Joule Heater Research Articles

High Ion-Conductive Hydrogel: Soft, Elastic, with Wide Humidity Tolerance and Long-Term Stability.

Ion-conductive hydrogels have received great attention due to their significant potential in flexible electronics. However, achieving hydrogels that simultaneously possess high ionic conductivity and stability under varying humidity conditions remains a challenge, limiting their practical applications. Herein, we propose a thermally controlled chemical cross-linking strategy to prepare an elastic and conductive hydrogel (ECH) of poly(vinyl alcohol) (PVA) with high content of H2SO4. The covalent cross-links formed effectively tackle the instability issue in high humidity of physically cross-linked PVA/H2SO4 hydrogels with high ionic conductivity, which were previously developed via the polymer-in-salt strategy. We systematically investigated the reaction conditions and clarified the methods to optimize the hydroxyl dehydration of PVA, resulting in excellent mechanical properties and ion conductivity simultaneously. The ECH demonstrates impressive ionic conductivity (up to 392 ± 49 mS cm-1) and elasticity (over 80% resilience upon stretching and compression after being equilibrated at various humidity levels for 24 days). Thanks to the excellent water retention of the high H2SO4 content, the ECH maintains an ionic conductivity exceeding 210 mS cm-1 for over 420 days at 50% relative humidity (RH) and retains over 100 mS cm-1 even after 3 days under extremely dry conditions (7% RH). These remarkable properties make the ECH an ideal candidate for applications requiring reliable ionic conductivity in diverse environmental conditions. Additionally, we demonstrated that the ECH can function as a stretchable Joule heater with high conformability for heating up objects with curved surfaces. The heating rate could reach a fast rate of ∼12 °C s-1 even when a human-safe alternating current voltage is below 36 V, attributed to the high ionic conductivity. We believe that the high performance and ease of fabrication make our hydrogels a promising candidate for use as electrolytes in flexible energy storage devices, electrolyte gates in electrochemical transistors, and artificial skin, which often face long-term stability challenges under varying humidity conditions.

High-Performance Wearable Joule Heater Derived from Sea-Island Microfiber Nonwoven Fabric.

A three-dimensional (3D) hierarchical microfiber bundle-based scaffold integrated with silver nanowires (AgNWs) and porous polyurethane (PU) was designed for the Joule heater via a facile dip-coating method. The interconnected micrometer-sized voids and unique hierarchical structure benefit uniform AgNWs anchored and the formation of a high-efficiency 3D conductive network. As expected, this composite exhibits a superior electrical conductivity of 1586.4 S/m and the best electrothermal conversion performance of 118.6 °C at 2.0 V compared to reported wearable Joule heaters to date. Moreover, the durable microfiber bundle-PU network provides strong mechanical properties, allowing for the stable and durable electrothermal performance of such a composite to resist twisting, bending, abrasion, and washing. Application studies show that this kind of Joule heater is suitable for a wide range of applications, such as seat heating, a heating jacket, personal thermal management, etc.

Recyclable and leakage-suppressed microcellular liquid–metal composite foams for stretchable electromagnetic shielding

The metallic conductivity and high liquidity of liquid metal (LM) make LM-polymer composites exhibit high electrical conductivity, large stretchability, and excellent mechanical–electrical decoupling, which provide significant advantages in the fabrication of stretchable electromagnetic interference (EMI) shielding materials. However, problems such as undesired LM leakage, high density, and poor recyclability due to the frequent use of chemically cross-linked polymers limit the applications of LM-polymer composites. Herein, we report the fabrication of stretchable and recyclable microcellular thermoplastic polyurethane (TPU)/LM composite foams (TLFs) with controllable LM distribution through a water–vapor-induced phase separation (WVIPS) process. The sedimentation of LM droplets helps to improve the shielding effectiveness (SE) of TLF, while the microcellular structure enables TLF with more uniform LM dispersion to achieve high leakage resistance. Moreover, the stretch-activated TLF shows high electrical stability with only slight resistance changes during stretching and exhibits a strain-insensitive shielding behavior. As a stretchable joule heater, the sample has outstanding Joule-heating performance, with stable temperature dropping only slightly under large tensile strains. More importantly, the excellent solubility of TPU, combined with a solution-based WVIPS process, allows our TLFs to be easily recycled into new products with very similar structure and performance to those before recycling, indicating the ideal recyclability of such materials.

