Waterproof,Breathable, and Antibacterial Self‐Powered e‐Textiles Based on Omniphobic Triboelectric Nanogenerators

Multifunctional electronic textiles (e‐textiles) incorporating miniaturized electronic devices will pave the way toward a new generation of wearable devices and human–machine interfaces. Unfortunately, the development of e‐textiles is subject to critical challenges, such as battery dependence, breathability, satisfactory washability, and compatibility with mass production techniques. This work describes a simple and cost‐effective method to transform conventional garments and textiles into waterproof, breathable, and antibacterial e‐textiles for self‐powered human–machine interfacing. Combining embroidery with the spray‐based deposition of fluoroalkylated organosilanes and highly networked nanoflakes, omniphobic triboelectric nanogenerators (R^F‐TENGs) can be incorporated into any fiber‐based textile to power wearable devices using energy harvested from human motion. R^F‐TENGs are thin, flexible, breathable (air permeability 90.5 mm s^?1), inexpensive to fabricate (<0.04$ cm^?2), and capable of producing a high power density (600 µW cm^?2). E‐textiles based on R^F‐TENGs repel water, stains, and bacterial growth, and show excellent stability under mechanical deformations and remarkable washing durability under standard machine‐washing tests. Moreover, e‐textiles based on R^F‐TENGs are compatible with large‐scale production processes and exhibit high sensitivity to touch, enabling the cost‐effective manufacturing of wearable human–machine interfaces.     

Seriography‐Guided Reduction of Graphene Oxide Biopapers for Wearable Sensory Electronics

Novel nacre‐mimic bio‐nanocomposites, such as graphene‐based laminates, are pushing the boundaries of strength and toughness as flexible engineering materials. Translating these material advances to functional flexible electronics requires methods for generating print‐scalable microcircuits (conductive elements surrounded by dielectric) into these strong, tough, lightweight bio‐nanocomposites. Here, a new paradigm for printing flexible electronics by employing facile, eco‐friendly seriography to confine the reduction of graphene oxide biopapers reinforced by silk interlayers is presented. Well‐defined, micropatterned regions on the biopaper are chemically reduced, generating a 10⁶ increase in conductivity (up to 10⁴ S m^?1). Flexible, robust graphene‐silk circuits are showcased in diverse applications such as resistive moisture sensors and capacitive proximity sensors. Unlike conductive (i.e., graphene‐ or Ag nanoparticle‐loaded) inks printed onto substrates, seriography‐guided reduction does not create mechanically weak interfaces between dissimilar materials and does not require the judicious formation of ink. The unimpaired functionality of printed‐in graphene‐silk microcircuits after thousands of punitive folding cycles and chemical attack by harsh solvents is demonstrated. This novel approach provides a low‐cost, portable solution for printing micrometer‐scale conductive features uniformly across large areas (>hundreds of cm²) in layered composites for applications including wearable health monitors, electronic skin, rollable antennas, and conformable displays.     

Flexible and Multifunctional Silk Textiles with Biomimetic Leaf‐Like MXene/Silver Nanowire Nanostructures for Electromagnetic Interference Shielding,Humidity Monitoring,and Self‐Derived Hydrophobicity

Although flexible and multifunctional textiles are promising for wearable electronics and portable device applications, the main issue is to endow textiles with multifunctionalities while maintaining their innate flexible and porous features. Herein, a vacuum‐assisted layer‐by‐layer assembly technique is demonstrated to conformally deposit electrically conductive substances on textiles for developing multifunctional and flexible textiles with superb electromagnetic interference (EMI) shielding performances, superhydrophobicity, and highly sensitive humidity response. The formed leaf‐like nanostructure is composed of silver nanowires (AgNWs) as the highly conductive skeleton (vein) and transition metal carbide/carbonitride (MXene) nanosheets as the lamina. The presence of MXene protects AgNWs from oxidation and enhances the combination of AgNWs with the fabric substrate, and the transformation of its functional groups leads to self‐derived hydrophobicity. The flexible and multifunctional textile exhibits a low sheet resistance of 0.8 Ω sq^?1, outstanding EMI shielding efficiency of 54 dB in the X‐band at a small thickness of 120 µm, and highly sensitive humidity responses, while retaining its satisfactory porosity and permeability. The self‐derived hydrophobicity with a large contact angle of >140° is achieved by aging the hydrophilic MXene coated silk. The wearable multifunctional textiles are highly promising for applications in intelligent garments, humidity sensors, actuators, and EMI shielding.     

