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For the need of direct contact with the skin, electronic skins (E‐skins) should not only fulfill electric functions, but also ensure comfort during wearing, including permeability, waterproofness, and easy removal. Herein, the study has developed a self‐adhesive, detach‐on‐demand, breathable, and waterproof E‐skin (PDSC) for motion sensing and wearable comfort by electrospinning styrene‐isoprene block copolymer rubber with carbon black nanosheets as the sensing layer and liner copolymers of N, N‐dimethylacrylamide, n‐octadecyl acrylate and lauryl methacrylate as the adhesive layer. The high elasticity and microfiber network structure endow the PDSC with good sensitivity and high linearity for strain sensing. The hydrophobic and crystallizable adhesive layer ensures robust, waterproof, and detaching‐on‐demand skin adhesion. Meanwhile, the fiber structure enables the PDSC good air and water permeability. The integration of electric and wearable functions endows the PDSC with great potential for motion sensing during human activities as both the sensing and wearable performances. [ABSTRACT FROM AUTHOR]

Only microstructures are used to improve the sensitivity of iontronic pressure sensors. By modulating the compressive modulus, a breakthrough in the sensitivity of the iontronic pressure sensor is achieved. Furthermore, it allows for programmatic tailoring of sensor performance according to the requirements of different applications. Such a new strategy pushes the sensitivity up to a record‐high of 25 548.24 kPa−1 and expands the linear pressure range from 15 to 127 kPa. Additionally, the sensor demonstrates excellent mechanical stability over 10 000 compression‐release cycles. Based on this, a well‐controlled robotic hand that precisely tracks the pressure behavior inside a balloon to autonomously regulate the gripping angle is developed. This paves the way for the application of iontronic pressure sensors in precise sensing scenarios. [ABSTRACT FROM AUTHOR]

Mechanical metamaterials (MMs) receive widespread attention due to their unprecedented mechanical properties. However, in the next‐generation MMs, the cognitive function of information processing can be realized while maintaining superior mechanical properties. Herein, a mechanical metamaterial‐based self‐powered electronic skin (e‐skin) with multimodal fusion perception capability and shape memory reconfigurability is proposed. Benefiting from an MM skeleton and its analytical model, e‐skin realizes biomimetic nonlinear mechanical behavior and mechanical reconfigurability to imitate target biotissues. Its integrated perovskite‐based elastic sensors enable high‐precision collection of physiological movements and auditory, tactile, and precontact distance signals. Further, by imitating the integration and interaction functions in biological multisensory neural networks, the system achieves advanced cognitive functions of acquiring, identifying, and integrating information across modalities. Applications of e‐skin are demonstrated in motion monitoring, speech recognition, and somatosensory game operation. These capabilities can be applied to cross‐modal perception robot systems based on multisensory neural networks. [ABSTRACT FROM AUTHOR]

Biomimetic electronic skins (e‐skins) are widely used in wearables, smart prosthesis and soft robotics. However, multimodal e‐skins, especially those based on hydrogels, face multiple challenges for practical applications, involving multi‐sensing signal mutual interference, low breathability and stretchability. Here, a breathable and stretchable multimodal e‐skin with a multilayer film microstructure is developed to achieve self‐calibrated sensing of any two of three stimuli: strain, temperature, and humidity, with minimal crosstalk. Hydrogel fibers with different shapes are designed for strain and temperature sensing modules, and the hydrogel film is developed as a humidity sensing module. The multimodal e‐skin exhibits impressive sensing performance, including a low strain detection limit (0.03%), strain linearity (R2 = 0.990), high‐temperature sensitivity (1.77%/°C), and a wide humidity detection range (33–98% RH). Interestingly, due to the directional anisotropy in strain sensitivity of different shaped fibers, the e‐skin realizes self‐calibrated detection of strain and temperature in different directions. By introducing porous elastomer encapsulation membranes, the breathability and wearing comfort of the e‐skin are attained, while the high stretchability (100% strain) is maintained. Furthermore, a personalized human‐machine interaction system is created by integrating the e‐skin with a wireless circuit to realize real‐time and wireless gesture recognition, physiological signals monitoring, and smart prosthesis. [ABSTRACT FROM AUTHOR]

Wearable and self‐healing soft electronics have led to a significant emphasis on their potential in creating versatile, conformable, and sustainable electronic modules. Among conductive additives, Liquid metals (LMs), combining both solid and liquid characteristics, have gained widespread attention due to their versatile physical, chemical, and electrical properties as well as self‐healing capability, biocompatibility, and recyclability. The fluidity of LMs facilitates adaptability to various experimental conditions and components for specific applications. Moreover, the oxide shell on LMs exhibits strong compatibility with surface functionalization and polymerization processes, enhancing the development of reliable composite materials. Herein, an in‐depth analysis of the fundamental properties and characteristics of LMs while addressing their current drawbacks, such as unpredictable reactivity and poor surface stability, is presented. To harness the advantages of LMs, their integration is extensively discussed with polymeric materials through various grafting strategies, leading to the development of macromolecular composites with exceptional softness, solubility, surface functionalization, and versatility. Furthermore, the applications of LMs within LM‐elastomer composites, particularly focusing on their relevance in specific fields such as flexible electronics, are investigated. Finally, LMs' future prospects are emphasized by highlighting their compatibility with self‐healing polymers, thereby providing pathways for major breakthroughs of LMs based devices. [ABSTRACT FROM AUTHOR]

Haptic perception of softness is a unique feature of the human skin that relies on the concurrent measurements of the lateral deformation and compression of the skin during object manipulation. This is challenging to implement in robotics because of combined requirements in sensing modalities, skin format, robotic structures, and synthetic materials. A soft sensory skin supporting distributed and bimodal mechanical sensing over large surface area and suitable for robotic hand manipulation is reported. Resistive pressure and strain sensors are prepared with spray‐coated liquid metal films embedded in a silicone matrix. Object softness is computed through a calibrated model based on both sensor response curves and the stiffness of the carrier robot. The soft sensory skin enables localization and discrimination of softness that promise interesting future implementation for robotic palpation or precise teleoperation. [ABSTRACT FROM AUTHOR]

The emergence of cutting‐edge cross‐disciplines has motivated the rapid development of wearable technology and flexible electronics. The flexibility and tunable properties of organic materials enable organic flexible electronics to adapt to complex surface deformations and achieve sensitive detection of physiological signals. The cost‐effectiveness of organic materials in mass production offers additional possibilities for the practical and commercialization of e‐skin technology. However, how to ensure stability and long‐term reliability while maintaining a highly sensitive, flexible, and stretchable is a challenge for e‐skins. In this review, the research progress and development trend of e‐skin is systematically summarized, especially the latest breakthroughs and innovations in the frontier of organic flexible electronics, and systematically review the applications of e‐skin in sensors, physiological monitoring, and energy supply. In addition, the review further discusses the prospects and current challenges for the application of organic flexible electronics in e‐skin, which provides a one‐stop reference for the development of e‐skin. [ABSTRACT FROM AUTHOR]

