Artificial Sweat Solution Research Articles

Percutaneous Absorption of Fireground Contaminants: Naphthalene, Phenanthrene, and Benzo[a]pyrene in Porcine Skin in an Artificial Sweat Vehicle.

Firefighters face significant risks of exposure to toxic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), during fire suppression activities. PAHs have been found in the air, on the gear and equipment, and in biological samples such as the skin, breath, urine, and blood of firefighters after fire response. However, the extent to which exposure occurs via inhalation, dermal absorption, or ingestion is unclear. In this study, three PAHs, naphthalene, phenanthrene, and benzo[a]pyrene, were applied to porcine skin in vitro in an artificial sweat solution to better gauge firefighters' dermal exposures while mimicking their sweaty skin conditions using an artificial sweat dosing vehicle. Multiple absorption characteristics were calculated, including cumulative absorption, percent dose absorbed, diffusivity, flux, lag time, and permeability. The absorption of the PAHs was greatly influenced by their molecular weight and solubility in the artificial sweat solution. Naphthalene had the greatest dose absorption efficiency (35.0 ± 4.6% dose), followed by phenanthrene (6.8 ± 3.2% dose), and lastly, benzo[a]pyrene, which had the lowest absorption (0.03 ± 0.04% dose). The lag times followed a similar trend. All chemicals had a lag time of approximately 60 min or longer, suggesting that chemical concentrations on the skin may be reduced by immediate skin cleansing practices after fire exposure.

Assessing the performance of a robust multiparametric wearable patch integrating silicon-based sensors for real-time continuous monitoring of sweat biomarkers

The development of wearable devices for sweat analysis has experienced significant growth in the last two decades, being the main focus the monitoring of athletes health during workouts. One of the main challenges of these approaches has been to attain the continuous monitoring of sweat for time periods over 1 h. This is the main challenge addressed in this work by designing an analytical platform that combines the high performance of potentiometric sensors and a fluidic structure made of a plastic fabric into a multiplexed wearable device. The platform comprises Ion-Sensitive Field-Effect Transistors (ISFETs) manufactured on silicon, a tailor-made solid-state reference electrode, and a temperature sensor integrated into a patch-like polymeric substrate, together with the component that easily collects and drives samples under continuous capillary flow to the sensor areas. ISFET sensors for measuring pH, sodium, and potassium ions were fully characterized in artificial sweat solutions, providing reproducible and stable responses. Then, the real-time and continuous monitoring of the biomarkers in sweat with the wearable platform was assessed by comparing the ISFETs responses recorded during an 85-min continuous exercise session with the concentration values measured using commercial Ion-Selective Electrodes (ISEs) in samples collected at certain times during the session. The developed sensing platform enables the continuous monitoring of biomarkers and facilitates the study of the effects of various real working conditions, such as cycling power and skin temperature, on the target biomarker concentration levels.

Electrochemical Behaviour of an Au-Ge Alloy in an Artificial Saliva and Sweat Solution

In modern times, more and more different materials (including alloys) are in direct contact with human electrolytes (sweat, saliva, lymph, blood, etc.). One of the most important properties for the use of these materials is therefore their chemical inertness or resistance to corrosion when they are in contact with human electrolytes. Consequently, during the development of such new materials, it is necessary to study and understand their basic electrochemical behaviour in a given environment. The purpose of this research was to monitor the electrochemical behaviour of the new Au-Ge alloy in artificial sweat and artificial saliva solutions, depending on the electrolyte composition and exposure time. This new alloy represents a potential material for use in dentistry or for jewellery. The obtained results of the study show that the immersion time and the pH value have a significantly greater influence on the corrosion resistance of the new Au-Ge alloy than the composition of the electrolyte solution. The results of the SEM/EDX analysis additionally confirm the main results of the electrochemical measurements.

Enhanced Sweat Biosensing with Thread-Embedded Microfluidic Devices.

