Improved Piezoelectric Sensing Performance of P(VDF–TrFE) Nanofibers by Utilizing BTO Nanoparticles and Penetrated Electrodes

Piezoelectric polymers with good flexibility have attracted tremendous attention in wearable sensors and energy harvesters. As the piezoelectricity of polymers such as polyvinylidene fluoride (PVDF) and polyvinylidene fluoride–trifluoroethylene [P­(VDF–TrFE)] is lower than that of their ceramic counterparts, various approaches have been employed to improve the piezoelectric output of PVDF-based sensors, such as electrospinning, heat annealing, nanoconfinement, polymer blending, and nanoparticle addition. Here, we report two strategies to improve the piezoelectric sensing performance of polymer-based piezoelectric nanofibers, which include the formation of barium titanate (BTO)/P­(VDF–TrFE) composite nanofibers and fabrication of penetrated electrodes to enlarge the interfacial area. BTO/P­(VDF–TrFE) nanofibers with a BTO weight fraction of 5 wt % exhibit the maximum β-phase crystallinity and piezoelectricity. The piezoelectric output of the BTO/P­(VDF–TrFE) nanofiber mat is significantly improved compared with that of pristine P­(VDF–TrFE), which is confirmed by piezoresponse force microscopy (PFM) and compression loading tests. In order to form the penetrated electrodes, oxygen (O2) plasma treatment is employed, followed by an electroless plating process. The BTO/P­(VDF–TrFE) nanofibers with penetrated electrodes demonstrate increased dielectric constants and enhanced piezoelectric outputs. A BTO/P­(VDF–TrFE) nanofiber-based sensor with penetrated electrodes is capable of discerning the energy of a free-falling ball as low as 0.6 μJ and sensing the movement of a walking ant.