Recent progress in nanomaterial enabled chemical sensors for wearable environmental monitoring applications

In the present era of the Internet of Things, wearable sensors have been receiving considerable attention owing to their great potential in a plethora of applications. Highly sensitive chemical type wearable sensors that can conformably adhere to the epidermis or textiles for monitoring personal microenvironment have gained incredible interest. Attributable to the large surface area and excellent mechanical, chemical, physical, thermal as well as biocompatible properties, nanomaterials have become a prominent building block to develop wearable sensors. In this review, recent progress in the development of nanomaterial enabled wearable chemical environmental sensors (WCESs) is presented by focusing on the chemistry-based transduction principles. The developments in sensor structures, selection of materials, and fabrication methods are highlighted. The recent WCESs are summarized by grouping in three major types according to their transduction principles: electrical, photochemical, and electrochemical. In addition, sensors with multimodal sensing capability as well as sensors immobilized in wireless tags are summarized. Finally, issues, challenges, and future perspectives are discussed to develop next-generation WCESs with long life, biocompatibility, self-healing, and real-time communication capabilities.