Flexible Piezoelectric-Electrochromic Synergistic Effect And Vibration Sensing Application

With the development of flexible electronics and self-powered electronic technology,green,efficient,and intelligent-interconnected devices are in serious demand.Meanwhile,structural health monitoring(SHM)can provide quantitative information for both structural health evaluations and early-warning maintenance.Most vibration sensors are rigid and difficult to use for specific parts such as curved surfaces.Moreover,the SHM systems are cumbersome and time-consuming to install,and require high power-consuming data acquisition systems.Consequently,they are expensive,inconvenient to operate and can not be used for curved structures.In turn,the realization of real-time vibration visualization sensors is an urgent task.Piezoelectric materials can sense mechanical vibration in the environment and convert mechanical energy into electrical signals.Electrochromic materials can exhibit different color reactions under external voltage.In order to address the above challenges,inspired by the chameleon,we combine both effects of piezoelectrity and electrochromic to design a flexible vibration visualization sensor for real-time structural health monitoring.In this thesis,lead zirconate titanate Pb Zr_0.52Ti_0.48O₃(PZT)and relaxor based ferroelectric single crystals of Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-Pb Ti O₃(PIMNT)are used as piezoelectric components.Two different types of flexible piezoelectric energy harvesters are respectively connected with the solid-state flexible WO₃ electrochromic device via the rectifier to prepare the vibration visualization sensors.Then,we explore the mechanism and performance of vibration sensing of the devices.Firstly,we successfully fabricate PZT thick films with a thickness of?2.4?m on flexible mica substrate by sol-gel method.Flexible piezoelectric energy harvester with interdigital electrodes(IDEs)/PZT/Mica structure has been designed and fabricated,which exhibits open-circuit voltage of 77 V and short-circuit current of 0.2?A.[001]^L*[1-10]^W*[110]^t PIMNT long flakes are prepared using mechanical-polishing method,and then are combined with Au circuit and ABS plastic substrate to form flexible array piezoelectric energy harvester by electrical parallel connection.They exhibit good piezoelectric property with open-circuit voltage of 35 V and short-circuit current of 160?A.Moreover,the maximum output instantaneous power is up to 610?W which can charge a 10?F capacitor to saturation in 25 seconds.Subsequently,the amorphous WO₃ film with a thickness of?535 nm is grown on the PET/ITO substrate by DC magnetron sputtering,which then is combined with the gel state Li⁺electrolyte to prepare a sandwich-structure electrochromic device.The device is colored at-4V and bleached at 3 V,whose transmittance modulation reaches to 64%at the 633 nm wavelength.The coloration and bleaching times are respectively 10.35 s and 3.75 s,indicating a fast response speed of the devices.Meanwhile it possesses good reversibility and color-memory effect.Both flexible piezoelectric energy harvesters are respectively integrated with WO₃electrochromic devices to form flexible vibration visualization sensors via the rectifying circuit.The PZT piezoelectric energy harvester has a small output energy,which is not enough to drive the cations into the WO₃ film,so there is no obvious color reaction.We successfully prepare flexible PIMNT-WO₃ vibration visualization sensor,and its transmittance modulation increases with the increase of vibration time and vibration amplitude.After vibrating for 15 mins at 4 Hz under 0.245%bending strain,the transmittance modulation of the device reaches to 45%,and the color difference is clearly distinguished by naked eyes.In summary,we studied the synergistic effect of piezoelectric and electrochromic.Based on the PIMNT single crystal and WO₃ film,a passive and flexible vibration visualization sensor with excellent performance is successfully fabricated.It is expected to solve the current SHM system's problems of cumbersome operation,high power consumption and non in-site detection,which can probably be applied in the field of road,bridge,aerospace and rail transit with great application prospect and commercial value.