The development of electronic skin with dual stealth functionality is crucial for enabling devices to operate effectively in dynamic electromagnetic environments, thereby facilitating intelligent electromagnetic protection for autonomous perception. However, achieving compatibility between terahertz (THz) and infrared (IR) stealth technologies remains largely unexplored due to their inherent contradictions. Herein, inspired by natural corals, a novel coral‐like multi‐scale composite foam (CMSF) was proposed that ingeniously reconciles these contradictions. The design capitalizes on the conductive network and heat insulation properties of the foam skeleton, the loss effects and low infrared emission of metal particles, and the infrared transparency of magneto‐optical materials. This approach leads to the realization of a THz‐IR bi‐stealth electronic skin concept. The CMSF exhibits a maximum reflection loss of 84.8 dB in the terahertz band, while its infrared stealth capability ensures environmental adaptability under varying temperatures. Furthermore, the electronic skin exhibits exceptional sensitivity and reliability as a wearable device for perceiving environmental changes. This advanced material, combining multispectral stealth with sensing capabilities, holds immense potential for applications ranging from camouflage technology to smart wearables. [ABSTRACT FROM AUTHOR]

Electronic skin (E‐skin) that can mimic the flexibility and stretchability of human skin with sensing capabilities, holds transformative potential in robotics, wearable technology, and healthcare. However, developing E‐skin poses significant challenges such as creating durable materials with skin‐like flexibility, integrating biosensing abilities, and using advanced fabrication techniques for wearable or implantable applications. To overcome these hurdles, a 3D‐printed electronic skin utilizing a novel class of nanoengineered hydrogels with tunable electronic and thermal biosensing capabilities is fabricated. This methodology takes advantage of the shear–thinning behavior in hydrogel precursors, allowing to construct intricate 2D and 3D electronic structures. The elasticity of skin using triple crosslinking in a robust fungal exopolysaccharide, and pullulan is simulated, while defect‐rich 2D molybdenum disulfide (MoS2) nanoassemblies ensure high electrical conductivity. The addition of polydopamine nanoparticles enhances adhesion to wet tissue. The hydrogel exhibits outstanding flexibility, stretchability, adhesion, moldability, and electrical conductivity. A distinctive feature of this technology is the precise detection of dynamic changes in strain, pressure, and temperature. As a human motion tracker, phonatory‐recognition platform, flexible touchpad, and thermometer, this technology represents a breakthrough in flexible wearable skins and holds transformative potential for the future of robotics and human‐machine interfaces. [ABSTRACT FROM AUTHOR]

The interfacial design of the electronic skins (E‐skins), which are increasingly crucial in areas like exercise monitoring, healthcare, etc., has a great impact on wearability and functions. The adhesion between E‐skin and human skin serves as the foundation for various functionalities. In addition to robust adhesion strength, detaching‐on‐demand, and waterproof abilities are also important for long‐time wearing and comfort detachment after use. Here, self‐adhesive, detach‐on‐demand, and waterproof hydrophobic E‐skins (PBIA) by copolymerization of acrylates with conductive ionic liquid and adhesive components as the strain sensor and triboelectric nanogenerator (TENG) is developed. The strong van der Waals self‐adhesion (shear adhesion of ≈574 kPa, peeling adhesion of ≈110 N m−1), and waterproof abilities under immersing, flushing, and penetrating situations enable the E‐skin to realize stable and long‐time monitoring for body motions in both the resistance sensing and TENG modes. Meanwhile, the easy detach‐on‐demand ability of van der Waals adhesion (574 to 35 kPa and 110 to 7 N m−1) guarantees the easy and comfortable detachment of PBIA after use, avoiding pain or injury to the skin. The adhesion strategy of PBIA can be expanded to other kinds of E‐skins and accelerate the pace of practical applications of E‐skins. [ABSTRACT FROM AUTHOR]

Neurofeedback training based on brain rhythm is appealing for both cognitive neuroscience and disorder treatment. However, electrodes that can integrate dual functions of recording and feedback without signal compromise still lack. Herein, an anisotropic cellulose carbon sponge (CCS) electrode by tailoring conductivity through the temperature that has the dual ability to record electrophysiological signals and sense pressures as feedback is developed. The electrode is fabricated via a gradient temperature annealing on CCS, which involves lower (300 °C) and higher (1000 °C) temperature treatments, namely CCS‐LT and CCS‐HT. CCS‐LT exhibits perpendicular resilience to the alignment direction of CCS, and CCS‐HT possesses lower sheet resistance (≈13 Ω sq−1) parallel to the alignment direction. As a pressure sensor, CCS‐LT can achieve excellent sensitivity (1.04 kPa−1), fast response time (27 ms), and reliable stability for 1000 cycles. CCS‐HT can serve as skin electrodes for electrophysiological sensing. The anisotropic functionality of annealed CCS allows it to be used in one sensing and regulation closed‐loop system driven by nerves, achieving accurate acquisition of human brain rhythm and machine movement information simultaneously. This not only helps rapid tracking of brain activity but also facilitates feedback regulation to enhance human brain function, having great potential applications in neurofeedback and disease rehabilitation. [ABSTRACT FROM AUTHOR]

On‐skin electronics can be conformably deployed on body for health monitoring, assisted living, and human/computer interfaces. However, developing corresponding energy devices is a critical challenge. Herein, a permeable and stretchable multifunctional liquid‐metal electronic skin that can generate electricity by recovering ambient electromagnetic pollution (from surrounding electrical appliances) and biomechanical energy (from body movements) is presented for epidermal energy and self‐powered sensing applications. To the best of the authors' knowledge, this is the first demonstration that a breathable on‐skin device can convert ambient electromagnetic pollution into useful electricity. The device is constructed using two stretchable microfibrous films sandwiching self‐organized mesh‐like and wrinkled liquid‐metal that affords electricity via induced electrification (±9.3 V, ±1.7 µA; 60 Hz) and triboelectricity (205.6 V, ±2.3 µA; 4 Hz). Its applicability in powering electronic devices is demonstrated. Moreover, it can serve as an epidermal self‐powered sensor for continuously monitoring whole‐body physiological signals and motions of the eyelids, face, throat, chest, and limbs, thus demonstrating its potential to remotely collect clinical and biomechanical information. Finally, it is used as an interface in diverse system‐level applications. These results shed light on new directions in on‐skin energy and sensing, enabling to usher electronics toward untethered and diversified applications. [ABSTRACT FROM AUTHOR]

