Emerging feedback systems based on tracking body conditions can save human lives. In particular, vulnerable populations such as disabled people, elderly, and infants often require special care. For example, the high global mortality of infants primarily owing to sudden infant death syndrome while sleeping makes request for extraordinary attentions in neonatal intensive care units or daily lives. Here, a versatile laser‐induced graphene (LIG)‐based integrated flexible sensor system, which can wirelessly monitor the sleeping postures, respiration rate, and diaper moisture with feedback alarm notifications, is reported. A tilt sensor based on confining a liquid metal droplet inside a cavity can track at least 18 slanting orientations. A rapid and scalable laser direct writing method realizes LIG patterning in both the in‐plane and out‐of‐plane configurations as well as the formation of nonstick conductive structures to the liquid metal. By rationally merging the LIG‐based tilt, strain, and humidity sensors on a thin flexible film, the multimodal sensor device is applied to a diaper as a real‐time feedback tracking system of the sleeping posture, respiration, and wetness toward secure and comfortable lives. User‐friendly interfaces, which incorporate alarming functions, provide timely feedback for caregivers tending to vulnerable populations with limited self‐care capabilities.

Skin‐like wearable sensors are regarded as key technologies toward home‐based healthcare, human–machine interfaces, robotics, prostheses, and enhanced augmented/virtual reality (AR/VR). Inspired by human somatosensory functions, artificial sensory feedback systems play vital roles in shaping interactions with complex environments and timely decision‐making. This study presents an overview of recent advances in feedback‐driven, closed‐loop skin‐inspired flexible sensor systems that make use of emerging functional nanomaterials and elaborate structures. Drawing on feedback solutions, four categories of sensor systems are highlighted, which include prosthesis‐ and AR/VR‐based human–machine interfaces, smartphone‐based approaches for point‐of‐care detection, and smart wearable displays for direct signal visualizations. Furthermore, the progress of machine learning on the reliable recognition of massive quantities of signals generated by flexible sensor networks is briefly discussed. The state‐of‐the‐art hybrid sensor techniques, along with other emerging strategies, will enable total sensory feedback loop systems to be developed for next‐generation electronic skins.

In the past decade, the global industry and research attentions on intelligent skin-like electronics have boosted their applications in diverse fields including human healthcare, Internet of Things, human–machine interfaces, artificial intelligence and soft robotics. Among them, flexible humidity sensors play a vital role in noncontact measurements relying on the unique property of rapid response to humidity change. This work presents an overview of recent advances in flexible humidity sensors using various active functional materials for contactless monitoring. Four categories of humidity sensors are highlighted based on resistive, capacitive, impedance-type and voltage-type working mechanisms. Furthermore, typical strategies including chemical doping, structural design and Joule heating are introduced to enhance the performance of humidity sensors. Drawing on the noncontact perception capability, human/plant healthcare management, human–machine interactions as well as integrated humidity sensor-based feedback systems are presented. The burgeoning innovations in this research field will benefit human society, especially during the COVID-19 epidemic, where cross-infection should be averted and contactless sensation is highly desired.

A disorder in the thermoregulator center in a human body leads to some potential diseases such as fever and hyperthyroidism. To predict these diseases early, monitoring the health condition of the human body due to the influence of thermoregulation disorders is important. Although extensive works are performed on sweat‐rate detection by constructing microfluidic channels, skin‐moisture evaporation before sweating remains unknown. This work proposes a wireless and flexible sensor sheet to investigate the thermoregulatory responses of different people under cold stimulation and exercise by measuring the temperature and moisture variations on the finger skin. An integrated flexible sensor system consists of a ZnIn2S4 nanosheet‐based humidity sensor and carbon nanotube/SnO2 temperature sensor. The results exhibit distinct thermoregulation abilities of five volunteers. Interestingly, the sudden increase in finger moisture that results from the excitation by the sympathetic nerve is observed during the cold‐stimulus test. Although further studies are required to predict the potential diseases resulted from thermoregulation disorders in human body, this study provides a possibility of continuous and real‐time monitoring of thermoregulatory activities via skin moisture and temperature detection using a flexible sensor sheet.