BACKGROUND This study explored the integration of conductive threads into a microfluidic compact disc (CD), developed using the xurographic method, for a potential sweat biosensing platform. MATERIAL AND METHODS The microfluidic CD platform, fabricated using the xurographic method with PVC films, included venting channels and conductive threads linked to copper electrodes. With distinct microfluidic sets for load and metering, flow control, and measurement, the CD's operation involved spinning for sequential liquid movement. Impedance analysis using HIOKI IM3590 was conducted for saline and artificial sweat solutions on 4 identical CDs, ensuring reliable conductivity and measurements over a 1 kHz to 200 kHz frequency range. RESULTS Significant differences in |Z| values were observed between saline and artificial sweat treatments. 27.5 μL of saline differed significantly from 27.5 μL of artificial sweat, 72.5 μL of saline from 72.5 μL of artificial sweat, and 192.5 μL of saline from 192.5 μL of sweat. Significant disparities in |Z| values were observed between dry fibers and Groups 2, 3, and 4 (varying saline amounts). No significant differences emerged between dry fibers and Groups 6, 7, and 8 (distinct artificial sweat amounts). These findings underscore variations in fiber characteristics between equivalent exposures, emphasizing the nuanced response of the microfluidic CD platform to different liquid compositions. CONCLUSIONS This study shows the potential of integrating conductive threads in a microfluidic CD platform for sweat sensing. Challenges in volume control and thread coating degradation must be addressed for transformative biosensing devices in personalized healthcare.

On-Chip Electrochemical Sensing with an Enhanced Detecting Signal Due to Concentration Polarization-Based Analyte Preconcentration.

Here, we integrated two key technologies within a microfluidic system, an electrokinetic preconcentration of analytes by ion Concentration Polarization (CP) and local electrochemical sensors to detect the analytes, which can synergistically act to significantly enhance the detection signal. This synergistic combination, offering both decoupled and coupled operation modes for continuous monitoring, was validated by the intensified fluorescent intensities of CP-preconcentrated analytes and the associated enhanced electrochemical response using differential pulse voltammetry and chronoamperometry. The system performance was evaluated by varying the location of the active electrochemical sensor, target analyte concentrations, and electrolyte concentration using fluorescein molecules as the model analyte and Homovanillic acid (HVA) as the target bioanalyte within both phosphate-buffered saline (PBS) and artificial sweat solution. The combination of on-chip electrochemical sensing with CP-based preconcentration renders this generic approach adaptable to various analytes. This advanced system shows remarkable promise for enhancing biosensing detection in practical applications while bridging the gap between fundamental research and practical implementation.

Cu-based thin rolled foils: relationship among alloy composition, micromechanical and antiviral properties against SARS-CoV-2

The healthcare-associated infections (HAIs) and pandemics caused by multidrug-resistant (MDR) and new-generation pathogens threaten the whole world community. Cu and its alloys have been attracting widespread interest as anti-contamination materials due to the rapid inactivation of MDR-superbugs and viruses. Applying thin Cu-based foils on pre-existing surfaces in hygiene-sensitive areas represents a quick, simple, cost-effective self-sanitising practice. However, the influence of chemical composition and microstructure should be deeply investigated when evaluating the antimicrobial capability and durability of Cu-based materials. The effect of composition on micromechanical and antiviral properties was investigated by comparing Cu15Zn and Cu18Ni20Zn (foil thickness from 13 to 27 μm) with Phosphorous High-Conductivity (PHC) Cu. The influence of recrystallisation annealing of PHC Cu was also investigated. Microstructural characterisation was carried out by optical (OM) and scanning electron (FEG-SEM) microscopy, Energy-dispersive Spectroscopy (EDS) and Electron-Backscattered Diffraction (EBSD). The micromechanical behaviour was assessed by microhardness, microscale abrasion and scratch tests. Cu-based foils were exposed to SARS-CoV-2 for different time points in quasi-dry conditions (artificial sweat solution), evaluating their antiviral capability by quantitative Reverse-Transcriptase Polymerase Chain Reaction (qRT-PCR). Surface morphology, contact angle measurements and Cu release were measured. All Cu-based surfaces completely inactivated SARS-CoV-2 in 10 min: pure Cu was the best option regarding antiviral efficiency, while Cu15Zn showed the best trade-off between micromechanical and antiviral properties.