Programmed multimaterial assembly by synergized 3D printing and freeform laser induction

In nature, structural and functional materials often form programmed three-dimensional (3D) assembly to perform daily functions, inspiring researchers to engineer multifunctional 3D structures. Despite much progress, a general method to fabricate and assemble a broad range of materials into functional 3D objects remains limited. Herein, to bridge the gap, we demonstrate a freeform multimaterial assembly process (FMAP) by integrating 3D printing (fused filament fabrication (FFF), direct ink writing (DIW)) with freeform laser induction (FLI). 3D printing performs the 3D structural material assembly, while FLI fabricates the functional materials in predesigned 3D space by synergistic, programmed control. This paper showcases the versatility of FMAP in spatially fabricating various types of functional materials (metals, semiconductors) within 3D structures for applications in crossbar circuits for LED display, a strain sensor for multifunctional springs and haptic manipulators, a UV sensor, a 3D electromagnet as a magnetic encoder, capacitive sensors for human machine interface, and an integrated microfluidic reactor with a built-in Joule heater for nanomaterial synthesis. This success underscores the potential of FMAP to redefine 3D printing and FLI for programmed multimaterial assembly.

Highly Efficient Cash Sterilization with Ultrafast and Flexible Joule‐Heating Strategy by Laser Patterning

AbstractSince ancient times, humans have learned to use fire and other heating methods to fight against dangerous pathogens, like cooking raw food, sterilizing surgical tools, and disinfecting other pathogen transmission media. However, it remains difficult for current heating methods to achieve extremely fast and highly efficient sterilization simultaneously. Herein, an ultrafast and uniform heating‐based strategy with outstanding bactericidal performance is proposed. Ultra‐precise laser manufacturing is used to fabricate the Joule heater which can be rapidly heated to 90 °C in 5 s with less than 1 °C fluctuation in a large area by real‐time temperature feedback control. An over 98% bactericidal efficiency on S. aureus for 30 s and on E. coli for merely 5 s is shown. The heating strategy shows a 360 times faster acceleration compared to the commonly used steam sterilization from the suggested guidelines by the Centers for Disease Control and Prevention (CDC), indicating that high temperatures with short duration can effectively disinfect microorganisms. As a proof of concept, this heating strategy can be widely applied to sterilizing cash and various objects to help protect the public from bacteria in daily life.

A Wearable All-Printed Textile-Based 6.78 MHz 15 W-Output Wireless Power Transfer System and Its Screen-Printed Joule Heater Application

While research in passive flexible circuits for Wireless Power Transfer (WPT) such as coils and resonators continues to advance, limitations in their power handling and low efficiency have hindered the realization of efficient all-printed high-power wearable WPT receivers. Here, we propose a screen-printed textile-based 6.78 MHz resonant inductive WPT system using planar inductors with concealed metal-insulator-metal (MIM) tuning capacitors. A printed voltage doubler rectifier based on Silicon Carbide (SiC) diodes is designed and integrated with the coils, showing a power conversion efficiency of 80-90% for 2-40 W inputs over a wide load range. Compared to prior wearable WPT receivers, it offers an order of magnitude improvement in power handling along with higher efficiency (approaching 60%), while using all-printed passives and a compact rectifier. The coils exhibit a simulated Specific Absorption Rate (SAR) under 0.4 W/kg for 25 W received power, and under 21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C increase in the coils' temperature for a 15 W DC output. Additional fabric shielding is investigated, reducing harmonics emissions by up to 17 dB. We finally demonstrate a wirelessly-powered textile-based carbon-silver Joule heater, capable of reaching up to 60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> C at 2 cm separation from the transmitter, as a wearable application which can only be wireless-powered using the proposed system.

