Comprehensive Review on Wearable Sweat-Glucose Sensors for Continuous Glucose Monitoring.

The incidence of diabetes is increasing at an alarming rate, and regular glucose monitoring is critical in order to manage diabetes. Currently, glucose in the body is measured by an invasive method of blood sugar testing. Blood glucose (BG) monitoring devices measure the amount of sugar in a small sample of blood, usually drawn from pricking the fingertip, and placed on a disposable test strip. Therefore, there is a need for non-invasive continuous glucose monitoring, which is possible using a sweat sensor-based approach. As sweat sensors have garnered much interest in recent years, this study attempts to summarize recent developments in non-invasive continuous glucose monitoring using sweat sensors based on different approaches with an emphasis on the devices that can potentially be integrated into a wearable platform. Numerous research entities have been developing wearable sensors for continuous blood glucose monitoring, however, there are no commercially viable, non-invasive glucose monitors on the market at the moment. This review article provides the state-of-the-art in sweat glucose monitoring, particularly keeping in sight the prospect of its commercialization. The challenges relating to sweat collection, sweat sample degradation, person to person sweat amount variation, various detection methods, and their glucose detection sensitivity, and also the commercial viability are thoroughly covered.

Energy-Aware QoS MAC Protocol Based on Prioritized-Data and Multi-Hop Routing for Wireless Sensor Networks.

Wireless sensor networks (WSNs) have received considerable interest in recent years. These sensor nodes can gather information from the surrounding environment and transmit it to a designated location. Each sensor node in WSN typically has a battery with a limited capacity. Due to their large number and because of various environmental challenges, it is sometimes hard to replace this finite battery. As a result, energy-efficient communication is seen as a critical aspect in extending the lifespan of a sensor node. On the other hand, some applications that require large coverage and generate various sorts of data packets require multi-hop routing and quality of service (QoS) features. Therefore, in order to avoid network failure, these applications need an energy-efficient QoS MAC protocol that can support multiple levels of data packet priority and multi-hop routing features while focusing on energy conservation. An energy-aware QoS MAC protocol based on Prioritized Data and Multi-hop routing (EQPD-MAC) is proposed in this article. The EQPD-MAC protocol offers a simple yet effective cross-layer communication method. It provides timely delivery of multi-priority packets, uses an adaptive active time to limit idle listening, and integrates a robust routing protocol. Finally, the EQPD-MAC protocol's performance was evaluated and compared to three other well-known QoS MAC protocols. The simulation findings show that the proposed protocol significantly decreases sensor node energy consumption by up to 30.3%, per-bit energy consumption by up to 29.6%, sink node energy consumption by up to 27.4% and increases throughput by up to 23.3%.

Fabric based printed-distributed battery for wearable e-textiles: a review.

Wearable power supply devices and systems are important necessities for the emerging textile electronic applications. Current energy supply devices usually need more space than the device they power, and are often based on rigid and bulky materials, making them difficult to wear. Fabric-based batteries without any rigid electrical components are therefore ideal candidates to solve the problem of powering these devices. Printing technologies have greater potential in manufacturing lightweight and low-cost batteries with high areal capacity and generating high voltages which are crucial for electronic textile (e-textile) applications. In this review, we present various printing techniques, and battery chemistries applied for smart fabrics, and give a comparison between them in terms of their potential to power the next generation of electronic textiles. Series combinations of many of these printed and distributed battery cells, using electrically conducting threads, have demonstrated their ability to power different electronic devices with a specific voltage and current requirements. Therefore, the present review summarizes the chemistries and material components of several flexible and textile-based batteries, and provides an outlook for the future development of fabric-based printed batteries for wearable and electronic textile applications with enhanced level of DC voltage and current for long periods of time.

Trustworthy Wireless Sensor Networks for Monitoring Humidity and Moisture Environments.

Wireless sensors networks (WSNs) are characterized by flexibility and scalability in any environment. These networks are increasingly used in agricultural and industrial environments and have a dual role in data collection from sensors and transmission to a monitoring system, as well as enabling the management of the monitored environment. Environment management depends on trust in the data collected from the surrounding environment, including the time of data creation. This paper proposes a trust model for monitoring humidity and moisture in agricultural and industrial environments. The proposed model uses a digital signature and public key infrastructure (PKI) to establish trust in the data source, i.e., the trust in the sensor. Trust in data generation is essential for real-time environmental monitoring and subsequent analyzes, thus timestamp technology is implemented here to further ensure that gathered data are not created or changed after the assigned time. Model validation is performed using the Castalia network simulator by testing energy consumption at the receiver and sender nodes and the delay incurred by creating or validating a trust token. In addition, validation is also performed using the Ascertia TSA Crusher application for the time consumed to obtain a timestamp from the free TSA. The results show that by applying different digital signs and timestamps, the trust entity of the WSN improved significantly with an increase in power consumption of the sender node by up to 9.3% and receiver node by up to 126.3% for a higher number of nodes, along with a packet delay of up to 15.6% and an average total time consumed up to 1.186 s to obtain the timestamp from the best chosen TSA, which was as expected.

