In the information age, sensors are already utilized in a variety of fields. Owing to excellent flexibility, stretchability/bendability and conformability on the curved surface of special-shaped objects, the piezoresistive flexible strain sensor plays a vital role in the fields of smart wear, human-computer interaction and structural service process monitoring. Generally, the piezoresistive flexible strain sensors have three different structures, including filling structure, sandwich structure and adsorption structure, which significantly differs in preparation complexity, repeatability, and sensing performance. Traditional preparation methods are usually employed to achieve structural construction. However, the disadvantages are obvious, e.g. complex operation, high cost and poor repeatability. With the rapid development of 3D printing technology, 3D printing can be used to prepare strain sensors efficiently, accurately and reproductively, which in turn promotes the development of sensors. Flexible matrix materials and conductive filler are required to prepare piezoresistive flexible strain sensors. Piezoresistive flexible strain sensors typically have three sensing mechanisms: crack propagation, conductive network disconnection and tunneling effect. And it is closely related to the structure and material of piezoresistive flexible strain sensors. Besides, sensing performance of the piezoresistive flexible strain sensor can be characterized by testing the sensitivity, sensing range, durability. However, how to achieve multiple excellent properties at the same time has become a research hotspot. Furthermore, the supporting devices and technologies of piezoresistive flexible strain sensor greatly limit its application, especially in terms of power supply and signal transmission. This review offers a retrospection of the research efforts with respect to the piezoresistive flexible strain sensors, and provides detailed descriptions of material selection, structure construction, mechanism exploration, performance optimization, and application development. Additionally, the current problems faced by piezoresistive flexible strain sensors and development prospects are assessed. © 2022 Cailiao Daobaoshe/ Materials Review. All rights reserved.