Human skin comprises multiple hierarchical layers that perform various functions such as protection, sensing, and structural support. Developing electronic skin (E‐skin) with similar properties has broad implications in health monitoring, prosthetics, and soft robotics. While previous efforts have predominantly concentrated on sensory capabilities, this study introduces a hierarchical polymer system that not only structurally resembles the epidermis‐dermis bilayer structure of skin but also encompasses sensing functions. The system comprises a polymeric hydrogel, representing the "dermis", and a superimposed nanoporous polymer film, forming the "epidermis". Within the film, interconnected nanoparticles mimic the arrangement of interlocked corneocytes within the epidermis. The fabrication process employs a robust in situ interfacial precipitation polymerization of specific water‐soluble monomers that become insoluble during polymerization. This process yields a hybrid layer establishing a durable interface between the film and hydrogel. Beyond the structural mimicry, this hierarchical structure offers functionalities resembling human skin, which includes (1) water loss protection of hydrogel by tailoring the hydrophobicity of the upper polymer film; (2) tactile sensing capability via self‐powered triboelectric nanogenerators; (3) built‐in gold nanowire‐based resistive sensor toward temperature and pressure sensing. This hierarchical polymeric approach represents a potent strategy to replicate both the structure and functions of human skin in synthetic designs. [ABSTRACT FROM AUTHOR]

To realize flexible pressure sensors with high sensitivity, surface‐textured soft films have often been adopted and the contact area can vary significantly depending on the applied pressure. However, the contact area modulation realized in such a way is subject to a limited dynamic range, and its infinitesimal zero‐pressure contact area raises concerns regarding durability. Herein, a flexible pressure sensor made of a texturing‐free piezocapacitive layer based on ion‐polymer networks is proposed. In this scheme, ion infiltration leads to electrical‐double‐layer modulation that gradually varies over a wide range of applied pressures. The proposed flexible pressure sensors with the optimal ion concentration are shown to exhibit both excellent mechanical durability and linear responses with high sensitivity over a wide pressure range up to 1 MPa. With the simple fabrication route, high performance, and reliability, the proposed approach may open up a new avenue for skin‐like pressure sensors ideal for many emerging applications. [ABSTRACT FROM AUTHOR]

Flexible tactile sensors with multifunctional sensing functions have attracted much attention due to their wide applications in artificial limbs, intelligent robots, human‐machine interfaces, and health monitoring devices. Here, a multifunctional flexible tactile sensor based on resistive effect for simultaneous sensing of pressure and temperature is reported. The sensor features a simple design with patterned metal film on a soft substrate with cavities and protrusions. The decoupling of pressure and temperature sensing is achieved by the reasonable arrangement of metal layers in the patterned metal film. Systematically experimental and numerical studies are carried out to reveal the multifunctional sensing mechanism and show that the proposed sensor exhibits good linearity, fast response, high stability, good mechanical flexibility, and good microfabrication compatibility. Demonstrations of the multifunctional flexible tactile sensor to monitor touch, breathing, pulse and objects grabbing/releasing in various application scenarios involving coupled temperature/pressure stimuli illustrate its excellent capability of measuring pressure and temperature simultaneously. These results offer an effective tool for multifunctional sensing of pressure and temperature and create engineering opportunities for applications of wearable health monitoring and human‐machine interfaces. [ABSTRACT FROM AUTHOR]

Developing electronic skins (e‐skins) that are comparable to or even beyond human tactile perception holds significant importance in advancing the process of intellectualization. In this context, a machine‐learning‐motivated micropyramid array bimodal (MAB) e‐skin based on capacitive sensing is reported, which enables spatial mapping applications based on bimodal sensing (proximity and pressure) implemented via fringing and iontronic effects, such as contactless measurement of 3D objects and contact recognition of Braille letters. Benefiting from the iontronic effect and single‐micropyramid structure, the MAB e‐skin in pressure mode yields impressive features: a maximum sensitivity of 655.3 kPa−1 (below 0.5 kPa), a linear sensitivity of 327.9 kPa−1 (0.5–15 kPa), and an ultralow limit of detection of 0.2 Pa. With the assistance of multilayer perceptron and convolutional neural network, the MAB e‐skin can accurately perceive 6 materials and 10 surface shapes based on the training and learning using the collected datasets from proximity and pressure modes, thus allowing it to achieve the precise perception of different objects within one proximity‐pressure cycle. The development of this MAB e‐skin opens a new avenue for robotic skin and the expansion of advanced applications. [ABSTRACT FROM AUTHOR]

The conformal integration of the electronic skin on the non‐developable surface is in great demand for the comprehensive tactile sensing of robotics and prosthetics. However, the current techniques still encounter obstacles in achieving conformal integration of film‐like electronic skin on non‐developable surfaces with substantial curvatures for contact pressure detection and tactile mapping. In this paper, by utilizing the 3D printing technology to prepare the 3D electrode array in the structural component following its surface curvature, and covering it with a molded functional shell to form the pressure sensitive iontronic interface, a device is proposed to achieve high‐sensitive pressure detection and high‐fidelity tactile mapping on a complicated non‐developable surface, called structural electronic skin (SES). The SES is prepared in a 3D printed fingertip with 46 tactile sensing units distributed on its curved surface, achieving the integration of both structural and tactile functions in a single component. By integrating the smart fingertip into a dexterous hand, a series of demonstrations are presented to show the dead‐zone free pressure detection and tactile mapping with high sensitivity, for instance, 2D pulse wave monitoring and robotic injection in a medical robot, object recognition and compliant control in a smart prosthesis. [ABSTRACT FROM AUTHOR]

As key interfaces for the disabled, optimal prosthetics should elicit natural sensations of skin touch or proprioception, by unambiguously delivering the multimodal signals acquired by the prosthetics to the nervous system, which still remains challenging. Here, a bioinspired temperature‐pressure electronic skin with decoupling capability (TPD e‐skin), inspired by the high‐low modulus hierarchical structure of human skin, is developed to restore such functionality. Due to the bionic dual‐state amplifying microstructure and contact resistance modulation, the MXene TPD e‐skin exhibits high sensitivity over a wide pressure range and excellent temperature insensitivity (91.2% reduction). Additionally, the high‐low modulus structural configuration enables the pressure insensitivity of the thermistor. Furthermore, a neural model is proposed to neutrally code the temperature‐pressure signals into three types of nerve‐acceptable frequency signals, corresponding to thermoreceptors, slow‐adapting receptors, and fast‐adapting receptors. Four operational states in the time domain are also distinguished after the neural coding in the frequency domain. Besides, a brain‐like machine learning‐based fusion process for frequency signals is also constructed to analyze the frequency pattern and achieve object recognition with a high accuracy of 98.7%. The TPD neural system offers promising potential to enable advanced prosthetic devices with the capability of multimodality‐decoupling sensing and deep neural integration. [ABSTRACT FROM AUTHOR]

