Kuntal Maity1 Dipankar Mandal1

1, Jadavpur University, Kolkata, , India

Rapid development of wearable electronics, accessible and environmentally sustainable energy generation has attracted an extensive attention in next generations. In spite of flexible piezoelectric nanogenerator (PNG) based on electrospun poly(vinylidine fluoride) (PVDF) nanofibers (NFs) having light weight are in great demand, the development of low throughput, electrode compatibility and high durability remains a challenging task in meeting the requirements of wearable electronics devices. Recently conducting electrospun nanofiber has gained immense attention in several researchers due to the rapid growth of technology development with nanofibers, such as sensors, actuators, supercapacitors, energy harvesters (e.g., photovoltaic, piezo-, pyro- and triboelectric nanogenerator). However, the brittleness, toxicity and high cost of inorganic materials have prohibited its use as a conducting electrode, in addition, direct adherence on electrospun nanofibers surface is one of the major challenges to build the permanent electrodes in device structures. In contrast, conducting organic materials are being presented as a viable alternative as an organic electronic devices, particularly if one can achieve adequate coating on the electrospun polymer fibers.
Here, we report a simple design strategy of all organic PNG (AOPNG) based on multilayer assembled PVDF NFs mat where conducting polymer poly (3, 4- ethylenedioxythiphene) (PEDOT) coated PVDF NFs are used as electrodes. The continuous electrospinning technique in combination with vapor phase polymerization (VPP) enables such multilayer structure followed by successive coating of PEDOT. The nanofibers are characterized by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and Field emission scanning electron microscope (FE-SEM) before and after the coating of conducting polymer. The electrical performances were clarified by measuring the current-voltage (I-V) characteristic. Owing to multilayer structure and excellent electrode contact-stability, AOPNG exhibits an effective conversion of mechanical energy of human finger movements into electrical energy. The coating of conducting polymer upon PVDF fiber opens the use of organic electrode in various applications especially for e-skin devices solving the so called electrode issues. Now a day, monitoring of human physiological signals is an effective approach for the assessment of health problems. So, we can monitor our physiological signals such as body temperature, heartbeat rates, acceleration, gravity or motion and so on by the use of such organic sensors. More importantly AOPNG can show ultra-sensitivity towards human movements such as walking, foot strikes. Fatigue test demonstration under continuous mechanical impact (over 6 months) shows great promise as a wearable energy harvester. Thus it will play an essential role in future wearable electronics and healthcare systems.