Sweat Transport Research Articles

Sweat‐Permeable, Microbiota‐Preserving, Mechanically Antibacterial Patch for Long‐Term Interfacing with Perspiring Skin

AbstractThe prolonged health monitoring using wearable technology faces challenges stemming from perspiration, including bacterial proliferation, compromised adhesion, signal quality deterioration, and user discomfort. Notably, excessive sweat fosters bacterial colonization, escalating infection risks, and compromising biomarker analysis. Existing antibacterial approaches, unfortunately, risk disrupting the delicate balance of skin microbiota. To address this, a Janus patch featuring Zn‐Al layered double hydroxide (LDH) modification is developed, which exhibits sustained antibacterial properties while preserving the epidermal microecology. It integrates a hydrophobic LDH fabric that mechanically eradicates bacteria via a nanoknife effect, and a laser‐engraved medical adhesive with microholes for unidirectional sweat transport. This innovative design not only enhances adhesion stability but also safeguards the skin microbiome by preventing direct contact with Zn‐Al LDH. Moreover, the patch seamlessly interfaces with sweat‐monitoring technologies like microfluidic paper‐based analytical devices (uPADs) sensors, ensuring 100% antibacterial efficacy and efficient sweat redirection for reliable detection while prioritizing user comfort. It can serve as a durable bridge between perspiring skin and epidermal sensors, revolutionizing the realm of long‐term health monitoring.

Sweat Pore-Inspired Functional Nanofiber Fabrics for Sweat Management and Simultaneous Detection.

Functional fabric with directional sweat transport and simultaneous sweat detection is highly desirable in daily life due to its crucial role in ensuring exercise comfort and promoting health. Herein, the inspiration is drawn from both the perspiration function of sweat pores and the backflow prevention feature of the surrounding solid skin to develop bioinspired hydrophobic nanofiber fabric. When combined with commercial cotton, this fabric enables rapid discharge of sweat through the sweat pore-like channels at an ultrafast speed of 240 g s-1 m-2, while effectively preventing backflow around these channels to ensure highly efficient personal drying. The performance of the bioinspired nanofiber fabric surpasses that of five commercially available moisture-wicking fabrics by effectively guiding liquid transport while minimizing residual moisture accumulation on the inner side. Furthermore, a colorimetric analysis system is integrated into the bioinspired nanofiber fabric, which facilitates convenient sampling of sweat samples and detection of biomarkers in sweat such as chloride ion, calcium ion, and pH level. This innovative design based on the concept of sweat pores opens up new possibilities for developing intelligent fabrics, electronic skins, and point-of-care devices.

Multi-inspired bump-liked medical protective clothing for effectively profuse perspiration management

Janus medical protective clothing (MPC) with asymmetric wetting properties can enhance the comfort of healthcare workers by transporting sweat from the skin to exterior surfaces. However, these textiles fail to promptly remove heavy sweat (e.g., several liters), resulting in soaked fabrics and reduced comfort. Herein, inspired by superabsorbent polymers (SAPs) and lotus leaves, we propose a bump-liked MPC (BPC) for profuse perspiration management. The fabrics can enable unidirectional sweat transport through the inner Janus fabric layer and sustained absorption of large amounts of sweat by the median layer of SAPs. The bump-liked structure can store SAPs and adapt them to swelling. An external polydimethylsiloxane (PDMS)-coated layer can effectively block water, blood, and ethanol from penetrating the skin (synthetic blood contact angle, 118°; anti-blood penetration resistance, 4.8 kPa), thereby ensuring excellent protective properties. More importantly, BPC possesses an unrivalled sweat removal rate of 5.9 ml cm−2 min−1, which is three orders of magnitude higher than the human sweat rate during high-intensity exercise. This work addresses the dual challenge of profuse perspiration management and resistance to liquid penetration, which represents a promising direction for improving the thermal-moisture comfort of medical protective clothing.

