Biomarkers In Sweat Research Articles

Skin-Interfaced Bifluidic Paper-Based Device for Quantitative Sweat Analysis.

The erratic, intermittent, and unpredictable nature of sweat production, resulting from physiological or psychological fluctuations, poses intricacies to consistently and accurately sample and evaluate sweat biomarkers. Skin-interfaced microfluidic devices that rely on colorimetric mechanisms for semi-quantitative detection are particularly susceptible to these inaccuracies due to variations in sweat secretion rate or instantaneous volume. This work introduces a skin-interfaced colorimetric bifluidic sweat device with two synchronous channels to quantify sweat rate and biomarkers in real-time, even during uncertain sweat activities. In the proposed bifluidic-distance metric approach, with one channel to measure sweat rate and quantify collected sweat volume, the other channel can provide an accurate analysis of the biomarkers based on the collected sweat volume. The closed channel design also reduces evaporation and resists contamination from the external environment. The feasibility of the device is highlighted in a proof-of-the-concept demonstration to analyze sweat chloride for evaluating hydration status and sweat glucose for assessing glucose levels. The low-cost yet highly accurate device provides opportunities for clinical sweat analysis and disease screening in remote and low-resource settings. The developed device platform can be facilely adapted for the other biomarkers when corresponding colorimetric reagents are exploited.

Simultaneous detection of urea and lactate in sweat based on a wearable sweat biosensor.

Urea and lactate are biomarkers in sweat that is closely associated with human health. This study introduces portable, rapid, sensitive, stable, and high-throughput wearable sweat biosensors utilizing Au-Ag nanoshuttles (Au-Ag NSs) for the simultaneous detection of sweat urea and lactate. The Au-Ag NSs arrays within the biosensor's microfluidic cavity provide a substantial surface-enhanced Raman scattering (SERS) enhancement effect. The limit of detection (LOD) for urea and lactate are 2.35 × 10-6 and 8.66 × 10-7 mol/L, respectively. This wearable sweat biosensor demonstrates high resistance to compression bending, repeatability, and stability and can be securely attached to various body parts. Real-time sweat analysis of volunteers wearing the biosensors during exercise demonstrated the method's practicality. This wearable sweat biosensor holds significant potential for monitoring sweat dynamics and serves as a valuable tool for assessing bioinformation in sweat.

Strain-insensitive and multiplexed potentiometric ion sensors via printed PMMA molecular layer

Wearable biomimetic electronics have aroused tremendous attention due to their capability to continuously detect and deliver real-time dynamic physiological signals pertaining to the wearer's environment. However, upon close contact with the human skins, a wearable sensor undergoes mechanical strain which inevitably degrades the electrical performance. To address this issue, we demonstrate a universal design approach for stretchable and multiplexed biosensors that can yield unaltered ion sensing performance under variable mechanical tensile strains, which is achieved by introducing a PMMA molecular layer between stretchable substrate and ion sensors. Such design demonstrates reliable multiplexed ion sensing capability and provides high sensitivity (>50 mV/decade), reliable selectivity, as well as wide working range (0.1–100 mM) for sodium, ammonium, potassium and calcium ions in complex sweat biomarkers. Via this introduced PMMA molecular layer, our sensor even exhibits 95 % electrical performance maintained up to 30 % tensile strain, whereas the mechanical tensile property is far superior to original sensor performance. Besides, the sensors were also utilized for real-time monitoring of ions in sweat to validate its biomedical electronics applications. This sensing platform can be easily extended to other biomimetic sensors to enable stable signal acquisition for biomedical electronics.

One-step synthesis of MXene-functionalized PEDOT:PSS conductive polymer hydrogels for wearable and noninvasive monitoring of sweat glucose

Wearable biosensors have gained substantial attention for their capacity to deliver real-time and continuous physiological information through noninvasive and dynamic monitoring of biochemical markers in biological fluids. In particular, wearable and flexible electrochemical sensors have found extensive usage for the detection of biomarkers in human sweat in a quantifiable and noninvasive manner. Herein, we present a novel MXene-functionalized PEDOT:PSS conducting composite hydrogels-based electrochemical biosensor for continuous noninvasive monitoring of human glucose. Ethylene glycol (EG) was added to the hydrogel throughout the preparation process, aiding in the expansion of the polymer chains and resulting in excellent electrical conductivity and porous networks, which helps to increase the film-forming properties, flexibility and stability of the material, and also improves the stacking and peeling problems of powdered materials. The limit of the hydrogel biosensor for glucose detection was as low as 1.9 μM and the sensitivity was 21.7 μA⋅mM−1⋅cm−2. Furthermore, the hydrogel incorporated with screen-printed carbon electrodes (SPCE) was employed to the human body for continuous noninvasive sweat glucose monitoring as the skin patch in vitro. The results of the biosensor showed good correlation with glucose meter readings. We believe that this glucose biosensor lays the foundation for noninvasive wearable monitoring of glucose in diabetic patients.

