Sweat Concentrations Research Articles

The Effect of Exercise Fluid Supplement on Human Metabolism after Load Exercise

Yang, Z.Y. and Xia, S.Y., 2020. The effect of exercise fluid supplement on human metabolism after load exercise. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 504–507. Coconut Creek (Florida), ISSN 0749-0208.Objective: In the process of load exercise training, with the discharge of sweat, the loss of water and electrolyte will destroy the balance of water and salt metabolism, and the athletic ability of athletes will also decline in varying degrees. Therefore, this paper studies the effect of exercise fluid supplementation on human metabolism after load exercise. The average value of the ionic concentration of athletes' sweat was used as the basis for the preparation of electrolyte sports drinks. Result: The results showed that the concentration of potassium ion in the sweat of male long-distance runners was significantly higher than that of female athletes; the concentration of potassium ion in male athletes of Sanda Team was significantly higher than that of female athletes; the test results of sodium, chlorine and potassium ion of long-distance runners were higher than that of Sanda athletes; Compared with the first week, the concentration of sodium, chloride and calcium ions in female athletes' serum increased in the fourth week, while the potassium ion concentration decreased slightly. Conclusion: After three weeks of load exercise, with the supplement of sports drinks containing appropriate electrolyte concentration, the concentration of serum chloride ion of athletes remained stable, slightly lower than that of the first week, but both were within the normal range; daily supplement of liquid supplement containing potassium ion and calcium ion had a slight decrease in serum potassium ion, and the decrease range was smaller than the former, and the calcium ion concentration was maintained compared with the first week During the period of load training, 800 ml of fluid was provided to athletes every day. After 3 weeks of rehydration, hematocrit remained stable, and there was no significant difference.

Facile preparation and characterization of nanostructured ZnO/CuO composite thin film for sweat concentration sensing applications

This research presents the morphological, structural, optical characterization and sweat sensing response of ZnO/CuO nanocomposite thin films synthesized by the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The particle and crystallite size were increased with increasing SILAR cycles. AFM studies showed that the increase in the number of SILAR cycles resulted a decrease in surface roughness from 60 nm to 23 nm. The optical band energy and transmittance of the nanocomposite thin films were determined from the UV–Vis. spectrum as well as Tauc's plot, which showed a decrease in the optical band energy (from 2.06 to 1.89) with the increase of film thickness. Human hydration level sensing of the nanocomposite ZnO/CuO thin films was investigated by artificial sweat application. It was observed that there was a monotonous increase with the sensing response with respect to the artificial sweat concentration.

Fiber organic electrochemical transistors based on multi-walled carbon nanotube and polypyrrole composites for noninvasive lactate sensing.

Multi-walled carbon nanotubes (MWCNT) play a synergistic role with conducting polymer in practical applications such as biological sensing. In this paper, multi-walled carbon nanotube and polypyrrole (PPy) composites were prepared on a fiber surface for the first time, and their morphology and electrical properties were characterized. Compared with PPy-coated fiber, the presence of carbon nanotubes induced the growth of large areas of PPy nanowires. In addition, fiber organic electrochemical transistors (FECTs) based on PPy and MWCNT were assembled, showing a higher on/off ratio, better stability, and greater flexibility. The lactate biosensor based on FECTs exhibits high sensitivity, with a correlation coefficient of R = 0.9889, quick response time of 0.6-0.8s, a wide linear response range of 1nM-1mM, and excellent selectivity for lactate. Furthermore, the lactate concentration in human sweat was successfully detected by a FECT-based sensor. The hybrid fibers can be easily woven and placed on fabric simply by stitching. This favorable performance of the FECT-based sensor makes it suitable for noninvasive sensing of lactate. Therefore, it provides a promising platform for future use in healthcare and detection applications. Graphical abstract.