Scalable Production of Graphene Inks via Wet‐Jet Milling Exfoliation for Screen‐Printed Micro‐Supercapacitors

The miniaturization of energy storage units is pivotal for the development of next‐generation portable electronic devices. Micro‐supercapacitors (MSCs) hold great potential to work as on‐chip micro‐power sources and energy storage units complementing batteries and energy harvester systems. Scalable production of supercapacitor materials with cost‐effective and high‐throughput processing methods is crucial for the widespread application of MSCs. Here, wet‐jet milling exfoliation of graphite is reported to scale up the production of graphene as a supercapacitor material. The formulation of aqueous/alcohol‐based graphene inks allows metal‐free, flexible MSCs to be screen‐printed. These MSCs exhibit areal capacitance (C_areal) values up to 1.324 mF cm^?2 (5.296 mF cm^?2 for a single electrode), corresponding to an outstanding volumetric capacitance (C_vol) of 0.490 F cm^?3 (1.961 F cm^?3 for a single electrode). The screen‐printed MSCs can operate up to a power density above 20 mW cm^?2 at an energy density of 0.064 µWh cm^?2. The devices exhibit excellent cycling stability over charge–discharge cycling (10 000 cycles), bending cycling (100 cycles at a bending radius of 1 cm) and folding (up to angles of 180°). Moreover, ethylene vinyl acetate‐encapsulated MSCs retain their electrochemical properties after a home‐laundry cycle, providing waterproof and washable properties for prospective application in wearable electronics.     

Lithium–Sulfur Battery Cable Made from Ultralight,Flexible Graphene/Carbon Nanotube/Sulfur Composite Fibers

The emergence of flexible and wearable electronic devices with shape amenability and high mobility has stimulated the development of flexible power sources to bring revolutionary changes to daily lives. The conventional rechargeable batteries with fixed geometries and sizes have limited their functionalities in wearable applications. The first‐ever graphene‐based fibrous rechargeable batteries are reported in this work. Ultralight composite fibers consisting of reduced graphene oxide/carbon nanotube filled with a large amount of sulfur (rGO/CNT/S) are prepared by a facile, one‐pot wet‐spinning method. The liquid crystalline behavior of high concentration GO sheets facilitates the alignment of rGO/CNT/S composites, enabling rational assembly into flexible and conductive fibers as lithium–sulfur battery electrodes. The ultralight fiber electrodes with scalable linear densities ranging from 0.028 to 0.13 mg cm^?1 deliver a high initial capacity of 1255 mAh g^?1 and an areal capacity of 2.49 mAh cm^?2 at C /20. A shape‐conformable cable battery prototype demonstrates a stable discharge characteristic after 30 bending cycles.     

Flexible Normal‐Tangential Force Sensor with Opposite Resistance Responding for Highly Sensitive Artificial Skin

An electronic skin (e‐skin) that can detect both normal and tangential forces with a differentiable signals output is essential for wearable electronics. A flexible, stretchable, and highly sensitive tactile sensor is presented that enables the detection of both normal and tangential forces, with specific opposite and thus easily being differentiated resistance changing outputs. The e‐skin, which is based on two‐sublayered carbon nanotubes (CNTs)/graphene oxide (GO) hybrid 3D conductive networks, that are anchored on a thin porous polydimethylsiloxane (PDMS) layer, is synthesized via a porogen (GO wrapped NaCl) assisted self‐assembling process. The fabricated CNTs/GO@PDMS‐based e‐skin shows superior sensitivity (gauge factor of 2.26 under a pressure loading of 1 kPa) to tangential force, moderate sensitivity (?0.31 kPa^?1 at 0.05–3.8 kPa, and ?0.03 kPa^?1 at 3.8–6.3 kPa, respectively) to normal force, and a high‐reproducible response over 5000 loading cycles including stretching, bending, and shearing. For applications, the e‐skin can not only detect wrist pulsing, discriminating different roughness of surfaces, but also produce an obvious responding to an extremely slight ticking (<20 mg) from a feather, and even can real‐timely monitor human's breath and music in rhythm.     

