Research On Flexible Magnetic Sensor Based On Magnetoelectric Composites

With the rapid development of modern information technology,human society has entered the Internet of Things era of the Internet of Everything.As the most popular Internet of Things applications,smart wearable devices have received more and more attention and have made great progress.As a core component of wearable devices,sensors have been extensively studied,and countries have also listed sensor technology as the top technology.As an important branch of sensing technology,magnetic sensors can not only directly measure changes in magnetic fields,but also detect a variety of related physical quantities by detecting changes in magnetic fields.Among them,the flexible magnetic sensor based on magnetoelectric transducer has become a research hotspot because of its high sensitivity,good linearity,simple preparation process and good flexibility.Magnetoelectric materials can achieve passive measurement,have a response frequency bandwidth,high sensitivity,good linearity,etc.,and show good development potential in the field of magnetic sensors.Among them,the magnetoelectric laminated composite material has excellent magnetoelectric performance at room temperature and has a simple preparation process,which is an ideal device for detecting a weak magnetic field.The magnetoelectric particle composite based on flexible piezoelectric polymer has excellent flexibility,simple preparation process,which has also caused extensive research.At present,the flexible magnetic sensing technology based on magnetoelectric composite materials is not mature.Under the support of the National Natural Science Foundation of China?No.51775070?,this paper takes the flexible magnetic sensor based on magnetoelectric composite materials as the research object.The magnetoelectric effect and the application of magnetoelectric sensing of magnetoelectric composites were studied theoretically and experimentally.The specific research work of the thesis is as follows:?1?Based on the research status of magnetoelectric transducers and flexible magnetoelectric composites,the effects of different working modes and different composite modes on the performance of magnetoelectric transducers are analyzed.The magnetic-mechanical-electric coupling model of laminated magnetoelectric composites in L-T mode is studied,and the magnetoelectric voltage coefficient formula of the composites is derived according to the respective performance parameters of magnetostrictive materials and piezoelectric materials.?2?A new type of flexible magnetoelectric transducer was developed by compositing flexible piezoelectric material and amorphous nano-alloy soft magnetic material.Experiments showed that the maximum resonant magnetoelectric voltage coefficient of the magnetoelectric transducer can reach 235V/?cm·Oe?.It was found that the composite material has good flexibility and self-bias characteristics.The magnetoelectric voltage coefficient of the transducer can reach 7.04V/?cm·Oe?at a bending angle of 50°when the bias magnetic field is zero.In view of the self-bias and bending characteristics of the flexible laminated magnetoelectric composite,a flexible self-bias magnetic sensor was proposed,which had good linearity and repeatability,and the sensitivity and resolution were up to 54.9mV/Oe and 2.56×10^-8T,respectively.It shows that the flexible magnetic sensor has a broad application prospect in wearable field.?3?Magnetic nanosphere particles with different particle sizes were prepared by solvothermal method.The dispersion was uniform and there was no agglomeration.The saturation magnetization reached 42.314emu/g.The flexible magnetoelectric particle composite film consist of P?VDF-TrFE?powder and CFO nanoparticles was prepared by solution casting method.The phase analysis of the flexible magnetoelectric composite film was carried out,and its morphology,piezoelectric properties and magnetoelectric properties were investigated.It was found that the low frequency and resonant magnetoelectric voltage coefficient are nearly linear with the applied bias magnetic field in the range of 600Oe applied bias magnetic field,which can reach6.43mV/?cm·Oe?at 600Oe.The sensing performance of the sensor was studied and found to have good linearity to the alternating magnetic field.