Real‐Time Multi‐Ion Detection in the Sweat Concentration Range Enabled by Flexible, Printed, and Microfluidics‐Integrated Organic Transistor Arrays

AbstractOrganic electrochemical transistors (OECTs) show remarkable promise as biosensors, thanks to their high signal amplification, simple architecture, and the intrinsic flexibility of the organic material. Despite these properties, their use for real‐time sensing in complex biological fluids, such as human sweat, is strongly limited due to the lack of cross‐sensitivity and selectivity studies and the use of rigid and bulky device configurations. Here, the development of a novel flexible microfluidics‐integrated platform with an array of printed ion‐selective OECTs enables multi‐ion detection in a wearable fashion. This is achieved by coating the poly(3,4‐ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) channels of the transistors with three different ion‐selective membranes (ISMs). Systematic electrical and sensing analysis of the OECTs with ISMs show a minimal impact of the membranes on the electrical and time responses of the transistors while providing high ion selectivity. This work combines for the first time real‐time and selective multi‐ion detection with an array of inkjet‐printed and flexible organic transistors coated with different ISMs, demonstrating state‐of‐the‐art sensing capabilities of≈10µA dec−1for potassium, sodium, and pH. This flexible OECTs sensing platform paves the way to the next generation devices for continuous electrolytes monitoring in body fluids.

AI/ML-Enabled 2-D - RuS2 Nanomaterial-Based Multifunctional, Low Cost, Wearable Sensor Platform for Non-Invasive Point of Care Diagnostics

We report the first of its kind artificial intelligence/machine learning (AI/ML) enabled nanomaterial based multifunctional sensing platform for simultaneous and continuous monitoring of certain vital body parameters viz. the hydration levels of the skin, glucose concentration and pH levels in biofluid sweat with high accuracy and speed. RuS 2 nanoparticles were synthesized using a facile hydrothermal method and detailed characterization revealed cubic crystal structure of laurite-RuS 2 with mesoporous morphology that provided enhanced electrocatalytic sites for sensing. The biochemical sensor was fabricated using layer-by-layer spincoating technique of RuS 2 on an interdigitated PDMS substrate. Further, to facilitate human-machine interface that can analyze data from large sample sizes (~ 50 sensors), the sensor was interfaced with the open-source microcontroller board (QueSSence) wherein Artificial Intelligence (AI) based K-Nearest Neighbors (KNN) algorithm enabled precise and faster data acquisition from complex mathematical conjunctures. The response of the sensor towards hydration levels for various skin conditions, glucose concentration, and pH of sweat were examined for both artificial skin and human skin. The RuS 2 based sweat-glucose sensor exhibited a sensitivity of 87.9 ± 0.6 μM -1 cm -2 in a physiologically relevant range of 10 nM - 0.1 mM and limit of detection of 4.87 nM. The pH sensor exhibited a sensitivity of 71.2 ± 0.5 pH -1 cm -2 across the pH range of 4 -8.5. The multifunctional sensor displayed high stability and reusability at room temperature. The optimized response was integrated with a smartphone via a customized application enabling user-friendly, real-time monitoring of the health conditions.

A Self-Powered Biosensor for Monitoring Maximal Lactate Steady State in Sport Training

A self-powered biosensor for monitoring the maximal lactate steady state (MLSS) during exercise has been developed for intelligently assisting training system. It has been presented to create poly (vinylidene fluoride) (PVDF)/Tetrapod-shaped ZnO (T-ZnO)/enzyme-modified nanocomposite film through an efficient and cost-effective fabrication process. This sensor can be readily attached to the skin surface of the tester. Due to the piezoelectric surface coupling effect, this biosensor can monitor/sense and analyze physical information in real-time under the non-invasive condition and work independently without any battery. By actively outputting piezoelectric signals, it can quickly and sensitively detect body movements (changes of joint angle, frequency relative humidity during exercise) and physiological information (changes of lactate concentration in sweat). A practical application has been demonstrated by an excellent professional speed skater (male). The purpose of this study is to increase the efficiency of MLSS evaluation, promote the development of piezoelectric surface coupling effect and motion monitoring application, develop an intelligently assisting training system, which has opened up a new direction for human motion monitoring.

Validating sweat ammonia as physiological parameter for wearable devices in sports science.

The measurement of physiological parameters in sweat has long been assumed to offer a non-invasive alternative to conventional blood testing. Recently, advances in sensor technology enable the production of printed sweat sensors applicable for the use in wearable devices. However, the remaining challenge is the determination of the physiological correlation between blood and sweat components. In this study, we conducted ammonia measurements in blood and sweat during a stepwise incremental cycle ergometer test in 40 subjects under completely controlled conditions in a clinical environment to determine the correlation between the ammonium concentrations in blood and sweat. Samples were taken for each workload step separately. Sweat was sampled directly from the upper body, blood was taken from an indwelling cannula at the end of each workload step, respectively. For meaningful classification of the measured quantities, blood lactate and heart rate were monitored additionally. The results for blood ammonium concentration show increasing behavior in good accordance with the established indicators for physical exhaustion, whereas sweat ammonium concentration seems to decrease with workload. This is found to be due to dilution, as sweat rate increases. The presented results provide insight in the correlation between blood and sweat parameters and therefore are of high importance for further development of wearable devices.Clinical Relevance-Sweat sensing opens up new possibilities for non-invasive, continuous in-situ monitoring of physiological parameters for healthcare and sports science applications.