Electronic skins (E‐skins) capable of biomechanical/bioelectrical signal acquisition are intensively pursued for human‐centered healthcare of daily life. For practical use, it is highly desired, yet challenging, to mass‐produce E‐skins that are soft and breathable for wearing comfort, skin‐adhesive for robust signal acquisition, multi‐signal sensing for enhanced healthcare data. Herein, a scalable fabrication strategy for a bioinspired E‐skin (SPRABE‐skin) with a multi‐layered architecture is reported that integrates skin‐like softness, self‐protection, self‐adhesion, breathability, and bimodal sensing in a single patch. The fibrous thermoplastic polyurethane (TPU) scaffold endows the SPRABE‐skin with tissue‐like softness (Young's modulus of 3.36 MPa) and stretchability, good permeability to water vapor, and self‐protection against adverse loading events. A strain sensing layer composed of MXene‐carbon nanotubes@TPU (MXene‐CNT@TPU) composition exhibits ultra‐high sensitivity in a wide sensing range (gauge factor at strain of 485% reaches 63 494). An electrode layer made of MXene‐waterborne polyurethane (MXene‐WPU) provides a highly adhesive electrode‐skin interface, which enables the acquisition of biopotentials, such as electrocardiograph (ECG), electromyograph (EMG), electroencephalo‐graph (EEG), with improved fidelity even under various dynamic interferences. Finally, a SPRABE‐skin based human‐centered healthcare system is demonstrated that realizes the wireless, long‐duration, and dynamic monitoring of ECG and running activities. [ABSTRACT FROM AUTHOR]

The past decades have seen the rapid development of tactile sensors in material, fabrication, and mechanical structure design. The advancement of tactile sensors has heightened the expectation of sensor functions, and thus put forward a higher demand for data processing. However, conventional analysis techniques have not kept pace with the tactile sensor development and still suffer from some severe drawbacks, like cumbersome models, poor efficiency, and expensive costs. Machine learning, with its prominent ability for big data analysis and fast processing speed, can offer many possibilities for tactile data analysis. Herein, the machine learning techniques employed for processing tactile signals are reviewed. Supervised learning and unsupervised learning for analog signals are covered, and processing spike signals with machine learning are summarized. Furthermore, the applications in robotic tactile perception and human activity monitoring are presented. Finally, the current challenges and future prospects in sensors, data, algorithms, and benchmarks are discussed. [ABSTRACT FROM AUTHOR]

Herein, a multimodal tactile sensing module that can improve the dexterous manipulation capabilities of robots with parallel grippers is reported. The tactile sensor consists of a 4 × 4 matrix 3‐axis force sensor array (with spacings of 2 mm) and a single‐temperature sensor. The tactile sensor uses inorganic silicon and gold as materials for the detection of strain and temperature and a polymer‐based elastomer to encapsulate the sensing layer. The sensing module is equipped with a readout circuitry for signal processing. Within the measurable force range (≈1.5 N) of the sensor cell, a prototype module exhibits a repeatability error within 2%, a hysteresis error within 3%, and a resolution as small as 10 mN. Furthermore, each sensor cell independently measures 3‐axis forces with a cross‐talk error of approximately 3%. The temperature sensor exhibits linear output properties in the approximate range of 5–75 °C. Experiments are performed by mounting the module on a parallel gripper to grasp a paper cup and a reflex hammer toy. According to the experimental results, the sensor can accurately detect the state of contact with an object by analyzing three tactile modalities (i.e., 3‐axis force distribution, vibration, and temperature). [ABSTRACT FROM AUTHOR]

Epidermal electronics have been attracting considerable attention due to their various potential applications in human‐computer interaction and health monitoring. However, because of the lack of a self‐adhesive and stable interconnect method between epidermal electronic sensors and rigid circuit boards, there remain difficulties in detecting body signals accurately by epidermal electronic sensors in daily life. Here, a 3D helical on‐skin interconnect is first introduced for epidermal electronics sensors. Inspired by the structure of the accordion lantern, the interconnect is composed of two electrospinning polyurethane (PU) fiber films and a helical metal fiber. The helical metal fiber acts as a stable conductor with stretchability, and the PU fiber film with polydimethylsiloxane provides a self‐adhesive substrate. Mechanical simulations and tests prove that the proposed interconnect can laminate conformally and unobtrusively onto human skin with excellent electrical stability (less than 0.5% electrical resistance change upon 100% elongation). Furthermore, based on the proposed interconnect, an all‐in‐one sensor‐interconnect design is presented, which endows the epidermal electronic systems with anti‐motion interference capability. A gesture identification wristband system realized by a single all‐in‐one strain sensor is demonstrated. Besides, a wireless on‐skin system that accurately monitors dynamic 12‐lead electrocardiographic is successfully built using all‐in‐one electrodes. [ABSTRACT FROM AUTHOR]

Electronic skins (e‐skins), which are mechanically compliant with human skin, are regarded as ideal electronic devices for noninvasive human–machine interaction and wearable devices. In order to fully mimic human skin, e‐skins should possess reliable mechanical properties and be able to resist external environmental factors like heat, cold, desiccation, and bacteria, while perceiving multiple external stimuli, such as temperature, humidity, and strain. Here, a transparent, mechanically robust, environmentally stable, versatile natural skin‐derived organohydrogel (NSD‐Gel) is nanoengineered through the integration of betaine, silver nanoparticles, and sodium chloride in a glycerol/water binary solvent. The transparent NSD‐Gel e‐skin exhibits outstanding tensile strength (7.33 MPa), puncture resistance, moisture retention, self‐regeneration, and antibacterial properties. Additionally, the NSD‐Gel e‐skin possesses enhanced cold/heat resistance and stimuli‐responsive characteristics that effectively sense environmental temperature and humidity changes, as well as physiological human body motion signals. In vitro and in vivo experiments show that the NSD‐Gel e‐skin confers desired biocompatibility and tissue protective properties even in extremely harsh environments (−196 °C to 100 °C). The NSD‐Gel e‐skin has great potential for applications in multidimensional wearable electronic devices, human‐machine interfaces, and artificial intelligence, generating a versatile platform for the development of high‐performance e‐skins with on‐demand properties. [ABSTRACT FROM AUTHOR]

Tactile sensor capable of detecting both normal and tangential forces is essential for the next‐generation robotic electronics. However, designing a reliable triaxial tactile sensor to decouple the normal and tangential forces is still a challenge for current research. Herein, a capacitive triaxial force sensor based on a microcone dielectric layer together with the force decoupling method is proposed. The lateral and vertical displacement of the top electrode relative to the bottom electrodes under the action of external forces can be perfectly detected according to the capacitance variations. The microcone‐structured sensor combined with the new decoupling method leads to a high sensitivity of 3.5 kPa−1 for normal force in a low‐pressure range of 0––50 Pa and 0.134 N−1 for tangential force in 0–0.5 N, and a fast response time of 26 ms. The sensors mounted on the fingers of a robotic arm can provide effective tactile information during the grasping task. Finally, a conceptual 3 × 3 tactile sensor array is fabricated and verified for spatial pressure mapping. This work provides new insight into piezocapacitive tactile sensor design and shows its great potential in robotic applications. [ABSTRACT FROM AUTHOR]

