Flexible strain sensors: Recent progress 2016-2023

This paper is dedicated to the fast-developing area of flexible sensors for various applications, including resistive, capacitive, optical, and other wearable strain sensors. These devices open opportunities in different fields and can serve personalized applications in healthcare care, human body motion detection in the sport of rehabilitation, soft robotics, precision and automated agriculture, and many other areas. Except for their implementation in practical cases, these sensors have a significant scientific interest in various aspects of research. A specific interest in sensor research that raises a high level of interest is the development of new sensitive materials with particular properties. Another important issue is mosaicking in various combinations of sensitive materials in the sensor design and creating arrays of sensors with corresponding signal data acquisition. Enhancement of sensors by using nanomaterials, microcracks in sensing films as an additional array for sensing improvement, and alternation of the tunneling resistance application for resistive-type sensors opens the door to many existing and new sensor implementation cases. The idea of circular economy promotes the reuse of discarded sensors and their parts and efficiently consumes materials. The same ideas demand us to reduce the consumption of nanocomposites, noble metals, and other expensive or dangerous materials for the environment. Another way to comply with environmental requirements is to use natural materials from plants. This review was built using the publication analysis and counting the keywords found according to the area of interest. The analysis focuses on stretchable strain sensors of various designs and their integrity with mounting media. Applications of stretch sensors are also not left behind and take a significant space within review. The last part of this paper contains an analysis of sensor disposal, recycling, and reuse. The study ends with a discussion and conclusions.