Ultrasensitive piezoelectric-like film with designed cross-scale pores.

Achieving efficient mechanical biosignal detection remains challenging due to these signals' weak and dispersed nature. Piezoelectrets, known for their piezoelectric properties, offer promising potential for pressure sensors and flexible energy-harvesting devices. In this study, we present a piezoelectret film of polyvinylidene fluoride-co-trifluoroethylene featuring cross-scale pores, sandwiched between two fluorinated ethylene propylene layers. The patterned pores enable the storage of substantial net charges, resulting in a dense network of oriented space charges. Under mechanical loadings, these charges undergo notably relative displacements and induce variations in local electric field, with an effective piezoelectric coefficient of up to 2.1 × 104 picocoulombs per newton. This sandwich-structured film allows for real-time monitoring of biosignals for minimal mechanical inputs. For example, a light finger touch generates charge pulses exceeding 100 V, whereas wrist pulses yield high-fidelity, high-voltage signals. This work advances the field of flexible, self-powered electronics by providing a high-performance piezoelectric material, setting a benchmark for sensitivity and scalability in biosignal detection.