Electronic skin (e‐skin) is facing new challenges owing to the development of artificial intelligence. Among the existing working modes, triboelectric‐based e‐skin (TES) can convert mechanical energy into electrical energy and can be used as a sensor to directly output an electrical signal without additional power supply. Therefore, with the advantages of self‐powering, low cost, and wide application of materials, TES provides a new concept for developing e‐skin and has been extensively studied. Starting from TES, this review describes the working principle and application of triboelectric nanogenerators (TENGs) in e‐skin. Existing materials for TES can be mainly divided into fiber textiles, gels, liquid‐based materials, and degradable materials. Therefore, the material section is divided into four chapters to describe the properties of each material. As for the structure of TES, the transition from single‐channel to multi‐channel for the multifunctionalization of TES is described, and the various links required for a TES‐based closed‐loop system are introduced. Based on these advanced units, the recent progress as well as the current challenges and future development prospects of TES are reviewed. [ABSTRACT FROM AUTHOR]

Flexible electronic skins (e‐skins) have a wide range of applications in health monitoring, human–machine interfaces, and robotics. Herein, a novel architecture of e‐skins with a combination of multimode measurement and low‐cost implementation is proposed. A single electronic skin layer is used to integrate both the pressure and temperature sensing properties. An e‐skin membrane is first developed with poly(vinylidene) fluoride incorporated with silicon dioxide nanoparticles. When combined with electrodes, this simple architecture allows the implementation of multimode pressure and temperature sensing. This e‐skin exhibits excellent pressure sensitivity with a response time of 1.6 ms. This sensing performance can be attributed to the uniform distribution of the embedded nanoparticles, leading to an enhancement of the electroactive β phase. This e‐skin generates a voltage, from the finger movements, that can be used to detect precisely the minute changes of the finger movement. This electronic skin demonstrates the detection of a linear range of temperature which can be attributed to the phonon‐assisted hopping mechanism. A 4 × 4 pressure sensing array is demonstrated, which is able to map the inserted pressure as well as temperature stimuli. Thus, this study provides a new conceptual design for the next‐generation green electronic skins. [ABSTRACT FROM AUTHOR]

Multimodal force identification by electronic skin (E‐skin) provides comprehensive and precise tactile information that can enhance elaborated functions of fine tactile discrimination, robotic manipulation, and gesture recognition. However, it remains a great challenge to realize such complicated functions from a highly simplified E‐skin sensing system. Here, mimicking the multi‐mechanoreceptor synergistic effect in human skin, a simple, thin, soft, intelligent tactile sensor composed of an asymmetrically arrangement of strain sensing units array for multimodal tactile information decoding is reported. The E‐skin type tactile sensor exhibits good performance with excellent sensitivity for shear force (2.5 N–1), vertical force (0.11 kPa–1), that enables 3D force refactoring, as well as accurate recognition of sliding force for direction tracking. Another unique feature of the E‐skin type tactile sensor is the side force screen effect, that allows the tactile sensor to yield great accuracy and a gauge factor of 1492 in strain measuring. Furthermore, integration of the sensors into E‐skin array offers the capability of capturing dynamic and real‐time stress distribution on the hand in various conditions. This work provides a new route for complex force‐sensing from the simple structure and shows great potential in robotics, human‐machine interface, and virtual reality/augmented reality (VR/AR). [ABSTRACT FROM AUTHOR]

Neuromorphic skin is an emerging electronic skin that demonstrates sensory, memory, learning, and motor responses in a neuromorphic way by using advanced artificial synaptic devices that emulate the biological nervous system and its neural plasticity. Many types of artificial synapses that emulate brain‐inspired computing have been developed and are being integrated in electronic skin to demonstrate artificial sensory and motor nervous systems. The neuromorphic skin, which operates using voltage spikes thereof, precisely mimics the energy‐efficient information processing of biological nervous system in the brain and body and enables the implementation of power‐ and time‐efficient cognitive sensors and computing, biomimetic robotics and electronics, and biocompatible neuroprosthetics. Here, biological synapses and emerging artificial synapses are introduced, and recent research is reviewed on neuromorphic skins that use artificial synapses for sensing, memory, learning, and motor systems. Finally, the outlook and challenges to be addressed are provided for future advanced neuromorphic skin in which all neuromorphic parts are integrated with brain‐inspired computing and bioinspired robotics. [ABSTRACT FROM AUTHOR]

Nature has proved that multiple sense and processing capabilities are critical for target recognition and race survival. As such, advanced robots that perform missions in an unstructured environment highly need organism‐similar multimodal sensing and processing systems for sophisticated unstructured environmental stimuli. Herein, recent progress in multimodal sensing and processing systems for advanced robotics is reviewed. Multimodal sensors including tactile sensors that capture surface properties of objects (i.e., thermal conductivity, temperature, softness, and electron affinity), visual sensors that capture the color and size of objects, and gas sensors that capture object smell are summarized. The multimodal data fusion algorithms that process multimodal signals from multimodal sensors to achieve object recognition and decision making are also presented. The challenges and future development of multimodal sensors and data fusion algorithms are further discussed. Advances in these areas open new avenues for advanced robotics applications in human–robot collaboration, rescue missions, garbage sorting, and intelligent prosthetics. [ABSTRACT FROM AUTHOR]

Recent advances in scalable fabrication methods based on printing technologies have improved the yield and lowered the cost of manufacturing epidermal sensors. However, modern technologies still require expensive multi‐bio‐ink raw materials. A laser‐centric fabrication method that realizes a cost‐effective, scalable, and streamlined fabrication process with easily used material and equipment is reported. The fabricated epidermal patch can quickly respond to the demands of personalized models. Here, the epidermal sensor patch is applied to continuous monitoring of the human cardiopulmonary system. The sensor performs conventional bio‐signal monitoring but is also extendible to other monitoring forms. The patch provides enhanced functions through its gas‐permeable and skin‐adhesive microporous layer and its stretchable, conformal, and biocompatible multimodal sensing layer. The utility of the proposed sensor patch in clinical diagnosis in a mobile healthcare environment is demonstrated in multiple bio‐signal‐morphology analyses. [ABSTRACT FROM AUTHOR]

Electronic skin (E‐skin) is widely used in bionic prosthesis, soft robotics, and wearable electronic devices. Waterproof and breathable membranes that provide a high level of protection and comfort are promising core materials for meeting the pressing demand for E‐skin. However, creating such materials exhibiting waterproofness, breathability, and ease of fabrication has proven to be a great challenge. In this paper, waterproof, breathable Modal‐based knitted fabric E‐skin is proposed by using a simple, low‐cost three‐step process including the graphene oxide (GO) loading, GO‐reducing, and polydimethylsiloxane loading. The prepared E‐skin is insensitive to common liquids in daily life including water, tea, milk, and coffee, showing superior waterproof capability. The breathability is also tested with a water vapor transmission rate of ≈13.6 mg cm−2 h−1. Besides, this E‐skin can achieve reliable human motion monitoring. The authors believe this E‐skin can provide a reliable principle for further design and development of waterproof and breathable electronic skin. [ABSTRACT FROM AUTHOR]

