raman spectra help to confirm the particles have a tetragonal crystal structure. The crystals also exhibit size- and facet-dependent bandgap shifts. BaTiO3 octahedra show larger piezoelectric, ferroelectric, and pyroelectric effects than truncated cubes and cubes. The measured dielectric constant differences should be associated with their various facet-dependent behaviors. Piezoelectric nanogenerators fabricated from BaTiO3 octahedra consistently show the best performance than those containing truncated cubes and cubes. In particular, a nanogenerator with 30 wt.%-incorporated octahedra displays an open-circuit voltage of 23 V and short-circuit current of 324 nA. The device performance is also highly stable. The maximum output power reaches 3.9 µW at 60 MΩ. The fabricated nanogenerator can provide sufficient electricity to power light-emitting diodes. This work further demonstrates that various physical properties of semiconductor crystals show surface dependence.

Platelet number plays an important role in several kinds of diseases such as leukemia, hepatitis C, diabetes, COVID-19, microbial infections, etc. These diseases can result in thrombocytopenia, a condition where patients suffer from reduced platelets, thus requiring the need to frequently monitor the platelet count. Currently existing techniques are complex, costly, and time consuming. The target diseases continue to evolve urging the need to develop rapid, facile point-of-care devices with high precision. In this regard, the current study is focused on the development of a platelet quantification technique based on trapping of platelets in a microfluidic channel adhered with collagen layer, and CuO NWs grown on Cu tube integrated on both the sides of the channel. This trapping of platelets results in a change in the triboelectric output performance from solid-liquid contact electrification due to change in flow rate of platelet content in the plasma. These changes in triboelectric output are enhanced by CuO NWs due to its high surface-area-to-volume ratio. The study of flow sensing by integrating the microfluidic device with solid-liquid contact electrification has been reported for the first time. The flow sensing signal was optimized by variation in viscosity of the flowing liquid, channel geometry, flow rate, and triboelectric voltage measuring methods. The platelet rich plasma (PRP) and platelet poor plasma (PPP) were prepared and mixed in different ratios to prepare the solutions with different concentration of platelets (0% - 100%). The calibration curve for platelet quantification has shown a variation of 9 V for change in platelet concentration from 0% to 100%. The proposed device exhibited a linear response with the variation in platelet counts. The obtained results prove its potential and feasibility as a point-of-care device.

Given the huge economic burden caused by chronic and acute diseases on human beings, it is an urgent requirement of a cost-effective diagnosis and monitoring process to treat and cure the disease in their preliminary stage to avoid severe complications. Wearable biosensors have been developed by using numerous materials for non-invasive, wireless, and consistent human health monitoring. Graphene, a 2D nanomaterial, has received considerable attention for the development of wearable biosensors due to its outstanding physical, chemical, and structural properties. Moreover, the extremely flexible, foldable, and biocompatible nature of graphene provide a wide scope for developing wearable biosensor devices. Therefore, graphene and its derivatives could be trending materials to fabricate wearable biosensor devices for remote human health management in the near future. Various biofluids and exhaled breath contain many relevant biomarkers which can be exploited by wearable biosensors non-invasively to identify diseases. In this article, we have discussed various methodologies and strategies for synthesizing and pattering graphene. Furthermore, general sensing mechanism of biosensors, and graphene-based biosensing devices for tear, sweat, interstitial fluid (ISF), saliva, and exhaled breath have also been explored and discussed thoroughly. Finally, current challenges and future prospective of graphene-based wearable biosensors have been evaluated with conclusion. Graphene is a promising 2D material for the development of wearable sensors. Various biofluids (sweat, tears, saliva and ISF) and exhaled breath contains many relevant biomarkers which facilitate in identify diseases. Biosensor is made up of biological recognition element such as enzyme, antibody, nucleic acid, hormone, organelle, or complete cell and physical (transducer, amplifier), provide fast response without causing organ harm.