A Textile-Based Microfluidic Platform for the Detection of Cytostatic Drug Concentration in Sweat Samples

This work presents a new multilayered microfluidic platform, manufactured using a rapid and cost-effective xurography technique, for the detection of drug concentrations in sweat. Textile fabrics made of cotton and polyester were used as a component of the platform, and they were positioned in the middle of the microfluidic device. In order to obtain a highly conductive textile, the fabrics were in situ coated with different amounts of polyaniline and titanium dioxide nanocomposite. This portable microfluidic platform comprises at least three layers of optically transparent and flexible PVC foils which were stacked one on top of the other. Electrical contacts were provided from the edge of the textile material when a microfluidic variable resistor was actually created. The platform was tested in plain artificial sweat and in artificial sweat with a dissolved cytostatic test drug, cyclophosphamide, of different concentrations. The proposed microfluidic device decreased in resistance when the sweat was applied. In addition, it could successfully detect different concentrations of cytostatic medication in the sweat, which could make it a very useful tool for simple, reliable, and fast diagnostics.

(Invited) Single-Strand Conducting Polymer Fiber-Based Wearable Sweat Sensors

Despite the great potential of polymer microfibers in human-friendly wearable electronics, most previous polymeric electronics have been limited to thin-film-based devices due to practical difficulties in fabricating microfibrillar devices, as well as defining the active channel dimensions in a reproducible manner. Herein, we report on conducting polymer microfiber-based organic electrochemical transistors (OECTs) and their application in single-strand fiber-type wearable ion concentration sensors. We developed a simple wet-spinning process to form very conductive poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) microfibers using aqueous sulfuric acid solutions and carefully examined their electrical/electrochemical properties. In conjunction with fabricating substrate-free PEDOT:PSS microfiber-based OECT devices, the proposed novel characterization method demonstrated that the current variation ratio can be a reliable method for evaluating the device performance for sensing ion concentrations, regardless of the actual channel dimensions. Finally, we developed single-strand fiber-type skin-mountable OECTs by introducing a source-gate hybrid electrode and demonstrated that the resultant microfiber sensors can perform real-time repetitive measurements of the ion concentration in human sweat.

Calcium loss in sweat does not stimulate PTH release: A study of Bikram hot yoga

It has been hypothesized that sweat loss during exercise causes a disruption in calcium homeostasis that activates bone resorption and over time leads to low bone mineral density. The purpose of this small pilot study was to determine whether dermal calcium loss from a bout of excessive sweating during light intensity physical activity triggers an increase in biomarkers of bone resorption. Biochemical markers related to bone homeostasis were measured before and after a 90 min Bikram hot yoga practice performed in a room heated to 105 °F with 40 % humidity. Participants were five females with a mean age of 47.4 ± 4.7 years. Nude body weight, serum total calcium (Ca2+), free ionized calcium, albumin, parathyroid hormone (PTH) and CTX-I were measured before and after a Bikram hot yoga practice. Mean estimated sweat loss was 1.54 ± 0.65 L, which elicited a 1.9 ± 0.9 % decrease in participant’s body weight. Mean Ca2+ concentration in sweat was 2.9 ± 1.7 mg/dl and the estimated mean total calcium lost was 41.3 ± 16.4 mg. Serum ionized Ca2+ increased from 4.76 ± 0.29 mg/dl to 5.35 ± 0.36 mg/dl after the Bikram hot yoga practice (p = 0.0118). Serum PTH decreased from pre- 33.9 ± 3.3 pg/ml to post- 29.9 ± 2.1 pg/ml yoga practice (p = 0.0015) when adjusted for hemoconcentration (PTHADJ), implying a decrease in PTH secretion. We conclude that calcium loss in sweat during 90 min of Bikram hot yoga did not trigger an increase in PTH secretion and did not initiate bone resorption.