Performances and Biosensing Mechanisms of Interdigitated Capacitive Sensors Based on the Hetero-mixture of SnO2 and In2O3.

This study aims to discuss the synthesis and fabrication of SnO2-In2O3-based thick-films and their biosensing applications. The structural characterization of SnO2-In2O3 nanocomposites was performed using X-ray diffraction, Raman spectroscopy and transmission electron microscopy. Furthermore, the screen-printing technology was used in the fabrication of conductive electrodes to form an interdigitated capacitive structure, and the sensor layer based on the mixture of SnO2 and In2O3. Moreover, the sensing performance of the developed structure was tested using Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) bacteria. In addition, the validation of sensing characteristics was performed by electrochemical impedance spectroscopic and self-resonant frequency analysis. Finally, the sensing properties were analyzed for two consecutive days, and changes in both P. aeruginosa and S. aureus pathogens growing media were also studied.

Novel Cost-Effective Microfluidic Chip Based on Hybrid Fabrication and Its Comprehensive Characterization.

Microfluidics, one of the most attractive and fastest developed areas of modern science and technology, has found a number of applications in medicine, biology and chemistry. To address advanced designing challenges of the microfluidic devices, the research is mainly focused on development of efficient, low-cost and rapid fabrication technology with the wide range of applications. For the first time, this paper presents fabrication of microfluidic chips using hybrid fabrication technology-a grouping of the PVC (polyvinyl chloride) foils and the LTCC (Low Temperature Co-fired Ceramics) Ceram Tape using a combination of a cost-effective xurography technique and a laser micromachining process. Optical and dielectric properties were determined for the fabricated microfluidic chips. A mechanical characterization of the Ceram Tape, as a middle layer in its non-baked condition, has been performed and Young's modulus and hardness were determined. The obtained results confirm a good potential of the proposed technology for rapid fabrication of low-cost microfluidic chips with high reliability and reproducibility. The conducted microfluidic tests demonstrated that presented microfluidic chips can resist 3000 times higher flow rates than the chips manufactured using standard xurography technique.

Comparative Analysis of Deformation Determination by Applying Fiber-optic 2D Deflection Sensors and Geodetic Measurements.

In the paper the description of an experiment for a comparative analysis of two different methods for deformation determination, geodetic and 2D deflection sensors based on fiber-optic curvature sensors (FOCSs) is given. The experiment is performed by a using specially designed assembly which makes it possible to apply both methods. For performing geodetic measurements, a geodetic micro-network is established. Measurements by applying a 2D deflection sensor and three total stations are carried out for comparison. The data processing comprises graphical and numerical analysis of the results. Based on the presented results the potential of 2D deflection sensor application in structural health monitoring (SHM) procedures is indicated. The analysis of the measurement results also indicates the importance of integrating various types of sensors for obtaining more accurate and more reliable deformation measurements results.

A Wireless LC Sensor Coated with Ba0.9Bi0.066TiO3 for Measuring Temperature.

This paper presents a passive LC wireless sensor for measuring temperature. The sensor is designed as a parallel connection of a spiral inductor and an interdigitated capacitor and it was fabricated in a conductive layer using LTCC (Low Temperature Co-fired Ceramic) technology. The inderdigitated capacitor electrodes were coated with a thin film of bismuth doped barium titanate (Ba0.9Bi0.066TiO3), whose permittivity changes with temperature, which directly induces changes in the capacitance of the interdigitated capacitor and consequently changes the resonant frequency of the sensor. The measurements of S-parameter of the sensor were performed using a Vector Network Analyzer (E5071B, Agilent Technologies, Santa Clara, CA, USA), whose port was connected to the antenna coil that was placed around the sensor in order to be able to wirelessly detect temperature, in the temperature range from 25 °C to 165 °C.

A fully textile-based, tunable, force and strain sensing resistor for e-textile applications.

This work presents a novel approach towards integrating electronic components with textiles, by successfully creating a fully textile-based element that is capable of detecting applied forces by variation in its resistance value. The fabrication of the device consists of a specialized siliconized conductive fabric, which is placed above and below a layer of switch fabric, which acts as a force sensor. In this paper, the effects of three different geometries are observed, as well as the washability of the device, along with tension testing. Μoreover, the device behavior is simulated as well as applied in a real-life scenario. The proposed element demonstrates a good dynamic range, high repeatability and stability, and minimal impact of washing, creating a great candidate for integration in e-textiles.

