Advanced functional fibers, which can endow common textiles with specific functionalities by traditional weaving processes without losing their basic features, including flexibility, breathability, and wash ability, are desired in flexible and wearable devices. However, the performance of piezoelectric wire sensors in previous studies has been unsatisfactory, especially in harsh environments. This article reports a thermally stable thin piezoelectric fiber with a lotus root structure, consisting of a core electrode, a perfluoroalkoxy alkane piezoelectret layer, a ground/shield electrode, and an outer jacket. The specific structure together with a small diameter of 0.4mm makes such fiber sensors very flexible and suitable to be woven into clothing or integrated into thin substrates. The piezoelectric sensitivity of the fibers, up to 1.50 pC/N at 0.25 MPa, is achieved and very stable in a broad operating temperature ranging from -79 to 150 degrees C, showing a promising application prospect in extreme environments. The fabrics and socks woven with such fibers can detect various motions, demonstrating their practicability in smart clothing for ordinary applications such as rehabilitation and gait analysis and special purposes such as functional clothing for astronauts and firefighters who may expose to very low- or high-temperature environments. Published under an exclusive license by AIP Publishing. https://doi.org/10.1063/5.0165390
