On‐skin electrodes function as an ideal platform for collecting high‐quality electrophysiological (EP) signals due to their unique characteristics, such as stretchability, conformal interfaces with skin, biocompatibility, and wearable comfort. The past decade has witnessed great advancements in performance optimization and function extension of on‐skin electrodes. With continuous development and great promise for practical applications, on‐skin electrodes are playing an increasingly important role in EP monitoring and human–machine interfaces (HMI). In this review, the latest progress in the development of on‐skin electrodes and their integrated system is summarized. Desirable features of on‐skin electrodes are briefly discussed from the perspective of performances. Then, recent advances in the development of electrode materials, followed by the analysis of strategies and methods to enhance adhesion and breathability of on‐skin electrodes are examined. In addition, representative integrated electrode systems and practical applications of on‐skin electrodes in healthcare monitoring and HMI are introduced in detail. It is concluded with the discussion of key challenges and opportunities for on‐skin electrodes and their integrated systems.

Traditional human emotion recognition is based on electroencephalogram (EEG) data collection technologies which rely on plenty of rigid electrodes and lack anti‐interference, wearing comfort, and portability. Moreover, a significant distribution difference in EEG data also results in low classification accuracy. Here, on‐skin biosensors with adhesive and hydrophobic bilayer hydrogel (AHBH) as interfaces for high accuracy emotion classification are proposed. The AHBH achieves remarkable adhesion (59.7 N m−1) by combining the adhesion mechanism of catechol groups and electrostatic attraction. Meanwhile, based on the synergistic effects of hydrophobic group rearrangements and surface energy reduction, the AHB‐hydrophobic layer exhibits 133.87° water contact angles through hydrophobic treatment of only 0.5 h. Hydrogen and electrostatic bonds are also introduced to form a seamless adhesive‐hydrophobic hydrogel interface and inhibit adhesion attenuation, respectively. With the AHBH as an ideal device/skin interface, the biosensor can reliably collect high‐quality electrophysiological signals even under vibration, sweating, and long‐lasting monitoring condition. Furthermore, the on‐skin electrodes, data processing, and wireless modules are integrated into a portable headband for EEG‐based emotion classification. A domain adaptive neural network based on the transfer learning technique is introduced to alleviate the effect of domain shift and achieve high classification accuracy.

Electronic-skin (E-skin) has been investigated extensively for robotic tactile sensing. However, E-skin sensors based on flexible metamaterials are still challenging to achieve. Moreover, the implementation of E-skin sensor arrays in the actual monitoring of robotic grasping and manipulation conditions are rather limited due to the difficulty in data processing. Herein, highperformance E-skin strain sensors based on flexible auxetic metamaterials are reported, which endow the sensors with the capability of measuring both compressive (40%) and tensile (>80%) strain in a wide range and superior sensitivity, as compared with sensors without the structure. With perception data collected by the sensors, a generic method for real-time detection of unstable robotic grasping is established. Through this method, the complicated problem of processing large-scale arrayed sensor signals is simplified into the calculation of two indices, which extract both time and frequency domain characteristics of the signals. The total detection time (including sensor measurement response and data processing) can be as short as 100 ms, in line with human skin response in slippage perception. Accurate detections in real-time during various grasping and manipulation tasks are presented, demonstrating the great value of the sensors and the detection approach in robotic perception and dexterous manipulation.

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In article number 2001938, Hao Wu, Zhuo Li, and co‐workers summarize the latest advancements in materials, devices, and systems of on‐skin electrodes. Analysis of strategies to enhance electrode performances are presented, with particular interest in adhesion to skin and device breathability. Representative integrated electrode systems and applications in electrophysiological monitoring and human‒machine interfaces are also discussed in detail.

Human hands are the most dexterous parts of the human body where the finger movements are mainly controlled by several specific forearm muscles. The accurate acquisition of surface electromyography (sEMG) signals from these target muscles is essential for hand gesture recognition widely applied in human−machine interface (HMI) systems. However, most of the existing sEMG sensors are designed as single bipolar electrode pairs or orthogonal electrode arrays, ignoring the irregular spatial distribution of slender forearm muscles, which limits their performances in signal acquisition. Herein, we propose customized four-channel electrode arrays where the electrode pairs are placed in accordance with the position and orientation of target muscles. By selecting materials with excellent properties for on-skin devices, the fabricated electrodes achieve low skin−electrode impedance and record sEMG signals with a high signal-to-noise ratio (SNR). Owing to the customized design, our electrode arrays can cover more muscles and record higher-quality multichannel sEMG signals than orthogonal arrays under the same condition, enhancing the accuracy of hand gesture classification. The customized electrode arrays proposed in this study are promising for various HMI applications in which EMG signals or hand gestures are adopted as control signals.

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Fabric‐based triboelectric nanogenerators (TENGs) exhibit superior output performance, flexibility, and wearability. However, the fabric structure often creates gaps that accumulate contaminants, which weaken the performance and durability of the TENGs. To address this challenge, a novel eco‐friendly superhydrophobic fabric‐based TENG (SF‐TENG) woven with superhydrophobic electroconductive bacterial cellulose fiber (SEBC fiber) is presented. To construct durable superhydrophobicity, an ingenious bio‐fabricated method is employed for the shell–core structure. SEBC fibers with bio‐fabricated shell–core structure exhibit excellent electroconductibility, mechanical property, biodegradability, and durable superhydrophobicity. SF‐TENG displays a maximum open‐circuit voltage of 266.0 V, a short‐circuit current of 5.9 µA, and an output power of 489.7 µW, and successfully powers devices such as stopwatch and calculator. Abilities of self‐cleaning and anti‐fouling guarantee the stable output performance of SF‐TENG under harsh environmental conditions such as liquids pouring. Furthermore, the intelligent clothing is designed based on SF‐TENG to detect motion signals, and it is further utilized to construct a Sports and Health Monitoring System as a deep application. In summary, this study provides a novel strategy of bio‐fabrication for the design and preparation of superhydrophobic electroconductive fiber with shell–core structure. The SF‐TENG demonstrates practicability, stability and is promising for wearable devices in harsh environmental conditions.