Large‐Area Ultrathin Graphene Films by Single‐Step Marangoni Self‐Assembly for Highly Sensitive Strain Sensing Application

Promoted by the demand for wearable devices, graphene has been proved to be a promising material for potential applications in flexible and highly sensitive strain sensors. However, low sensitivity and complex processing of graphene retard the development toward the practical applications. Here, an environment‐friendly and cost‐effective method to fabricate large‐area ultrathin graphene films is proposed for highly sensitive flexible strain sensor. The assembled graphene films are derived rapidly at the liquid/air interface by Marangoni effect and the area can be scaled up. These graphene‐based strain sensors exhibit extremely high sensitivity with gauge factor of 1037 at 2% strain, which represents the highest value for graphene platelets at this small deformation so far. This simple fabrication for strain sensors with highly sensitive performance of strain sensor makes it a novel approach to applications in electronic skin, wearable sensors, and health monitoring platforms.     

High‐Energy Asymmetric Supercapacitor Yarns for Self‐Charging Power Textiles

Rapid growth of electronic textile increases the demand for textile‐based power sources, which should have comparable lightweight, flexibility, and comfort. In this work, a self‐charging power textile interwoven by all‐yarn‐based energy‐harvesting triboelectric nanogenerators (TENG) and energy‐storing yarn‐type asymmetric supercapacitors (Y‐ASC) is reported. Common polyester yarns with conformal Ni/Cu coating are utilized as 1D current collectors in Y‐ASCs and electrodes in TENGs. The solid‐state Y‐ASC achieves high areal energy density (≈78.1 µWh cm^?2), high power density (14 mW cm^?2), stable cycling performance (82.7% for 5000 cycles), and excellent flexibility (1000 cycles bending for 180°). The TENG yarn can be woven into common fabrics with desired stylish designs to harvest energy from human daily motions at high output (≈60 V open‐circuit voltage and ≈3 µA short‐circuit current). The integrated self‐charging power textile is demonstrated to power an electronic watch without extra recharging by other power sources, suggesting its promising applications in electronic textiles and wearable electronics.     

Inkjet Printed Large‐Area Flexible Few‐Layer Graphene Thermoelectrics

Graphene‐based organic nanocomposites have ascended as promising candidates for thermoelectric energy conversion. In order to adopt existing scalable printing methods for developing thermostable graphene‐based thermoelectric devices, optimization of both the material ink and the thermoelectric properties of the resulting films are required. Here, inkjet‐printed large‐area flexible graphene thin films with outstanding thermoelectric properties are reported. The thermal and electronic transport properties of the films reveal the so‐called phonon‐glass electron‐crystal character (i.e., electrical transport behavior akin to that of few‐layer graphene flakes with quenched thermal transport arising from the disordered nanoporous structure). As a result, the all‐graphene films show a room‐temperature thermoelectric power factor of 18.7 µW m^?1 K^?2, representing over a threefold improvement to previous solution‐processed all‐graphene structures. The demonstration of inkjet‐printed thermoelectric devices underscores the potential for future flexible, scalable, and low‐cost thermoelectric applications, such as harvesting energy from body heat in wearable applications.     

Knittable and Washable Multifunctional MXene‐Coated Cellulose Yarns

Textile‐based electronics enable the next generation of wearable devices, which have the potential to transform the architecture of consumer electronics. Highly conductive yarns that can be manufactured using industrial‐scale processing and be washed like everyday yarns are needed to fulfill the promise and rapid growth of the smart textile industry. By coating cellulose yarns with Ti₃C₂T_x MXene, highly conductive and electroactive yarns are produced, which can be knitted into textiles using an industrial knitting machine. It is shown that yarns with MXene loading of ≈77 wt% (≈2.2 mg cm^?1) have conductivity of up to 440 S cm^?1. After washing for 45 cycles at temperatures ranging from 30 to 80 °C, MXene‐coated cotton yarns exhibit a minimal increase in resistance while maintaining constant MXene loading. The MXene‐coated cotton yarn electrode offers a specific capacitance of 759.5 mF cm^?1 at 2 mV s^?1. A fully knitted textile‐based capacitive pressure sensor is also prepared, which offers high sensitivity (gauge factor of ≈6.02), wide sensing range of up to ≈20% compression, and excellent cycling stability (2000 cycles at ≈14% compression strain). This work provides new and practical insights toward the development of platform technology that can integrate MXene in cellulose‐based yarns for textile‐based devices.     