Profited from the rapid development of flexible skin‐like electronic materials and artificial intelligent technology, remarkable achievements have been witnessed in wearable health monitoring devices in recent years. The wearable intelligent systems featured with tailored structures and compositions as well as enriched functions enable human beings to access to next‐generation closed‐loop platform for early disease prevention and diagnosis. In this context, this mini‐review focuses on the recent progress and applications of flexible wearable intelligent health monitoring devices. Specifically, the basic sensing mechanisms and corresponding property requirements for wearable healthcare devices are examined firstly. Secondly, the versatile applications of advanced wearable devices for detecting temperature, heart rate, blood pressure and glucose are scrutinized exclusively. Finally, a brief summary is presented accompanying with future outlook in terms of material preparation, mechanism development and integration design of monitoring systems. This manuscript is expected to provide critical guidelines to those working in skin‐like electronics, flexible sensors, wearable intelligent devices, health monitoring and other related disciplines, especially for the beginners. [ABSTRACT FROM AUTHOR]

Electronic skin (e‐skin) is widely studied for its ability to detect physiological information and provide feedback through electrical signals. Biocompatible stimulus‐responsive DNA‐based hydrogels exhibit high sensitivity, which makes them outstanding candidates for biomedical applications. However, several disadvantages, such as weak mechanical properties, expensive manufacturing costs, cumbersome double chain design, and difficulty obtaining bulk size, seriously limit their practical application. Based on the double network (DN) strategy, a universal, low‐cost, and high‐toughness deoxyribonucleic acid/poly(N‐hydroxyethyl acrylamide) (DNA/pHEAA) DN hydrogel is designed. The transparent hydrogel shows tensile stress/strain of 0.96 ± 0.043 MPa/2537.55 ± 23.24%, rapid self‐recovery ability (peak stress/energy dissipation recovery rate of 99.72%/95.38% after 30 s resting), excellent fatigue resistance (peak stress/energy dissipation retention rate of 91.08%/81.05% after 100 loading‐unloading cycles with strain of 50%), reversible adhesive ability (≈45 KPa), and good biocompatibility. Thus, the DNA/pHEAA DN hydrogel can be used as an e‐skin. Sensing signals are displayed on a smartphone as images sent through wireless technology; the images change with the collected signals, achieving motion detection. The universal and low‐cost design of stimulus‐responsive DNA‐based hydrogels with high toughness, excellent self‐recovery, and anti‐fatigue performance is expected to promote their application in the biomedical field. [ABSTRACT FROM AUTHOR]

In this work, we developed a novel method to prepare a hydrogel‐based electronic skin by self‐assembling cross‐linking. The conductive hydrogel (named PGRS) integrates multiple properties. The hydrogel has good moisture retention (70 °C, 14 days), adhesion, and high elongation (2799 %). When the hydrogel is damaged externally, it can repair itself without external stimulation. The hydrogel adheres to the skin surface and monitors large strain movements, such as finger joints, wrist joints, elbow joints, head lowering and head lifting. It can also detect small movements, such as drinking and talking. It is used as an adhesive in liquid nitrogen (−196 °C). PGRS conductive hydrogel with multiple synergistic functions. It has great potential in the direction of flexible electronic skin. It indicates that PGRS conductive hydrogels have highly prospective applications in wearable devices. [ABSTRACT FROM AUTHOR]

With the rapid advances in wearable technology, several excellent strain sensors have been developed. Recent strain sensors have met various requirements, such as mechanical applicability, rapid responsiveness, and high sensitivity. Nevertheless, the processing technology, wearing comfort, and safety of strain sensors, which have received inadequate attention, have greatly hindered their commercial development and large‐scale use. Through mature electrospinning and screen‐printing, a high‐performance, safe, comfortable, waterproof, breathable, economical, and reliable wearable strain sensor is simply and quickly prepared. This strain sensor has excellent repeatability and stability with remarkable sensitivity (maximum gauge factor = 520), a broad working strain range (500%), and an ultrafast response time (100 ms). Notably, the mechanical properties of the proposed strain sensor are similar to those of natural skin, making the sensor a good match to the skin. Additionally, the strain sensor has incomparable biofriendly, enabling long‐term harmless contact with the skin. To the best of the authors' knowledge, this is the first report on the optimization of flexible electronic equipment in terms of the manufacturing process, sensing performance, and wearing experience. The results of this study have important implications for the development and practical application of flexible electronics. [ABSTRACT FROM AUTHOR]

Electronic skins (e‐skins) are a promising design paradigm for health care systems and human–machine interactions. Piezoresistive sensors made with simple structures, high sensitivity, mass production methods, light weight, and comfort for long‐term wearing and physiological signal monitoring remain a challenge and are urgently desirable. Here, a breathable and lightweight all‐nanofiber piezoresistive (ANFP) sensor is presented, which is composed of three layers of electrospun nanofibers (NFs). A specific interpenetrating network of conductive polyvinylpyrrolidone NFs coated by polypyrrole (PVP@PPy) and insulating polyacrylonitrile NFs is constructed by controlling the vapor growth position of PPy to enhance the sensitivity. The ANFP sensor can achieve the real‐time monitoring of multiple parts of physiological signals, and a wireless detection system is designed for the online monitoring of human pulses. The NF network endows excellent breathability and heat dissipation to the ANFP sensors during practical application, which ensures comfort and device stability during long‐term wearing. Finally, a pressure sensing array with 5 × 5 pixels is fabricated to demonstrate the potential applications in spatial pressure detection. This work provides a viable strategy to improve the wearability of e‐skins, which can promote health care and human–machine interaction applications. [ABSTRACT FROM AUTHOR]

Whether for organic life or intelligent machines (robots, Actuators), skin plays an important role as a barrier and sensor, and a lot of research is centered on making multifunctional skins. Here, the authors report an electronic skin with high stretchability, excellent mechanical sensing, and biochemical detection capabilities obtained by combining photonic crystals and sponge‐like filled liquid metal (LM)–polyurethane (PU)–spidroin (SP) composite materials. Inspired by geckos and mussels, a micropillar array is designed and coated with polydopamine to synergistically improve adhesion. P(MMA‐BA) elastic copolymer nanoparticles (are assembled into a photonic crystal pattern to endow electronic skin biochemical detection capabilities. The regionalization of the photonic crystal pattern allows the electronic skin to detect multiple target compounds simultaneously. The base material is an LM–PU–SP composite material with excellent stretchability and pressure sensitivity and is used for motion monitoring and tactile sensing. It is envisioned that this multifunctional electronic skin can be attached to animal skins for health monitoring to facilitate the diagnosis of metabolic diseases and wound inflammation. Alternatively, electronic skins can be attached to robots and soft robots for the collection of samples from heavily polluted areas, to obtain real‐time feedback information during the collection process. [ABSTRACT FROM AUTHOR]