Peroxidase-Like Behavior of Ni Thin Films Deposited by Glancing Angle Deposition for Enzyme-Free Uric Acid Sensing.

We present a nanozyme-based biosensor fabricated from nanostructured Ni films deposited onto a silicon wafer by glancing angle deposition (GLAD) for enzyme-free colorimetric monitoring of uric acid (UA), a biomarker for gout, high blood pressure, heart disease, and kidney disease. The helically structured Ni GLAD nanozymes exhibit excellent peroxidase-like activity to accelerate the oxidation reaction of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to a blue product, oxidized TMB (oxTMB), mediated by H2O2. In the presence of UA, oxTMB is reduced, decreasing the optical absorbance by an amount determined by the concentration of UA in the solution. The nanozyme not only mimics peroxidase but also possesses the notable qualities of reusability, simple operation, and reliability, making it environment-friendly and suitable for on-demand analysis. We optimized essential working parameters (pH, TMB concentration, and H2O2 concentration) to maximize the initial color change of the TMB solution. The catalytic activity of this nanozyme was compared with conventional nanofilms using the Michaelis–Menten theory. Based on this, enzyme-free biosensors were developed for colorimetric detection of UA, providing a wide detection range and a limit of detection (3.3 μM) suitable for measurements of UA concentration in sweat. Furthermore, interference from glucose and urea was studied so as to explore the potential of the biosensor for use in the clinical diagnosis of UA biomarkers.

Comparison of Sweat versus Serum IL‐1α and IL‐1β Concentrations during Exercise

Interleukin (IL) 1 cytokines, IL‐1α and IL‐1β, are well known for their immunological responses as blood biomarkers; however, it is unclear if sweat cytokine concentrations can be used to predict that of blood. The purpose of this study was to determine the correlations between sweat and serum for IL‐1α and IL‐1β concentrations measured during exercise. Nine moderately‐trained recreational athletes (35±7 y, 73.9±14.4 kg, VO2max 46.2±8.0 ml/kg/min) completed 90 min of cycling at 80±5% HRmax in the heat (31°C, 50% RH). Preceding exercise, left ventral forearm (LVF) was cleaned with alcohol and deionized water, and an absorbent patch (10 cm2 absorbent pad, 3M Tegaderm™ + Pad) was applied 10 min into exercise. The patch was removed at the end of 90 min of exercise alongside a synchronous blood draw. Sweat and serum IL‐1α and IL‐1β were measured using Multiplex (EMD Millipore, MagPix) IL‐1α and IL‐1β kits. Spearman correlation was performed to determine the relation between sweat and serum for IL‐1α and IL‐1β. Non parametric sign test was used to determine mean differences between sweat and serum. Cytokine measurements are shown as mean ± SD. There were no significant correlations between sweat and serum for IL‐1α (r=−0.19, p=0.61) or IL‐1β (r=0.20, p=0.61). There were significant mean differences in IL‐1α expression between sweat (1004.5±613.8 pg/mL) and serum (24.9±58.1 pg/mL) (p=0.004), and non‐significant mean differences in IL‐1β between sweat (2.3±1.9 pg/mL) and serum (1.3±1.3 pg/mL) (p=0.45). These results suggest that there were no significant correlations between sweat and serum IL‐1 cytokine concentrations. Unlike IL‐1β, IL‐1α expression in sweat was significantly different between sweat and serum. Therefore, it seems that IL‐1 expression in sweat may have limited utility in predicting blood IL‐1 concentrations.Support or Funding InformationThis study was funded by the Gatorade Sports Science Institute, a division of PepsiCo, Inc. The views expressed in this abstract are those of the authors and do not necessarily reflect the position or policy of PepsiCo, Inc.

Wearable non-invasive monitors of diabetes and hypoxia through continuous analysis of sweat

We present here wearable devices for continuous monitoring of diabetes and hypoxia based on continuous analysis of sweat. To induce sweating the clinically relevant procedure (pilocarpine electrophoresis) is used. Being a sufficient requirement for diagnostics, positive correlations in variation rates between glucose and lactate concentrations in sweat and the corresponding values in blood are shown. Continuous monitoring of human condition is possible only with the use of flow-through wearable devices providing a delivery of sweat to the biosensor almost immediately after secretion. Evaluating blood glucose through continuous sweat analysis upon glucose tolerance test, we clearly show that diabetics can actually be monitored reliably via non-invasive approach.

