Energy harvesting with piezoelectric poly(γ-benzyl-ʟ-glutamate) fibers prepared through cylindrical near-field electrospinning

In this study, we examined the electrical energy conversion and mechanical characteristics of piezoelectric fibers of the synthetic polypeptide poly(γ-benzyl-ʟ-glutamate) (PBLG), prepared through cylindrical near-field electrospinning (CNFES) of a uniform macromolecular solution of PBLG in CH₂Cl₂. A high electric field (from 5 × 10⁶ to 1.5 × 10⁷ V m^-1) provided the electrostatic force to pull the polymer solution into a Taylor cone, from which the PBLG fibers were electrospun, yielding piezoelectric PBLG fibers highly oriented in an α-helical conformation, as determined through Fourier transform infrared spectroscopic analysis. The orientation of the α-helical conformation of these polypeptide fibers was greater than those of other polymer piezoelectric materials; indeed, micro-tensile testing revealed that the Young's modulus and tensile stress of the fibers were 3.64 GPa and 60.54 MPa, respectively, greater than those of the typical piezoelectric polymer poly(vinylidene difluoride). The voltage outputs of single piezoelectric fibers reached as high as 89.14 mV with 8 MΩ resistance, with a maximum power output of 138.42 pW. PBLG piezoelectric fibers directly patterned on a cicada wing, with an interdigitated electrode for energy harvesting and a vibrational frequency of approximately 10-30 Hz, produced voltages ranging from 7.64 to 14.25 mV; such systems have potential applications as sensors and harvesters. © The Royal Society of Chemistry 2014