Fabrication of Bilayer Nanofibrous-Hydrogel Scaffold from Bacterial Cellulose, PVA, and Gelatin as Advanced Dressing for Wound Healing and Soft Tissue Engineering.

Tissue engineering is currently one of the fastest-growing areas of engineering, requiring the fabrication of advanced and multifunctional materials that can be used as scaffolds or dressings for tissue regeneration. In this work, we report a bilayer material prepared by electrospinning a hybrid material of poly(vinyl alcohol) (PVA) and bacterial cellulose (BC NFs) (top layer) over a highly interconnected porous 3D gelatin-PVA hydrogel obtained by a freeze-drying process (bottom layer). The techniques were combined to produce an advanced material with synergistic effects on the physical and biological properties of the two materials. The bilayer material was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a water contact measurement system (WCMS). Studies on swelling, degradability, porosity, drug release, cellular and antibacterial activities were performed using standardized procedures and assays. FTIR confirmed cross-linking of both the top and bottom layers, and SEM showed porous structure for the bottom layer, random deposition of NFs on the surface, and aligned NFs in the cross section. The water contact angle (WCA) showed a hydrophilic surface for the bilayer material. Swelling analysis showed high swelling, and degradation analysis showed good stability. The bilayer material released Ag-sulfadiazine in a sustained and controlled manner and showed good antibacterial activities against severe disease-causing gram + ive and -ive (Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa) bacterial strains. In vitro biological studies were performed on fibroblasts (3T3) and human embryonic kidneys (HEK-293), which showed desirable cell viability, proliferation, and adhesion to the bilayer. Thus, the synergistic effect of NFs and the hydrogel resulted in a potential wound dressing material for wound healing and soft tissue engineering.

Fundamental properties of smart hydrogels for tissue engineering applications: A review.

Tissue engineering is an advanced and potential biomedical approach to treat patients suffering from lost or failed an organ or tissue to repair and regenerate damaged tissues that increase life expectancy. The biopolymers have been used to fabricate smart hydrogels to repair damaged tissue as they imitate the extracellular matrix (ECM) with intricate structural and functional characteristics. These hydrogels offer desired and controllable qualities, such as tunable mechanical stiffness and strength, inherent adaptability and biocompatibility, swellability, and biodegradability, all crucial for tissue engineering. Smart hydrogels provide a superior cellular environment for tissue engineering, enabling the generation of cutting-edge synthetic tissues due to their special qualities, such as stimuli sensitivity and reactivity. Numerous review articles have presented the exceptional potential of hydrogels for various biomedical applications, including drug delivery, regenerative medicine, and tissue engineering. Still, it is essential to write a comprehensive review article on smart hydrogels that successfully addresses the essential challenging issues in tissue engineering. Hence, the recent development on smart hydrogel for state-of-the-art tissue engineering conferred progress, highlighting significant challenges and future perspectives. This review discusses recent advances in smart hydrogels fabricated from biological macromolecules and their use for advanced tissue engineering. It also provides critical insight, emphasizing future research directions and progress in tissue engineering.

Membrane-based microfluidic systems for medical and biological applications.

Microfluidic devices with integrated membranes that enable control of mass transport in constrained environments have shown considerable growth over the last decade. Membranes are a key component in several industrial processes such as chemical, pharmaceutical, biotechnological, food, and metallurgy separation processes as well as waste management applications, allowing for modular and compact systems. Moreover, the miniaturization of a process through microfluidic devices leads to process intensification together with reagents, waste and cost reduction, and energy and space savings. The combination of membrane technology and microfluidic devices allows therefore magnification of their respective advantages, providing more valuable solutions not only for industrial processes but also for reproducing biological processes. This review focuses on membrane-based microfluidic devices for biomedical science with an emphasis on microfluidic artificial organs and organs-on-chip. We provide the basic concepts of membrane technology and the laws governing mass transport. The role of the membrane in biomedical microfluidic devices, along with the required properties, available materials, and current challenges are summarized. We believe that the present review may be a starting point and a resource for researchers who aim to replicate a biological phenomenon on-chip by applying membrane technology, for moving forward the biomedical applications.

Wearable humidity sensor embroidered on a commercial face mask and its electrical properties.

