Research On Flexible Energy Harvesting Devices Based On Piezoelectric Nanofibers

Harvesting clean and renewable energy from the environment has been attracting immense interest in the scientific community which provides an effective way to power nanodevices and wireless sensors.Among the various renewable energy sources such as light,vibration,heat,and microwave radiation,vibration appears to be the most ubiquitous power source.Several transduction mechanisms have been suggested to scavenge mechanical and vibrational energy into electricity,including electro-magnetic,electrostatic,and piezoelectric mechanisms.Of these mechanisms,harvesters based on the piezoelectric effect have the advantages of high energy density and potential for miniaturization and thus attracted much attention in recentyears.In present work,eletrospinning has been utilized to fabricate Ba TiO₃and BNT-BT nanofibers due to the advantages of low-cost,high-efficiency,and long fiber production and high-quality nanofibers were obtained.Furthermore,flexible piezoelectric devices were proposed and inter-digital electrode on a flexible substrate was incorporated to enhance the output signal.The main results in this dissertation are as follows:1.Based on the eletrospinning and sol-gel process,high-quality lead-free perovskite ferroelectric BTO fibers were fabricated.The influence of the electric field,concentration on the fiber morphologies were studied.The results indicated that the fiber diameters decreased with the field amplitude increasing,while with the concentration increasing,the fiber diameter increased.This is consistent with the theoretical predications.Under the concentration of 0.3 mol/L,long nanofibers with diameters of 100²00 nm and grain size of⁴0 nm was obtained.Good electromechanical response was obtained based on PFM with an effective piezoelectric constant of⁴0 pm/V.Aligned BTO fibers were fabricated using two parallel electrodes.A flexible piezoelectric device was further designed and fabricated based on the aligned BTO fibers.Under a bending excitation at⁴5 Hz,an output peak–peak voltage of⁰.45 V under a load resistance of 1 M?was obtained.2.High-qualityBNT-BTnanofiberswerefurtherfabricatedbythe electrospinning method.Dense,uniform and long fibers were obtained with diameters of 450 nm and grain sizes of 80 nm.An excellent piezoelectric response was achieved for the obtained fibers with an effective piezoelectric constant of up to 109 pm/V.A flexible piezoelectric energy harvester was further developed based on the BNT-BT nanofibers.A high voltage output of 30 V was obtained under 1 M?resistance and the average power could reach 1.5?W.