Threadlike Piezoelectric Sensors Based on Ferroelectrets and Their Application in Washable and Breathable Smart Clothing

Abstract Ferroelectrets, featuring strong piezoelectric activity, flexibility, lightweight, and low cost, are advanced material and have attractive prospects for various sensors and actuators. However, large‐scale production of ferroelectret‐based devices and their straightforward implementation in complicated structures remain difficult tasks. In this study, a novel self‐shielding threadlike piezoelectric pressure sensor based on irradiation cross‐linked polypropylene (IXPP) ferroelectrets with a symmetric coaxial structure, named Ferroelectret Coaxial Sensor (FCS), is designed, prepared, and characterized. Besides, such sensors with a length of up to 300 m are successfully produced by an industrial continuous production line, confirming that the fabrication procedure is compatible with it and that the FCS can be mass‐produced in the future. The results show that the hydrostatic piezoelectric coefficient up to 55 pC/N is achieved in the FCS, which is around four times of magnitude higher than those of commercially available piezo‐cables made of poly (vinylidene fluoride). Smart carpets and wristers weaved with an integrated FCS, that can be produced by an industrial production line, are sensitive, flexible/stretchable, washable, and breathable, demonstrating great potential in motion recognition for health care. A laboratory prototype of traffic sensors based on the FCS indicates its capability in speed meauring and dynamic weighing for vehicles. This study will greatly promote applications of ferroelectrets in wearable devices, smart housing, intelligent transportation, etc.