There are now numerous emerging flexible and wearable sensing technologies that can perform a myriad of physical and physiological measurements. Rapid advances in developing and implementing such sensors in the last several years have demonstrated the growing significance and potential utility of this unique class of sensing platforms. Applications include wearable consumer electronics, soft robotics, medical prosthetics, electronic skin, and health monitoring. In this review, we provide a state-ofthe-art overview of the emerging flexible and wearable sensing platforms for healthcare and biomedical applications. We first introduce the selection of flexible and stretchable materials and the fabrication of sensors based on these materials. We then compare the different solid-state and liquid-state physical sensing platforms and examine the mechanical deformation-based working mechanisms of these sensors. We also highlight some of the exciting applications of flexible and wearable physical sensors in emerging healthcare and biomedical applications, in particular for artificial electronic skins, physiological health monitoring and assessment, and therapeutic and drug delivery. Finally, we conclude this review by offering some insight into the challenges and opportunities facing this field.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201902133.Wearable electronics have revolutionized the way physiological parameters are sensed, detected, and monitored. In recent years, advances in flexible and stretchable hybrid electronics have created emergent properties that enhance the compliance of devices to our skin. With their unobtrusive attributes, skin conformable sensors enable applications toward real-time disease diagnosis and continuous healthcare monitoring. Herein, critical perspectives of flexible hybrid electronics toward the future of digital health monitoring are provided, emphasizing its role in physiological sensing. In particular, the strategies within the sensor composition to render flexibility and stretchability while maintaining excellent sensing performance are considered. Next, novel approaches to the functionalization of the sensor for physical or biochemical stimuli are extensively covered. Subsequently, wearable sensors measuring physical parameters such as strain, pressure, temperature, as well as biological changes in metabolites and electrolytes are reported. Finally, their implications toward early disease detection and monitoring are discussed, concluding with a future perspective into the challenges and opportunities in emerging wearable sensor designs for the next few years. Wearable SensorsRecent progress in flexible and stretchable electronic systems has ignited exciting applications in consumer electronics, human computer interactions, augmented reality devices, and electronic skins. [1][2][3] Among these, a significant interest lies in health monitoring, [4][5][6] where vital functions may be measured continuously. Continuous health monitoring is far more superior than conventional healthcare workflow as the conventional approach can only offer snapshots of the physiological condition Figure 3. Material substrates for flexible and stretchable electronics, highlighting the advantages of choices for each material type. a) Common polymeric materials by order of glass transition temperatures. Reproduced with permission. [29] Copyright 2015, Elsevier. b) Schematic representation of crosslinked elastomeric substrates possessing configuration entropy. Reproduced with permission. [22]

Cardiovascular diseases account for the highest mortality globally, but recent advances in wearable technologies may potentially change how these illnesses are diagnosed and managed. In particular, continuous monitoring of cardiovascular vital signs for early intervention is highly desired. To this end, flexible wearable sensors that can be comfortably worn over long durations are gaining significant attention. In this review, advanced flexible wearable sensors for monitoring cardiovascular vital signals are outlined and discussed. Specifically, the functional materials, configurations, mechanisms, and recent advances of these flexible sensors for heart rate, blood pressure, blood oxygen saturation, and blood glucose monitoring are highlighted. Different mechanisms in bioelectric, mechano‐electric, optoelectric, and ultrasonic wearable sensors are presented to monitor cardiovascular vital signs from different body locations. Present challenges, possible strategies, and future directions of these wearable sensors are also discussed. With rapid development, these flexible wearable sensors will potentially be applicable for both medical diagnosis and daily healthcare use in tackling cardiovascular diseases.

Despite the emergence of flexible and stretchable actuators, few possess sensing capabilities. Here, we present a facile method of integrating a flexible pneumatic actuator with stretchable strain sensor to form a soft sensorized actuator. The elastomeric actuator comprises a microchannel connected to a controlled air source to achieve bending. The strain sensor comprises a thin layer of screen‐printed silver nanoparticles on an elastomeric substrate to achieve its stretchability and flexibility while maintaining excellent conductivity at ≈8 Ω sq–1. By printing a mesh network of conductive structures, our strain sensor is able to detect deformations beyond 20% with a high gauge factor beyond 50 000. The integration of a pneumatic soft actuator with our sensing element enables the measurement of the extent of actuator bending. To demonstrate its potential as a rehabilitation sensing actuator, we fit the sensorized actuator in a glove to further analyze finger kinematics. With this, we are able to detect irregular movement patterns in real time and assess finger stiffness or dexterity.