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or proximity sensor [7] have been widely applied in safe human-machine interac tion, [8] environmental monitoring, [9] and healthcare management. [10] Unlike conventional sensor platforms that deliver one or two sensing function alities by separate devices, multimodal sensors endeavor to integrate multiple physical or chemical perceptions into a single device, and thus endow individuals with superior intelligence and interac tivity. [11] For instance, Jung et al. demon strated a flexible sensor array capable of detecting pressure and temperature based on piezoresistive and thermoelectric effects, respectively. [12] Temperature and pressure sensing arrays are separated by an insulating film to ensure independent measurements. Similar functions were achieved in a more delicate fingertip shaped resistive sensor, [13] where mate rial tuning and strain isolation reduced coupling between measured variables. To further promote the versatility of sensors, Zhao et al. integrated strain, pressure, and proximity percep tions into a stretchable capacitor array, realizing contact and noncontact interactions. [14] In addition, multiple sensory modal ities were also applied in plant growth management. Takei et al. proposed a flexible sensor sheet mainly based on ZnIn 2 S 4 nanosheets for optical, humidity, and temperature measure ments. [15] Nevertheless, additional efforts should be made to bypass relatively complicated fabrications accompanied by intri cate 3D structures. [13,14,16,17] Printing methods are considered as a versatile category of fabrication technologies to realize functional flexible elec tronics, including screen printing, inkjet printing and dispenser printing, etc. Their merits of customized prototyping, facile manufacturing steps and scalable fabrication [18,19] are prom ising to overcome the sophisticated fabrications for multimodal sensors. Besides, most printing technologies rely on human friendly functional inks rather than hazard chemicals [20,21] (e.g., photoresists or etchants in photolithography). Therefore, the printingbased scheme is environmentfriendly and has the potential to massively produce intelligent multimodal sensors for daily applications.To extend the functionality of multimodal sensors while maintaining facile fabrication processes and overall perfor mance after integration, a trimodal sensor sheet that can be fully manufactured by printing technologies is proposed. It integrates 4 × 4 pressure sensor units, 2 × 2 temperature sensor Flexible multimodal sensors are an indispensable part of Internet of Things for human-machine interfaces, health monitoring, and soft robots. Despite tremendous research efforts dedicated to high sensitivity, flexibility, and multifunctionality, these merits are conventionally accompanied with sophisticated fabrications that hinder practical applications. Herein, a fully printed flexible trimodal sensor sheet containing 4 × 4 pressure sensor units, 2 × 2 temperature sensor units, and 1 proximity sensor unit is proposed. Its elaborate structure featured by a...

Robots equipped with bionic skins for enhancing the robot perception capability are increasingly deployed in wide applications ranging from healthcare to industry. Artificial intelligence algorithms that can provide bionic skins with efficient signal processing functions further accelerate the development of this trend. Inspired by the somatosensory processing hierarchy of humans, the bioinspired co‐design of a tactile sensor and a deep learning‐based algorithm is proposed herein, simplifying the sensor structure while providing computation‐enhanced tactile sensing performance. The soft piezoresistive sensor, based on the carbon black‐coated polyurethane sponge, offers a continuous sensing area. By utilizing a customized deep neural network (DNN), it can detect external tactile stimulus spatially continuously. Besides, a novel data augmentation method is developed based on the sensor's hexagonal structure that has a sixfold rotation symmetry. It can significantly enhance the generalization ability of the DNN model by enriching the collected training data with generated pseudo‐data. The functionality of the sensor and the robustness of the proposed data augmentation strategy are verified by precisely recognizing five touch modalities, illustrating a well‐generalized performance, and providing a promising application prospect in human–robot interaction.

Sweat, as a biofluid with the potential for noninvasive collection, provides profound insights into human health conditions, because it contains various chemicals and information to be utilized for the monitoring of well-being, stress levels, exercise, and nutrition. Recently, wearable sweat sensors have been developed as a promising substitute to conventional laboratory sweat detection methods. Such sensors are promising to realize low-cost, real-time, in situ sweat measurements, and provide great opportunities for health status evaluation analysis based on personalized big data. This review first presents an overview of wearable sweat sensors from the perspective of basic components, including materials and structures for specific sensing applications and modalities. Current strategies and specific methods of the fabrication of wearable power management are also summarized. Finally, current challenges and future directions of wearable sweat sensors are discussed.