Research paper of the month
November 2014 - Electric Field-Modulated Non-Ohmic Behavior of Carbon Nanotube Fibers in Polar Liquids
Nanogenerators based on piezoelectric materials can convert ever-present mechanical vibrations into electrical power for energetically autonomous wireless and electronic devices. Nanowires of piezoelectric polymers are particularly attractive for harvesting mechanical energy in this way, as they are flexible, lightweight and sensitive to small vibrations. Previous studies have focused exclusively on nanowires grown by electrospinning, but this involves complex equipment, and high voltages of ~10 kV that electrically pole the nanowires and thus render them piezoelectric. In the present paper, nanowires of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], grown using a simple, scalable, and cost-effective template-wetting technique, are shown to be successfully exploited in high-output nanogenerators without the need for electrical poling. The “self-poled” nanowires reported here exhibit high mechanical-to-electrical conversion efficiency comparable to the best previously reported values. This work therefore offers a scalable means of achieving high-performance nanogenerators for the next generation of self-powered electronics, and also for the development of low-cost strain sensors in applications ranging from biomedicine to robotics.
Figure: The top panel shows a schematic and the corresponding cross-sectional scanning electron microscope image of a nanogenerator comprising self-poled, aligned piezoelectric polymer nanowires embedded within a porous aluminum oxide template and encapsulated in poly(dimethylsiloxane). The bottom panel shows the typical electrical output arising when the nanogenerator is subjected to periodic low-level impacting. The harvested electrical energy can be used to light a commercial light emitting diode.
R. A. Whiter, V. Narayan & S. Kar-Narayan, "A Scalable Nanogenerator Based on Self-Poled Piezoelectric Polymer Nanowires with High Energy Conversion Efficiency", Advanced Energy Materials (2014).