Thermally manageable and scalable reactor configurations towards efficient hydrogen release from liquid organic hydrogen carriers

In the global pursuit to minimize carbon emissions, hydrogen has emerged as a prominent alternative energy solution. This research introduces a thermally efficient, scalable, and potentially carbon–neutral system for releasing hydrogen, employing methylcyclohexane as a liquid organic hydrogen carrier (LOHC). Our heat supply mechanism utilizes benzyltoluene as a liquid–gas phase change material (PCM) to facilitate effective heat transfer from the heating units to the reactor. We have developed catalysts with high dispersion and Pt loading of Pt/γ-Al2O3 that maintain performance over extended periods, achieving a hydrogen extraction rate of 2.3 Nm3H2(g)/h (equivalent to 5 kgH2/day) in a bench-scale reactor. The bench-scale setup achieves near-equilibrium conversion at a space velocity of 2 LLOHC/(Lcat-h) and 310 °C. The PCM-enhanced system supports a scalable catalytic bed design and simplifies heat supply and startup through the use of various heating methods. We then compare catalytic dehydrogenation reactor setups using single and hybrid heat sources; the former includes an internal Joule heater, offering simplicity and reduced heat loss but depends heavily on electrical energy, while the latter combines the internal Joule heater with an external fuel combustor, facilitating rapid startup albeit with increased heat loss. Lastly, we suggest future research directions to address existing technological hurdles and to expand the application of this system in scaling up hydrogen release processes.

Intense thermal shock generators made of micron-thick SnO2 layers for the on-chip rapid thermal processing in air

Thermal shock-resistant heaters are essential in various electronic devices, including chemical sensors and pyroelectric electron emitters. The advent of ultrafast high-temperature sintering and shock synthesis of nanomaterials has increased the demand for air-operating high-rate joule heaters. Moreover, incorporating such heaters at the chip level would revolutionize current rapid thermal processing methods in semiconductor technology. Here, transparent micron-thick SnO2 resistors are grown by spray pyrolysis on alumina, silica, and oxidized silicon chips and used as thermal shock-resistant air-operating heaters. These heaters can generate repeated heating cycles at rates of 15,000 °C/s up to 900 °C/s. Tin is a group IV element and its impact on Si- and SiO2-based devices is minimal making the presented device silicon compatible. The superior performance of the presented heaters is attributed to the tin oxide’s unique combination of physicochemical properties including high-temperature chemical stability in oxidizing atmospheres, suitable intrinsic conductivity, and optimal negative temperature coefficient of resistance. The application of the SnO2 heaters for the rapid on-chip high-temperature oxidation and sintering of low-melting-point metal thin films, while preserving the metal layer’s nanotexture, is demonstrated.

Stretchable and translucent liquid-metal composite mesh for multifunctional electromagnetic shielding/sensing and Joule heating

Flexible liquid metal (LM)-based composite materials with strain-undiminished electromagnetic interference (EMI) shielding effectiveness (SE) and multifunctional integration are attracting great attention due to the urgent need for flexible electronic and wearable devices. Herein, stretchable and translucent polydimethylsiloxane/LM composite mesh (PLM) is developed by introducing highly deformable LM filler into elastomer and constructing conductive mesh structures by cast molding and mechanical sintering, which shows strain-enhanced EMI SE without a significant decrease in light transmittance due to the contribution of stretch-induced enhanced conductivity, mesh densification, and orientation. The linear response of relative SE change with tensile strain allows the PLM to exhibit ideal EM sensing characteristics, superior to most reported stretchable EMI shields. The oriented mesh structure endows the stretched PLM with anisotropic EMI SE under rotation, revealing a feasible means to realize tunable SE in a tensile state. More importantly, the high conductivity and deformability of the LM network further provide the PLM with excellent and relatively stable Joule-heating performance when served as a stretchable Joule heater. This work offers a new strategy for developing multifunctional stretchable LM-based composites that can achieve strain-enhanced EMI SE and ideal EM sensing capability without significantly sacrificing the light transmittance and Joule-heating performances under stretching.

Injection Molding of Liquid Metal by Harnessing Nonstick Molds.

The fluid nature of liquid metals combined with their ability to form a solid native oxide skin enables them to be patterned in ways that would be challenging for solid metals. The present work shows a unique way of patterning liquid metals by injecting liquid metals into a mold. The mold contains a nonstick coating that enables the removal of the mold, thereby leaving just the liquid metal on the target substrate. This approach offers the simplicity and structural control of molding but without having the mold become part of the device. Thus, the metal can be encapsulated with very soft polymers that collapse if used as microchannels. The same mold can be used multiple times for high-volume patterning of liquid metal. The injection molding method is rapid and reliably produces structures with complex geometries on both flat and curved surfaces. We demonstrate the method by fabricating an elastomeric Joule heater and an electroadhesive soft gripper to show the potential of the method for soft and stretchable devices.