Determination of the Levels of Heavy Metals and Formaldehyde in Baby Clothes in South Africa: A Case Study of Stores in the Greater Cape Town Region

Herein, we report on the determination of formaldehyde, pH, and heavy metals (Pb, As, Co, Cr, Ni, and Cd) in various baby apparel (cotton, polyester, nylon, elastane, and polyethylene) of different colours (light, medium, and dark) purchased from both high-end and low-end market stores. The concentrations of the heavy metals were determined by inductively coupled plasma (ICP) after wet digestion and also after extraction using artificial sweat for a selected range of skin-contact baby apparel. The relative standard deviation for the determination of all heavy metals was less than 5% except for nickel which was 10.49%. The concentrations of the heavy metals in wet digested samples were found to be in the following range: Pb (0.02–23.662 mg/kg), As (0.009–0.033 mg/kg), Co (0.001–1.053 mg/kg), Cr (0.053–6.373 mg/kg), Ni (0.039–36.715 mg/kg), and Cd (0.001–0.914 mg/kg), whereas the concentrations in artificial sweat extracted samples were in the following range: Pb (0.006–1.658 mg/kg), As (not detected), Co (0.001–1.05 mg/kg), Cr (0.112–0.371 mg/kg), Ni (0.062–0.121 mg/kg), and Cd (0.001–0.018 mg/kg). The highest concentrations of Pb, Cr, and Co after wet digestion were found in baby apparel purchased from low-end market stores, whereas for As, Ni, and Cd were from high-end market stores. All the samples had a formaldehyde concentration within the acceptable limits recommended by Oeko-Tex. Out of the thirty-four samples analysed, fifteen samples were found to have a pH higher than Oeko-Tex limits. The pH values for the samples that exceeded the Oeko-Tex limits were in the alkali region, and the highest was 11.31 which exceeded by 3.81.

Noninvasive monitoring of diabetes and hypoxia by wearable flow-through biosensors

Abstract Noninvasively collected sweat via clinically relevant procedure can be used for assessing the human condition, particularly for monitoring of diabetes and hypoxia. Positive correlations in variation rates, claimed as sufficient requirements for diagnostics, between glucose and lactate concentrations in sweat and the corresponding values in blood are shown. Continuous monitoring of human condition is possible only with the use of flow-through wearable devices providing a delivery of sweat to the biosensor almost immediately after excretion. Owing to both low sweat glucose content and inactivation of platinum by sweat components, the use of Prussian blue–based biosensors for wearable devices is preferable. Operation of the latter in power generation mode allows significant noise reduction and clear readout of the signal. Evaluating blood glucose through sweat analysis upon glucose tolerance test, we clearly show that humans can actually be monitored reliably via noninvasive approach.

Effects of exposure to high temperatures on serum, urine and sweat concentrations of iron and copper.

The objective of this research was to determine the acute effect of a maximum test until exhaustion in normothermia and hyperthermia, and after repeated exposure to heat at high temperatures on the homeostasis of Fe and Cu. The sample was composed of twenty-nine male university students. The participants were divided into a control group (CG) and an experimental group (EG). All of them underwent an incremental test until exhaustion in normothermia and hyperthermia before and after the repeated exposure of EG to heat at high temperatures, consisting of 9 heat acclimatisation sessions in the sauna. Samples of urine and blood were taken before and after each test. Additionally, sweat samples were collected in the hyperthermia test. The samples were frozen at -80°C for further analysis by ICP-MS. None of the metal concentrations in serum were affected by hyperthermia or exposure to heat. Urinary Fe increased in CG in the hyperthermia test before Heat exposure at High Temperature (HEHT)(p<0.05) and in both groups after HEHT (p<0.05). In EG there was an increase in the urinary excretion of Cu after HEHT (p<0.01) in both trials. Fe suffered a decrease in sweat in EG after exposure to heat (p<0.05). The concentrations of Fe and Cu in serum were not affected by acute exercise and exposure to high temperatures. However, there was a decrease in excretion of Fe in sweat due to HEHT, and an increase in urinary excretion in both. Therefore, we think that in conditions of high temperatures for long periods of time, attention should be paid to the body levels of these metals.