Skin-Attachable Ink-Dispenser-Printed Paper Fluidic Sensor Patch for Colorimetric Sweat Analysis.

In situ analysis of sweat biomarkers potentially provides noninvasive lifestyle monitoring and early diagnosis. Quantitative detection of sweat rate is crucial for thermoregulation and preventing heat injuries. Here, a skin-attachable paper fluidic patch is reported for in situ colorimetric sensing of multiple sweat markers (pH, glucose, lactate, and uric acid) with concurrent sweat rate tracking. Two sets of fluidic patterns-multiplexed detection zones and a longitudinal sweat rate channel-are directly printed by an automated ink dispenser from a specially developed ceramic-based ink. The ceramic ink thermal-cures into an impervious barrier, confining sweat within the channels. The ceramic-ink-printed boundary achieves higher pattern resolution, prevents fluid leakage, attains pattern thermal stability, and resistant to organic solvents. The cellulose matrix of the detection zones is modified with nanoparticles to improve the color homogeneity and sweat sensor sensitivity. The sweat rate channel is made moisture sensitive by incorporating a metal-salt-based dye. The change in saturation/color of the detection zones and/or channels upon sweat addition can be visually detected or quantified by a smartphone camera. A cost-effective way is provided to fabricate paper fluidic sensor patches, successfully demonstrating on-body multiplexed evaluation of sweat analytes. Such skin wearables offer on-site analysis, meaningful to an increasingly health-conscious population.

An Integrated Sweat Sensor for Synchronous Detection of Multiple Atherosclerosis Biomarkers.

Atherosclerosis conditions are often assessed in the clinic by measuring blood viscosity, blood flow, and blood lesion levels. In alignment with precision medicine, it is essential to develop convenient and noninvasive approaches for atherosclerosis diagnostics. Herein, an integrated electrochemical sensor was successfully demonstrated for simultaneously detecting cholesterol, transferrin, and K+ in sweat, all biomarker indicators of atherosclerosis. The sensing substrate was based on carbon quantum dots integrated within multiwalled carbon nanotubes, creating a hybrid framework with low electron transfer resistance and highly efficient electron transfer rate, yielding a highly electrochemical active platform for ultrasensitive detection of trace sweat biomarkers. To ensure specificity to corresponding targets, the sensing mechanisms were based on molecular recognition reactions of cholesterol and β-cyclodextrin, transferrin and molecular cavities, and K+ and ion-selective permeation membrane. Moreover, the integrated nonenzymatic sensor exhibited excellent long-term stability. Furthermore, the practical utility of the sensor was successfully demonstrated by the simultaneous detection of three atherosclerosis biomarkers in sweat from volunteers who underwent predesigned daily activities. The sensor shows promise for convenient indexing of atherosclerosis conditions in a noninvasive way.

A highly sensitive and long-term stable wearable patch for continuous analysis of biomarkers in sweat.

Although increasing efforts have been devoted to the development of non-invasive wearable or stretchable electrochemical sweat sensors for monitoring physiological and metabolic information, most of them still suffer from poor stability and specificity over time and fluctuating temperatures. This study reports the design and fabrication of a long-term stable and highly sensitive flexible electrochemical sensor based on nanocomposite-modified porous graphene by simple and facile laser treatment for detecting biomarkers such as glucose in sweat. The laser-reduced and patterned stable conductive nanocomposite on the porous graphene electrode provides the resulting glucose sensor with an excellent sensitivity of 1317.69 μAmM-1cm-2 with an ultra-low limit of detection (LOD) of 0.079 μM. The sensor can also detect pH and exhibit extraordinary stability to maintain more than 91% sensitivity over 21 days in ambient conditions. Taken together with a temperature sensor based on the same material system, the dual glucose and pH sensor integrated with a flexible microfluidic sweat sampling network further results in accurate continuous on-body glucose detection calibrated by the simultaneously measured pH and temperature. The low-cost, highly sensitive, and long-term stable platform could facilitate and pave the way for the early identification and continuous monitoring of different biomarkers for non-invasive disease diagnosis and treatment evaluation.

