Preparation Of PVDF/BNBT Composite Nanofiber And Flexible Piezoelectric Sensor

With the rapid development of portable electronic products,wearable energy harvesters and sensors have been attracting great attention.Piezoelectric sensors based on piezoelectric effect are widely utilized and investigated due to their simple structure,low power consumption,long life,high sensitivity,and advantages for integration and miniaturization.Current flexible piezoelectric sensors have a small voltage output,which is far from meeting the performance requirements of micro-mini portable devices,so it is necessary to further increase the device output.At the present stage,flexible piezoelectric sensors are mainly based on polyvinylidene fluoride?PVDF?and its polymer materials,poor piezoelectric performance of which resulting in low signal output of the devices.It has been found that the quality of nanofiber can be improved by means of doping materials,thereby obtaining devices with high output performance.Based on the inspiration of these reports,a flexible,environmentally friendly,wearable piezoelectric sensor was designed and fabricated in this paper.In order to improve the performance of current flexible piezoelectric sensor,the organic flexible PVDF and inorganic one-dimensional sodium bismuth titanate-barium titanate nanofiber(0.93(Na_0.5Bi_0.5)TiO₃-0.07 BaTiO₃,which is considered to be one of the most potential alternatives for current lead-based piezoelectric materials)with great piezoelectric response,high electromechanical coupling coefficient and environment friendly were composited.In the process of production and preparation,such lead-free materials can reduce the environmental and physical hazards caused by lead-based piezoelectric materials,as well as achieving the requirements of the micro-portable devices.The main research results are as follows:Since the process parameters of the equipment will directly affect the quality of the nanofiber,investigation on the optimal electrospinning process parameters is the capital consideration.In the experiment,one-dimensional PVDF nanofiber was prepared by sol-gel method combined with electrospinning process.The effects of instrument parameters on the morphology of nanofiber were studied by altering the electrospinning voltage,drum rotation speed,receiving distance and solution propulsion speed.Among them,the electrospinning voltage,drum rotation speed and solution propulsion speed had comparatively large influence on the morphology of nanofiber.The optimized process parameters were finally determined as 25 kV voltage,15 cm distance,1.5 ml/h propulsion speed,and 4000 rpm rotation speed.One-dimensional PVDF nanofiber,BNBT particle,BNBT nanofiber and PVDF-BNBT composite nanofiber were prepared under the optimized process parameters.For the sake of whether the prepared nanofiber and nanoparticle meet the experimental requirements of the next step,all of the samples need to be tested and characterized.The results of X-ray diffraction?XRD?,scanning electron microscopy?SEM?and Fourier transform infrared spectroscopy?FITR?showed that the nanoparticle and nanofiber were of moderate diameter,both of which had pure phase structure before and after the compounding,with no impurity phase detected.The results of piezoelectric force microscopy?PFM?indicated that both the single PVDF and BNBT nanofiber had good piezoelectric response.Based on high-quality composite nanofiber,devices based on PVDF nanofibers,PVDF-BNBT?particle?and PVDF-BNBT?fiber?composite nanofibers were prepared and tested.A sandwich structure prototype device was designed,and the device was packaged with polydimethylsiloxane?PDMS?and the output voltage signal under periodic tap excitation was acquired by an oscilloscope.The results showed that device based on pure PVDF fiber can produce an output voltage of 10 V,while based on PVDF-BNBT?particle?and PVDF-BNBT?fiber?composite nanofiber can generate output voltages up to 30 V and 60 V respectively,which were three and six times higher than that of the pure PVDF device.Among them,the PVDF-BNBT?fiber?composite nanofiber-based device had the largest output performance and was superior to the PVDF-BNBT?particle?composite nanofiber-based device.Throughout the research process,the optimal electrospinning process parameters were explored and PVDF-BNBT composite nanofiber with excellent performance was prepared based on this.The composite nanofiber was used to design and fabricate sandwich-type piezoelectric sensor devices and thus a signal output of up to 60 V is obtained.This lead-free piezoelectric nanocomposite method optimizes the performance of piezoelectric materials and improves the performance of the sensor,which not only provides new ideas for developing new composite materials and optimizing device performance,but also promotes lead-free piezoelectric composites and it has laid a good foundation in the application of the sensors.