Biodegradable and Bioabsorbable Polylactic Acid Ferroelectrets with Prominent Piezoelectric Activity

Ferroelectrets have promoted a variety of exciting flexible sensors, actuators, and microenergy harvesters. However, most ferroelectrets have been fabricated from non-degradable petro-based resins, and thus the recycling of these materials constitutes a big challenge. This article reports biodegradable and bioabsorbable ferroelectret films made from polylactic acid (PLA) resins for highly sensitive transducer applications, which can operate either in piezoelectric 33 or 31/32 mode. By modification of the microstructure and polarization, pronounced longitudinal and transverse piezoelectric activities are realized in a single material. For samples with a thickness of 400 µm and a bulk density of 350 kg m⁻³, the Young's moduli in thickness and plane direction are ranging from 0.1 to 10 MPa, respectively. After polarization in the thickness direction, quasi-static piezoelectric d₃₃, g₃₃, d₃₁ (d₃₂), and g₃₁ (g₃₂) coefficients in the PLA films, up to 500 pC N⁻¹, 40 Vm N⁻¹, −44 pC N⁻¹, and −3.6 Vm N⁻¹, are achieved, respectively. The longitudinal piezoelectric coefficients of the PLA films are comparable to non-degradable polymer ferroelectrets, while the transverse piezoelectric activity is superior, which may be attributed to the reduction of Young's moduli in the plane direction. The preparation procedure of the PLA ferroelectrets is compatible with large-scale production lines and thus can greatly promote their applications in green electronics.