Sweat Analysis-Based Fatigue Monitoring during Construction Rebar Bending Tasks

This study proposes a novel approach to monitor the fatigue levels of construction rebar benders by measuring chemical biomarkers using sweat sensors. Fatigue resulting from dehydration and energy depletion can severely endanger the safety and health of construction workers. Sodium, lactate, glucose, and sweat rate were chosen as detectable biomarkers in this study, as their concentrations can indicate hydration status, energy consumption, and electrolyte balance, making them suitable for fatigue monitoring. The results were used to construct a fatigue model using supervised machine learning approaches. Construction rebar experiments were conducted while the sweat-based biosensors were applied to rebar workers to evaluate their fatigue with five different classifiers, demonstrating accuracy rates ranging from 71.43% to 96.43%. The results suggested that sweat-based biomarkers offer a noninvasive and accessible fatigue monitoring alternative. This can potentially help alleviate fatigue-related adverse ill effects like dehydration or cramping by enabling instant fluid or nutrient supply recommendations during construction manual tasks. It also provides valuable insights into the physiological effects of rebar work. Besides, this study presents a valuable model for predicting workers’ fatigue levels, which could be applied in the construction industry to improve workers’ safety and productivity. Furthermore, the study highlights the importance of maintaining appropriate hydration, nutrition, and electrolyte balance during physically demanding tasks like construction manual work.Practical ApplicationsThe study demonstrates that sweat biomarkers, including sweat rate, sodium, lactate, and glucose, can be utilized to assess fatigue among construction rebar workers. Sweat biosensors offer advantages of small size and non-invasiveness, making them suitable for a wide range of scenarios in both the construction industry and sports fields. Moreover, sweat rate and sodium levels can indicate hydration status, and their measurements can be used to recommend immediate fluid intake. Also, lactate and glucose are essential resources that sustain the body, and their measurements can suggest appropriate nutritional intake. These instant recommendations can alleviate the adverse effects of fatigue, consequently reducing fatigue levels. Thus, it is a promising methodology for enhancing the health and safety of the construction industry. In addition, the results of the study will be shared with construction companies, allowing them to introspect fatigue development and chalk out further interventions and policies to manage fatigue effectively.

Oriented Antibody-Assembled Metal-Organic Frameworks for Persistent Wearable Sweat Cortisol Detection.

The level of cortisol can reflect people's psychological stress, help diagnose adrenal gland diseases, and is also related to several mental diseases. In this study, we developed a cortisol monoclonal antibody-oriented approach to modify an immunosensor for wearable label-free and persistent sweat cortisol detection. On such an antibody-oriented immunosensor, the fragment crystallizable (Fc) region is partially inserted within the metal-organic framework (MOF), and antibody-binding regions of the cortisol monoclonal antibody (Cmab) were exposed on the MOF surface via selective growth and self-assembly. Such ordered and oriented embedding of antibodies in the MOF resulted in excellent antibody activity and improved stability and antigen-binding capacity. We also engineered the full integrated system for on-body sweat cortisol biosensing performance in several volunteers, and the results indicated that this wearable sensor is suitable for practical cortisol detection with a good linear detection range from 1 pg/mL to 1 μg/mL with a lower limit of detection of 0.26 pg/mL. Moreover, the wearable sensor demonstrated good persistence in detecting cortisol, with only 4.1% decay after 9 days of storage. The present work represents a simple oriented antibody assembling approach to improve the stability of antibodies, providing an important step toward long-term continuous sweat biomarker detection.