Owing to the rapid development in the field of e-textile-based flexible and portable sensors, the present work demonstrates a fully textile-based stretchable face mask humidity sensor which was created using digital embroidery technique. The design of the sensor was comprised of interdigitated structured electrodes made up of polymer core-based conductive silver-coated threads and hygroscopic threads embedded between them. The fabricated sensor performed well towards moisture detection in accordance with the principle where resistance of the face mask sensor decreased with the increase in the relative humidity along with the changing operational frequency in the range from 1 Hz to 200 kHz. The electrical response (resistance, impedance, capacitance and phase angle) of the novel thread-based sensor towards change in relative humidity was recorded and showed in the present work. The embroidery of polymer-based threads onto the face mask towards humidity sensing offers a novel wearable platform for more extended biomedical applications for detection of various breath biomarkers and thus early diagnosis of diseases. Supplementary Information: The online version contains supplementary material available at 10.1007/s10853-022-08135-2.

Paper card-like electrochemical platform as a smart point-of-care device for reagent-free glucose measurement in tears.

This communication describes the development of polyvinyl chloride electrochemical system in which a paper layer loaded with reagents is inserted into the device, demonstrating a new concept of a paper card-like pad for a reagent-free and easy measurement of the target analyte in solution. This device detects glucose in artificial tears in the range of 0.2-2 mM with a detection limit of 50 µM by simply adding the artificial tears to the paper card-like pad. The novel configuration goes beyond the state of the art, widening the application range of paper in the design of smart analytical devices.

Toothpaste ingestion-evaluating the problem and ensuring safety: systematic review and meta-analysis.

This systematic review and meta-analysis aimed to evaluate the ingestion of toothpaste and its sequelae. The study adhered to the PRISMA guidelines and was registered in the PROSPERO database. A comprehensive search strategy was conducted across multiple databases, resulting in the inclusion of 18 relevant publications. Eligible studies encompassed various designs and included both children and adults as the study population. Data extraction was carried out systematically, and relevant information on study characteristics, interventions, and outcomes were collected. The assessment of bias was performed using the Joanna Briggs Institute's Critical Appraisal Tools showing variations of bias among the included studies. The overall risk of systemic toxicity was found to be low, and no severe or life-threatening events were reported in the included studies. Furthermore, some toothpaste formulations containing higher concentrations of fluoride were associated with an increased risk of dental fluorosis. These findings have several implications for practice and policy. Healthcare providers and dental professionals should emphasize the importance of promoting safe toothpaste use, especially in vulnerable populations such as young children who are more prone to accidental ingestion. Public health campaigns and educational initiatives should aim to raise awareness about appropriate toothpaste usage and the potential risks. In addition, toothpaste manufacturers and regulatory bodies should consider revising guidelines and regulations to ensure the safety of oral care products, including the appropriate concentration of active ingredients. Future research should focus on investigating the long-term effects of toothpaste ingestion, exploring potential interactions between different active ingredients, and evaluating the efficacy of current preventive measures.

A novel method for in-situ extracting bio-impedance model parameters optimized for embedded hardware.

A novel method for embedded hardware-based parameter estimation of the Cole model of bioimpedance is developed and presented. The model parameters R∞, R1 and C are estimated using the derived set of equations based on measured values of real (R) and imaginary part (X) of bioimpedance, as well as the numerical approximation of the first derivative of quotient R/X with respect to angular frequency. The optimal value for parameter α is estimated using a brute force method. The estimation accuracy of the proposed method is very similar with the relevant work from the existing literature. Moreover, performance evaluation was performed using the MATLAB software installed on a laptop, as well as on the three embedded-hardware platforms (Arduino Mega2560, Raspberry Pi Pico and XIAO SAMD21). Obtained results showed that the used platforms can perform reliable bioimpedance processing with the same accuracy, while Raspberry Pi Pico is the fastest solution with the smallest energy consumption.

A novel microfluidic compact disc to investigate electrochemical property changes between artificial and real salivary samples mixed with mouthwashes using electrical impedance analysis.

Diagnosing oral diseases at an early stage may lead to better preventive treatments, thus reducing treatment burden and costs. This paper introduces a systematic design of a microfluidic compact disc (CD) consisting of six unique chambers that run simultaneously from sample loading, holding, mixing and analysis. In this study, the electrochemical property changes between real saliva and artificial saliva mixed with three different types of mouthwashes (i.e. chlorhexidine-, fluoride- and essential oil (Listerine)-based mouthwashes) were investigated using electrical impedance analysis. Given the diversity and complexity of patient's salivary samples, we investigated the electrochemical impedance property of healthy real saliva mixed with different types of mouthwashes to understand the different electrochemical property which could be a foundation for diagnosis and monitoring of oral diseases. On the other hand, electrochemical impedance property of artificial saliva, a commonly used moisturizing agent and lubricant for the treatment of xerostomia or dry mouth syndrome was also studied. The findings indicate that artificial saliva and fluoride-based mouthwash showed higher conductance values compared to real saliva and two other different types of mouthwashes. The ability of our new microfluidic CD platform to perform multiplex processes and detection of electrochemical property of different types of saliva and mouthwashes is a fundamental concept for future research on salivary theranostics using point-of-care microfluidic CD platform.

