Polypyrrole-coated Silk Fabric And Its Application In Flexible Electronic Devices

With development of electronic technology,intelligent wearable electronic devices gradually enter the market.In comparison with traditional electronic devices,wearable electronic devices possess excellent flexibility,which renders it great potentials in daily health monitoring.In order to meet the requirements of people on health,great efforts have been dedicated to developing flexible electronic devices that can be used for human physiological signal monitoring.Silk is a kind of natural protein fiber,mainly composed of silk fibroin and sericin.Thanks to its softness,high hygroscopicity,air-permeability and skin affinity,silk has been widely used in textile industry for thousands of years.Therefore,it is highly desirable to develop silk fabric-based flexible electronic devices,which integrate conductivity,energy supply and physiological sensing,for human health tracking.This thesis commits to combining traditional silk fabrics with flexible electronic technologies for the development of devices with the properties such as conductivity,energy storage and sensing.Three works were mainly carried out:1.Highly Conductive Polypyrrole-modified Silk Fiber via a Repeated-coating ApproachIn this study,a highly conductive silk fiber was successfully fabricated by modifying polypyrrole on its surface via a repeated-coating approach.During the coating process,the conductive polymer was in-situ synthesized by oxidative polymerization.The reaction temperature,reaction time and number of cyclic modification were optimized to be 15°C,12 h and 7 cycles,respectively.By using the optimized condition,the conductivity of an as-prepared silk fiber can reach 5.32×10³?/cm,which is much higher than those of conductive natural fibers reported so far.2.Flexible All-solid-state Supercapacitor Based on Polypyrrole-modified Silk FabricsIn this study,polypyrrole-modified silk fabrics with a resistance of 4.34×10^-2?/cm has been prepared successfully,and further utilized as both current collector and active materials to construct an all-solid-state supercapacitor.Scanning electron microscopy,Fourier transform infrared spectroscopy and X-ray diffraction graphs were collected to show the successfully modification of polypyrrole on silk fabrics.The electrochemical properties of the devices were characterized by cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy,showing that the device has the maximum energy density of 26.24?Wh/cm² at a power density of 1.44 mW/cm².After 100 times of bending and twisting,the performance of the device could be still maintained at 99.81%and98.81%,demonstrating the good flexibility of the supercapacitor.3.Flexible Humidity Sensor Based on Silk Fabric for Human Respiration MonitoringIn this work,a silk fabric-based human respiration sensor was fabricated by successive electroless plating of conductive interdigital electrodes and spray-coating of graphene oxide?GO?sensing layer.Surface morphologies of the device after each modification were characterized to show the successful construction of the sensor.The uniform surface distribution of GO was also exhibited using Raman mapping technique.After optimization of GO density,the as-prepared device could accurately detect the human respiration rate and effectively differentiate normal,deep as well as fast breath.The flexibility data indicate that the device can tolerate 2500 times of bending and twisting without influencing its performance.Moreover,by designing the spray-coating mask,GO layers with various patterns could be deposited for the achievement of both functionality and aesthetics.This work may not only develop a silk fabric-based sensor for potential applications in assessing of human basic health-status,but also provide a facile approach to preparing textile-based wearable electronic devices.The success of this study is expected to provide a new method for the fabrication of flexible electronic devices,and broaden the application of silk fabrics in wearable electronic applications.