Emerging flexible sensors based on nanomaterials: recent status and applications

Flexible sensors have received tremendous attention over the several decades due to their outstanding properties such as high stretchability, excellent biocompatibility, great conformability and low cost. The main problem that the flexible sensor faces is that the flexible material has poor resulting obtained flexible sensors possess poor sensitivity. Many kinds of nanomaterials with excellent conductivity have been integrated with flexible materials to improve the conductivity of flexible sensor, such as carbon nanomaterials and metal nanomaterials. In terms of molding, 3D printing serves as an ideal technology for producing flexible sensors because of it enables generate previously unattainable geometric structures compared with most traditional fabrications. Understanding the features of flexible materials, nanomaterials, 3D printing technology and assessing the possibility of their fabrication are therefore critical for the development and application of flexible sensors. Herein, we review the recent literature on the flexible materials, nanomaterials, fabrication strategy of flexible sensors, with a particular focus on stretchable and self-healing properties. Then we discuss the application of flexible sensor such as biomedical devices, wearable devices and soft robots. Finally, we provide the key challenge and opportunities of the flexible sensors that lie ahead.