Fiber-based hydrophobic and stretchable UV-photochromic textile

Wearable sensors composed of fabric have attracted considerable research interest as they can detect various environmental factors that affect the human body, such as ultraviolet (UV) radiation, temperature, and humidity. Among these sensors, color-conversion sensors are especially valuable as they can provide a visual representation of data without the need for additional electrical devices. For a sensor to be used on the human body, it must maintain its sensing capabilities even when exposed to solutions such as rainwater, sweat, and various cleansing liquids or when subjected to mechanical deformation. Therefore, this study was aimed at fabricating a UV-photochromic fiber that can maintain its color-change reaction to UV light even when exposed to chemical and physical stressors. To this end, UV-photochromic pigment was infused into porous and hydrophobic silica aerogels to create UV-photochromic aerogels, which were then placed between the inner strands of spandex fibers. During the drying process, the UV-photochromic aerogels adhered firmly to the spandex strands and were not separated even when the fibers were stretched and contracted up to 100 times under 200% tensile conditions. The resulting UV-photochromic fibers initially appeared white but transformed to magenta when exposed to UV light. This color change persisted through seven repeated on–off cycles of UV light. Moreover, the hydrophobic nature of the fibers ensured that the color-change reactivity remained stable even under exposure to water, artificial sweat, and detergent solutions. Overall, the proposed UV-photochromic fibers, with enhanced reversibility, stability, and reliability, can promote the commercialization of wearable-based colorimetric sensors.

Wearable Health Monitoring System Based on Human Sweat Analysis using Electrochemical Sensors

With the recent development in the field of electronics, it has made possible to continuous monitor health of patients and elderly and even of normal person. Since many years we are using blood-based diagnosis for diagnosis of various health conditions and diseases. However, recent research done by many researchers shows that there are other potential biomarkers such as, sweat which can provide diagnosis of various health conditions and diseases. Sodium and chloride concentration in sweat provides status of hydration status in human body. Here we have designed a health monitoring device based on sweat analysis using different types of electrochemical sensors. Ion-selective electrodes for Na+ and Cl- are used which gives details about a person’s hydration status and a glucose sensor is also used to measure the sweat glucose levels. The sensors are calibrated for artificial sweat solutions with different concentrations of Na+, Cl- and glucose. On body testing is done to confirm functionality of designed system for sweat analysis. The system is compact so can be used as a wearable device that is capable of continuously monitoring and wirelessly transmitting sensor data to the personal computer or smartphone.

Measuring the Salt Content of Sweat inside a Sweat-Absorbing Skin Adhesive.

Biofluids contain a wealth of different biomarkers, and their concentrations are indicative of the state of the body. As one of those biofluids, sweat is easily accessible, and its composition can, for example, be related to particular diseases or sports performance. Due to the relatively low sweat flow rates, however, adequate sampling is paramount. Here, we aim to explore the potential use of sweat-absorbing skin adhesives as a sweat sampling system for wearable sensors with a simple construction. Upon absorption of sweat, the electrochemical properties of the skin adhesive are determined by the composition of sweat and the amount of sweat within the skin adhesive (i.e., hydration). Through the incorporation of two polarizable electrodes within the skin adhesive, its electrical properties can be monitored using impedance spectroscopy. Here, the double layer capacitance is used as an indicator of hydration, while the conductance depends on both the ion concentration and hydration (the mobility of ions). By evaluating the conductance as a function of hydration, the ion concentration within an electrolyte solution can be estimated. We demonstrate the concept based on a simple model sensor patch, which is exposed to electrolyte solutions containing various concentrations of NaCl and an artificial sweat solution. Finally, we show that ion concentrations in human sweat can be estimated when the model sensor patch is worn during exercise.

Electrochemical Nonenzymatic Acetone Sensing: A Novel Approach of Biosensor Platform Based on CNT/CuO Nanosystems

AbstractA promising approach for noninvasive medical diagnosis may be to measure the VOCs produced by metabolic changes or pathological disorders in human sweat, such as measuring the acetone levels in the presence of diabetes. Acetone is a by‐product of fat catabolism and serves as an indicator of ketosis and diabetes. The measurement of acetone may be used instead of glucose monitoring. Current research aims to develop and improve noninvasive methods of detecting acetone in sweat that are accurate, sensitive, and stable. The carbon nanotubes (CNTs)–copper oxide (CuO) nanocomposite (NC) improves direct electron transport to the electrode surface in this study. The complex‐precipitation method is used to make this NC. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) are used to investigate the crystal structure and morphology of the prepared catalyst. Using cyclic voltammetry (CV) and amperometry, the electrocatalytic activity of the as‐prepared catalyst is evaluated. The electrocatalytic activity in artificial sweat solution is examined at various scan rates and acetone concentrations. The detection limit of the CNTs‐CuO NC catalyst is 0.05 mm, with a sensitivity of 16.1 mA cm−2 µm−1 in a linear range of 1–50 mm. Furthermore, this NC demonstrates a high degree of selectivity for various biocompounds found in sweat, with no interfering cross‐reactions from these species. The CNT‐CuO NC, as produced, has good sensitivity, rapid reaction time (2 s), and stability, indicating its potential for acetone sensing.