Design of nature-inspired patterns on knitted fabrics for directional transportation of sweat and study of their performances

The human body in a hot environment or during intense training will sweat a lot. Traditional cotton fabrics are soft and breathable, but they tend to absorb moisture easily and evaporate it slowly, which makes people feel cold and wet. Sweat staying on fabrics for a long time could also cause bacteria to grow. Thus, it is necessary to transport the excessive sweat from the gathering section to the collection points along the surface paths in time to minimize such problems. The mechanism of directional water transport of desert beetles, cacti, nepenthes, and river meanders was referenced in this paper. The paths in dot, tree, V-shape, and river meander patterns were designed and manufactured from the inspiration of these natural architectures. The paths were coated on the surfaces of selected knitted fabrics with different structures through a one-step coating process. The optimal recipe of hydrophobic solution was determined when 0.1 g hydroxyethyl-cellulose (HEC) was added into MS-S002 solution. The results showed that sweat movement is mainly influenced by FL, FWD, FG, and knitted structure. The continuous and enclosed paths such as tree and river contribute to a better sweat moving track than those of dot and V-shape ones. Terry structure is more suitable for surface sweat transport than plain and pique. The highest movement speed of the terry structure with a tree pattern reaches 0.43 cm/s, followed by that of the terry structure with river pattern 0.35 cm/s. The coated fabrics also have ideal moisture and air permeability for wearing.

A Double-Layer Polyurethane Electrospun Membrane with Directional Sweat Transport Ability for Use as a Soft Strain Sensor.

Wearable electronics for long-term monitoring of physiological signals should be capable of removing sweat generated during daily motion, which significantly impacts signal stability, human comfort, and safety of the electronics. In this study, we developed a double-layer polyurethane (PU) membrane with sweat-directional transport ability that can be applied for monitoring strain signals. The PU membrane was composed of a hydrophilic, conductive layer and a relatively hydrophobic layer. The double-layer PU composite membrane exhibited varied pore size and opposite hydrophilicity on its two sides, enabling the spontaneous pumping of sweat from the hydrophobic side to the hydrophilic side, i.e., the directional transport of sweat. The membrane can be used as a strain sensor to monitor motion strain over a broad working range of 0% to 250% with high sensitivity (GF = 4.11). The sensor can also detect simple human movements even under sweating conditions. We believe that the strategy demonstrated here will provide new insights into the design of next-generation strain sensors.

Correction: Advanced Janus Membrane with Directional Sweat Transport and Integrated Passive Cooling for Personal Thermal and Moisture Management

Correction: Advanced Janus Membrane with Directional Sweat Transport and Integrated Passive Cooling for Personal Thermal and Moisture Management

A wearable nanozyme–enzyme electrochemical biosensor for sweat lactate monitoring

In this study, we developed a wearable nanozyme–enzyme electrochemical biosensor that enablies sweat lactate monitoring. The biosensor comprises a flexible electrode system prepared on a polyimide (PI) film and the Janus textile for unidirectional sweat transport. We obtained favorable electrochemical activities for hydrogen peroxide reduction by modifying the laser-scribed graphene (LSG) electrode with cerium dioxide (CeO2)–molybdenum disulphide (MoS2) nanozyme and gold nanoparticles (AuNPs). By further immobilisation of lactate oxidase (LOx), the proposed biosensor achieves chronoamperometric lactate detection in artificial sweat within a range of 0.1–50.0 mM, a high sensitivity of 25.58 μA mM−1cm−2 and a limit of detection (LoD) down to 0.135 mM, which fully meets the requirements of clinical diagnostics. We demonstrated accurate lactate measurements in spiked artificial sweat, which is consistent with standard ELISA results. To monitor the sweat produced by volunteers while exercising, we conducted on-body tests, showcasing the wearable biosensor's ability to provide clinical sweat lactate diagnosis for medical treatment and sports management.

Advanced Janus Membrane with Directional Sweat Transport and Integrated Passive Cooling for Personal Thermal and Moisture Management

Advanced Janus Membrane with Directional Sweat Transport and Integrated Passive Cooling for Personal Thermal and Moisture Management

3D Wetting Gradient Janus Sports Bras for Efficient Sweat Removal: A Strategy to Improve Women's Sports Comfort and Health.