Highly Elastic Graphene‐Based Electronics Toward Electronic Skin

Epidermal electronics are extensively explored as an important platform for future biomedical engineering. Epidermal devices are typically fabricated using high‐cost methods employing complex vacuum microfabrication processes, limiting their widespread potential in wearable electronics. Here, a low‐cost, solution‐based approach using electroconductive reduced graphene oxide (RGO) sheets on elastic and porous poly(dimethylsiloxane) (PDMS) thin films for multifunctional, high‐performance, graphene‐based epidermal bioelectrodes and strain sensors is presented. These devices are fabricated employing simple coatings and direct patterning without using any complicated microfabrication processes. The graphene bioelectrodes show a superior stretchability (up to 150% strain), with mechanical durability up to 5000 cycles of stretching and releasing, and low sheet resistance (1.5 kΩ per square), and the graphene strain sensors exhibit a high sensitivity (a gauge factor of 7 to 173) with a wide sensing range (up to 40% strain). Fully functional applications of dry bioelectrodes in monitoring human electrophysiological signals (i.e., electrocardiogram, electroencephalography, and electromyogram) and highly sensitive strain sensors for precise detection of large‐scale human motions are demonstrated. It is believed that our unique processing capability and multifunctional device platform based on RGO/porous PDMS will pave the way for low‐cost processing and integration of 2D materials for future wearable electronic skin.     

Conductive Hierarchical Hairy Fibers for Highly Sensitive,Stretchable, and Water‐Resistant Multimodal Gesture‐Distinguishable Sensor,VR Applications

Conductive fibers, which are highly adaptable to the morphologies of the human body, are attractive for the development of wearable systems, smart clothing, and textronics to detect various biological signals and human motions. A fiber‐based conductive sensor interconnected with hierarchical microhairy architectures, exhibiting remarkable stretchability (<200%) and sensitivity for various stimuli (pressure, stretching, and bending), is developed. For distinguishability of multiple gestures, two hierarchical hairy conductive fibers are twisted to fabricate a fiber‐type sensor, which monitors distinct waveforms of electrical signals retrieved from pressure, stretching, and bending. This sensor is highly robust under repeated appliances of external stimuli over multiple cyclic tests of various modes (<2200 cycles for each stimulus). Upon formation of a self‐assembled monolayer, it exhibits stable performance even under wet conditions. For practical applications, this sensor can be weaved into a smart glove to demonstrate a pressure and gesture‐discernible wearable controller for virtual reality (VR) interface, shedding light on advances in wearable electronics with medical and healthcare functionalities and VR systems.     

Multifunctional and Water‐Resistant MXene‐Decorated Polyester Textiles with Outstanding Electromagnetic Interference Shielding and Joule Heating Performances

Although multifunctional, flexible, and wearable textiles with integrated smart electronics have attracted tremendous attention in recent years, it is still an issue to balance new functionalities with the inherent performances of the textile substrates. 2D early transition metal carbides/nitrides (MXenes) are considered as ideal nanosheets for fabricating multifunctional and flexible textiles on the basis of their superb intrinsic electrical conductivity, tunable surface chemistry, and layered structure. Herein, highly conductive and hydrophobic textiles with exceptional electromagnetic interference (EMI) shielding efficiency and excellent Joule heating performance are fabricated by depositing in situ polymerized polypyrrole (PPy) modified MXene sheets onto poly(ethylene terephthalate) textiles followed by a silicone coating. The resultant multifunctional textile exhibits high electrical conductivity of ≈1000 S m^?1 in conjunction with an exceptional EMI shielding efficiency of ≈90 dB at a thickness of 1.3 mm. The thin silicone coating renders the hydrophilic PPy/MXene‐decorated textile hydrophobic, leading to an excellent water‐resistant feature while retaining a satisfactory air permeability of the textile. Interestingly, the multifunctional textile also exhibits an excellent moderate voltage‐driven Joule heating performance. Thus, the deposition of PPy‐modified MXene followed by silicone coating creates a multifunctional textile that holds great promise for wearable intelligent garments, EMI shielding, and personal heating applications.     