Wearable electrochemical sensors that can detect chemical analytes non-invasively are a fast developing next-generation digital-health technology. Because of their excellent performance, intrinsic compactness, and low cost, electrochemical-based sensors are capable of detecting biomarkers through a non-invasive approach for the continuous monitoring of real-time health status, which holds a lot of potential as wearable sensors for a tremendous promise for a plethora of applications. These wearable electrochemical sensors have been incorporated into various materials systems and even directly on the epidermis for different monitoring purposes because of their unique potential to process chemical analytes in a minimal/non-invasive and non-obtrusive manner. With ongoing innovation and a focus on critical challenges, such minimal/non-invasive electrochemical biosensors are anticipated to open up a new exciting path in the field of wearable wireless sensing devices and body-sensor networks, and thus find abundant use in a wide range of personal healthcare monitoring as well as in sport and military applications. Hence, this review article examines current advancements and discoveries in the field of wearable biosensors, with a focus on a subset of these devices that can conduct very sensitive electrochemical analysis. Recent insights into novel sampling strategies, various electrochemical sensing mechanisms and power management techniques have been discussed in detail in this review article. Finally, present unmet challenges and opportunities in wearable electrochemical biosensors are explored to motivate future technological breakthroughs.

Triboelectric nanogenerators (TENGs) based energy harvesting is considered as a highly efficient approach for mechanical-to-electrical energy conversion based on contact electrification and electrostatic induction. Although triboelectrification is exhibited by almost all substances, chemists and material scientists have performed extensive investigations through theoretical analysis and practical applications to promote further development of TENGs. However, there are various parameters related to triboelectric materials and its output performance, which are required to be optimized for further improvement of efficiency and stability of TENGs. Especially, extensive research effort has been dedicated in engineering triboelectric materials to improve the output performance. However, the industrial application of TENG is still limited by low charging and power conversion efficiency. This review comprehensively discusses the recent progress in improvement of the output performance of TENGs based on different strategies and principles. Moreover, this review also suggests a holistic approach for the design and integration of charge boosting and power management with TENGs. The key impact of this review includes the discussion regarding physical and chemical modification based multidimensional engineering as well as different charge boosting, and power management strategies for the further advancement of TENGs. Moreover, the review also further introduces the applications of TENGs in emerging fields, such as wearable electronic devices and implantable medical devices. Finally, the challenges and future prospective are discussed, thereby guiding further research priorities.

Label-free and rapid detection of pathogenic microorganisms carry an utmost importance for human health as well as environmental monitoring and diagnostics purposes. However, concurrent bacterial detection techniques are either time consuming or associated with expensive reagents and sophisticated equipments. Herein, surface engineered nanoparticles and solid-liquid contact electrification are applied to study the carbohydrate-protein interactions and to develop a self-powered and label-free nanosensor for the detection of Escherichia coli (E. coli) for the first time. D-Mannose functionalized gold nanoparticles (m-Au NPs) and PBS (Phosphate buffer saline) buffer are utilized as the solid triboelectric sensing layer and contact liquid, respectively. The transferred charges generated from the contact electrification of m-Au NPs and PBS result in self-powered electric outputs as signals to investigate the interaction between D-mannose and concanavalin A (Con A). In addition, m-Au NPs also show its ability to specifically recognize the FimH of type 1 pili in E. coli and enable the triboelectric nanosensor (TENS) with selective and sensitive detection towards E. coli. The sensing mechanism has been fully studied and supported in light of surface modification mediated change in interfacial charge transfer phenomena. Attachment of Con A or E. coli decreases the work function of the solid triboelectric sensing layer leading to the enhancement of output voltage and thereby provides the necessary sensing platform. Moreover, the developed TENS shows the reusable potential and can detect E. coli in a wide range from 2 x 104 to 2 x 107 CFU/ml with a limit of detection (LOD) of 4 x 103 CFU/ml. The current work highlights the bright prospect of TENS as a new prototype of sensing technology for label-free and rapid analysis of carbohydrate-protein interactions as well as other pathogenic microorganisms.

