سنسور های پوشیدنی نانو موادی در مراقبت از سلامتی Nanomaterial-Enabled Wearable Sensors for Healthcare

1. Introduction Driven by the increasing demand for continuous health monitoring, fitness tracking, and virtual reality, there has been a fast-growing market for wearable devices. The total value of wearable devices was estimated to be around $22.0 billion in 2016 and the worldwide revenue is expected to reach $97.8 billion by 2023, growing at a compound annual growth rate of around 24.1% from 2017 to 2023.[1] Wearable sensors that can be laminated onto the surface of skin or integrated with textiles have received tremendous attention from both academia and industry. Such sensors can monitor individual health parameters and environmental exposures with high sensitivity. Tracking of key health indicators such as body temperature, pulse rate, respiration rate, blood pressure, electrocardiogram (ECG), and glucose level can greatly benefit diagnosis, disease treatment, and postoperative rehabilitation. Long-term and continuous monitoring of vital signs is particularly important in early diagnosis of diseases, management of chronic diseases such as diabetes, asthma, hypertension, and severe obesity, and timely response to life-threatening situations such as seizure and cardiac arrest.[2,3] Tracking of environmental conditions such as ambient temperature, ultraviolet (UV) radiation humidity level, and concentration of harmful gases, and airborne particulates can provide valuable information for the prediction, management, and treatment of chronic diseases.[4,5] In addition to the applications in wearable health monitoring, continuous tracking of daily and sports activities can offer an efficient way to assess the well-being and athletic performances.[6] In order to ensure a robust and conformal contact with the curvilinear, coarse, and dynamic surface of skin without impeding daily activities, the wearable sensor should have low modulus and high stretchability. The epidermis has a modulus of 140–600 kPa while the dermis has an even lower modulus of 2–80 kPa.[7] Skin itself can be stretched elastically up to 15% and with the help of wrinkles and creases, the overall stretchability can reach as high as 100% during daily motions.[8] In addition to good wearability, wearable sensors should be highly sensitive, lightweight, low-cost, and with low power consumption. To achieve these features, nanomaterials that are compliant, possessing larger surface area and exceptional material properties, and compatible with low-cost fabrication processes are widely employed as building blocks for developing wearable sensors. In this review, we start from a brief overview of nanomaterials, their related structural designs and fabrication processes (Section 2). Following that, recent advances of nanomaterialenabled wearable sensors including temperature, electrophysiological, strain, tactile, electrochemical, and other sensors will be summarized (Section 3). A survey on the integration of multiple sensors and other components into wearable systems will be given in Section 4. The application of nanomaterialenabled wearable sensors for healthcare including health monitoring, activity tracking, and electronic skin will be presented in Section 5. The challenges and opportunities will be discussed at the end.