Developing Janus fabrics with excellent one-way sweat transport capacity is an attractive way for providing comfort sensation and protecting the health during exercise. In this work, a 3D wetting gradient Janus fabric (3DWGJF) is first proposed to address the issue of excessive sweat accumulation in women's breasts, followed by integration with a sponge pad to form a 3D wetting gradient Janus sports bra (3DWGJSB). The 3D wetting gradient enables the prepared fabric to control the horizontal migration of sweat in one-way mode (x/y directions) and then unidirectionally penetrate downward (z direction), finally keeping the water content on the inner side of 3DWGJF (skin side) at ≈0%. In addition, the prepared 3DWGJF has good water vapor transmittance rate (WVTR: 0.0409gcm-2h-1) and an excellent water evaporation rate (0.4704gh-1). Due to the high adhesion of transfer prints to the fabrics and their excellent mechanical properties, the 3DWGJF is remarkably durable and capable of withstanding over 500 laundering cycles and 400 abrasion cycles. This work may inspire the design and fabrication of next-generation moisture management fabrics with an effective sweat-removal function for women's health.

Double-side super-hydrophilic/superspreading fabric for ultrafast asymmetric sweat transport and in-situ power generation

Asymmetric (viz. Janus or one-way transport) fabrics that can promote directional sweat transport from the next-to-the-skin surface to the outer surface by the hydrophobic-hydrophilic difference across the fabric thickness have been developed. However, the hydrophobic next-to-the-skin surface inevitably increases the inherent resistance to sweat transportation into the fabric, fundamentally hampering its moisture management property. In this work, by selectively coating a poly-pyrrole (ppy) film with Turing patterns on one side of the fabric to achieve superspreading property, we demonstrated an all-hydrophilic asymmetric fabric with outstanding one-way liquid sweat transport property. Benefiting from the low resistance of sweat absorption, the all-hydrophilic fabric exhibited a dramatically increased directional sweat transport rate of 13.6 mm/s, which is 5.9 times that of the untreated fabric, and significantly enhanced sweat evaporation rate (1.56 times of the untreated fabric) and cooling performance. Furthermore, the conductive ppy-fabric, during the process of ultra-fast sweat transport, generated a potential of 150 mV over an area of 2×2 cm2 or scalable electrical energy output of 2.5 mW/m2 under continuous sweat transportation. The finding in this work not only provided new insight into the design and development of asymmetric fabric for ultrafast sweat transport but also proposed a novel method for the in-situ energy harvesting during the sweat transportation process, which has potential applications in self-powered smart wearables and functional clothing.

Micropatterned Polymer Nanoarrays with Distinct Superwettability for a Highly Efficient Sweat Collection and Sensing Patch.

Wearable sweat sensor offers a promising means for noninvasive real-time health monitoring, but the efficient collection and accurate analysis of sweat remains challenging. One of the obstacles is to precisely modulate the surface wettability of the microfluidics to achieve efficient sweat collection. Here a facile initiated chemical vapor deposition (iCVD) method is presented to grow and pattern polymer nanocone arrays with distinct superwettability on polydimethylsiloxane microfluidics, which facilitate highly efficient sweat transportation and collection. The nanoarray is synthesized by manipulating monomer supersaturation during iCVD to induce controlled nucleation and preferential vertical growth of fluorinated polymer. Subsequent selective vapor deposition of a conformal hydrogel nanolayer results in superhydrophilic nanoarray floor and walls within the microchannel that provide a large capillary force and a superhydrophobic ceiling that drastically reduces flow friction, enabling rapid sweat transport along varied flow directions. A carbon/hydrogel/enzyme nanocomposite electrode is then fabricated by sequential deposition of highly porous carbon nanoparticles and hydrogel nanocoating to achieve sensitive and stable sweat detection. Further encapsulation of the assembled sweatsensing patch with superhydrophobic nanoarray imparts self-cleaning and water-proof capability. Finally, the sweat sensing patch demonstrates selective and sensitive glucose and lactate detection during the on-body test.