Enhancing the Longevity and Functionality of Ti-Ag Dry Electrodes for Remote Biomedical Applications: A Comprehensive Study.

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode's surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.

Drug Delivery through Epidermal Tissue Cells by Functionalized Biosilica from Diatom Microalgae.

Diatom microalgae are a natural source of fossil biosilica shells, namely the diatomaceous earth (DE), abundantly available at low cost. High surface area, mesoporosity and biocompatibility, as well as the availability of a variety of approaches for surface chemical modification, make DE highly profitable as a nanostructured material for drug delivery applications. Despite this, the studies reported so far in the literature are generally limited to the development of biohybrid systems for drug delivery by oral or parenteral administration. Here we demonstrate the suitability of diatomaceous earth properly functionalized on the surface with n-octyl chains as an efficient system for local drug delivery to skin tissues. Naproxen was selected as a non-steroidal anti-inflammatory model drug for experiments performed both in vitro by immersion of the drug-loaded DE in an artificial sweat solution and, for the first time, by trans-epidermal drug permeation through a 3D-organotypic tissue that better mimics the in vivo permeation mechanism of drugs in human skin tissues. Octyl chains were demonstrated to both favour the DE adhesion onto porcine skin tissues and to control the gradual release and the trans-epidermal permeation of Naproxen within 24 h of the beginning of experiments. The evidence of the viability of human epithelial cells after permeation of the drug released from diatomaceous earth, also confirmed the biocompatibility with human skin of both Naproxen and mesoporous biosilica from diatom microalgae, disclosing promising applications of these drug-delivery systems for therapies of skin diseases.

Printable and Flexible Iridium Oxide-Based pH Sensor by a Roll-to-Roll Process

A flexible pH sensor based on using iridium oxide (IrOx) as the sensing film was developed by the roll-to-roll (R2R) process. The inert and biocompatible properties of IrOx make it a desired metal oxide for pH-sensing applications. The flexible substrates being continuously processed by the R2R technique provides the advantages of scalability, reconfigurability, resiliency, on-demand manufacturing, and high throughput, without the need for vacuum systems. Potential sweeps by cyclic voltammetry across the IrOx film against commercial and planar Ag/AgCl electrodes validated the reversible electrochemical mechanisms. Multiple IrOx electrodes showed similar output potentials when continuously tested in the pH range of 2–13, indicating good fabrication uniformity. For practical applications, planar IrOx/Ag-AgCl pairs developed on polyimide substrates were tested, with a good linear fit within pH 2–13, achieving Nernstian responses of around −60.6 mV/pH. The pH sensors showed good repeatability when analyzed with hysteresis, drift, fluctuation, and deviation as the stability factors. The selectivity of the interference ions and the effect of temperature were studied and compared with the reported values. The electrodes were further laminated in a process compatible with the R2R technique for packaging. The flexible sensors were tested under flat and curved surface conditions. Tests in artificial sweat and viscous solutions were analyzed in the Clarke error grid, showing reliable pH-sensing performance. The materials used during the manufacturing processes were sustainable, as the active materials were in small amounts and there was no waste during processing. No toxic chemicals were needed in the fabrication processes. The cost-effective and efficient materials and the fabrication process allow for rapid production that is necessary for disposable and point-of-care devices. Flexible electronics provide a platform for device and sensor integration and packaging, which enables Internet-of-things (IoT) network applications.

One-step electrodeposition to fabricate superhydrophobic surfaces on flexible conductive films: Optimization of metallic compounds

