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Stretchable, self‐healing, and breathable skin‐biomimetic‐sensing iontronics play an important role in human physiological signal monitoring and human–computer interaction. However, previous studies have focused on the mimicking of skin tactile sensing (pressure, strain, and temperature), and the development of more functionalities is necessary. To this end, a superior humidity‐sensitive ionic skin is developed based on a self‐healing, stretchable, breathable, and biocompatible polyvinyl alcohol–cellulose nanofibers organohydrogel film, showing a pronounced thickness‐dependent humidity‐sensing performance. The as‐prepared 62.47‐μm‐thick organohydrogel film exhibits a high response (25,000%) to 98% RH, excellent repeatability, and long‐term stability (120 days). Moreover, this ionic skin has excellent resistance to large mechanical deformation and damage, and the worn‐out material can still retain its humidity‐sensing capabilities after self‐repair. Humidity‐sensing mechanism studies show that the induced response is mainly related to the increase of proton mobility and interfacial charge transport efficiency after water adsorption. The superior humidity responsiveness is attributed to the reduced thickness and the increased specific surface area of the organohydrogel film, allowing real‐time recording of physiological signals. Notably, by combining with a self‐designed printed circuit board, a continuous and wireless respiration monitoring system is developed, presenting its great potential in wearable and biomedical electronics. Stretchable, self‐healable, and breathable biomimetic ionic skin with superior humidity‐sensing performance is developed based on fully physical cross‐linked organohydrogel film, which features a superior responsiveness, excellent repeatability, and long‐term stability. Particularly, it can be used for real‐time and remote respiration monitoring and to implement a breathing interruption alarm system for sleep apnea syndrome patients after combining with a specially designed circuit and mask, showing its great potential in wearable and biomedical electronics.

Stretchable hydrogel‐based strain sensors suffer from limited sensitivity, which urgently requires further breakthroughs for precise and stable human‐computer interaction. Here, an efficient microstructural engineering strategy is proposed to significantly enhance the sensitivity of hydrogel‐based strain sensors by sandwiching an emulsion‐polymerized polyacrylamide organohydrogel microsphere membrane between two Ecoflex films, which are accompanied by crack generation and propagation effects upon stretching. Consequently, the as‐developed strain sensor exhibits ultrahigh sensitivity (gauge factor (GF) of 1275), wide detection range (100% strain), low hysteresis, ultralow detection limit (0.05% strain), good fatigue resistance, and low fabrication cost. In addition, the sensor features good water, dehydration, and frost resistance, enabling real‐time strain monitoring in various complex conditions due to the encapsulation of Ecoflex film and the addition of glycerol and KCl. Through further structural manipulation, the device achieves superior response to tiny strains, with a GF value of 98.3 in the strain range of less than 1.5%. Owing to the high strain sensing performance, the sensor is able to detect various human activities from swallowing to finger bending even under water. On this basis, a wireless sensing system with apnea warning and single‐channel gesture recognition capabilities is successfully demonstrated, demonstrating its great promise as wearable electronics. An ultrasensitive, stretchable, and environmental‐tolerant strain sensor based on crack mechanism with an Ecoflex‐microspheres‐Ecoflex sandwich structure is created successfully. It features ultra‐high sensitivity (gauge factor: 1275), wide detection range (0–100%), ultralow detection limit, wide operating temperature range, and good waterproofness. A wireless monitoring system is also developed, providing a more effective strategy to realize human–computer interfacing.

HighlightsStretchable MXene organohydrogel contains MXene network for electron conduction and water/glycerin binary solvent for ion transmission was prepared.The MXene organohydrogel exhibits exceptionally enhanced EMI shielding performance compared to hydrogel, as well as low-temperature tolerance, anti-drying ability.Conductive hydrogels have potential applications in shielding electromagnetic (EM) radiation interference in deformable and wearable electronic devices, but usually suffer from poor environmental stability and stretching-induced shielding performance degradation. Although organohydrogels can improve the environmental stability of materials, their development is at the expense of reducing electrical conductivity and thus weakening EM interference shielding ability. Here, a MXene organohydrogel is prepared which is composed of MXene network for electron conduction, binary solvent channels for ion conduction, and abundant solvent-polymer-MXene interfaces for EM wave scattering. This organohydrogel possesses excellent anti-drying ability, low-temperature tolerance, stretchability, shape adaptability, adhesion and rapid self-healing ability. Two effective strategies have been proposed to solve the problems of current organohydrogel shielding materials. By reasonably controlling the MXene content and the glycerol-water ratio in the gel, MXene organohydrogel can exhibit exceptionally enhanced EM interference shielding performances compared to MXene hydrogel due to the increased physical cross-linking density of the gel. Moreover, MXene organohydrogel shows attractive stretching-enhanced interference effectiveness, caused by the connection and parallel arrangement of MXene nanosheets. This well-designed MXene organohydrogel has potential applications in shielding EM interference in deformable and wearable electronic devices.

Conductive hydrogel flexible sensors have attracted widespread attention in the field of wearable electronic devices, which typically possess the properties of stretch resistance, moisture retention, antifreeze, adhesion, and self-healing. Herein, a silk nanofiber–tannic acid (SNF@TA) is successfully introduced into a polyvinyl alcohol (PVA) hydrogel to prepare a rigid and adhesive PVA–SNF@TA organohydrogel, exhibiting good mechanical strength (up to 365 kPa) and excellent self-healing properties. Due to the presence of conductive ions and ethylene glycol, the PVA–SNF@TA organohydrogel presents high sensitivity and cold resistance (− 18 °C). Moreover, the PVA–SNF@TA organohydrogel maintains a good transparency of 91% and ultraviolet filtration capacity. A strain sensor made of PVA–SNF@TA organohydrogel has good adhesion and accurate sensing signals. Generally, the designed sensor can significantly monitor small deformations, such as frowning, blinking, smiling, and swallowing motions, showing an impressive sensitivity (gauge factor 1.094) and stable (1000 stretching cycles) variable sensing characteristics. More specifically, a pressure sensor consisted of a PVA–SNF@TA organohydrogel cylinder keeps good sensing stability, thereby desirably detecting different large movements of the human body (finger pressing, walking and running). Our work can offer a broad avenue for the advanced architecture of functional hydrogel materials, which has great potential in the field of human exercise and health monitoring. Graphical abstract

In this paper, we propose a simple organohydrogel based capacitive humidity sensor for noncontact artificial sensation applications. The sensor is simple in design and consists of a transparent polyacrylamide organohydrogel thin film attached on a flexible inter-digit electrode layer. The process of water absorption and desorption is reversible, thus the dielectric of the organohydrogel film as well as the overall capacitance is dependent on environmental humidity. The water absorption capacity and structural reliability of the device have been largely improved by adding glycerol in the organohydrogel network. By optimizing both the glycerol concentration and organohydrogel film thickness, the sensor can respond to cyclic humidity changes in a period of 300 ms. In addition, this sensor achieves a high relative capacitance increase (by 20 folds) in a wide relative humidity range (12%–95%). The sensor also exhibits high stability under different bending curvatures (up to 6.81 mm), wide temperature changes (20°C–40°C) and external pressures (0–8 N). To demonstrate the applications in wearable electronics, we found that the sensor was successful in detecting respiration intensity and rate as well as the difference in moisture content in various objects, i.e., human skin and leaf surface. This sensor is highly sensitive and can be useful in the detection of the wide-range of humidity changes.