An array of shear sensors is essential in tactile sensation as well as the pressure sensors. Surprisingly, however, the shear sensor array is rarely investigated mainly due to the structural complexity to measure the horizontal forces from various directions and also due to the mechanical softness required for preventing the slip of an object. Here, an array of small shear sensors that can recognize both shear force and shear rotational angle is fabricated. All the device components are made of deformable materials to acquire the softness of the sensor. This work presents a novel design for the small‐sized shear sensor array and the required material conditions for the design. By using an ion gel as the capacitive sensing material, the shear sensor array shows high sensitivity and excellent reliability under repeated shear forces. This work demonstrates playing computer game with the shear sensor and sensing the frictional force distribution, which is possible through the recognition of multiple shear stimuli and spatial shear distribution (force, rotational angle) when static/dynamic shear forces are simultaneously applied from various directions. [ABSTRACT FROM AUTHOR]

Flexible electronic skin with features that include sensing, processing, and responding to stimuli have transformed human–robot interactions. However, more advanced capabilities, such as human‐like self‐protection modalities with a sense of pain, sign of injury, and healing, are more challenging. Herein, a novel, flexible, and robust diffusive memristor based on a copolymer of chlorotrifluoroethylene and vinylidene fluoride (FK‐800) as an artificial nociceptor (pain sensor) is reported. Devices composed of Ag/FK‐800/Pt have outstanding switching endurance >106 cycles, orders of magnitude higher than any other two‐terminal polymer/organic memristors in literature (typically 102–103 cycles). In situ conductive atomic force microscopy is employed to dynamically switch individual filaments, which demonstrates that conductive filaments correlate with polymer grain boundaries and FK‐800 has superior morphological stability under repeated switching cycles. It is hypothesized that the high thermal stability and high elasticity of FK‐800 contribute to the stability under local Joule heating associated with electrical switching. To mimic biological nociceptors, four signature nociceptive characteristics are demonstrated: threshold triggering, no adaptation, relaxation, and sensitization. Lastly, by integrating a triboelectric generator (artificial mechanoreceptor), memristor (artificial nociceptor), and light emitting diode (artificial bruise), the first bioinspired injury response system capable of sensing pain, showing signs of injury, and healing, is demonstrated. [ABSTRACT FROM AUTHOR]

The simultaneous achievement of multiple functional attributes, such as flexibility, stretchability, transparency, comfortability, biodegradability, and self‐powered ability into electronic skins (e‐skins) is vital to their long‐term practical applications. Due to the internal contradiction between functional material combination and simple structural design, this kind of multifunctional e‐skin has rarely been fabricated or even reported. To this end, chitosan (CS), a natural material with remarkable biocompatibility, biodegradability, and electron‐donating ability, is integrated with a single‐mode triboelectric nanogenerator (TENG) to develop a multifunctional e‐skin, which includes sweat permeability, controllable biodegradability, high transparency, and self‐powered sensing ability. In addition, a facile, efficient, and large‐scale fabrication strategy is proposed to construct stretchable, ultrathin, transparent, and shape‐adaptable gold nanofibers (Au NFs) electrodes. Furthermore, the e‐skin can achieve a voltage response pressure sensitivity of 0.012 kPa−1 in the pressure range of 0–70 kPa and a fast response time of 70 ms. Finally, it shows controllable and excellent degradability in various solutions. It is believed that the proposed e‐skin based on the design and integration of CS and Au NFs will provide a paradigm shift for the next‐generation self‐powered transient electronics. [ABSTRACT FROM AUTHOR]

With the high flexibility, good conformability and lightweight, the next‐generation energy harvesters could exist in the format of epidermal electronics. They are able to convert the mechanical energy from daily body motions into electrical signals for energy harvesting and human‐machine interfaces. Triboelectric nanogenerators (TENGs) have proven to be excellent candidates for wearable energy harvesters, however, the reported TENGs commonly face the hurdles of poor adhesion to skin and relative thick in geometry up to several cm. Herein, a series of ultrathin, soft, tattoo‐like triboelectric nanogenerators (TL‐TENGs) with well‐designed aesthetic patterns are introduced. With the ultrathin materials applied and state of art processing techniques in epidermal electronics, the TL‐TENGs present an outstanding mechanical property of high robustness and thickness of tens of μm. Besides, TL‐TENGs own remarkable electrical characteristics, the open‐circuit voltage and short circuit current can reach up to ≈180 V and ≈2.2 μA under constant tapping (≈16 kPa), respectively. With the well structural mechanics designs, the TL‐TENGs can be customized into various tattoo patterns, such as twelve Chinese zodiac signs. Demonstrations of TL‐TENGs in energy harvesting and the human‐machine interface indicate great potential in next generation wearable nanogenerators and internet of things. [ABSTRACT FROM AUTHOR]

Device–body interface is significant for acquiring high quality bio‐signals, preventing skin‐irritation, and minimizing the motion artifacts. However, low breathability of the typical substrate used in a flexible electronic device usually deteriorates the stability of device–body interface, which is imperative for long‐term application but commonly disregarded. In paper, a directional sweat transport and breathable electrode with three‐layer sandwiched structure is reported. The top hydrophilic hydrolyzed‐polyacrylonitrile (HPAN) layer and middle hydrophobic thermoplastic‐polyurethane (TPU) layer form Janus structure; and the bottom layer is an electrode layer of Ag nanowires (AgNWs). This dedicatedly designed electrode can transport sweat from skin to the top HPAN layer, while keeping low noise electrocardiogram (ECG) signal detection. In the trial of ECG monitoring, the results show that the electrode can achieve reliable recording with high signal noise rate (SNR) both in calm state (10.5 dB) and sweaty state (10.1 dB) with sweat tolerance. No allergy or obvious SNR degeneration is observed when utilizing the electrode owing to the effective sweat transport away from the device–body interface rather than accumulation. Finally, the application of the anti‐sweat accumulating electrode in wearable electronics is demonstrated. [ABSTRACT FROM AUTHOR]

Wearable piezoresistive sensors are being developed as electronic skins (E‐skin) for broad applications in human physiological monitoring and soft robotics. Tactile sensors with sufficient sensitivities, durability, and large dynamic ranges are required to replicate this critical component of the somatosensory system. Multiple micro/nanostructures, materials, and sensing modalities have been reported to address this need. However, a trade‐off arises between device performance and device complexity. Inspired by the microstructure of the spinosum at the dermo epidermal junction in skin, a low‐cost, scalable, and high‐performance piezoresistive sensor is developed with high sensitivity (0.144 kPa‐1), extensive sensing range (0.1–15 kPa), fast response time (less than 150 ms), and excellent long‐term stability (over 1000 cycles). Furthermore, the piezoresistive functionality of the device is realized via a flexible transparent electrode (FTE) using a highly stable reduced graphene oxide self‐wrapped copper nanowire network. The developed nanowire‐based spinosum microstructured FTEs are amenable to wearable electronics applications. [ABSTRACT FROM AUTHOR]