Superhydrophobic surfaces were fabricated by a simple one-step electrodeposition technique to deposit three distinct micro/nano hierarchical structures of Ce, Mg, or Cu-based compounds on Ag films on a flexible polymer substrate. Scanning electron microscopy was used to examine the surface morphologies of obtained structures with different deposition. Compared with the bare Ag films, one-step electrodeposition process resulted in superhydrophobicity, including a water contact angle of 159.7° for Ce-modified surfaces, 157.0° for Mg-modified surfaces, and 153.8° for Cu-modified surfaces. Besides, these surfaces showed high thermal stability below 120 ℃, and good flexibility but low electrical conductivity. EDS and XPS results suggest the production of low surface energy materials that formed the superhydrophobic features on the Ag films. Besides, because of the formation of CeO2, Ce-SHS had better superhydrophobicity than Mg-SHS and Cu-SHS. In addition, the potentiodynamic polarization experiments showed that the electrodeposited superhydrophobic surfaces had lower Icorr, higher Ecorr and impedance values in NaCl solution, Na2SO4 solution and Simulated body fluid, and artificial sweat solution compared with the bare silver film, indicating that the electrodeposited protective film has good anti-corrosion properties. These results suggest that the one-step electrodeposition method is a promising strategy to fabricate conducting films with superhydrophobic surfaces for surface protection under various corrosive environments.

A novel wearable biosensor for real-time alcohol detection

Alcohol misuse has become a major public health concern worldwide. The development of an accurate, non-invasive, and cost-effective method for real-time alcohol detection would have important applications for monitoring and preventing alcohol misuse. This paper proposes a novel wearable biosensor for real-time alcohol detection in sweat. The biosensor uses alcohol oxidase immobilized on a screen-printed electrode to amperometrically detect ethanol in sweat samples. An artificial sweat solution was used to optimize the sensor design and evaluate its analytical performance. The optimized biosensor demonstrated a linear response to ethanol in the concentration range of 0.1–1.0 g/dL, with a limit of detection of 0.02 g/dL. On-body trials of the wearable biosensor provided rapid measurements that strongly correlated with blood alcohol content. This approach could offer a convenient solution for continuous, non-invasive alcohol monitoring to help reduce alcohol misuse and promote healthy behaviors. Further research on long-term use, alternate electrode geometries, and fully integrated wearable designs is warranted.

Corrosion assessment of passivation film generated on solder surface in artificial sweat solution

As the electric joint, the reliability of solder alloy is very important for the circuit card. Since the corrosion might lead to the failure of solder, various characterization methods have been used to assess the corrosion property of Sn-0.7Cu solder alloy in artificial sweat such as the potentiodynamic (PD) polarization, the potentiostatic (PS) polarization, the electrochemical impedance spectroscopy (EIS) and Motty-Schottky (MS) measurement. The EIS results showed that the passivation film owns better barrier properties in alkaline artificial sweat solution. The analysis of electrical equivalent circuit suggested that the passivation film resistance in alkaline solution is two orders of magnitude higher than that in acid solution, which were also supported by MS measurement. The better barrier properties of intact passivation surface contributed to corrosion resistance in alkaline artificial sweat solution. After a typical PD polarization process, the scanning electron microscope (SEM) with energy dispersive spectrometer (EDS) has been employed to characterize surface morphology and chemical composition of passivation surfaces. This work can provide some suggestions for the personalized design of wearable devices by considering the sweat corrosion effect.

잠재지문 연구를 위한 인공지문 캐스트 제작

Most of the fingerprints found at crime scenes are in latent fingerprint forms, and it is difficult to observe those fingerprints with the naked eye. Even if it is assumed that a latent fingerprint is remaining on an object, the method of developing the latent fingerprint differs depending on the surface type of the object. Therefore, a study must be performed by imprinting a latent fingerprint on an object, which is similar to the evidence found at a crime scene, to find an appropriate latent fingerprint development method. To do this, time and costs occur to recruit research participants, and these may cause disruption on arresting a suspect in a short time. Lothar Schwarz’s artificial latent fingerprint printing method, using an artificial sweat solution and an inkjet printer, can be used in a latent fingerprint research instead of using real human fingerprints. Although the major purpose of Schwarz’s method is to print out uniform fingerprint images on an A4 paper. Therefore, this approach has a limitation that it can only make imprints of fingerprints on thin and flexible materials such as copy papers and PVC films. To address this shortcoming, a Synthetic Fingerprint Generator(SFinGe, University of Bologna) computer program, a Printed Circuit Board(PCB) technique, and liquid latex are used to create an artificial fingerprint cast. With this new method, artificial latent fingerprint can be made on any surface types of material to find an appropriate latent fingerprint development method quickly during police investigations.

Aggregation Kinetics of TiO2 Nanoparticles in Human and Artificial Sweat Solutions: Effects of Particle Properties and Sweat Constituents.