Efficient Joule heaters based on mineral-impregnated carbon-fiber reinforcing grids: An experimental and numerical study on a multifunctional concrete structure as an electrothermal device

This study introduces the design and realization of an electrothermal-enabled reinforcing grid based on mineral-impregnated carbon-fibers (MCFs) for efficient and low-power-consuming de-icing of a geopolymer (GP) concrete surface. Initially, carbon fiber (CF) yarns were impregnated with a GP suspension through a custom-made production line. Then, particular fresh MCFs were further processed via vacuum bagging, resulting in two different profile shapes with differentiated mechanical and physicochemical properties. The as-produced MCF structures were assessed regarding their electrothermal performance whereby the most efficient were employed as heating elements for assembling the reinforcing grid as Joule heater device. The obtained multifunctional reinforced concrete composite demonstrated de-icing effectiveness for an applied DC voltage of 2.2 V, corresponding to a surface temperature of 45 °C with a significantly low required heating power of 95.6 W/m2 in relation to similar studies. The experimental work was validated using a coupled field of electrothermal modelling. The proposed modular design offers unique potential and flexibility for large-area uniform and responsive de-icing applications via multiple interconnected multifunctional reinforcing grids.

Self‐Destructible Electromagnetic Interference Shielding Films

AbstractIn response to the increasing utilization of communication technology, there is a growing need for electromagnetic interference (EMI) shielding materials to adapt to diverse application scenarios. In this study, the self‐destructible EMI shielding films (SEFs) that possess the unique capability to reduce conductivity and shielding efficiency through temperature elevation are introduced. The SEFs effectively fulfill the requirement of triggering EMI shielding failure under specific conditions, which can be achieved by simply spraying a mixture of thermally expandable microspheres (TEMs), conductive fillers, and resin substrates. The segregated structures resulting from the incorporation of TEMs confer exceptional electrical conductivity and superior EMI shielding performance at low conductive filler content. When the ambient temperature surpasses the glass transition temperature of the TEM shell, the thermally expandable characteristics cause a disruption in the conductive path of the SEFs, leading to a significant decline in shielding effectiveness. Additionally, the SEFs exhibit outstanding Joule heating effects (90 °C) at low voltage (1.5 V) within a brief time frame (10 s). Importantly, when employed as Joule heaters, the SEFs possess an intrinsic safety mechanism that automatically ceases operation in the event of circuit overload, thus minimizing any potential risks.

Fully Integrated Pneumatic-Free and Magnet-Free CMOS Ferrofluidic Platform for Comprehensive Biomolecular Processing.

This article presents a fully integrated CMOS ferrofluidic platform featuring on-chip three-electrode electrochemical cells, temperature regulators, and magnetic sensors. The proposed platform consists of 25 ferrofluidic pixels and 2 magnetic sensors. Each ferrofluidic pixel comprises a spiral inductor, a three-electrode electrochemical cell, a temperature sensor, and a localized Joule heater. Unlike pneumatic-based platforms, this ferrofluidic platform does not require an external pneumatic pump to drive droplets. Instead, the on-chip spiral inductors generate magnetic fields to manipulate the ferrofluidic droplets. Additionally, these inductors are repurposed as heat radiators. The CMOS ferrofluidic platform is implemented using a 45-nm CMOS SOI process. Theoretical analyses of ferrofluidic control and magnetic sensing are conducted to understand the relationship between ferrofluidic movement conditions and the integrated magnetic sensor. The on-chip electrochemical potentiostat is characterized using various concentrations of methylene blue solution, and the variation in the electrochemical sensor is measured. As proof of concept, biological measurements with on-chip real-time recombinase polymerase amplification (RT-RPA) are demonstrated. The proposed platform offers a fully integrated solution for ferrofluidic manipulation, sensing, and temperature regulation without the need for external bulky equipment, thereby supporting advanced biomolecular processing. While RT-RPA is used here solely for demonstration purposes, our ferrofluidic multi-functional CMOS array platform is also capable of processing a wide range of other molecular analytes. This versatility underscores the platform's potential for broad applications in molecular diagnostics and bioanalytical research.

Liquid Metal-Based Stable and Stretchable Zn-Ion Battery for Electronic Textiles.