Robust Fabrication of Nonstick,Noncorrosive, Conductive Graphene‐Coated Liquid Metal Droplets for Droplet‐Based,Floating Electrodes

Nontoxic liquid metals (conductive materials in a liquid state at room temperature) are an emerging class of materials for applications ranging from soft electronics and robotics to medical therapy and energy devices. Their sticky and corrosive properties, however, are becoming more of a critical concern for circuits and devices containing other metals as these are easily destroyed or contaminated by the liquid metals. Herein, a feasible method for fabricating highly conductive graphene‐coated liquid metal (GLM) droplets is reported and their application as nonstick, noncorrosive, movable, soft contacts for electrical circuits is demonstrated. The as‐prepared GLM droplets consist of a liquid‐phase soft core of liquid metal and a slippery outer layer of graphene sheets. These structures address the issue of simultaneous control of the wettability and conductivity of a soft electronic contact by combining extraordinary properties, i.e., nonstick, noncorrosive, yet exhibiting high electronic conductivity while in contact with metal substrates, e.g., Au, Cu, Ag, and Ni. As proof‐of‐concept, the as‐prepared GLM droplets are demonstrated as floating electrodes for movable, recyclable electronic soft contacts in electrical circuits.     

Fluid-Dynamics-Processed Highly Stretchable,Conductive, and Printable Graphene Inks for Real-Time Monitoring Sweat during Stretching Exercise

With the development of wearable electronics, the use of engineered functional inks with printing technologies has attracted attention owing to its potential for applications in low-cost, high-throughput, and high-performance devices. However, the improvement in conductivity and stretchability in the mass production of inks is still a challenge for practical use in wearable applications. Herein, a scalable and efficient fluid dynamics process that produces highly stretchable, conductive, and printable inks containing a high concentration of graphene is reported. The resulting inks, in which the uniform incorporation of exfoliated graphene flakes into a viscoelastic thermoplastic polyurethane is employed, facilitated the screen-printing process, resulting in high conductivity and excellent electromechanical stability. The electrochemical analysis of a stretchable sodium ion sensor based on a serpentine-structured pattern results in excellent electrochemical sensing performance even under strong fatigue tests performed by repeated stretching (300% strain) and release cycles. To demonstrate the practical use of the proposed stretchable conductor, on-body tests are carried out in real-time to monitor the sweat produced by a volunteer during simultaneous physical stretching and stationary cycling. These functional graphene inks have attractive performance and offer exciting potential for a wide range of flexible and wearable electronic applications.     

Green Biocomposites for Thermoelectric Wearable Applications

The materials commonly used to fabricate thermoelectric devices are tellurium, lead, and germanium. These materials ensure the best thermoelectric performance, but exhibit drawbacks in terms of availability, sustainability, cost, and manufacturing complexity. Moreover, they do not guarantee a safe and cheap implementation in wearable thermoelectric applications. Here, p‐Type and n‐type flexible thermoelectric textiles are produced with sustainable and low‐cost materials through green and scalable processes. Cotton is functionalized with inks made with biopolyester and carbon nanomaterials. Depending on the nanofiller, i.e., graphene nanoplatelets, carbon nanotubes, or carbon nanofibers, positive or negative Seebeck coefficient values are obtained, resulting in a remarkable electrical conductivity value of 55 S cm^?1 using carbon nanotubes. The best bending and washing stability are registered for the carbon nanofiber‐based biocomposites, which increase their electrical resistance by 5 times after repeated bending cycles and only by 30% after washing. Finally, in‐plane flexible thermoelectric generators coupling the best p‐ and n‐type materials are fabricated and analysed, resulting in an output voltage of ≈1.65 mV and a maximum output power of ≈1.0 nW by connecting only 2 p/n thermocouples at a temperature difference of 70 °C.     

Nitrogen‐Doped Graphene Ribbon Assembled Core–Sheath MnO@Graphene Scrolls as Hierarchically Ordered 3D Porous Electrodes for Fast and Durable Lithium Storage