The bio‐inspired sensory memory device functions as a multifunctional artificial perceptual learning system that can effectively analyze and retain multiple sensory signals. In this work, the multiscale hierarchical surface of reed leaves is templated to prepare CNTs/PDMS films, and a new type of electronic skin (E‐skin) is constructed. Due to its unique multi‐scale sensing layer surface, E‐skin exhibits a wide pressure detection range and ultrahigh sensitivity (235.95 kPa−1) and linearity (0.99 under 1.95–12.4 kPa). The memristor serving as artificial synapse is formed with HfO2 film as resistive switch layer, which has remarkable uniformity, large memory window of 102 and excellent plasticity. After integration of E‐skin with artificial synapse, the artificial synapse could be activated by the electrical information from the E‐skin to generate excitatory postsynaptic currents and the pressure information could be well retained by the memristor element. An artificial tactile perceptual neuron system with excellent retention performance, good stability and accurately recognition memory is realized, and meanwhile, the accurate decoding of Morse code by recognizing external pressure is realized. The present work transduces the concept of carbon‐based biology into a silicon‐based electronic device, which is of great significance to the development of hardware architecture in artificial intelligence. [ABSTRACT FROM AUTHOR]

Laser‐scribed graphene (LSG), with programmable patterns and superior electronic properties, has attracted considerable attention and has been widely investigated for various wearable electronics. However, its characteristics such as easy peeling and weak stretchability have prevented it from further industrial applications. Herein, this work has demonstrated a durable, biodegradable, skin‐conformable LSG‐based strain sensor by using a transfer technology and the dehydration characteristic of a commercial make‐up accessory (nose film colloid), which has been declared as a pollution‐free and skin‐friendly flexible substrate. The sensor exhibits relatively high sensitivity of a gauge factor over 1200, large stretch range of more than 70% and stable piezoresistance responses after 5000 cyclic tests. It has an admirable durability that can maintain a stable resistance after rubbing and scratching of sandpaper, and a biodegradability that can be totally dissolved within a few minutes. A series of human computer interaction applications, such as music glove, have been presented to prove the availability and sweat permeability of the sensor. The environmentally friendly properties of the sensor and the printable fabrication process reveal the possibility of the large‐scale preparation of the flexible strain sensor. [ABSTRACT FROM AUTHOR]

Electronic skins have received increasing attention in biomedical areas. Current efforts about electronic skins are focused on the development of multifunctional materials to improve their performance. Here, the authors propose a novel natural‐synthetic polymers composite structural color hydrogel film with high stretchability, flexibility, conductivity, and superior self‐reporting ability to construct ideal multiple‐signal bionic electronic skins. The composite hydrogel film is prepared by using the mixture of polyacrylamide (PAM), silk fibroin (SF), poly(3,4‐ethylenedioxythiophene):poly (4‐styrene sulfonate) (PEDOT:PSS, PP), and graphene oxide (GO) to replicate colloidal crystal templates and construct inverse opal scaffolds, followed by subsequent acid treatment. Due to these specific structures and components, the resultant film is imparted with vivid structural color and high conductivity while retaining the composite hydrogel's original stretchability and flexibility. The authors demonstrate that the composite hydrogel film has obvious color variation and electromechanical properties during the stretching and bending process, which could thus be utilized as a multi‐signal response electronic skin to realize real‐time color sensing and electrical response during human motions. These features indicate that the proposed composite structural color hydrogel film can widen the practical value of bionic electronic skins. [ABSTRACT FROM AUTHOR]

Inspired by the human skin, electronic skins (e-skins) composed of various flexible sensors, such as strain sensor, pressure sensor, shear force sensor, temperature sensor, and humility sensor, and delicate circuits, are emerged to mimic the sensing functions of human skins. In this review, the strategies to realize the versatile functionalities of natural skin-like e-skins, including strain-, pressure-, shear force-, temperature-and humility-sensing abilities, as well as self-healing ability and other functions are summarized. Some representative examples of high-performance e-skins and their applications are outlined and discussed. Finally, the outlook of the future of e-skins is presented. [ABSTRACT FROM AUTHOR]

Electronic skin (e‐skin) is driving significant advances in flexible electronics as it holds great promise in health monitoring, human–machine interfaces, soft robotics, and so on. Flexible sensors that can detect various stimuli or have multiple properties play an indispensable role in e‐skin. Despite tremendous research efforts devoted to flexible sensors with excellent performance regarding a certain sensing mode or property, emerging e‐skin demands multifunctional flexible sensors to be endowed with the skin‐like capability and beyond. Considering outstanding superiorities of electrical conductivity, chemical stability, and ease of functionalization, carbon materials are adopted to implement multifunctional flexible sensors. In this review, the latest advances of carbon‐based multifunctional flexible sensors with regard to the types of detection modes and abundant properties are introduced. The corresponding preparation process, device structure, sensing mechanism, obtained performance, and intriguing applications are highlighted. Furthermore, diverse e‐skin systems by integrating current cutting‐edge technologies (e.g., data acquisition and transmission, neuromorphic technology, and artificial intelligence) with carbon‐based multifunctional flexible sensors are systematically investigated in detail. Finally, the existing problems and future developing directions are also proposed. [ABSTRACT FROM AUTHOR]

Flexible conductive materials and flexible electronic devices are driving the development of the next generation of cutting‐edge wearable electronics. However, the existing hydrogel‐based flexible conductive materials have limited tensile capacity, low toughness, and poor anti‐fatigue performance, resulting in narrow sensing area and insufficient durability. In this paper, a conductive nanocomposite hydrogel with high ductility, toughness, and fatigue resistance is prepared by combining silver coated copper (Ag@Cu) nanoparticles with gelatin followed by one‐step immersion in sodium sulfate (Na2SO4) solution. The salting‐out of gelatin in Na2SO4 solution greatly improve the mechanical properties of this gelatin‐based hydrogel. The uniform distribution of Ag@Cu nanoparticles inside the whole hydrogel endow the composite hydrogel with excellent electrical conductivity (1.35 S m−1). In addition, it displayed high and stable tensile strain sensitivity over a wide strain range (gauge factor = 2.08). Therefore, the Ag@Cu‐Gel hydrogel is sensitive and stable enough to be successfully utilized as flexible wearable sensor for detecting human motion signals in real time, such as bending of human joints, swallowing, and throat vocalization. Furthermore, this hydrogel is also suitable for application as electronic skin for bionic robots. The above results demonstrate the promising application of Ag@Cu‐Gel hydrogel for wearable electronics. [ABSTRACT FROM AUTHOR]

Sensors and algorithms are two fundamental elements to construct intelligent systems. The recent progress in machine learning (ML) has produced great advancements in intelligent systems, owing to the powerful data analysis capability of ML algorithms. However, the performance of most systems is still hindered by sensing techniques that typically rely on rigid and bulky sensor devices, which cannot conform to irregularly curved and dynamic surfaces for high‐quality data acquisition. Skin‐like stretchable sensing technology with unique characteristics, such as high conformability, low modulus, and light weight, has been recently developed to solve this issue. Here, the recent progress in the fusion of emerging stretchable electronics and ML technology, for bioelectrical signal recognition, tactile perception, and multimodal integration is summarized, and the challenges and future developments are further discussed. These efforts aim to accelerate various perception and reasoning tasks for advanced intelligent applications, such as human–machine interfaces, healthcare, and robotics. [ABSTRACT FROM AUTHOR]