Prototyping and evaluation of piezoelectret made of isobutylene isoprene rubber and FEP film and development of its power generation model

Background Functional materials such as piezoelectrics can be used as sensors. Increases in the performance and output power of functional materials will open up new applications. Piezoelectric materials generate electricity when pressure is applied or when they are deformed. Piezoelectrets are materials that store electric charge when a high voltage is applied and generate electricity when electrodes are brought closer or moved apart. This study focused on inexpensive, mass-producible general-purpose rubber. Previously conducted testing with general-purpose rubber mixed with various amounts of lead zirconate titanate revealed that rubber without lead zirconate titanate can also generate electricity. Objective In this study, a piezoelectret composed of isobutylene isoprene rubber (IIR) and fluorinated ethylene propylene film (FEP) is proposed. IIR is made of commonly used materials. The power generation model of the proposed piezoelectret is developed and evaluated. Methods Surface potential measurements and a cyclic forced overload experiment were conducted. The results obtained using the power generation model for the piezoelectret were compared to experimental results. Results The surface potential and piezoelectric stress constant d 33 decreased immediately after the corona charge process but were maintained beyond day 7. The average d 33 value after 2 weeks was 475.2 pC/N, which is much higher than that for polyvinylidene fluoride (∼40 pC/N), a representative piezoelectric material. The results obtained using a power generation model that considers piezoelectric- and electrostatic-type generation showed qualitatively reasonable agreement with the experimental results. Conclusions A piezoelectret made of IIR has potential for high power generation. It was confirmed that piezoelectrets based on general-purpose rubber exhibit high power generation performance. The power generation model showed qualitative agreement with the experimental results.