Role of Graphene Oxide in Bacterial Cellulose-Gelatin Hydrogels for Wound Dressing Applications.

Biopolymer-based hydrogels have several advantages, including robust mechanical tunability, high biocompatibility, and excellent optical properties. These hydrogels can be ideal wound dressing materials and advantageous to repair and regenerate skin wounds. In this work, we prepared composite hydrogels by blending gelatin and graphene oxide-functionalized bacterial cellulose (GO-f-BC) with tetraethyl orthosilicate (TEOS). The hydrogels were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscope (AFM), and water contact angle analyses to explore functional groups and their interactions, surface morphology, and wetting behavior, respectively. The swelling, biodegradation, and water retention were tested to respond to the biofluid. Maximum swelling was exhibited by GBG-1 (0.01 mg GO amount) in all media (aqueous = 1902.83%, PBS = 1546.63%, and electrolyte = 1367.32%). All hydrogels were hemocompatible, as their hemolysis was less than 0.5%, and blood coagulation time decreased as the hydrogel concentration and GO amount increased under in vitro standard conditions. These hydrogels exhibited unusual antimicrobial activities against Gram-positive and Gram-negative bacterial strains. The cell viability and proliferation were increased with an increased GO amount, and maximum values were found for GBG-4 (0.04 mg GO amount) against fibroblast (3T3) cell lines. The mature and well-adhered cell morphology of 3T3 cells was found for all hydrogel samples. Based on all findings, these hydrogels would be a potential wound dressing skin material for wound healing applications.

Oral micro-electronic platform for temperature and humidity monitoring.

Intraoral theranostics, the integration of diagnostics and therapeutics within the oral cavity, is gaining significant traction. This pioneering approach primarily addresses issues like xerostomia (dry mouth), commonly resulting from cancer treatment, with a specific focus on monitoring temperature and humidity. This paper introduces the innovative Intra-Oral Portable Micro-Electronic (IOPM) fluidic theranostic device platform. It leverages conventional dental spoons by incorporating advanced sensors for precise measurements of oral temperature and humidity. Personalization options include a microfluidic chip and a tooth model, enabling targeted delivery of therapeutic agents to optimize treatment outcomes. The electronic control system simplifies the administration of fluid dosages, intelligently adjusted based on real-time oral cavity temperature and humidity readings. Rigorous experimental evaluations validate the platform's precision in delivering fluid volumes at predefined intervals. This platform represents a transformative advancement for individuals contending with oral health challenges such as xerostomia (dry mouth). Furthermore, it has the potential to elevate oral healthcare standards by providing advanced diagnostics and tailored therapeutic solutions, benefiting both patients and dental professionals alike.

Graphene Oxide-Functionalized Bacterial Cellulose-Gelatin Hydrogel with Curcumin Release and Kinetics: In Vitro Biological Evaluation.

Biopolymer-based bioactive hydrogels are excellent wound dressing materials for wound healing applications. They have excellent properties, including hydrophilicity, tunable mechanical and morphological properties, controllable functionality, biodegradability, and desirable biocompatibility. The bioactive hydrogels were fabricated from bacterial cellulose (BC), gelatin, and graphene oxide (GO). The GO-functionalized-BC (GO-f-BC) was synthesized by a hydrothermal method and chemically crosslinked with bacterial cellulose and gelatin using tetraethyl orthosilicate (TEOS) as a crosslinker. The structural, morphological, and wettability properties were studied using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and a universal testing machine (UTM), respectively. The swelling analysis was conducted in different media, and aqueous medium exhibited maximum hydrogel swelling compared to other media. The Franz diffusion method was used to study curcumin (Cur) release (Max = 69.32%, Min = 49.32%), and Cur release kinetics followed the Hixson-Crowell model. Fibroblast (3T3) cell lines were employed to determine the cell viability and proliferation to bioactive hydrogels. Antibacterial activities of bioactive hydrogels were evaluated against infection-causing bacterial strains. Bioactive hydrogels are hemocompatible due to their less than 0.5% hemolysis against fresh human blood. The results show that bioactive hydrogels can be potential wound dressing materials for wound healing applications.