A molecularly imprinted screen-printed carbon electrode for electrochemical epinephrine, lactate, and cortisol metabolites detection in human sweat

This study presents a novel approach to the detection of epinephrine, lactate, and cortisol biomarkers in human sweat using molecularly-imprinted polymers (MIP) embedded screen printed carbon electrode (SPCE) sensors. The epinephrine and lactate MIP SPCE sensors were fabricated by epinephrine or lactate-imprinted polyaniline co-polymerized with 3-aminophenylboronic acid and gold nanoparticles (PANI-co-PBA/AuNP) selective membrane on a commercial SPCE. The cortisol sensor was comprised of a cortisol-imprinted poly(glycidyl methacryate-co-ethylene glycol dimethacrylate) (poly (GMA-co-EGDMA)@AuNP selective membrane deposited on a SPCE. Both cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used as modes of analysis for the MIP SPCE sensors. All sensors exhibited a rapid (∼1 min) and selective response to the epinephrine, lactate, and cortisol target analytes, with excellent precision between scans for both CV and DPV analysis modes. For CV, the LOD for epinephrine, lactate, and cortisol was 8.2 nM, 13 mM, and 0.042 μM, respectively. The LOD for DPV were 0.60 nM, 2.2 mM, and 0.025 μM for epinephrine, lactate, and cortisol, respectively. The MIP SPCE sensor platforms were further validated through the successful quantification of epinephrine, lactate, and cortisol in human sweat.

Dual-valved skin-interfaced microfluidic device for programmed time-control sweat collection

Biomarkers in human sweat can provide valuable insights into physiological states, identify diseases, and help clinicians understand patients without invasive measurements. However, obtaining accurate long-term data from sweat using current sweat collection methodology raises doubts. Here, we describe a soft-bioelectronic platform that uses a thermal expansion valve to collect sweat under programmed time control. By incorporating expandable microspheres, the skin-interfaced microfluidic device platform merges capillary burst valves and irreversible-thermal expansion valves. An expansion layer below the microfluidic channels expands irreversibly upon heat delivery from underlying microheaters. The thermal expansion valve isolates the collected sweat into separate chambers to minimize internal mixing. The human study demonstrates that our novel time-programmed sweat collection device improved sweat analyte data (sweat volume, pH, lactate, and cortisol) from the conventional sweat collection. In addition, the human study results indicate a correlation between sweat rate and sweat lactate with aerobic and anaerobic exercises. Our approach can be integrated with past and current microfluidic systems and other chemical sensing modalities, such as colorimetric and electrochemical measurements of sweat analytes present in current sweat devices for advanced on-board diagnostics.

A novel biosensor based on molecularly imprinted polymer coated nanofiber composite for uric acid analysis in body fluids

There are biomarkers in sweat and urine that can reveal a subject's level of health. Colorimetric techniques can be used to analyze these biomarkers, which is important for noninvasive tracking without the need to take blood samples. A novel, polymer-imprinted, polymer-coated nanofiber composite was synthesized using a colorimetric technique to noninvasively monitor uric acid in sweat and urine. Then, the new adsorbent has been characterized using SEM, STEM and FTIR spectroscopy, the optimization of parameters such as pH, time, and various interference ions' effects was investigated. Results showed that the newly synthesized adsorbent is very selective and efficient for the extraction and determination of uric acid. The method's ability to determine uric acid without interference from nearly all other biochemical compounds present in biological fluids is a noteworthy advantage. Both real and synthetic urine and sweat were measured for uric acid content using the current method and HPLC-DAD. The findings were satisfactorily comparable, allowing the suggested method's applicability to actual samples to be verified. Additionally, the sensing device's adaptability and durability allowed for the successful, highly sensitive, and semi-quantitative analysis of uric acid in sweats. The colorimetric method's clear feedback is demonstrated in real-time, on-body experiments using healthy human subjects. The described wearable sweat-based monitoring system is dependable and simple to use.

Multisensing Wearables for Real-Time Monitoring of Sweat Electrolyte Biomarkers During Exercise and Analysis on Their Correlation With Core Body Temperature.