Electronic textiles harmoniously interact with the human body and the surrounding environment, offering tremendous interest in smart wearable electronics. However, their wide application faces challenges due to the lack of stable and stretchable power electrodes/devices with multifunctional design. Herein, an intrinsically stretchable liquid metal-based fibrous anode for a stable Zn-ion battery (ZIB) is reported. Benefiting from the liquid feature and superior deformability of the liquid metal, optimized Zn ion concentration distribution and Zn (002) deposition behavior are observed, which result in dendrite-free performance even under stretching. With a strain of 50%, the ZIB maintains a high capacity of 139.8 mAh cm-3 (corresponding to 83.0% of the initial value) after 300 cycles, outperforming bare Zn fiber-based ZIB. The fibrous ZIB seamlessly integrates with the sensor, Joule heater, and wirelessly charging device, which provides a stable power supply for human signal monitoring and personal thermal management, holding promise for the application of wearable multifunctional electronic textiles.

Multifunctional metal–organic frameworks nanoengineered laser-induced graphene for health electronics

Laser-induced graphene (LIG) has great application potential in flexible electronics. Incorporating other functional nanomaterials into LIG is an important way to improve its performance. However, there are few studies on in-situ modification of LIG morphology by nanomaterials to improve its performance. Herein, to modify the morphology of LIG films, NiCo-metal–organic frameworks (NiCo-MOFs) were added to the LIG precursors to participate in the carbonization forming process of LIG films for the first time, and the NiCo nanoporous carbon (NiCo-NPC)/LIG films with cauliflower-like surface microstructure were obtained. Since the formation process of LIG is affected by the carbonization of NiCo-MOFs, the NiCo-NPC/LIG film has a fluffier porous structure and rougher surface morphology than that of the LIG film. Therefore, the NiCo-NPC/LIG-based flexible piezoresistive sensor exhibits an ultra-high sensitivity of 226 kPa−1 in 0–45 kPa, which is 54 % higher than that of the LIG-based sensor. Meanwhile, the NiCo-NPC/LIG film exhibits an electromagnetic interference (EMI) shielding effectiveness of 171 dB/mm in the band of 8.2–12.4 GHz, which is 104 % higher than that of the corresponding LIG film. In addition, the NiCo-NPC/LIG-based Joule heater exhibits fast response and good flexibility. The experimental results indicate that using MOFs additives to modify the morphology of LIG in situ can effectively improve LIG performance, which provides a new way for developing high-performance LIG-based composite films.

Chemresistor Smart Sensors from Silk Fibroin-Graphene Composites for Touch-free Wearables.

With the rapid development of wearable electronics, low-cost, multifunctional, ultrasensitive touch-free wearables for human-machine interaction and human/plant healthcare management have attracted great attention. The experience of fighting the COVID-19 epidemic has also confirmed the great significance of contactless sensation. Herein, a wearable smart-sensing platform using silk fibroin-reduced graphene oxide (SF-rGO) as bifunctional sensing active layers has been fabricated and integrated with a noncontact moisture/thermo sensor and Joule heater. As a result, the as-prepared smart sensor operated at 0.1 V exhibits good stability and sensitivity (sensor response of 60 for 97% RH) under a wide linear range of 6-97% RH, fast response/recover speed (real test: 21.51 s/85.62 s) toward touch-free humidity/temperature sensing for wearables, and thermal readings that can be accurately corrected by Joule heater. Impressively, it can achieve breath monitoring, mental state prediction, or elevator switching by identifying fingertip humidity variation. Prospectively, this all-in-one wearable smart sensor would set an example for improving sensing performance from structure-function relationship points of view and building a noncontact sensing system for daily life.

A polyester/spandex blend fabrics-based e-textile for strain sensor, joule heater and energy storage applications

Electronic textiles (e-textiles), as a new class of wearable electronics, have shown diverse applications in modern technologies. However, the development of multi-functional e-textiles with both high strength and elasticity to satisfy different working conditions remains challenge. Herein, the e-textiles based on polyester/spandex blend (PSB) fabrics have been fabricated and their applications in strain sensors, heaters and supercapacitors have been systematically studied. The carbon nanotubes (CNTs) are coated on PSB fabrics via polydopamine (PDA) adhesion. As a strain sensor, the air-permeable PSB-CNT e-textiles show a gauge factor of 18.9 at high strain with a fast response time of 114 ms. The PSB-CNT strain sensor can work better than the cotton-based sensor even at high temperature of 100 °C due to the high heat resistance of polyester, securing its application in severe environment. As a joule heater, the PSB-CNT e-textiles can raise up to 110 °C at 12 V. Further electrodeposition of polypyrrole (PPy) on PSB-CNT can obtain the e-textile electrodes for micro-supercapacitor (MSC). The all-solid-state MSC using PSB-CNT-PPy delivers high specific capacitance of 550 mF cm−2 at 1 mA cm−2. This work offers a simple route for e-textile fabrications and promises potential applications in wearable sensors, heaters, and power sources.

