Direct Piezoelectricity of Soft Composite Electrospun Fibers

Recently soft fiber mats electrospun from solutions of Barium Titanate (BT) ferroelectric ceramics particles and poly lactic acid (PLA) were found to have large (d33~1nm/V) converse piezoelectric signals offering a myriad of applications ranging from active implants to smart textiles. Here we report direct piezoelectric measurements (electric signals due to mechanical stress) of the BT/PLA composite fiber mats at various BT concentrations. A testing apparatus was designed and constructed solely for these measurements involving AC stresses provided by a speaker in 10Hz-10kHz frequency range. The piezoelectric constant d33 $\sim$1nC/N was found to be in agreement with the prior converse piezoelectric measurements. The largest signals were obtained with 6\% BT/PLA composites, probably because the BT particles at higher concentrations could not be dispersed homogeneously. Importantly the direct piezoelectric signal is large enough to power a small LCD by simply pressing a 0.2mm thick 2 cm2 area mat by a finger. We expect to use these mats in active Braille cells and in liquid crystal writing tablets.\\[4pt] Reference: J. Morvan, E. Buyuktanir, J.L. West, A. J\'akli, ``Highly-piezoelectric Biocompatible and Soft Composite Fiber Mats,'' Appl. Phys. Lett., 100, 063901-1-4 (2012)