The Application Of Electrospun Nanofibers In The Fields Of Humidity-sensitive Color Change Sensors And Piezoelectric-pyroelectric Nano-power Generation

Nanotechnology is the most cutting-edge technology in the world today,and it is a strategic-level technology that countries around the world are striving to develop.Nanomaterials have become a hotspot in the field of high performance materials because of their unique properties that are different from conventional materials.Electrospinning technology has attracted wide attention as a low cost,simple method to produce continuous and large scale nanofibers.The electrospun nanofibers have shown great potential in the fields of sensors,biomedicine,energy and environment,and so on.The main research content of this thesis consists of two parts,including electrospun nanofibers as humidity sensors and nanogenerators?NGs?.First,the colorimetric humidity sensors based on electrospun polyamide 66/cobalt chloride?PA66/CoCl₂?nanofibers membranes?NFMs?were introduced.It is now believed that humidity sensors based on the electrospun NFMs show high sensitivity and rapid response performance due to their large surface area to volume ratio,providing an increased number of sites for analyte interaction.While the sensitivity of the humidity sensors based on electrospun sensing materials can be detected by precise instrument,it may do not work in practical application limits to conditions.Therefore,such an electrospun NFM humidity indicator that can display different colors depending on the environmental humidity was proposed.A series of NFMs with various weight percentage of cobalt chloride to PA66 were fabricated in the experiment,and their humidity sensitivity based on color changing was studied.In addition,the humidity-sensitive NFM was combined with quartz crystal microbalance to create highly sensitive humidity sensor,and it showed high humidity sensitivity,fast response-recovery characteristics,small hysteresis,and good repeatability and stability.It shows that the PA66/CoCl₂ NFM has potential applications in humidity detection.In addition,we mainly introduces the general situation of NGs,and finds that NGs based on electrospun polyvinylidene fluoride?PVDF?only paid attention to the piezoelectricity of PVDF and ignored its pyroelectricity.Therefore,a flexible hybrid piezoelectric–pyroelectric NG based on electrospun PVDF was developed.The flexibility of the device was enhanced by using an electrospun NFM as a substrate and a conductive NFM and a carbon nanotube layer as the electrodes.The capabilities of the NG to harvest mechanical and thermal energies were demonstrated.Mechanical impacting and bending can effectively stimulate the piezoelectric output of the NG,moreover,a hybrid piezoelectric–pyroelectric current of the NG was detected upon simultaneous application of strain and a thermal gradient.Based on the flexible structure,the NG can further harvest energy from body motion and airflows.Furthermore,its mechanical durability,robustness and practicality were investigated by charging a capacitor.These results indicate that this flexible hybrid piezoelectric–pyroelectric NG has potential applications in self-powered electronic textiles.