Graphene scroll is an emerging 1D tubular form of graphitic carbon that has potential applications in electrochemical energy storage. However, it still remains a challenge to composite graphene scrolls with other nanomaterials for building advanced electrode configuration with fast and durable lithium storage properties. Here, a transition‐metal‐oxide‐based hierarchically ordered 3D porous electrode is designed based on assembling 1D core–sheath MnO@N‐doped graphene scrolls with 2D N‐doped graphene ribbons. In the resulting architecture, porous MnO nanowires confined in tubular graphene scrolls are mechanically isolated but electronically well‐connected, while the interwoven graphene ribbons offer continuous conductive paths for electron transfer in all directions. Moreover, the elastic graphene scrolls together with enough internal voids are able to accommodate the volume expansion of the enclosed MnO. Because of these merits, the as‐built electrode manifests ultrahigh rate capability (349 mAh g^?1 at 8.0 A g^?1; 205 mAh g^?1 at 15.0 A g^?1) and robust cycling stability (812 mAh g^?1 remaining after 1000 cycles at 2.0 A g^?1) and is the most efficient MnO‐based anode ever reported for lithium‐ion batteries. This unique multidimensional and hierarchically ordered structure design is believed to hold great potential in generalizable synthesis of graphene scrolls composited with oxide nanowires for mutifuctional energy storage.     

Durable Ultraflexible Organic Photovoltaics with Novel Metal‐Oxide‐Free Cathode

Flexible and stretchable organic photovoltaics (OPVs) are promising as a power source for wearable devices with multifunctions ranging from sensing to locomotion. Achieving mechanical robustness and high power conversion efficiency for ultraflexible OPVs is essential for their successful application. However, it is challenging to simultaneously achieve these features by the difficulty to maintain stable performance under a microscale bending radius. Ultraflexible OPVs are proposed by employing a novel metal‐oxide‐free cathode that consists of a printed ultrathin metallic transparent electrode and an organic electron transport layer to achieve high electron‐collecting capabilities and mechanical robustness. In fact, the proposed ultraflexible OPV achieves a power conversion efficiency of 9.7% and durability with 74% efficiency retention after 500 cycles of deformation at 37% compression through buckling. The proposed approach can be applied to active layers with different morphologies, thus suggesting its universality and potential for high‐performance ultraflexible OPV devices.     

Inkjet Process for Conductive Patterning on Textiles: Maintaining Inherent Stretchability and Breathability in Knit Structures

In this work, a novel technique of inkjet printing e‐textiles with particle free reactive silver inks on knit structures is developed. The inkjet‐printed e‐textiles are highly conductive, with a sheet resistance of 0.09 Ω sq^‐1, by means of controlling the number of print passes, annealing process, and textile structures. It is notable that the inkjet process allows textiles to maintain its inherent properties, including stretchability, flexibility, breathability, and fabric hand after printing process. This is achieved by formation of ultrathin silver layers surrounding individual fibers. The silver layers coated on fibers range from 250 nm to 2.5 µm, maintaining the size of interstices and flexibility of fibers. The annealing process, structure of fibers, and printed layers significantly influence the electrical conductivity of the patterned structures on textiles. Outstanding electrical conductivity and durability are demonstrated by optimizing print passes, controlling textile structures, and incorporating an in situ annealing process. The electrical resistance dependence on the strain rate of the textiles is examined, showing the ability to maintain electrical conductivity to retain light‐emitting diode use, stable more than 500 consecutive strain cycles. Most importantly, inkjet‐printed e‐textiles maintain their characteristic washability, breathability, and fabric hands for applications in wearable technology.     

Liquid‐Gated Transistors Based on Reduced Graphene Oxide for Flexible and Wearable Electronics

Graphene is regarded as the ultimate material for future flexible, high‐performance, and wearable electronics. Herein, a novel, robust, all‐green, highly reliable (yield ≥ 99%), and upscalable technology is reported for wearable applications comprising reduced graphene oxide (rGO) as the electroactive component in liquid‐gated transistors (LGTs). rGO is a formidable material for future flexible and wearable applications due to its easy processability, excellent surface reactivity, and large‐area coverage. A novel protocol is established toward the high‐yield fabrication of flexible rGO LGTs combining high robustness (>1.5 h of continuous operation) with state‐of‐the‐art performances, being similar to those of their rigid counterparts operated under liquid gating, including field‐effect mobility of ≈10^?1 cm² V^?1 s^?1 and transconductance of ≈25 µS. Permeable membranes have been proven crucial to operate flexible LGTs under mechanical stress with reduced amounts of solution (<20 µL). Our rGO LGTs are operated in artificial sweat exploiting two different layouts based on lateral‐flow paper fluidics. These approaches pave the road toward future real‐time tracking of perspiration via a simple and cost‐effective approach. The reported findings contribute to the robust and scalable production of novel graphene‐based flexible devices, whose features fulfill the requirements of wearable electronics.