Ultrasensitive and highly accurate bioassays are critically required for the early detection of various biomarkers and diagnosis of cancer. Electrogenerated chemiluminescence (ECL) is one such technique which shows powerful analytical ability by incorporating ECL active species for sensitive detection of targets. In this regard, the development of ECL as an assay technique is constantly being pushed for better performance and lower detection limits. Incorporation of sensitive immunosensing and aptasensing methods with ECL has the ability to multiply the advantages several-fold. The recent progress in and methods utilized for the enhancement and amplification of ECL detection techniques based on highly sensitive immunosensors and aptasensors have been discussed in this review with regard to widely popular techniques.

In recent years, triboelectric nanogenerators (TENGs) are proved to be as the prime backbone for developing a self-powered sensing system. However, solid-solid contact electrification based nanogenerators suffer mostly due to inefficient contact which poses a major bottleneck for the development of long term durable and stable nanosensors. In this regard, we have reported a strategic methodology to develop a highly sensitive mercury ion sensor based on solid-liquid contact electrification, which has prime importance for the self-powered monitoring of mercury ion due to its high health risk and environmental pollution toxicity. In this work, 3-mercaptopropionic acid (MPA) capped Au nanoparticles (NPs) are employed as the solid friction layer as well as the recognition element for mercury ion detection. In addition, volatile organic solvent acetone is utilized as the contact liquid instead of water. The developed nanosensor exhibits long term stability and contact frequency independent sensing performance compared to previously reported solid-solid triboelectric nanosensors (TENS) for mercury ion detection. The large binding affinity of Hg2+ and the carboxylic groups results in the increase of transferred charges and enhanced surface potential. It is interesting to observe that the work function reduces after the binding of Hg2+ ions onto MPA molecules, which is also favorable for electron transfer during the contact electrification process. The developed nanosensor can provide a wide linear detection range from 10 nM to 1 μM as well as a low detection limit of 10 nM. As a whole, this work demonstrates a novel paradigm for designing a rapid, low-cost, and portable self-powered sensing system for real time highly selective monitoring of mercury ion from complex environmental samples.

In this study, a self-powered triboelectric nanosensor (TENS) based on chemically enhanced solid-liquid contact electrification has been demonstrated. The TiO2 nanosheet (NS) arrays, grown by two step hydrothermal process is employed as solid triboelectric material. On the other side volatile organic solvent acetone is utilized as contact liquid to obtain higher triboelectric performance. The chemical modification of TiO2 NS surface with catechin promotes enhanced response voltage due to ligand to metal charge transfer complex between Ti molecules and enediol ligands of catechin, exhibiting 1 nM LOD and wide linear range (1 µM to 100 µM). The output voltage has been chemically enhanced 1.59 times for 10 mM catechin concentration. The study not only demonstrates a self-powered cost effective nanosensor but also explores the possibility to improve the electrical performance of solid-liquid based contact electrification through surface chemical environment engineering and utilizing volatile organic solvents as contact liquid.

The abundance of water on earth provides a large window to utilize the mechanical energy within river currents and ocean waves. In this regard, hydropower harvesting through solid-liquid contact electrification has received considerable interest in the recent past. Despite advancements in nanotechnology, liquid energy harvesting devices, especially solid-liquid triboelectric nanogenerators (S-L TENGs), require efficient engineering of the interfacial properties of their substrates to transfer liquid mass and momentum rapidly with the effective generation/transfer of surface charges. To face this challenge, several parameters such as the selection of material, surface morphology and surface properties are currently being studied to develop a better system architecture for energy harvesting and self-powered application platforms with three different interacting modes of liquid contact. Moreover, several parameters of the contact solvents such as the ionic activity and polarity have been studied to understand the practical applicability of S-L TENGs to harvest energy from different natural and artificial resources. In addition, the scope of harvesting mechanical energy from other volatile organic compounds has been studied recently. Self-powered applications of S-L TENGs in various fields have also been demonstrated by different research groups. This work reviews recent progress in the development of S-L TENGs for the first time in terms of the different properties of solid and liquid contact materials along with their respective applications. Furthermore, the work concludes with perspectives, future opportunities, and major challenges of fabricating S-L TENGs as an efficient energy harvester.