Self‐Regulated Self‐Healing Robotic Gripper for Resilient and Adaptive Grasping

Flexible, soft materials are increasingly used for the fabrication of soft robots, as the inherent compliance and shock‐absorbance protect the robot from mechanical impact. Soft universal grippers take full advantage of this adaptability, facilitating effective and safe grasping of various objects. However, due to their predominantly soft material composition, these grippers have limited lifetimes, especially when operating in unstructured and unfamiliar environments. The self‐healing universal gripper (SHUG) is proposed, which can grasp various objects and recover from substantial realistic damages autonomously. It integrates damage detection, heat‐assisted healing, and healing evaluation. Notably, unlike other universal grippers, the entire SHUG can be fully reprocessed and recycled. The gripper's functionality relies on the particle jamming of steel balls enclosed within a self‐healing membrane. Thanks to the thermoreversible covalent Diels–Alder bonds in self‐healing polymer membrane, the gripper is able to recover from macroscopic damages including scratches and punctures. Temperature‐assisted healing is regulated in a closed‐loop manner using an embedded thermocouple and Joule heater. Experimental validation demonstrates the adaptability, resilience, and recyclability of the SHUG.

Super-strong and high-performance electrical film heater derived from silver nanowire/aligned bacterial cellulose film

High-performance electrical Joule heaters with high mechanical properties, low driving voltage, rapid response, and flexibility are highly desirable for portable thermal management. Herein, by using aligned bacterial cellulose (BC) and silver nanowire (AgNW), we fabricated a novel film heater based on Joule heating phenomena. The aligned BC film prepared by stretching BC hydrogel and hot-pressing drying technology showed outstanding mechanical properties and flexibility. The ultrahigh strength of up to 1018 MPa and the toughness of 20 MJ/m3 were obtained for the aligned BC film with 40% wet-stretching (BC-40). In addition, the aligned BC film could be folded into desirable shapes. The AgNW was spray-coated on the surface of aligned BC-40 film and then covered with polydimethylsiloxane to form a P@AgNW@BC heater. P@AgNW@BC heater showed excellent conductivity, which endowed the film heater with an outstanding Joule heating performance. P@AgNW@BC heater could reach ~ 98 ℃ at a very low driving voltage of 4 V with a rapid heating response (13 s) and long-term temperature stability. The P@AgNW@BC heater with such an outstanding heating performance can be used as a flexible heating device for different applications in daily life like deicing/defogging device, wearable thermotherapy, etc.Affiliations: Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.yes, we confirmed the affiliations are correct.Article title: Kindly check and confirm the edit made in the article title.Thanks, the title is no problem.Graphical

Impermeable Graphene Skin Increases the Heating Efficiency and Stability of an MXene Heating Element.

A Joule heater made of emerging 2D nanosheets, i.e., MXene, has the advantage of low-voltage operation with stable heat generation owing to its highly conductive and uniformly layered structure. However, the self-heated MXene sheets easily get oxidized in warm and moist environments, which limits their intrinsic heating efficiencies. Herein, an ultrathin graphene skin is introduced as a surface-regulative coating on MXene to enhance its oxidative stability and Joule heating efficiency. The skin layer is deposited on MXene using a scalable solution-phased layer-by-layer assembly process without deteriorating the excellent electrical conductivity of the MXene. The graphene skin comprises narrow and hydrophobic channels, which results in ≈70 times higher water impermeability of the hybrid film of graphene and MXene (GMX) than that of the pristine MXene. A complementary electrochemical analysis confirms that the graphene skin facilitates longer-lasting protection than conventional polymer coatings owing to its tortuous pathways. In addition, the sp2 planar carbon surface with a low heat loss coefficient improves the heating efficiency of the GMX, indicating that this strategy is promising for developing adaptive heating materials with a tractable voltage range and high Joule heating efficiency.