Sweat secreted by the human eccrine sweat glands can provide valuable biomarker information during exercise. Real-time non-invasive biomarker recordings are therefore useful for evaluating the physiological conditions of an athlete such as their hydration status during endurance exercise. This work describes a wearable sweat biomonitoring patch incorporating printed electrochemical sensors into a plastic microfluidic sweat collector and data analysis that shows the real-time recorded sweat biomarkers can be used to predict a physiological biomarker. The system was placed on subjects carrying out an hour-long exercise session and results were compared to a wearable system using potentiometric robust silicon-based sensors and to commercially available HORIBA-LAQUAtwin devices. Both prototypes were applied to the real-time monitoring of sweat during cycling sessions and showed stable readings for around an hour. Analysis of the sweat biomarkers collected from the printed patch prototype shows that their real-time measurements correlate well (correlation coefficient ≥ 0.65) with other physiological biomarkers such as heart rate and regional sweat rate collected in the same session. We show for the first time, that the real-time sweat sodium and potassium concentration biomarker measurements from the printed sensors can be used to predict the core body temperature with root mean square error (RMSE) of 0.02 °C which is 71% lower compared to the use of only the physiological biomarkers. These results show that these wearable patch technologies are promising for real-time portable sweat monitoring analytical platforms, especially for athletes performing endurance exercise.

Direct Laser Writing of the Porous Graphene Foam for Multiplexed Electrochemical Sweat Sensors.

Wearable electrochemical sensors provide means to detect molecular-level information from the biochemical markers in biofluids for physiological health evaluation. However, a high-density array is often required for multiplexed detection of multiple markers in complex biofluids, which is challenging with low-cost fabrication methods. This work reports the low-cost direct laser writing of porous graphene foam as a flexible electrochemical sensor to detect biomarkers and electrolytes in sweat. The resulting electrochemical sensor exhibits high sensitivity and low limit of detection for various biomarkers (e.g., the sensitivity of 6.49/6.87/0.94/0.16 μA μM-1 cm-2 and detection limit of 0.28/0.26/1.43/11.3 μM to uric acid/dopamine/tyrosine/ascorbic acid) in sweat. The results from this work open up opportunities for noninvasive continuous monitoring of gout, hydration status, and drug intake/overdose.

Optical Fiber Semi-Distributed Interferometer Assisted by an FBG for Thermorefractometry and Sweat Sensing

Among optical fiber biosensors, the use of thermorefractometry is a promising approach for dual detection of refractive index (RI) and temperature with a single device, and it can find application in sweat analytes. We propose an optical fiber-based thermorefractometer made of a semi-distributed interferometer (SDI) supported by a fiber Bragg gratings (FBG), for the possible application of the detection of sweat biomarkers. The sensor is composed of two parts (SDI and FBG) integrated in a compact probe; the resulting spectrum is a composition of a periodic-like pattern throughout the whole spectrum (SDI) and a narrow-band reflection peak at the Bragg wavelength (FBG). The thermorefractometer detects the refractive index changes with a sensitivity of 75.752 dB/RIU, while the FBG detects thermal changes at 9.94 pm/°C with negligible cross-sensitivity. We demonstrate the use of the SDI/FBG probe for the detection of two sweat markers. We tested the performance of the sensor in artificial sweat with azelaic acid and suberic acid achieving a sensitivity of 0.629/% dB and -0.088 dB/%.

Wearable Ion Sensors for the Detection of Sweat Ions Fabricated by Heat-Transfer Printing.

Wearable ion sensors for the real-time monitoring of sweat biomarkers have recently attracted increasing research attention. Here, we fabricated a novel chloride ion sensor for real-time sweat monitoring. The printed sensor was heat-transferred onto nonwoven cloth, allowing for easy attachment to various types of clothing, including simple garments. Additionally, the cloth prevents contact between the skin and the sensor and acts as a flow path. The change in the electromotive force of the chloride ion sensor was -59.5 mTV/log CCl-. In addition, the sensor showed a good linear relationship with the concentration range of chloride ions in human sweat. Moreover, the sensor displayed a Nernst response, confirming no changes in the film composition due to heat transfer. Finally, the fabricated ion sensors were applied to the skin of a human volunteer subjected to an exercise test. In addition, a wireless transmitter was combined with the sensor to wirelessly monitor ions in sweat. The sensors showed significant responses to both sweat perspiration and exercise intensity. Thus, our research demonstrates the potential of using wearable ion sensors for the real-time monitoring of sweat biomarkers, which could significantly impact the development of personalized healthcare.