Thermoresponsive Skin-like Fabric for Personal Comfort and Protection.

Acting as a "second skin", clothing plays an indispensable role in providing comfort and protection in the wide range of environments in which we live. However, comfort and protection are often competing requirements and are difficult to improve simultaneously. By mimicking the exceptional thermoresponsive one-way liquid transport property of human skin, here we developed a scalable and ecofriendly skin-like fabric that has a tunable directional water transport rate while having excellent water repellency. The water transport rate is also temperature-responsive, just like skin. As the temperature increases, the wettability gradient in the spatially distributed channels (acting like "sweat glands") increases, promoting sweat transport and evaporative heat dissipation. As the temperature decreases, on the other hand, the wettability gradient diminishes, reducing liquid transport and evaporative heat loss, thereby promoting heat retention. The fabric is highly suitable for sportswear and functional clothing and can have wider applications, such as oil-water separation, fog harvesting, etc.

Multi‐Bioinspired Droplet Self‐Actuated Sweat Transport Platform for Continuous Wearable Biochemical Monitoring

AbstractWearable sweat sensors exhibit significant promise in the realm of smart healthcare. Efficient and non‐contaminating continuous sweat collection, transport, and disposal are crucial for enhancing detection accuracy. In this study, a novel wearable sweat sensor is presented that integrates various biomimetic structures, including cactus‐inspired spine, shorebird‐inspired conical through‐holes, and frog‐foot‐inspired micro‐grooves. These structures facilitate sweat droplets to be automatically transported from the skin to the sensing chamber and discharged without external power. First, theoretical analysis, simulation, and experiments based on self‐driven droplet mechanisms to determine the optimal transport efficiency parameters for biomimetic structures are conducted. Next, a novel sweat transport module is fabricated through ultra‐precision 3D printing according to these optimal parameters. And this module has excellent sweat collection performance contrastively. Finally, the novel biomimetic sweat transport module is integrated with a high‐sensitivity glucose detection electrode, resulting in a wearable sweat glucose detection system. Human experiments monitoring glucose metabolism in sweat verify the correlation between glucose concentrations in blood and sweat, which proves the feasibility of reflecting changes in the body's circulatory system by monitoring changes in sweat composition.

Multi-inspired Janus fabrics with asymmetric coolmax patterns for rapid sweat diffusion and effective sweat-shedding

Janus fabrics with unidirectional liquid transport property have attracted wide attention for their ability to remove excess sweat and lower skin temperature. However, most Janus fabrics face the sweat removal issue on their outer surface when the sweat absorption capacity of their hydrophilic surface reaches limit, which inevitably slows down one-way sweat transport rate and induces the fabrics to become heavy/clingy. Herein, inspired by natural Namib Desert beetles and drip tips, circular Coolmax patterns (severed as sweat extraction points near the skin) and triangular Coolmax patterns (severed as sweat removal zones on the outside of the fabric) are asymmetrically sewn on superhydrophobic cotton fabrics to enable continues one-way sweat transport and allow effective sweat diffusion/shedding on its outer surface. During the sweat transporting and evaporation process, a large amount of heat is dissipated. As a result, the created Janus fabrics can maintain human body temperature about 1.3 ℃ lower than the conventional cotton fabric. Moreover, the low adhesion (∼0.2 mN cm−2) between the wet skin and the fabric makes wearers feel more comfortable. The method can be potentially used for the large-scale commercial production of Janus fabrics and provide insights for the development of smart fabrics in the future.

