Influence of soft x-ray and ultraviolet irradiations on sensitivity of sensors made with piezoelectret films

Abstract

Abstract Piezo/ferroelectrets are a kind of cellular electret materials exhibiting piezoelectric effect. Owing to their large piezoelectric activity, flexibility, lightweight, low cost and large area, a list of promising applications have been suggested, including wearable sensors, actuators, micro energy harvesters, and etc. In terms of actual application, one of the most important performance indexes is the stability of piezoelectric response in complex application environments. This article mainly focuses on the influence of soft x-ray and ultraviolet irradiations on piezoelectric sensitivity of two kinds of sensors, made with irradiation cross-linked polypropylene (IXPP) and air-filled parallel-tunnel fluorinated ethylene propylene (FEP) piezoelectret films. A versatile encapsulation process with silica gel for sensor fabrication was introduced to improve the stability against radiations. The results show that soft x-ray irradiation can accelerate the depolarization of the piezoelectrets, while the influence of ultraviolet irradiation on piezoelectrets is not prominent. Encapsulation of the sensors with silica gel may significantly improve their stability under the radiation of soft x-ray. As indicated, the piezoelectric sensitivities of the encapsulated samples, made with IXPP and parallel-tunnel FEP piezoelectret films, are 50.2% and 6.9% of the initial values after 150 min irradiation of the soft x-ray with an energy of 9.5 keV, respectively.