Introducing "Insertive Stripping Voltammetry": Electrochemical Determination of Sodium Ions Using an Iron(III) Phosphate-Modified Electrode.

A new type of stripping voltammetry is introduced, in which the preconcentration step includes ion insertion into a solid phase followed by a quantification step in which the ion is expelled via linear sweep voltammetry. Specifically, sodium-ion concentrations in both aqueous solution and synthetic sweat are electrochemically determined using iron(III) phosphate-modified glassy carbon electrodes. The electrochemical method consists of a potentiostatic step, holding the potential of -0.5 V vs saturated calomel electrode (SCE) for 100 s, followed by linear sweep voltammetry. It is shown that a thermal and mechanical pretreatment at 800 °C and with a ball mill, respectively, improve the electrochemical response of the iron(III) phosphate toward Na+. The involved structural and morphological changes were assessed by thermogravimetric analysis, scanning electron microscopy, and powder X-ray diffraction. The sensor exhibits a good selectivity toward Li+ and K+ and shows a linear response between 0.025 and 0.2 M Na+. As a proof-of-principle, the sensor was used to determine the sodium level in synthetic sweat.

Relationship Between Sweat and Blood Lactate Levels During Exhaustive Physical Exercise

AbstractIn contrast to the generally accepted view, that sweat lactate is irrelevant to blood, we report on the suitability of sweat lactate for diagnostics. We demonstrate a significant increase in lactate concentration in sweat from the working muscle area simultaneously with the rise of blood lactate content during exhaustive physical exercise. The variation rates of lactate concentration in sweat from working and latent muscle areas correlate positively with blood lactate levels (r&gt;0.8 and r=0.7, respectively), thus offering the prospect of a non‐invasive approach for the monitoring of sportsperson training. Moreover, sweat lactate, being the faster indicator of muscle metabolism, would be even more important for sports medicine than the nowadays‐used blood lactate.

Two Distinct Types of Sweat Profile in Healthy Subjects While Exercising at Constant Power Output Measured by a Wearable Sweat Sensor

Wearable sweat sensors have enabled real-time monitoring of sweat profiles (sweat concentration versus time) and could enable monitoring of electrolyte loss during exercise or for individuals working in extreme environments. To assess the feasibility of using a wearable sweat chloride sensor for real-time monitoring of individuals during exercise, we recorded and analyzed the sweat profiles of 50 healthy subjects while spinning at 75 Watts for 1 hour. The measured sweat chloride concentrations were in the range from 2.9–34 mM. The sweat profiles showed two distinct sweat responses: Type 1 (single plateau) and Type 2 (multiple plateaus). Subjects with Type 2 profiles had higher sweat chloride concentration and weight loss, higher maximum heart rate, and larger changes in heart rate and rating of perceived exertion during the trial compared to subjects with Type 1 profiles. To assess the influence of level of effort, we recorded sweat profiles for five subjects at 75 W, 100 W, and 125 W. While all five subjects showed Type 1 sweat profiles at 75 W, four of the subjects had Type 2 profiles at 125 W, showing an increase in sweat chloride with exercise intensity. Finally, we show that sweat profiles along with other physiological parameters can be used to predict fluid loss.

Human sweat monitoring using polymer-based fiber

Lightweight nano/microscale wearable devices that are directly attached to or worn on the human body require enhanced flexibility so that they can facilitate body movement and overall improved wearability. In the present study, a flexible poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fiber-based sensor is proposed, which can accurately measure the amount of salt (i.e., sodium chloride) ions in sweat released from the human body or in specific solutions. This can be performed using one single strand of hair-like conducting polymer fiber. The fabrication process involves the introduction of an aqueous PEDOT:PSS solution into a sulfuric acid coagulation bath. This is a repeatable and inexpensive process for producing monolithic fibers, with a simple geometry and tunable electrical characteristics, easily woven into clothing fabrics or wristbands. The conductivity of the PEDOT:PSS fiber increases in pure water, whereas it decreases in sweat. In particular, the conductivity of a PEDOT:PSS fiber changes linearly according to the concentration of sodium chloride in liquid. The results of our study suggest the possibility of PEDOT:PSS fiber-based wearable sensors serving as the foundation of future research and development in skin-attachable next-generation healthcare devices, which can reproducibly determine the physiological condition of a human subject by measuring the sodium chloride concentration in sweat.