Gap junction-mediated contraction of myoepithelial cells induces the peristaltic transport of sweat in human eccrine glands

Eccrine sweat glands play an essential role in regulating body temperature. Sweat is produced in the coiled secretory portion of the gland, which is surrounded by obliquely aligned myoepithelial cells; the sweat is then peristaltically transported to the skin surface. Myoepithelial cells are contractile and have been implicated in sweat transport, but how myoepithelial cells contract and transport sweat remains unexplored. Here, we perform ex vivo live imaging of an isolated human eccrine gland and demonstrate that cholinergic stimulation induces dynamic contractile motion of the coiled secretory duct that is driven by gap junction-mediated contraction of myoepithelial cells. The contraction of the secretory duct occurs segmentally, and it is most prominent in the region surrounded by nerve fibers, followed by distension-contraction sequences of the excretory duct. Overall, our ex vivo live imaging approach provides evidence of the contractile function of myoepithelial cells in peristaltic sweat secretion from human eccrine glands.

High-Performance Liquid-Repellent and Thermal-Wet Comfortable Membranes Using Triboelectric Nanostructured Nanofiber/Meshes.

Skin-like functional membranes with liquid resistance and moisture permeability are in growing demand in various applications. However, the membranes have been facing a long-term dilemma in balancing waterproofness and breathability, as well as resisting internal liquid sweat transport, resulting in poor thermal-wet comfort. Herein, a novel electromeshing technique, based on manipulating the ejection and phase separation of charged liquids, is developed to create triboelectric nanostructured nano-mesh consisting of hydrophobic ferroelectric nanofiber/meshes and hydrophilic nanofiber/meshes. By combining the true nanoscale diameter (≈22nm), small pore size, and high porosity, high waterproofness (129kPa) and breathability (3736g m-2 per day) for the membranes are achieved. Moreover, the membranes can break large water clusters into small water molecules to promote sweat absorption and release by coupling hydrophilic wicking and triboelectric field polarization, exhibiting a satisfactory water evaporation rate (0.64g h-1 ) and thermal-wet comfort (0.7°C cooler than the cutting-edge poly(tetrafluoroethylene) protective membranes). This work may shed new light on the design and development of advanced protective textiles.

Multi-bioinspired Janus-shedding fabric: One-way sweat transport and rapid sweat removal for improved personal moisture management

In recent years, Janus fabrics that can effectively facilitate personal moisture management have received great attention. However, they are still limited in sweat shedding issue of their superhydrophilic outer surface. Here, inspired by the lotus leaf and Namib Desert beetles, we propose a Janus-shedding fabric with superhydrophilic/hydrophobic patterns and asymmetric wetting property. Through femtosecond-laser microfabrication, we successfully construct superhydrophilic/hydrophobic patterns on the outside surface of Janus fabrics. The method prevents the usage of toxic chemical reagent, thus is completely environmentally-friendly. The as-prepared Janus-shedding fabrics possess one-way liquid transport property. More importantly, the fabrics can achieve rapid liquid/sweat removal on their hydrophilic outer surfaces. The liquid shedding mechanism can be explained that the hydrophilic/hydrophobic patterns on the outer fabric surface can create less surface tension of water which can only fix small volume of water. Moreover, they can maintain human body temperature 3.2 ℃ lower than covered with pristine cotton fabrics. This work provides new insights for the design and fabrication of advanced smart fabrics with both sweat transport and removal property for satisfying the growing demands of personal comfort.

Micropatternable Janus Paper as a Wearable Skin Patch for Sweat Collection and Analysis

AbstractSingle‐use paper‐based wearable devices are receiving increasing attention as a novel platform for disposable, inexpensive, noninvasive, and real‐time sweat monitoring. The bidirectional liquid transport nature of paper is the most critical barrier to effectively controlling sweat samples for reliable and accurate sweat analysis. Excessive or additionally released sweat significantly interferes with analysis when mixed with old sweat. Moreover, bio‐receptors pre‐loaded in the sensing areas can backflow and move to another sensing region generating a cross‐talk issue. This work enables effective sweat sampling and delivery in paper by facilitating unidirectional sweat transport from the skin to the sensing reservoir. The design and fabrication of a single‐layered paper membrane to achieve Janus‐type properties, which only allow moisture to flow in one direction is introduced. When the hydrophobic side of the Janus paper is placed on the skin, sweat is unidirectionally self‐pumped from the hydrophobic side to the hydrophilic sensing areas, but not the reverse. The fabrication takes two steps including easy automatic and scalable printing of hydrophobic micropatterns on paper and simple heating of the printed paper for the wax penetration. Quantitative colorimetric assessment of pH, chloride, sodium, and glucose in sweat is simultaneously performed without cross‐talk between the sensing regions.