Digital microfluidic (DMF) platforms have contributed immensely to the development of multifunctional lab-on-chip systems for performing complete sets of biological and analytical assays. Electrowetting-on-dielectric (EWOD) technology, due to its outstanding flexibility and integrability, has emerged as a promising candidate for such lab-on-chip applications. Triggered by an electrical stimulus, EWOD devices allow precise manipulation of single droplets along the designed electrode arrays without employing external pumps and valves, thereby enhancing the miniaturization and portability of the system towards transcending important laboratory assays in resource-limited settings. In recent years, the simple fabrication process and reprogrammable architecture of EWOD chips have led to their widespread applications in food safety analysis. Various EWOD devices have been developed for the quantitative monitoring of analytes such as food-borne pathogens, heavy metal ions, vitamins, and antioxidants, which are significant in food samples. In this paper, we reviewed the advances and developments in the design of EWOD systems for performing versatile functions starting from sample preparation to sample detection, enabling rapid and high-throughput food analysis.

Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. Accepted Manuscript View Article Online

Triboelectric nanogenerators (TENGs) and triboelectric nanosensors (TENSs) are the prime backbones for the realization of environmental mechanical energy harvesting and self-powered sensing applications. However, the low efficiency of concurrent solid-solid contact electrification creates a major bottleneck for the growth of highly promising technologies. To address this problem, herein, we report a strategic protocol to design a TENS by solid-liquid contact electrification for chemical sensing purposes as well as an efficient approach for the chemical enhancement of solid-liquid TENGs. In particular, TiO2 nanosheet arrays and various solvents (including water, ethanol and acetone) are employed as solid triboelectric materials and contact liquids, respectively, for the demonstration of solid-liquid contact electrification for mechanical energy harvesting and catechin detection. As a self-powered sensor, the TiO2 nanosheet array-based TENS provides superior advantages such as long-term stability, frequency-independent output and humidity-insensitive properties compared to previously reported solid-solid TENSs. The chemically enhanced sensing mechanism of the TiO2 nanosheet array-based TENS for catechin detection is further confirmed with the decrease in the work function and can provide a wide linear window (100 nM-100 mu M) and a low detection limit (30 nM). All the results support that solid-liquid TENSs pave a new path toward efficient self-powered sensors for environmental and healthcare monitoring.

A simple, label-free and cost effective sensor have been studied for reliable urea/glucose sensing, and common serum analyte detection comparable with market available urea "Assay Kit" is also performed by using SiO2 and CdSe-ZnS nanoparticles in electrolyte-insulator-semiconductor structure for the first time. Thermally grown SiO2 membrane has shown lower pH detection limit (0.081) and lowest drift rate (2.9 mV/hr) than those of the sputtering and E-beam deposited SiO2 membranes. The urea detection at physiological buffer pH 7.4 with sensitivity of similar to 1.6 mV/mg. dl(-1) at linear range of 6 to 36 mg/dl is shown. The pH detection limit is further reduced (0.074) by using chaperonin protein mediated CdSe-ZnS nanoparticles assembly over SiO2 surface owing to high pH sensitivity of 55 mV/pH. The sensing mechanism is due to the SiOx content decreased with increasing pH value. This suggests the lower H+ ions absorption on the sensing membrane surface, which is observed by X-ray photo-electron spectroscopy. The glucose concentration is detected by using the core-shell CdSe-ZnS nanoparticles through H2O2 sensing because of reduction/oxidation (redox) properties of Zn as well as Zn2+ ions generation. Due to the high catalytic activity for H2O2 sensitivity, low detection limit of 1 mu M is obtained, which will help to detect glucose using this bio-chip in future. (C) The Author(s) 2016. Published by ECS.