Dermal penetration potentials of titanium dioxide nanoparticles (TiO2 NPs) may be affected by aggregation upon contact with sweat. This study investigated the aggregation kinetics of three TiO2 NPs in thirty human sweat samples and four artificial sweat standards. Effects of particle concentration, sweat type, and inorganic (sodium chloride, disodium hydrogen phosphate, and sodium dihydrogen phosphate) and organic (l-histidine, lactic acid, and urea) constituents were examined. Three TiO2 NPs remained colloidally stable in >20/30 human sweat samples and showed significant negative correlations (P < 0.01) between aggregation rates and |zeta potentials|. They aggregated rapidly over 20 min to >750 nm in three artificial sweat standards, while remained more stable in the International-Standard-Organization-pH-5.5 standard. Aggregation behaviors of three TiO2 NPs mostly followed the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, allowing for determining their critical coagulation concentrations in inorganic constituents (15-491 mM) and Hamaker constants (3.3-7.9 × 10-21 J). Higher concentrations of particles, inorganic constituents, and l-histidine destabilized three TiO2 NPs, whereas urea inhibited aggregation. Three TiO2 NPs adsorbed organic sweat constituents via complexation with amino or carboxyl groups, with isotherms following the Langmuir model. Correlation analyses further suggested that the adsorbed organic constituents may stabilize three TiO2 NPs against aggregation in sweat by steric hindrance.

A Smart Wristband Integrated with an IoT-Based Alarming System for Real-Time Sweat Alcohol Monitoring.

Breathalyzer is a common approach to measuring blood alcohol concentration (BAC) levels of individuals suspected of drunk driving. Nevertheless, this device is relatively high-cost, inconvenient for people with limited breathing capacity, and risky for COVID-19 exposure. Here, we designed and developed a smart wristband integrating a real-time noninvasive sweat alcohol metal oxide (MOX) gas sensor with a Drunk Mate, an Internet of Thing (IoT)-based alarming system. A MOX sensor acquired transdermal alcohol concentration (TAC) which was converted to BAC and sent via the IoT network to the Blynk application platform on a smartphone, triggering alarming messages on LINE Notify. A user would receive an immediate alarming message when his BAC level reached an illegal alcohol concentration limit (BAC 50 mg%; TAC 0.70 mg/mL). The sensor readings showed a high linear correlation with TAC (R2 = 0.9815; limit of detection = 0.045 mg/mL) in the range of 0.10–1.05 mg/mL alcohol concentration in artificial sweat, achieving an accuracy of 94.66%. The sensor readings of ethanol in water were not statistically significantly different (p > 0.05) from the measurements in artificial sweat and other sweat-related solutions, suggesting that the device responded specifically to ethanol and was not affected by other electrolytes in the artificial sweat. Moreover, the device could continuously monitor TAC levels simulated in real-time in an artificial sweat testing system. With the integration of an IoT-based alarming system, the smart wristband developed from a commercial gas sensor presented here offers a promising low-cost MOX gas sensor monitoring technology for noninvasive and real-time sweat alcohol measurement and monitoring.

The ability of sweat and buffer solutions to reduce hexavalent chromium of relevance for leather extraction

The European Union restricted the amount of hexavalent chromium (Cr(VI)) in leather in 2015, but skin allergy cases due to Cr-tanned leather are not declining. Standardized extraction methods have been criticized to both over- and underestimate the expected amount of bioavailable Cr(VI) in leather. This study aims to evaluate the ability of four extraction solutions to reduce or preserve Cr(VI): artificial sweat solutions (ASWs) of pH 4.7, 6.5, and 8.0, and phosphate buffer (PB) of pH 8.0. This was investigated by incubating each solution with added Cr(VI) as a function of time, and then measuring the recovered Cr(VI). All solutions, especially PB, preserved Cr(VI) for 24 h. These solutions were also pre-exposed to Cr-free vegetable-tanned leather (VTL) before incubation with Cr(VI). Released vegetable tannin species strongly reduced Cr(VI), with up to 4000 μg/L added Cr(VI) reduced in all solutions after 24 h. However, after 1 h, Cr(VI) was still detectable in extraction solutions at pH 6.5 and above. The reduction of Cr(VI) in relevant extraction solutions is hence a process dependent on time, pH, and the presence of co-released leather species. All extraction solutions, but least PB, have the potential to underestimate any Cr(VI) present on the surface of leather.