Spreading of water microdroplets simulating human sweating in polyester yarns and fabrics

Thermo-physiological comfort of human body is highly influenced by the moisture transmission behaviour of the fabric. For active sportswear, intimate apparels and inner layer of extreme cold weather clothing, moisture transport is very crucial. The liquid moisture transport of fabrics is analysed using standardised test methods like vertical wicking, absorbency test and moisture management through moisture management tester. These test methods use large reservoir of liquid in contrast to human sweating behaviour. The human skin generates sweats in the form of microdroplets through sweating glands. Hence, the standard test procedures employed to assess the fabric’s liquid moisture transport fail to capture preciously the sweat transport from human skin to the fabrics. Hence, in this work, the spreading behaviour of water microdroplets simulating human sweat through yarns which are the building block of fabrics and knitted fabrics that are widely used as sportswear or inner layer of extreme cold weather clothing are investigated. The purpose of this study is to understand how the microfluid move along the capillary channels in yarns (in the forms of network of yarns crossing over each other and fabric) by keeping yarn count and twist same for all yarns. A single micro drop representing accumulated sweat droplets and multiple drops showing continuous sweating through sweat glands were allowed to wick through the yarns made up of coarser and finer fibres to understand the role of fibre diameter on wicking kinetics. Results from the conventional wicking test were compared with microfluidic wicking. It is found that the initial wicking speed in coarser-fibres yarn is faster in comparison to finer-fibres yarn, but the final wicking height is longer in finer fibre yarn. Overall liquid spreading length found to be similar for both the yarns. Yarn to yarn liquid transfer at crossover junctions is faster with finer-fibre yarn compared to coarser-fibre yarn. Same trends are found in fabrics constructed with these yarns. The effect of yarn tortuosity on liquid spreading behaviour has also been studied. As the yarn path becomes torturous (straight yarn to fabric form) wicking length also decreases.

Influence of Stretching on Liquid Transport in Knitted Fabrics

The transport of liquid sweat in clothing worn close to human skin is very important from the point of view of the thermo-physiological comfort of clothing users. It ensures the drainage of sweat secreted by the human body and condensed on the human skin. In the presented work, knitted fabrics made of cotton and cotton blends with other fibers (elastane, viscose, polyester) were measured in the range of liquid moisture transport using the Moisture Management Tester MMT M290. The fabrics were measured in unstretched form and stretched to 15%. Stretching of the fabrics was performed using the MMT Stretch Fabric Fixture. Obtained results confirmed that stretching significantly changed the values of parameters characterizing the liquid moisture transport in the fabrics. Before stretching, the best liquid sweat transport performance was stated for the KF5 knitted fabric made of 54% cotton and 46% polyester. For this, the greatest value (10 mm) of maximum wetted radius for the bottom surface was obtained. The Overall Moisture Management Capacity (OMMC) of the KF5 fabric was 0.76. This was the highest value among all values obtained for the unstretched fabrics. The lowest value of the OMMC parameter (0.18) was stated for the KF3 knitted fabric. After stretching, the KF4 fabric variant was assessed as the best one. Its OMMC improved from 0.71 before stretching to 0.80 after stretching. The value of the OMMC for the KF5 fabric remained after stretching at the same level (0.77) than before stretching. The most significant improvement was observed for the KF2 fabric. Before stretching, the value of the OMMC parameter for the KF2 fabric was 0.27. After stretching, the OMMC value increased to 0.72. It was also stated that the changes in the liquid moisture transport performance of the investigated knitted fabrics were different for the particular fabrics being investigated. Generally, in all cases, the ability of the investigated knitted fabrics to transfer liquid sweat was improved after stretching.