Analytical assessment of sodium ISFET based sensors for sweat analysis

Body thermoregulation during exercise induces sweating with the consequent loss of water, electrolytes and other compounds. The use of sweat for bioanalytical purposes has recently widespread because it is an easily accessible biofluid that can be noninvasively collected and/or directly monitored using wearable devices. Different sweat biomarkers can be monitored as indicators of the physiological status of an individual. The concentration of sweat Na+ electrolyte provides information about dehydration or hyponatremia events. Among the different sensor technologies applied for Na+ ion detection in sweat, ion-sensitive field-effect transistors (ISFETs) show superior features in terms miniaturization, key for working with the low volumes of sweat available, robustness, scalability and reproducibility. They also offer fast response and low impedance output signal. This work reports an in-depth study that thoroughly assesses the potential of ISFET sensors for sweat Na+ analysis. Results show a reproducible sensitivity of 60.7 ± 0.5 mV (-Log aNa)− 1, high repeatability, and lifetime up to one month. Sensor reliability is demonstrated by analysing 20 sweat samples and results are compared with the ones provided with the standard ion chromatography technique (IC). The statistical analysis demonstrates that Na+ concentrations estimated with the ISFET sensor and IC are in good agreement showing a relative error of up to 20%. Results demonstrate that the sensor presented in this work can potentially be used for the continuous monitoring of Na+ changes in sweat during exercise.

Radiative cooling and anisotropic wettability in E-textile for comfortable biofluid monitoring

Long-term wearing comfort is essential for future advanced electronic textiles (e-textiles). Herein, we fabricate a skin-comfortable e-textile for long-term wearing experience on human epidermis. Such e-textile was simply fabricated through two different dip coating methods and single-side air plasma treatment, which couples radiative thermal and moisture management for biofluid monitoring. The silk-based substrate with improved optical properties and anisotropic wettability can provide a temperature drop of 1.4 °C under strong sunlight. Moreover, the anisotropic wettability of the e-textile can provide a dryer skin microenvironment by comparing with traditional fabric. The fiber electrodes weaving into the inner side of the substrate can noninvasively monitor multiple sweat biomarkers (i.e., pH, uric acid, and Na+). Such a synergistic strategy may pave a new path to design next-generation e-textiles with significantly improved comfort.

Inkjet-Printed Soft Intelligent Medical Bracelet for Simultaneous Real-Time Sweat Potassium (K+), Sodium (Na+), and Skin Temperature Analysis

Truly wearable, fully flexible, multi-parametric sweat analysis with soft and socially discrete packaging offers tremendous potential to enable the next generation of non-invasive digital biomarkers analysis. Several examples of miniaturized potentiometric ion selective electrodes (ISE) have been proposed. However, several challenges remain unsolved concerning their long-term stability due to variations in physical sweat parameters. We hypothesize that the simultaneous monitoring of such parameters (e.g., skin-surface temperature, sweat rate, and pH) may pave the way for accurate and robust sweat biomarker analysis. Therefore, we propose a flexible multiparameter sensory interface fabricated on Kapton polyimide (PI) foil with high-resolution inkjet printing using silver nanoparticles (AgNPs). A facile controlled drop-casting of a custom synthesized ion-selective membrane ensures the selectivity of the biosensing. Next, we interfaced the fabricated sensory array with a custom-designed compact flexible biosignals conditioning embedded system, which enables system calibration, data processing, and wireless data transmission to a smartphone device. Later, we validate the proposed system in simultaneous sweat multi-ion (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> and Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) and skin-surface temperature recording. After that, we characterize the system by embedding the smart medical bracelet in a soft microfluidic platform to mimic <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> analysis on the body. Overall, the reported results represent the fundamental evidence proof for the development of the wearable multimodal sweat parameter analyzer.

Recent Progress on Non-invasive Wearable Epidermal Biosensors

Wearable biosensors have the potential to provide valuable information about our physiological states and transform traditional healthcare. Compared to traditional blood sampling, on-body analysis of non-invasive biofluids can offer continuous and painless monitoring of relevant biomarkers. Recent developments in epidermal sensors feature integrated systems capable of sensing multiple factors while providing easy readout and great skin conformity. Innovative solutions based on advanced material fabrication and novel designs have also emerged to address challenges such as power, sensor sensitivity and selectivity, and communication. As a result, more possibilities have emerged to develop sophisticated integrations with more functionalities, optimized skin conformity, and less disruption of daily routine. While sensing performance and functions continue to improve, attention should also be drawn to practical problems such as biofouling, contamination, and complex composition dynamics. Moreover, although past and current research have highlighted studies investigating the use of sweat in diagnostics, more evidence of correlations between sweat biomarker levels and physiological conditions is needed to promote the utility of these systems.